JP4911949B2 - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier which can be adapted to a cleanerless system, which has excellent charging property and wide allowance for carrier spent, which results in a high-quality image without fog or irregular density, and which has excellent environmental stability and high durability. <P>SOLUTION: The carrier comprises a core having a ferrite component, and a coating layer, wherein the ferrite component contains each specified amount of metal oxide containing at least one kind of metal element selected from Mg, Li and Ca and of metal oxide containing at least one metal element selected from Mn, Cu, Cr and Zn. The 50%-particle size on a basis of volume distribution of the carrier is 15.0 &mu;m to 55.0 &mu;m; unevenness of the carrier ranges from 1.05 to 1.30; and the coating layer contains particles having 10 nm to 500 nm primary average particle size. <P>COPYRIGHT: (C)2006,JPO&amp;NCIPI

Description

The present invention is an electrophotographic method, an electrostatic recording method, electrostatic printing method, or a two-component developer having a career and toner used in developer for developing an electrostatic latent image in the toner jet method The present invention relates to the image forming method used.

  Conventionally, many methods are known as image forming methods. In particular, the following image forming method is generally used. First, an electric latent image is formed on a photoconductor by various means using a photoconductive substance, and then the latent image is developed with toner to form a toner image as a visible image. If necessary, the toner image is transferred to a transfer material such as paper, and then the toner image is fixed on the recording material by heat and / or pressure to obtain a copy. Toner that is not transferred and remains on the photoreceptor is cleaned by various methods, and the above-described steps are repeated.

  In recent years, image forming apparatuses using such an image forming method have been strictly pursued to be smaller, lighter, faster and more reliable. In addition, it is not only used as a general-purpose copier for copying original documents, but also used for copying high-definition images such as digital printers or graphic designs as computer output.

  Conventionally, cleaning means such as blade cleaning, fur brush cleaning, and roller cleaning have been used for the photosensitive member cleaning process. The cleaning means mechanically scrapes or clogs the transfer residual toner on the photoconductor to collect the transfer residual toner in a waste toner container. Therefore, problems are likely to occur due to the members constituting such cleaning means being pressed against the surface of the photoreceptor. For example, the surface of the photoreceptor is worn by strongly pressing the cleaning member. Furthermore, since the cleaning device is provided, the entire apparatus is inevitably enlarged, which has become a bottleneck when aiming to make the apparatus compact. From the viewpoint of ecology, a system without waste toner is desired.

  In order to solve the above-described problems, an image forming apparatus employing a technique called development / cleaning or cleaner-less has been proposed (see, for example, Patent Document 1). In the image forming apparatus, one image is formed per one rotation of the photosensitive member so that the influence of the transfer residual toner does not appear in the same image. Further, a technique has also been proposed in which the transfer residual toner is scattered on the photosensitive member by a scattering member and non-patterned, so that even when the same surface of the photosensitive member is used multiple times for one image, it is difficult to be manifested on the image. (For example, refer to Patent Documents 2 to 5).

  In addition, recent user needs are demanding higher image quality and higher definition. As one method for achieving this, toner fine particles are used. Certainly, the effect of making the toner fine particles is great in terms of faithfully reproducing the latent image. However, it is necessary to improve fog in order to provide a stable image over a long period of time. That is, by reducing the particle diameter of the toner, the surface area of the toner particles is increased, so that the width of the charge amount distribution is increased and fogging is likely to occur. As the toner surface area increases, the charging characteristics of the toner are more susceptible to environmental influences. Further, when the toner particle diameter is reduced, the dispersion state of the charge control agent and the colorant greatly affects the chargeability of the toner. When such a small particle size toner is applied to a high-speed machine, it becomes overcharged especially under low humidity, and fogging and density reduction may occur.

  Further, when the above-mentioned small particle size toner is used, a cleaning failure is likely to occur in a system for cleaning the transfer residual toner on the photosensitive member. On the other hand, in the cleanerless system described above, the residual toner due to fog toner increases, and the presence of the toner inhibits the charging of the photoconductor, which is a latent image carrier at the charged portion, and causes further deterioration of fog. It becomes difficult to provide quality images.

  In order to cope with high image quality and environmental protection from the point of not generating ozone, a contact charging method such as roller charging has become the mainstream in place of conventional corona charging as a charging method for the photoreceptor. In terms of image quality, when corona charging is used, the scattered toner easily contaminates the charging wire, resulting in insufficient discharge at the contaminated portion, making it difficult to apply a predetermined potential to the photoreceptor. Therefore, an image defect called a streak image is likely to occur. Among the contact charging methods, a charging method in which alternating current is superimposed on a direct current charge and applied is used from the viewpoint of sufficiently charging a photosensitive member, which is a latent image carrier, over a long period of time.

  A charging method in which alternating current is superimposed on and applied to direct current charge can maintain high image quality over a long period of time, but by applying an alternating current component, the toner intervening in the charged portion easily adheres firmly to the charging member or the photoreceptor. When the toner adheres to the photoreceptor, so-called toner fusion occurs, and when the toner adheres to the charging member, charging failure occurs, and both cause image defects according to the adhered portion. As described above, various proposals have been made for the system, but there are still some problems regarding the developer suitable for matching with the system.

  The two-component developer has a feature such as good controllability because the carrier has functions such as stirring, transporting and charging of the toner and the function as the developer is separated, and is widely used at present. . In particular, it is suitably used in full-color image forming apparatuses such as full-color copying machines or full-color printers that require high image quality.

  As a magnetic carrier used for a two-component developer, an iron powder carrier, a ferrite carrier, and a magnetic material-dispersed resin carrier in which magnetic fine particles are dispersed in a binder resin are known. Among them, the iron powder carrier has a low specific resistance of the carrier, so that the charge of the electrostatic charge image leaks through the carrier and disturbs the electrostatic charge image, which may cause an image defect. Therefore, ferrite carriers and magnetic material-dispersed resin carriers are currently widely used as magnetic carriers.

  The magnetic substance dispersion type resin carrier has advantages such as a low specific gravity and a reduction in stirring torque, and prevents carrier spent by reducing damage to the carrier during stirring. However, although the life of the developer can be extended, the uniformity of the magnetic properties may be insufficient, so that carrier adhesion is likely to occur and image defects are likely to occur.

  Moreover, in the conventional ferrite carrier, the heavy metal containing ferrite carrier has been generally used. However, in that case, since the magnetic brush becomes stiff because the specific gravity of the carrier is large and has a larger saturation magnetization, deterioration of the developer such as carrier spent and toner external additive deterioration tends to be large, and A magnetic brush was formed on the toner image. Therefore, a light metal ferrite carrier is disclosed for the purpose of lowering the specific gravity. (For example, see Patent Documents 6 to 8). However, these are all ferrite carriers composed only of light metals, and the mutual adhesion of the constituent components is poor and the particle strength is insufficient. In particular, in the case of cleanerless, the stress on the developer during agitation is large in order to improve the rising of toner charging. For this reason, irregularly shaped particles are likely to exist and image defects are likely to occur.

  Furthermore, the conventional ferrite carrier has a problem of how to use the particle surface properties. Until now, in order to smooth the surface of the ferrite carrier having minute irregularities, a technique for increasing the firing temperature during production has been performed. However, this method tends to cause particle union and image defects. On the other hand, the surface of the ferrite carrier having minute irregularities is coated with a large amount of resin to smooth the carrier surface, impart carrier fluidity, and prevent carrier spent (for example, Patent Documents) 9 and 10). However, with this method, it was necessary to add a large amount of coating until the surface of the carrier became smooth. For this reason, the toner is excessively charged, the image density may not be increased, and a ground fog may occur. On the other hand, it has been practiced to improve the charge imparting property by causing minute irregularities on the surface of the carrier by the coating agent (for example, Patent Documents 11 and 12). However, this method may cause peeling due to long-term use on minute uneven portions, which may cause problems with carrier durability.

Thus, there is a demand for a carrier that has a favorable charge rise that can be suitably applied to a cleaner-less system and can maintain high image quality over a long period of time.
In addition, in order to suppress changes in the charge amount of the toner and stabilize the image density, when replenishing the toner consumed by development, the carrier is replenished together with the toner, and the carrier in the developing device is slightly depleted. There has been proposed an image forming method in which replacement is performed one by one. In such an image forming method, there is a demand for a carrier that has good charge rise and can maintain high image quality over a long period of time.

Japanese Patent Publication No. 5-69427 JP-A 64-20587 JP-A-2-259784 JP-A-4-50886 JP-A-5-165378 JP 2001-154416 A Japanese Patent Application Laid-Open No. 07-225497 JP 07-333910 A JP-A-8-292607 JP 2003-156877 A JP 2002-287431 A Japanese Patent Laid-Open No. 10-104884

The object of the present invention is a carrier that can solve the above-mentioned problems and can stably form an image satisfying high definition , specifically, can be applied to a cleaner-less system, and has excellent chargeability. tolerance to carrier spent widely widely fog from a low area image to a high area images, high-quality image can be obtained without uneven density, two-component comprising a magnetic carrier having an environment excellent stability, yet a high durability An object is to provide an image forming method using a developer.

  The present invention can solve the above problems by adopting the following configuration.

Area：面積
Perimeter：周囲長〕
該被覆層に粒子を有し、該粒子の一次個数平均粒径が２５ｎｍ以上４００ｎｍ以下であり、該粒子の添加量は、コート被覆量に対して５質量％以上３０質量％以下であることを特徴とする画像形成方法に関する。 The present invention forms an electrostatic image on an electrostatic charge image carrier, forms a magnetic brush from a toner and a carrier on a developer carrier that contains magnetic field generating means, and forms a magnetic brush on the developer carrier. An image forming method in which an electrostatic charge image is developed with a brush to form a toner image on the electrostatic charge image carrier, wherein the magnetic brush contains 2 parts by mass or more and 20 parts by mass of toner with respect to 100 parts by mass of the carrier. A replenishment developer is replenished to the developer, and the excess carrier in the developer is discharged from the developer, and the replenishment developer contains at least a binder resin and a colorant. And a carrier having at least a carrier core and a coating layer of a resin for coating the carrier core, and the coating amount of the carrier by the resin is 0.5 mass% or more and 5.0 % By mass or less The rear core has a ferrite component, and the ferrite component contains a metal oxide having at least one metal element selected from the group consisting of Mg, Li and Ca, and at least one metal element of the Mg, Li and Ca The sum of the content of the metal oxide having 15 to 30 mol% with respect to the total ferrite component, the metal oxide having Mn and Cu, and the metal oxide having Mn and Cu The total content is 50 ppm or more and 4000 ppm or less on a mass basis with respect to the total ferrite component, and the 50% particle size (D50) based on the volume distribution of the carrier is 20.0 μm or more and 50.0 μm or less, and the carrier core The unevenness degree of the carrier is 1.10 or more and 1.35 or less, and the unevenness degree of the carrier is 1.10 or more and 1.25 or less,
[However, the unevenness of the carrier and the carrier core is a value obtained from the following formula (1).

Area: Area
Perimeter
It has particles in the coating layer, the primary number average particle diameter of the particles is 25 nm or more and 400 nm or less, and the addition amount of the particles is 5% by mass or more and 30% by mass or less with respect to the coat coating amount. The present invention relates to a characteristic image forming method.

The magnetic carrier used in the present invention can stably form an image satisfying high definition. In other words, it can be applied to cleaner-less systems, has excellent chargeability, has a wide tolerance for carrier spent, has a wide range of fogging from low-area images to high-area images, and provides high-quality images with no uneven density and environmental stability. It has excellent durability and high durability.

  In the carrier having at least a carrier core and a coating layer for coating the carrier core, the carrier core has a ferrite component, and the ferrite component is at least selected from the group consisting of Mg, Li and Ca. A metal oxide having one kind of metal element, and the total content of the metal oxide having at least one kind of metal element of Mg, Li and Ca is 10 mol% or more and 40 mol% or less with respect to the total ferrite component; And a metal oxide having at least one metal element selected from the group consisting of Mn, Cu, Cr and Zn, and having at least one metal element of Mn, Cu, Cr and Zn The total content is 50 ppm or more and 4000 ppm or less on a mass basis with respect to the total ferrite component, and the carrier The volume distribution standard 50% particle size (D50) is 15.0 μm or more and 55.0 μm or less, the unevenness of the carrier is 1.05 or more and 1.30 or less, and the coating layer has particles, It has been found that by using a carrier characterized in that the primary number average particle diameter of the particles is 10 nm or more and 500 nm or less, it is possible to provide a carrier that can impart high charge rising property to the toner and is excellent in durability. .

  In the present invention, the ferrite component contains a metal oxide having at least one metal element selected from the group consisting of Mg, Li and Ca, and has at least one metal element of Mg, Li and Ca The total content of is 10 mol% or more and 40 mol% or less with respect to the total ferrite component. This makes it possible to control the specific gravity of the magnetic carrier to be smaller than in the past. Therefore, even in the cleanerless system, the mixing property with the toner is good, the charge rising of the toner is good, the stress applied to the carrier during the mixing can be reduced, and a long-term stable image can be provided.

  As described in Patent Documents 9, 11, and 12, when a heavy metal oxide having a heavy metal element such as Mn, Cu, Cr, and Zn is contained in a large amount, the specific gravity is high and the magnetic brush becomes rigid. In particular, in a cleaner-less system in which it is important to impart charging to the toner, strong agitation is required when the carrier and the toner are mixed. As a result, the magnetic carrier is subjected to an impact more than necessary, and the durability may not be sustained. The total content of the metal oxides containing at least one metal element of Mg, Li, and Ca is preferably 13 mol% or more and 35 mol% or less, and more preferably 15 mol% or more and 30 mol% or less.

The ferrite component further contains a metal oxide having at least one metal element selected from the group consisting of Mn, Cu, Cr and Zn, and at least one metal element of the Mn, Cu, Cr and Zn The sum total of the content of the metal oxides having the above is 50 ppm or more and 4000 ppm or less on the mass basis with respect to the total ferrite component. Fe ₂ O ₃ is contained as an essential component in the ferrite component. Therefore, not only light metal oxides having light metal elements such as Mg, Li and Ca, but also the uniformity of the material can be obtained by containing a small amount of heavy metal oxide. Increase. Therefore, the carrier strength and magnetic force are uniform. As in Patent Documents 7, 8, and 9, a carrier composed of only a light metal oxide and Fe ₂ O ₃ cannot maintain the uniformity of the material at the time of manufacture, and the carrier particle strength and the magnetic force uniformity are not maintained. Insufficient image quality may occur due to carrier adhesion. The total content of the metal oxides containing at least one metal element of Mn, Cu, Cr and Zn is preferably 50 ppm or more and less than 4000 ppm, more preferably 50 ppm or more and 3500 ppm or less, most preferably It is 50 ppm or more and 3000 ppm or less.

  The carrier of the present invention is characterized in that the 50% particle size (D50) based on the volume distribution is 15.0 μm or more and 55.0 μm or less. When the 50% particle size based on the volume distribution exceeds 55.0 μm, it becomes insufficient to give a uniform and good charge to the toner, making it difficult to faithfully reproduce the latent image, and fogging and toner scattering. Cause. On the other hand, if it is smaller than 15.0 μm, the carrier adheres to the latent image carrier. The preferred 50% particle size (volume average particle size) based on volume distribution is 15.0 μm or more and less than 55.0 μm, more preferably 20.0 μm or more and 50.0 μm or less, and most preferably 25.0 μm or more. 45.0 μm or less.

  Further, as the particle size distribution of the carrier, 15 μm or less is 10% by volume or less, 20 μm or less is 30% by volume or less, 50 μm or more is 30% by volume or less, and 65 μm or more is preferably 5% by volume or less. . When the amount of small fine particles is large, carrier adhesion to the latent image carrier becomes intense, and the fluidity of the developer is deteriorated, so that the coating tends to be non-uniform. Therefore, not only image density unevenness is likely to occur, but also the electrostatic latent image is likely to be disturbed via the carrier. When the abundance on the coarse particle side is large, it becomes insufficient to give a uniform and good charge to the toner, and it becomes difficult to faithfully reproduce the latent image. May cause life.

  It is characterized in that the unevenness of the carrier is 1.05 or more and 1.30 or less. The ferrite carrier surface has fine irregularities due to crystal growth during the formation of particles. If the unevenness is present after the carrier coating, a spent in which toner fine particles adhere to the recessed portion is likely to occur. Therefore, the surface of the coated carrier is preferably smooth. In particular, in a cleanerless system, the developer is likely to be stressed in order to improve toner charge rising. Therefore, in the carriers of Patent Documents 11 and 12 having irregularities on the carrier surface, the carrier surface peels off, and durability is difficult to maintain. Further, if the carrier is spherical and the surface is too smooth, the contact surface between the carrier and the toner is too small, and it is difficult to charge the toner properly. The degree of unevenness of the carrier is more preferably 1.10 or more and 1.25 or less.

  Furthermore, the unevenness of the carrier core is preferably 1.05 or more and 1.40 or less, more preferably 1.10 or more and 1.35 or less. As for the carrier core, since particles are added to the carrier coating agent described later, it is preferable that surface irregularities exist. Further, the presence of irregularities on the surface of the carrier core is more preferable because the specific gravity is lowered. However, if the degree of unevenness is greater than 1.40, even if the carrier is coated with a coating resin, the number of voids will be excessive, and toner will accumulate in that part, and the toner will tend to be unevenly charged, which is not preferable.

Further, it is preferable that the saturation magnetization of the carrier with respect to an applied magnetic field of 240 kA / m is 30 Am ² / kg or more and 80 Am ² / kg or less, and the residual magnetization is 10 Am ² / kg or less. The saturation magnetization is more preferably 35 Am ² / kg or more and 70 Am ² / kg or less, and still more preferably 40 Am ² / kg or more and 65 Am ² / kg or less. The residual magnetization is more preferably 7 Am ² / kg or less, and further preferably 5 Am ² / kg or less.

When the saturation magnetization exceeds 80 Am ² / kg, the ears on the magnetic brush become hard, and when stirring, the impact on the developer regulating blade or the like becomes large and it is difficult to maintain the durability. When the saturation magnetization is less than 30 Am ² / kg, carrier scattering may occur. Further, if the residual magnetization deviates from the above value, the developer transportability in the developing device tends to become unstable, and the durability may be inferior. If the residual magnetization exceeds 10 Am ² / kg, the fluidity of the developer may deteriorate.

It is preferred apparent density of the carrier is less than 1.30 g / cm ³ or more 2.40 g / cm ^3. More preferably not more than 1.50 g / cm ³ or more 2.00 g / cm ^3. When the apparent density is larger than 2.40 g / cm ³ , the stress on the developer is increased, and the toner is deteriorated in durability. ^{On the other hand, if it is} less than 1.30 g / cm ³ , carrier adhesion to the photoreceptor further occurs.

A well-known method can be employ | adopted for the manufacturing method of carrier core particle. For example, first, a predetermined amount of a metal oxide, iron oxide (Fe ₂ O ₃ ), and an additive are weighed and mixed. Next, the obtained mixture is calcined at 700 to 1000 ° C. for 0.5 to 5 hours, and then pulverized to a particle size of about 0.3 to 3 μm. The obtained pulverized product is added with a binder and a foaming agent as necessary, spray-dried in a heated atmosphere at 100 to 200 ° C., granulated, and then sintered at 800 to 1400 ° C. for 1 to 24 hours. Bake. Thereby, particles having a crystal grain size of about 1 to 50 μm are obtained. Next, the sintered ferrite particles are heat treated. By this heat treatment, many fine irregularities can be formed on the surface of the crystal grains constituting the ferrite particles. The heat treatment is performed at 750 to 1200 ° C., preferably 800 to 1150 ° C. for 0.5 to 3 hours in an inert gas (eg, N ₂ gas) atmosphere having an oxygen concentration of 5% or less, preferably 2% or less. It is carried out while leaving it alone or flowing an inert gas in a rotary kiln or the like.

  The carrier in the present invention is formed by coating the surface of the core material with a resin. Examples of the resin used for coating include a silicone resin, an acrylic-modified silicone resin, an epoxy resin, a polyester resin, a styrene-acrylic resin, Melamine-based resins, fluorine-based resins, fluorine-acrylic resins, and the like, and mixtures of these resins may be mentioned. Particularly preferred are silicone-based resins, acrylic-modified silicone resins, fluorine-based resins, fluorine-acrylic resins, and the like. Can be mentioned.

  Examples of the acrylic-modified silicone resin include methacrylic ester-modified silicone resins, acrylic ester-modified silicone resins, styrene-methacrylic ester-modified silicone resins, and styrene-acrylic ester-modified silicone resins. These may be used alone or in combination.

  More specifically, the silicone resin may be any conventionally known silicone resin, such as a straight silicone resin consisting only of an organosiloxane bond represented by the following formula and an alkyd, polyester, epoxy, urethane, etc. Examples thereof include modified silicone resins.

In the above formula, R ₁ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a phenyl group, R ₂ and R ₃ are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, phenyl Group, an alkenyl group having 2 to 4 carbon atoms, an alkenyloxy group having 2 to 4 carbon atoms, a hydroxy group, a carboxyl group, an ethylene oxide group, a glycidyl group, or a group shown below.

In the above formula, R ₄ and R ₅ are a hydroxy group, a carboxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, and an alkenyl having 2 to 4 carbon atoms. An oxy group, a phenyl group, a phenoxy group, k, l, m, n, o, p represents a positive number of 1 or more.

  Each of the above substituents may have a substituent such as an amino group, a hydroxy group, a carboxyl group, a mercapto group, an alkyl group, a phenyl group, an ethylene oxide group, or a halogen atom in addition to an unsubstituted group. For example, commercially available straight silicone resins include KR271, KR255, KR152 manufactured by Shin-Etsu Chemical Co., Ltd., SR2400, SR2405 manufactured by Toray Dow Corning Co., Ltd., and modified silicone resins include KR206 (alkyd modified) manufactured by Shin-Etsu Chemical Co., Ltd. There are KR5208 (acrylic modification), ES1001N (epoxy modification), KR305 (urethane modification), SR2115 (epoxy modification) and SR2110 (alkyd modification) manufactured by Toray Dow Corning.

  In the present invention, the carrier coat resin may contain a coupling agent. As a coupling agent to be used, a silane coupling agent is used, but other examples include a titanium coupling agent and an aluminum coupling agent. Examples of the silane coupling agent preferably used in the present invention include γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, and γ-methacryloxypropyltrimethoxysilane. N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxy Silane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, hexamethyldisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl] an Nitric chloride, γ-chloropropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane (made by Torre Silicone), allyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltri Examples include methoxysilane, dimethyldiethoxysilane, 1,3-divinyltetramethyldisilazane, and methacryloxyethyldimethyl (3-trimethoxysilylpropyl) ammonium chloride (manufactured by Chisso Corporation).

  The coverage of the carrier with the resin is preferably 0.5% by mass or more and 5.0% by mass or less. If it is less than 0.5% by mass, the core material is likely to be exposed from the resin coating layer when a surface irregular core material is used, and the developability may be adversely affected. The electrical resistance as a developer tends to be high, and image quality deterioration such as deterioration of gradation and generation of edge effect is induced. A more preferable coating amount is 0.8% by mass or more and 4.0% by mass or less, and further preferably 1.0% by mass or more and 3.0% by mass or less.

  In addition, the carrier of the present invention has particles in the coating layer, and the primary number average particle diameter of the particles is 10 nm or more and 500 nm or less. When these particles are coated, they provide an effect of smoothing the carrier surface by filling in the concave portions of minute irregularities present on the carrier surface. As a result, the toner can be effectively charged, and the durability of the carrier can be maintained. Furthermore, the present inventors have also found that these particles have an effect of reducing the difference in environmental charge (friction charge).

Conventionally, ferrite carriers containing a large amount of light element oxides have the disadvantage of large differences in environmental charge (friction charge). The formation reaction of ferrite begins with the reaction of light element oxides alone, the reaction between light element oxides, the reaction between light element oxides and Fe ₂ O ₃ and finally the reaction between all elements, resulting in a uniform spinel structure. The ferrite which has is produced | generated. This is because the number of contact points of the metal oxide is determined by its weight. Therefore, in ferrite containing a large amount of light element oxide, the weight ratio is extremely different from that of Fe ₂ O _3, and thus the reaction between the light element oxides proceeds rapidly. The inventors consider that the light element oxide component is caused by a relatively large amount in the recess. Even if the concave portion is simply coated with resin, it is only uniformly coated on the entire carrier surface and does not contribute to reducing the environmental difference. As in the present invention, it is possible to reduce the environmental difference by covering the concave portion with particles.

  When the primary number average particle diameter is smaller than 10 nm, the effect of smoothing the surface of the carrier cannot be obtained. On the other hand, if it is larger than 500 nm, the size of the particle becomes larger than the size of the uneven portion on the surface of the carrier, and the desorption of the particle occurs in the developing machine to deteriorate the charge imparting ability. The preferred primary number average particle diameter is 25 nm or more and 400 nm or less, and more preferably 50 nm or more and 300 nm or less.

  The addition amount of the particles is preferably 1% by mass or more and 40% by mass or less, and more preferably 5% by mass or more and 30% by mass or less with respect to the coat coating amount. When the addition amount is less than 1% by mass, the effect of smoothing the surface of the carrier cannot be obtained. On the other hand, if it is larger than 40% by mass, the charge imparting ability of the carrier becomes too small and fog occurs.

  As additive particles, particles such as resin particles, carbon black, silicon oxide, titanium oxide, and alumina can be used.

  Examples of the resin used for the resin fine particles include a polymer obtained by homopolymerization or copolymerization using a polymerizable monomer exemplified below. Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methoxystyrene, p-ethylstyrene, α-methylstyrene, and p-tertiarybutylstyrene; acrylic Acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, Acrylic esters such as phenyl acrylate; methacrylic acid, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, methacrylic acid 2 − Methacrylic acid esters such as tilhexyl, stearyl methacrylate, phenyl methacrylate, dimethylaminomethyl methacrylate, diethylaminoethyl methacrylate; 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, etc .; In addition, vinyl derivatives, specifically, for example, alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl ether, isobutyl ether, β-chloroethyl vinyl ether, phenyl vinyl ether, p-methylphenyl ether, p-chlorophenyl Ether, p-bromophenyl ether, p-nitrophenyl vinyl ether, p-methoxyphenyl vinyl ether, 2 Vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, N- vinylpyrrolidone, 2-vinylimidazole, N- methyl-2-vinylimidazole, N- vinylimidazole, it may be mentioned butadiene. In particular, polymethyl methacrylate (PMMA) fine particles and melamine resin fine particles are more preferable. As the PMMA fine particles, known ones can be used, and materials necessary for the intended electrophotographic developing toner can be selected. However, it is preferable to use a cross-linked organic material such as cross-linked PMMA fine particles. Two or more kinds of fine particles may be used in combination, or may be surface-treated.

  The term “crosslinked organic material” as used herein refers to a material having a molecular chain having a three-dimensional network structure, more preferably a material having a decomposition temperature of 230 ° C. or higher, more preferably 260 ° C. or higher. .

  In addition, as a granulation method of the resin fine particles used in the present invention, a method of pulverizing the above polymer, a particle polymerization method such as emulsion polymerization, soap-free emulsion polymerization, suspension polymerization, dispersion polymerization, or the like may be used. it can. Two or more kinds of particles may be used in combination, or may be surface-treated.

  As a method for coating the surface of the carrier core with a resin layer, it is common to dilute the resin with a solvent and coat the surface of the carrier core. The solvent used here may be any one that is soluble in each resin. When the resin is soluble in an organic solvent, the organic solvent may be toluene, xylene, cellosolve, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, or methanol. In the case of a water-soluble resin or emulsion type, water may be used. The carrier core surface is coated with a resin diluted with a solvent by a coating method such as a dipping method, a spray method, a brush coating method, or a kneading method, and then the solvent is volatilized. In addition, it is also possible to coat the resin powder on the surface of the carrier core by a dry method instead of a wet method using such a solvent.

  When the resin is coated on the surface of the carrier core and then baked, either an external heating method or an internal heating method may be used, for example, a fixed or fluid electric furnace, a rotary electric furnace, a burner furnace, or a microwave baking. But you can. The baking temperature varies depending on the resin to be used, but a temperature higher than the melting point or glass transition point is necessary, and in the case of a thermosetting resin or a condensation type resin, it is necessary to raise it to a temperature at which the curing proceeds sufficiently.

  Thus, after the resin is coated and baked on the surface of the carrier core, it is cooled, crushed and subjected to particle size adjustment to obtain a resin-coated carrier.

  The resin fine particles may be present on the carrier surface. However, as a method of inclusion, it is preferable to disperse the resin fine particles in a solvent at the time of resin coating and to disperse the resin fine particles together with the carrier coating resin. As the solvent to be dispersed at this time, it is preferable to select a solvent in which the resin fine particles do not swell.

  It is preferable that the surface roughness of the carrier obtained after coating is finally removed mechanically. By applying mechanical stress, the carrier surface is subjected to compression, shearing, impact, friction or a combination thereof by collision between carriers or collision with a stirring member. Thereby, the surface smoothness of the carrier is increased, and the effect of the present invention is further increased. Although it does not specifically limit as a mechanical processing method, Specifically, apparatuses, such as a tumbler mixer, a cone blender, a ball mill, a vibration mill, a sand mill, a pulverizer, an attritor, a Henschel type mixer, and a Nauta mixer, are mentioned. Among them, it is preferable to mechanically treat the carrier with a Nauter mixer.

  As the binder resin for the toner combined with the carrier of the present invention described above, polyester, polystyrene; polymer compound obtained from styrene derivatives such as poly-p-chlorostyrene and polyvinyltoluene; styrene-p-chlorostyrene copolymer, Styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer Styrene copolymer such as polymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenol resin, modified phenol Tree A monomer selected from maleic resins, acrylic resins, methacrylic resins, polyvinyl acetate, silicone resins; aliphatic polyhydric alcohols, aliphatic dicarboxylic acids, aromatic dicarboxylic acids, aromatic dialcohols and diphenols Polyester resin as structural unit: polyurethane resin, polyamide resin, polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin.

  A toner having a core / shell structure and a core formed of a low softening point material is also preferably used. Since the toner uses a low softening point material, it is advantageous for low-temperature fixing, but it is disadvantageous in terms of heat generation due to mechanical share and may cause toner spent in the developing device. By using the carrier of the present invention, the concern is solved.

  As a method of encapsulating the low softening point substance in the toner particles, the polarity of the material in the aqueous medium is set smaller than that of the main monomer, and the low softening point substance is further reduced, and a small amount of a large polar resin or single substance is used. By adding the monomer, toner particles having a so-called core / shell structure in which a low softening point substance is coated with an outer shell resin can be obtained.

  Toner particle size distribution control and particle size control can be achieved by a method of changing the kind and amount of a slightly water-soluble inorganic salt or a dispersant that acts as a protective colloid, or mechanical device conditions such as the peripheral speed of a roller, A predetermined toner can be obtained by controlling the number of passes, stirring conditions such as the shape of a stirring blade, container shape, or solid content concentration in an aqueous medium.

  Examples of the outer shell resin of the toner include a styrene- (meth) acryl copolymer, a polyester resin, an epoxy resin, and a styrene-butadiene copolymer.

  In the method of directly obtaining toner particles by a polymerization method, those monomers are preferably used. Specifically, styrene; styrene monomer such as o (m-, p-)-methylstyrene, m (p-)-ethylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate, (meth ) Propyl acrylate, butyl (meth) acrylate, octyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, ( (Meth) acrylic acid ester monomers such as dimethylaminoethyl acrylate and diethylaminoethyl (meth) acrylate; ene monomers such as butadiene, isoprene, cyclohexene, (meth) acrylonitrile and acrylamide are preferably used. It is done.

  In these toners, it is preferable to use at least silica fine particles and / or titanium oxide fine particles as an external additive because fluidity can be favorably imparted to the developer and the life of the developer is improved. Further, by using these fine powders, a developer with less environmental fluctuation is obtained.

  Other external additives include metal oxide fine powder (aluminum oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide, zinc oxide, etc.), nitride fine powder (silicon nitride, etc.), carbide fine powder Body (silicon carbide, etc.), metal salt fine powder (calcium sulfate, barium sulfate, calcium carbonate, etc.), fatty acid metal salt fine powder (zinc stearate, calcium stearate, etc.), carbon black, resin fine powder (polytetrafluoroethylene, Polyvinylidene fluoride, polymethyl methacrylate, polystyrene, silicone resin, etc.) are preferred. These external additives may be used alone or in combination. It is more preferable that the external additives including the silica fine powder have been subjected to a hydrophobic treatment.

  The above-mentioned external additive preferably has a number average particle size of 0.2 μm or less. When the number average particle diameter exceeds 0.2 μm, the fluidity is lowered, and the image quality is lowered during development and transfer.

  The amount of the external additive used is preferably 0.01 parts by mass or more and 10 parts by mass or less, more preferably 0.05 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the toner particles.

The external additive preferably has a specific surface area by nitrogen adsorption by the BET method of preferably 30 m ² / g or more, more preferably 50 m ² / g or more and 400 m ² / g or less.

  The mixing treatment of the toner particles and the external additive can be performed using a mixer such as a Henschel mixer.

  In the present invention, examples of the colorant used in the toner include the following.

  As the yellow colorant, compounds typified by condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds are used. Specifically, C.I. I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 168 can be suitably used.

  As the magenta colorant, condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds are used. Specifically, C.I. I. Pigment Red 2, 3, 5, 6, 7, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 144, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221, and 254 can be suitably used.

  Examples of cyan colorants include copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, and basic dye lake compounds. Specifically, C.I. I. Pigment Blue 1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, 66 can be preferably used.

  These colorants can be used alone or in combination and further in the form of a solid solution.

  Examples of the black colorant include carbon black and those prepared by using the yellow / magenta / cyan colorant described above toned to black. Further, as a full color application, magnetic monocomponent development may be applied using magnetic toner only for black toner.

  In the case of a color toner, the colorant is selected in consideration of hue angle, saturation, brightness, weather resistance, OHP transparency, and dispersibility in the toner. The content of the colorant is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin for toner.

  Known charge control agents can be used for the toner. In the case of a color toner, in particular, a charge control agent that is colorless or light in color, has a high toner charging speed, and can stably maintain a constant charge amount is preferable. Furthermore, in the present invention, when a toner is produced using a polymerization method, a charge control agent free from a solubilized product in an aqueous medium having a polymerization inhibition property is particularly preferable.

  Examples of the negative charge control agent include salicylic acid, dialkylsalicylic acid, naphthoic acid, dicarboxylic acid, or a metal compound thereof. Polymer type compound having sulfonic acid or carboxylic acid in the side chain; boron compound; urea compound; Silicon compounds; and calixarene are preferably used. As the positive charge control agent, for example, a quaternary ammonium salt; a polymer compound having the quaternary ammonium salt in the side chain; a guanidine compound; and an imidazole compound are preferably used. The content of the charge control agent is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin. However, the addition of a charge control agent to the toner particles is not essential.

  The toner particles can be produced by melting and kneading the binder resin, colorant, and other internal additives, cooling the kneaded material, and then pulverizing and classifying it, and directly producing toner particles using a suspension polymerization method. A dispersion polymerization method in which toner particles are directly produced using a water-based organic solvent that is soluble in the monomer and insoluble in the obtained polymer, or directly polymerized in the presence of a water-soluble polar polymerization initiator to form toner particles. Examples thereof include a method of producing toner particles using an emulsion polymerization method typified by a soap-free polymerization method to be generated.

  In the present invention, a method for producing toner particles by a suspension polymerization method, which can relatively easily obtain a fine particle toner having a sharp particle size distribution and a weight average particle diameter of 3 to 10 μm, is preferred.

  When toner particles are produced by a polymerization method, 2,2′azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′- is used as a polymerization initiator. Azo polymerization initiators such as azobis (cyclohexane-1-carbonitrile, 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile; benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxy Peroxide polymerization initiators such as carbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide are used.

  Although the addition amount of a polymerization initiator changes with the target degree of polymerization, generally 0.5 mass% or more and 20 mass% or less are added and used with respect to a monomer. The kind of the polymerization initiator varies slightly depending on the polymerization method, but can be used alone or in combination with reference to the 10-hour half-life temperature. A known crosslinking agent, chain transfer agent, polymerization inhibitor and the like for controlling the degree of polymerization can be further added and used.

  When suspension polymerization is used as a toner production method, the inorganic oxide used as the dispersant is tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, magnesium carbonate, water. Examples include calcium oxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, silica, and alumina. Examples of the organic compound include polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, ethyl cellulose, sodium salt of carboxymethyl cellulose, starch and the like. These are used by being dispersed in an aqueous phase. These dispersants are preferably used in an amount of 0.2 to 10.0 parts by mass with respect to 100 parts by mass of the polymerizable monomer.

  As these dispersants, commercially available ones may be used as they are, but in order to obtain dispersed particles having a fine uniform particle size, the inorganic compound can be produced in a dispersion medium under high-speed stirring. For example, in the case of tricalcium phosphate, a preferred dispersant for the suspension polymerization method can be obtained by mixing an aqueous sodium phosphate solution and an aqueous calcium chloride solution under high-speed stirring. Moreover, you may use together 0.001 to 0.1 mass part surfactant for refinement | miniaturization of these dispersing agents. Specifically, commercially available nonionic, anionic or cationic surfactants can be used, for example, sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pendadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, potassium stearate. Calcium oleate is preferably used.

  When a direct polymerization method is used as a toner production method, the toner can be produced specifically by the following production method. Monomer composition in which a release agent, a colorant, a charge control agent, a polymerization initiator and other additives composed of a low softening substance are added to the monomer and dissolved or dispersed uniformly by a homogenizer, ultrasonic disperser, etc. The product is dispersed in an aqueous phase containing a dispersion stabilizer by a usual stirrer, homomixer, homogenizer or the like. Preferably, the droplets made of the monomer composition are granulated by adjusting the stirring speed and time so as to have a desired toner particle size. Thereafter, stirring may be performed to such an extent that the particle state is maintained and the sedimentation of the particles is prevented by the action of the dispersion stabilizer. Polymerization is carried out at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. The temperature may be raised in the latter half of the polymerization reaction, and for the purpose of improving the durability, a part of the aqueous medium is retained after the latter half of the reaction or after the completion of the reaction in order to remove unreacted polymerizable monomers and byproducts. You may leave. After completion of the reaction, the produced toner particles are recovered by washing and filtration and dried. In the suspension polymerization method, it is usually preferable to use 300 parts by mass or more and 3000 parts by mass or less of water as a dispersion medium with respect to 100 parts by mass of the monomer composition.

  The toner may be classified to control the particle size distribution. As the method, a multi-division classifying device using inertial force is preferably used. By using this apparatus, a toner having a preferable particle size distribution in the present invention can be efficiently produced.

  In the toner of the present invention, the toner preferably has an average circularity of 0.930 or more and 0.985 or less, and more preferably 0.940 or more and 0.980 or less, in particles having an equivalent circle diameter of 3 μm or more.

  In the present invention, when a two-component developer is prepared by mixing a toner and a carrier, the mixing ratio is preferably 2% by mass or more and 20% by mass or less as the toner concentration in the developer. Is 2 mass% or more and 15 mass% or less, More preferably, it is 4 mass% or more and 13 mass% or less. With such a toner concentration, a good toner image can be obtained. When the toner concentration is less than 2% by mass, the image density tends to be low, and when it exceeds 20% by mass, fogging and in-machine scattering are likely to occur, and the useful life of the developer tends to be reduced.

  The image forming method of the present invention will be described in more detail. The image forming method of the present invention comprises (I) a charging step for charging the surface of the photoreceptor, (II) a latent image forming step for forming an electrostatic latent image on the charged surface of the photoreceptor, and (III) in the developing unit. A developing step of forming a toner image by supplying the toner to the electrostatic latent image and visualizing the electrostatic latent image by the action of electrolysis between the developer containing the toner and the photoreceptor; (IV) A transfer step of transferring the toner image onto a transfer material with or without an intermediate transfer member, and (V) a nip formed by a fixing member and a pressure member pressed against the fixing member. And a fixing step in which the transfer material is passed through and the toner image is heated and pressed against the transfer material.

  Hereinafter, an example of the image forming method of the present invention will be described below with reference to the drawings.

  FIG. 1 is a partial schematic view showing an example of an image forming apparatus to which the image forming method of the present invention is applied. Although details will be described later, this image forming apparatus includes a photosensitive drum 1 as a photosensitive member carrying an electrostatic latent image, a charging means 2 for charging the surface of the photosensitive drum 1, and a surface on the surface of the charged photosensitive drum 1. Formed by an information writing means (not shown) for forming an electrostatic latent image, a developing device 4 for developing the toner image by visualizing the electrostatic latent image formed on the surface of the photosensitive drum 1 with toner, and the developing device 4 A transfer blade 27 as transfer means for transferring the toner image to the transfer material 25.

  As a developing method using the toner of the present invention, for example, development can be performed using a developing means as shown in FIG. In the present invention, the developing step is preferably a step of developing by applying an oscillating electric field in which an alternating current component is superimposed on a direct current component. Specifically, it is preferable to perform development while applying an alternating electric field while the magnetic brush is in contact with a photosensitive member that is a latent image carrier, such as the photosensitive drum 1. The distance (S-D distance) B between the developer carrying member (developing sleeve) 11 and the photosensitive drum 1 is 100 to 800 μm, which is favorable in preventing carrier adhesion and improving dot reproducibility. If B is narrower than 100 μm, the supply of developer tends to be insufficient, resulting in low image density, and if it exceeds 800 μm, the lines of magnetic force from the magnetic pole S 1 spread and the density of the magnetic brush decreases, resulting in poor dot reproducibility and magnetic properties. The force that restrains the coat carrier is weakened, and carrier adhesion is likely to occur.

  The voltage between the peaks of the alternating electric field is preferably 300 to 3000 V, and the frequency is 500 to 10000 Hz, preferably 1000 to 7000 Hz, which can be appropriately selected depending on the process. In this case, a triangular wave, a rectangular wave, a sine wave, a waveform with a changed duty ratio, an intermittent alternating superimposed electric field, or the like can be selected and used as the waveform. When the applied voltage is lower than 300 V, it is difficult to obtain a sufficient image density, and the fog toner in the non-image portion may not be recovered well. If the voltage exceeds 5000 V, the latent image may be disturbed via the magnetic brush, resulting in a decrease in image quality.

  When the frequency is lower than 500 Hz, although it is related to the process speed, when the toner in contact with the photosensitive member is returned to the developing sleeve, sufficient vibration is not applied and fogging is likely to occur. If it exceeds 10,000 Hz, the toner cannot follow the electric field, and the image quality is likely to deteriorate.

  By using a two-component developer with well-charged toner, the anti-fogging voltage (Vback) can be lowered and the primary charge of the photoreceptor can be lowered, thus extending the life of the photoreceptor. it can. Vback is 350 V or less, more preferably 300 V or less, although it depends on the developing system.

  The contrast potential is preferably 100 to 500 V so that a sufficient image density is obtained.

  What is important in the developing method of the present invention is that the contact width of the magnetic brush on the developing sleeve 11 with the photosensitive drum 1 in order to achieve a sufficient image density, excellent dot reproducibility and development without carrier adhesion ( The development nip C) is preferably 3 to 8 mm. If the development nip C is narrower than 3 mm, it is difficult to satisfactorily satisfy a sufficient image density and dot reproducibility. If the development nip C is wider than 8 mm, developer packing occurs and the operation of the machine stops or the carrier adheres. It is difficult to sufficiently suppress As a method for adjusting the developing nip, the nip width is appropriately adjusted by adjusting the distance A between the regulating blade 15 as the developer regulating member and the developing sleeve 11 or by adjusting the distance B between the developing sleeve 11 and the photosensitive drum 1. adjust.

  The image forming method of the present invention uses the developer and the developing method of the present invention, particularly in the output of an image that places importance on halftone, and in combination with a developing system that has formed a digital latent image, through the toner. Therefore, it is possible to develop the dot latent image faithfully without disturbing the latent image. Even in the transfer process, a high transfer rate can be achieved by using a toner having a fine particle size distribution that has been finely powder-cut. Therefore, high image quality can be achieved in both the halftone part and the solid part.

  In addition to the improvement in the initial image quality, the use of the above-mentioned two-component developer reduces the change in the toner charge amount in the developing unit, and the effect of the present invention is sufficient without causing a deterioration in image quality even when copying many sheets. Can demonstrate.

  Preferably, an image forming apparatus having developing units for magenta, cyan, yellow, and black is used, and a blackened image can be obtained by performing black development last.

  The image forming method of the present invention will be further described with reference to FIG.

  In the image forming apparatus shown in FIG. 1, a magnetic brush made of magnetic particles 23 is formed on the surface of the conveying sleeve 22 by the magnetic force of the magnet roller 21, and this magnetic brush is brought into contact with the surface of the photosensitive drum 1. Is charged. A charging bias is applied to the conveying sleeve 22 by a bias applying means (not shown).

  A digital electrostatic latent image is formed by irradiating the charged photosensitive drum 1 with a laser beam 24 by an exposure device (not shown) as a latent image forming unit. The electrostatic latent image formed on the photosensitive drum 1 is developed by the toner 19a in the developer 19 carried on the developing sleeve 11 including the magnet roller 12 and applied with a developing bias by a bias applying device (not shown). Is done.

  The interior of the developing device 4 is partitioned into a developer chamber R1 and a stirring chamber R2 by a partition wall 17, and developer transport screws 13 and 14 are installed, respectively. Above the agitation chamber R2, a developer storage chamber R3 containing the replenishment developer 18 is installed, and a supply port 20 is provided below the developer storage chamber R3.

  The developer conveying screw 13 rotates to convey the developer in the developer chamber R1 in one direction along the longitudinal direction of the developing sleeve 11 while stirring. The partition wall 17 is provided with openings (not shown) on the front side and the back side of the drawing, and the developer conveyed to one side of the developer chamber R1 by the screw 13 is stirred through the opening of the partition wall 17 on one side. It is fed into the chamber R2 and delivered to the developer conveying screw 14. The direction of rotation of the screw 14 is opposite to that of the screw 13, while stirring and mixing the developer in the stirring chamber R 2, the developer delivered from the developer chamber R 1 and the toner replenished from the developer storage chamber R 3. 13 is conveyed in the agitating chamber R2 in the opposite direction to 13 and sent into the developer chamber R1 through the other opening of the partition wall 17.

  In order to develop the electrostatic latent image formed on the photosensitive drum 1, the developer 19 in the developer chamber R <b> 1 is drawn up by the magnetic force of the magnet roller 12 and is carried on the surface of the developing sleeve 11. The developer carried on the developing sleeve 11 is conveyed to a regulating blade 15 as the developing sleeve 11 rotates, and after being regulated to a developer thin layer having an appropriate layer thickness, the developing sleeve 11, the photosensitive drum 1, and the like. Reaches the opposite development area. A magnetic pole (development pole) N1 is located at a position corresponding to the development area of the magnet roller 12, and the development pole N1 forms a development magnetic field in the development area, and the developer spikes by this development magnetic field, A developer magnetic brush is generated in the development area. Then, the magnetic brush comes into contact with the photosensitive drum 1, and the toner adhering to the magnetic brush and the toner adhering to the surface of the developing sleeve 11 are applied to the electrostatic latent image area on the photosensitive drum 1 by the reversal development method. Transfer and adhere, and the electrostatic latent image is developed to form a toner image.

  The developer that has passed through the developing region is returned to the developing device 4 as the developing sleeve 11 rotates, and is peeled off from the developing sleeve 11 by the repulsive magnetic field between the magnetic poles S1 and S2, and the developer chamber R1 and the stirring chamber R2 are removed. It is dropped and collected.

  When the T / C ratio (mixing ratio of toner and carrier, that is, the toner concentration in the developer) of the developer 19 in the developing device 4 is reduced by the above developing process, the replenishing developer 18 is removed from the developer storage chamber R3. The stirring chamber R2 is replenished with an amount suitable for the amount consumed in the development, and the T / C of the developer 19 is maintained at a predetermined amount. To detect the T / C ratio of the developer 19 in the developing device 4, a toner concentration detection sensor that measures a change in the magnetic permeability of the developer using the inductance of the coil is used. The toner concentration detection sensor has a coil (not shown) therein.

  The regulating blade 15 that is disposed below the developing sleeve 11 and regulates the layer thickness of the developer 19 on the developing sleeve 11 is a nonmagnetic blade made of a nonmagnetic material such as aluminum or SUS316. The distance between the end portion and the surface of the developing sleeve 11 is 150 to 1000 μm, preferably 250 to 900 μm. If this distance is less than 150 μm, the magnetic carrier is clogged in the meantime, and the developer layer is likely to be uneven, and it is difficult to apply the developer necessary for good development, and a developed image with a small density and unevenness is formed. Easy to be. In order to prevent non-uniform application (so-called blade clogging) due to unnecessary particles mixed in the developer, this distance is preferably 250 μm or more. If it is larger than 1000 μm, the amount of developer applied on the developing sleeve 11 increases, and it is difficult to regulate the predetermined developer layer thickness, and the magnetic carrier particles adhere to the photosensitive drum 1 more and the developer is circulated and regulated. Development regulation by the blade 15 is weakened, and the triboelectric charge of the toner is lowered and fogging easily occurs.

  Further, the developed toner image is transferred onto a transfer material (recording material) 25 being conveyed by a transfer blade 27 which is a transfer means to which a transfer bias is applied by a bias applying means 26 and transferred onto the transfer material. The toner image thus fixed is fixed on the transfer material by a fixing device (not shown). The transfer residual toner that is not transferred to the transfer material in the transfer process and remains on the photosensitive drum 1 is adjusted in the charging state in the charging process and collected during development.

  The image forming method of the present invention further includes a charge amount control step of charging the transfer residual toner remaining on the surface of the photoreceptor after the transfer step to a normal polarity, and the charging step is performed after the charge amount control step. It is also preferable that the transfer residual toner is collected in the development process. FIG. 2 is a schematic sectional view showing an example of an image forming apparatus in which an image forming method having such a charge amount control step is preferably used. Hereinafter, the image forming method of the present invention further including a charge amount control step will be described with reference to FIG.

  The image forming apparatus according to this embodiment includes a photosensitive drum 1 as a photosensitive member, a charging roller 2 as a charging unit that charges the surface of the photosensitive drum 1, and an information writing unit that forms an electrostatic latent image on the photosensitive drum 1. The laser system 3, the electrostatic latent image formed on the surface of the photosensitive drum 1 by the laser system 3 is visualized with toner, the toner image is formed, and the toner image formed by the developing device 4 is transferred. The transfer roller 5 as a transfer means for transferring to the material P, the fixing means 6 for fixing the toner image transferred to the transfer material P on the transfer material, and the transfer roller 5 transfer the toner image to the transfer material P. And a charge amount control member 7 for charging the transfer residual toner remaining on the surface of the photosensitive drum 1 to a normal polarity.

  As shown in FIG. 2, a predetermined charging bias is applied to the charging roller 2 from the power source S1 to charge the photosensitive drum. The charging bias at this time is preferably an oscillating voltage obtained by superimposing a DC voltage (Vdc) and an AC voltage (Vac). Thereafter, image exposure is performed by a known method by the laser system 3 to form an electrostatic latent image.

  The electrostatic latent image formed on the photosensitive drum 1 is developed by the developing device 4 and becomes a toner image. In the developing device 4, the developing sleeve 4 b is disposed so as to face the surface of the photosensitive drum 1 on which the electrostatic latent image is formed. A facing portion between the photosensitive drum 1 and the developing sleeve 4b is a developing portion c. The developing sleeve 4b is preferably driven to rotate in the direction opposite to the traveling direction of the photosensitive drum 1 in the developing unit c. The developing sleeve 4b includes a magnet roller 4c. Due to the magnetic force of the magnet roller 4c, a part of the two-component developer 4e contained in the developing container 4a is formed on the outer peripheral surface of the developing sleeve 4b as a magnetic brush layer. Adsorbed and held. The two-component developer 4e adsorbed and held on the developing sleeve 4b is rotated and conveyed as the sleeve 4b rotates, and is layered into a predetermined thin layer by the developer coating blade 4d. The photosensitive drum surface is rubbed moderately in contact with the surface.

  A predetermined developing bias is applied to the developing sleeve 4b from the power source S2. In the present embodiment, the developing bias applied to the developing sleeve 4b is an oscillating voltage obtained by superimposing a DC voltage (Vdc) and an AC voltage (Vac). As a result, the latent image on the photosensitive drum 1 is developed with the toner in the developer 4e, and a toner image is formed. The formed toner image is transferred to the transfer material P (or an intermediate transfer member or the like) by the transfer roller 5 at the transfer portion d. The toner remaining on the surface of the photosensitive drum 1 (transfer residual toner) undergoes the following charge amount control process.

  A predetermined voltage is applied from the power source S4 to the charge amount control member 7 disposed in contact with the photosensitive drum 1. The transfer residual toner on the photosensitive drum 1 is brought into contact with the brush contact portion e, which is a contact portion between the charge amount control member 7 and the photosensitive drum 1, so that the normal polarity is adjusted. In the case of negatively charged toner, a negative voltage is applied to the photosensitive drum, and in the case of positively charged toner, a positive voltage is applied to the photosensitive drum. By passing through such a process, in the case of a cleaner-less system, the transfer residual toner can be recovered well during development. Although not explicitly shown in FIG. 2, in the present invention, it is used in the charge amount control step for the purpose of removing the residual charge on the photosensitive drum and improving the drum ghost between the transfer step and the charge amount control step. It is also an effective means to further include a step of applying a potential difference of opposite polarity applied in the charging step to the photosensitive drum using a member similar to the charge amount control member 7 to be applied.

  The image forming method of the present invention also forms an electrostatic charge image on an electrostatic charge image carrier, forms a magnetic brush from a toner and a carrier on a developer carrier containing a magnetic field generating means, and forms a developer carrier. An image forming method in which an electrostatic image is developed with a magnetic brush formed thereon to form a toner image on the electrostatic image bearing member, wherein the magnetic brush applies toner to 100 parts by mass of a carrier. 2 to 20 parts by mass, and a step of replenishing the developer for replenishment to the developer and discharging the excess carrier inside the developer to the developer.

  An example of an auto carrier refresh (ACR) type image forming apparatus that replenishes a developer for replenishment to the developer and discharges excess carrier inside the developer from the developer will be described below with reference to the drawings. By using this ACR type replenishment developer, the effect of the present invention can be sufficiently suppressed, such as the reduction in image quality can be suppressed even when the amount of replenishment of the carrier from the replenishment developer for auto carrier refresh is small. Can demonstrate.

  The color laser printer shown in FIG. 4 has a plurality of developing units, and is a quadruple drum system (inline) that obtains a full-color print image by once continuously transferring multiple images onto an intermediate transfer belt 60 as a second image carrier. ) Printer.

  In FIG. 4, an endless intermediate transfer belt 60 is suspended from a drive roller 6a, a tension roller 6b, and a secondary transfer counter roller 6c, and rotates in the direction of the arrow in the figure.

  Four developing units are arranged in series along the intermediate transfer belt 60 corresponding to each color.

Hereinafter, an image forming method in the printer will be described.
The photosensitive drum 1 disposed in the developing unit for developing the yellow toner is uniformly charged to a predetermined polarity and potential by the primary charging roller 2 during the rotation process, and then image exposure means (not shown) (color original) The image exposure 3 by the image color separation / imaging exposure optical system, the scanning exposure system by laser scanning which outputs a laser beam modulated in accordance with the time series electric digital pixel signal of the image information, etc. An electrostatic latent image corresponding to the first color component image (yellow component image) of the color image is formed.

  Next, the electrostatic latent image is developed by the first developer (yellow developer) 4 with yellow toner as the first color.

  In FIG. 4, the yellow image formed on the photosensitive drum 1 enters the primary transfer nip portion between the photosensitive drum 1 and the intermediate transfer belt 60. In the transfer nip portion, the flexible electrode 63 is brought into contact with the back side of the intermediate transfer belt 60. The flexible electrode 63 has a primary transfer bias source 68 so that a bias can be applied independently at each port. The intermediate transfer belt 60 first transfers yellow at the port of the first color, and then multiple-transfers each of the magenta, cyan, and black colors that have undergone the same process as described above from the photosensitive drum 1 corresponding to each color.

  The four-color full-color image formed on the intermediate transfer belt 60 is then collectively transferred to the transfer material P by the secondary transfer roller 69 and melted and fixed by a fixing device (not shown) to obtain a color print image.

  The secondary transfer residual toner remaining on the intermediate transfer belt 60 is subjected to blade cleaning by the intermediate transfer belt cleaner 9 to prepare for the next image forming process.

  In selecting the material of the transfer belt 60, in order to improve registration at each color port, a material that expands and contracts is not desirable, and a resin belt, a rubber belt with a metal core, or a resin + rubber belt is desirable.

  An auto carrier refresh development method that can be used in the present invention will be described with reference to FIG.

  In the developing operation of the developing device 4 of FIG. 5 using the auto carrier refresh developing method, the replenishment developer in which the toner and the magnetic carrier are mixed is supplied from the developer storage chamber R3 to the developing device 4 through the replenishing port 20. To be replenished.

  When the developing operation is repeated, the excess carrier overflows from the developer-side developer discharge port 34 provided in the developing device 4 and passes from the developer intermediate recovery chamber 35 through the developer recovery auger 36. It is discharged into a developer collection container (not shown).

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  In addition, the measuring method used in the Example in this invention is as follows.

1) Measuring method of 50% particle size (D50) based on the volume distribution of the carrier Using the SRA type of Microtrac particle size analyzer (Nikkiso Co., Ltd.), measuring the particle size distribution of the carrier with a range setting of 0.7 to 125 μm Thus, the 50% particle size (D50) based on the volume distribution of the carrier was determined.

2) Measuring Method of Carrier Saturation Magnetization, Residual Magnetization, and Coercive Force The magnetic properties of the carrier were measured using an oscillating magnetic field type magnetic property automatic recording device BHV-30 manufactured by Riken Denshi Co., Ltd. The carrier was put in a cylindrical plastic container having a volume of about 0.07 cm ³ and packed so as to be sufficiently dense. In this state, the magnetization moment was measured, the actual volume when the sample (carrier) was inserted was measured, and the strength of magnetization per unit volume was obtained from this. In the measurement, an applied magnetic field was gradually applied and changed to 240 (KA / m), then the applied magnetic field was decreased, and finally a hysteresis curve of the sample was obtained on the recording paper. From this, saturation magnetization, residual magnetization, and coercive force were obtained.

3) Measuring method of primary number average particle diameter of particles on carrier surface A sample was processed and observed using a focused ion beam processing observation apparatus (FIB) and FB-2000C (Hitachi). For the preparation of the sample, a carbon paste aqueous solution is applied to the sample stage, and a small amount of the sample (carrier) is placed thereon. Thereafter, the sample is set in the FIB apparatus without performing platinum vapor deposition, and the surface of the target sample is irradiated with the beam. Thereby, the convex part resulting from particle | grains can be observed. The diameter of the convex part is measured. This measurement was performed by extracting 3 locations from 20 randomly extracted cross-sectional photographs of the carrier, a total of 60 locations, and taking the average value of the measurements as the primary number average particle size of the particles.

4) Measuring method of apparent density of carrier Using the container attached to the powder tester manufactured by Hosokawa Micron Corporation, the apparent density of the carrier was measured according to the procedure of the instruction manual of the powder tester.

5) Measuring method of unevenness of carrier The unevenness of the carrier and the carrier core was calculated as follows using a multi-image analyzer (manufactured by Beckman Coulter).

  The multi-image analyzer is a combination of a particle size distribution measuring apparatus based on an electrical resistance method and a function of photographing a particle image with a CCD camera and a function of analyzing the photographed particle image. Specifically, the measurement particles dispersed uniformly in the electrolyte solution by ultrasonic waves or the like are detected by the change in electric resistance when the particles pass through the aperture of the multisizer, which is a particle size distribution measuring device by the electric resistance method. Synchronously, a strobe is emitted and a particle image is taken with a CCD camera. This particle image is taken into a personal computer and analyzed after binarization.

  This device has various shapes such as average circularity, unevenness, aspect ratio, envelope circumference to circumference ratio, etc., as well as particle size data of circle equivalent diameter, longest diameter, area, sphere equivalent diameter from particle images. It can be analyzed. Furthermore, since the sample is introduced continuously, the specific gravity is heavy and the liquid carrier is likely to settle, and it is possible to measure with good reproducibility using a magnetic carrier that is difficult to disperse in the solution.

Area：面積
Perimeter：周囲長 The unevenness of the carrier and the carrier core can be obtained by the following formula (1). The closer it is to a circle, the closer it is to 1;

Area: Area
Perimeter: Perimeter

  The specific measurement method is as follows. First, a few drops of a surfactant are added to 100 to 300 ml of water from which fine dust has been removed through a filter. An appropriate amount (for example, 2 to 50 mg) of a measurement sample (carrier or carrier core) is added to this, and dispersion treatment is performed for 3 minutes with an ultrasonic disperser, and measurement is performed using a sample dispersion liquid in which the particle concentration of the measurement sample is adjusted. . A strobe is emitted using a pulse of an electric resistance change when the particle passes through a 100 μm aperture as a trigger, and a particle image is taken with a CCD camera. At this time, the pulse height of the electric resistance change equal to or greater than a certain value is set as a threshold, and a pulse having a height equal to or higher than the threshold is set as a trigger signal for causing the strobe to emit light. At this time, it is necessary to set a threshold so that particles having a circle-equivalent diameter of 3 μm or more can be reliably photographed. In order to increase the accuracy of the strobe's synchronized light emission with respect to the passage of particles and obtain a particle image with less blur, it is necessary to set the number of synchronized light emissions of the strobe (that is, the imaging speed of the particle image) to 60 times / second or less. is there. In addition, it is preferable to adjust the number of particles passing through the aperture by adjusting the concentration of the sample dispersion, the stirring conditions, and the like so that the number of synchronized light emission of the strobe is 30 times / second or less. Actually, the measurement was performed at a particle image capturing speed of 10 to 20 particles / second.

  For taking a particle image, a CCD camera having approximately 300,000 effective pixels is used through an optical system having a 40 × optical magnification by combining a 20 × objective lens and a 2 × converter lens. The resolution is about 0.25 μm / 1 pixel. This particle image is taken into a personal computer and binarized and then analyzed. Particle shape data of the degree of unevenness was obtained through image analysis.

6) Method for Measuring Weight Average Particle Size of Toner In the present invention, the weight average particle size and particle size distribution of the toner can be measured with a Coulter Counter TA-II or Coulter Multisizer (manufactured by Coulter Multisizer). As the electrolytic solution, a 1% NaCl aqueous solution is prepared using primary sodium chloride. In the present invention, ISOTON R-II (manufactured by Coulter Scientific Japan) was used. As a measuring method, 0.1 to 5 ml of a surfactant, preferably alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample (toner) is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion process for about 1 to 3 minutes with an ultrasonic disperser, and the volume and the number of toners of 2.00 μm or more are measured by using the 100 μm aperture as the aperture by the measuring device. The distribution and the number distribution were calculated, and the weight average particle diameter (D4) (the median value of each channel was taken as the representative value for each channel) was determined.

  As a channel, it is 2.00 micrometers or more and less than 2.52 micrometers; 2.52 micrometers or more and less than 3.17 micrometers; 3.17 micrometers or more and less than 4.00 micrometers; 4.00 micrometers or more and less than 5.04 micrometers; 5.04 micrometers or more and less than 6.35 micrometers; .35 μm or more and less than 8.00 μm; 8.00 μm or more and less than 10.08 μm; 10.08 μm or more and less than 12.70 μm; 12.70 μm or more and less than 16.00 μm; 16.00 μm or more and less than 20.20 μm; 13 channels of less than 40 μm; 25.40 μm or more and less than 32.00 μm; 32.00 μm or more and less than 40.30 μm were used.

7) Measuring method of toner average circularity The average circularity of the toner was measured using a flow type particle image measuring device “FPIA-2100 type” (manufactured by Sysmex Corporation), and calculated using the following formula.

  Here, the “particle projected area” is the area of the binarized toner particle image, and the “peripheral length of the particle projected image” is the length of the contour line obtained by connecting the edge points of the toner particle image. Define. The measurement used the perimeter of the particle image when image processing was performed at an image processing resolution of 512 × 512 (pixels of 0.3 μm × 0.3 μm).

  The circularity in the present invention is an index indicating the degree of unevenness of the toner, and is 1.000 when the toner is a perfect sphere. The more complicated the surface shape, the smaller the circularity.

  As a specific measuring method, first, 10 ml of ion-exchanged water from which impure solids are removed in advance is prepared in a container. After adding a surfactant, preferably an alkyl benzene sulfonate, as a dispersant, 0.02 g of a measurement sample was further added and dispersed uniformly. As a means for dispersion, an ultrasonic disperser “Tetora 150 type” (manufactured by Nikka Ki Bios) was used for dispersion treatment for 2 minutes to obtain a dispersion for measurement. In that case, it cools suitably so that the temperature of this dispersion may not be 40 degreeC or more. In order to suppress variation in circularity, the installation environment of the apparatus is controlled at 23 ° C. ± 0.5 ° C. so that the temperature inside the flow type particle image analyzer FPIA-2100 is 26 to 27 ° C. Preferably, autofocusing was performed using 2 μm latex particles every 2 hours.

  To measure the circularity of the toner, the flow type particle image measuring device is used, the concentration of the dispersion is readjusted so that the toner concentration at the time of measurement is 3000 to 10,000 / μl, and 1000 or more toners are measured. To do. After the measurement, using this data, data having an equivalent circle diameter of less than 2 μm was cut to determine the average circularity of the toner.

  The carrier used in the present invention will be described.

<Example of manufacturing carrier core>
(Example of manufacturing carrier core 1)
12.9 mol% of LiO, 6.5 mol% of MgO, 80.6 mol% of Fe ₂ O ₃ , 0.02 mol% of MnO and 0.002 mol% of CuO were ground and mixed in a wet ball mill for 5 hours. After drying, it was kept at 850 ° C. for 1 hour, and calcination was performed. This was pulverized with a wet ball mill for 7 hours to 3 μm or less. To this slurry, 2.5% by mass of a dispersant and a binder (polyvinyl alcohol) are added together, and then granulated and dried with a spray dryer, and held in an electric furnace at 1200 ° C. for 4 hours to perform main firing. It was. Thereafter, the mixture was crushed and sieved with a sieve having an opening of 250 μm to remove coarse particles, and then further classified by air classification (Elbow Jet: manufactured by Nippon Steel Mining Co., Ltd.) to adjust the particle size. A carrier core 1 having a volume average particle diameter of 38.2 μm was obtained. The components and physical properties of the obtained carrier core are shown in Table 1.

(Example of manufacturing carrier cores 2 to 6)
Carrier cores 2 to 6 were obtained in the same manner as the carrier core 1 except that the carrier composition was changed as described in Table 1. The components and physical properties of the obtained carrier core are shown in Table 1.

(Example of manufacturing carrier cores 7 and 8)
Carrier cores 7 and 8 were obtained in the same manner as the carrier core 5 except that the conditions for adjusting the particle size were changed. The components and physical properties of the obtained carrier core are shown in Table 1.

(Example of manufacturing carrier cores 9 and 10)
Carrier cores 9 and 10 were obtained in the same manner as the carrier core 6 except that the carrier composition was changed as shown in Table 1 and the amount of heavy metal oxide was changed as shown in Table 1. The components and physical properties of the obtained carrier core are shown in Table 1.

  Due to the difference in the amount of the heavy metal component, the carrier core 9 has a high magnetization amount, and the carrier core 10 contains a slightly deformed carrier.

(Example of manufacturing carrier cores 11 and 12)
Carrier cores 11 and 12 were obtained in the same manner as carrier core 1 except that the carrier composition was changed as shown in Table 1 and the amount of light metal oxide was changed as shown in Table 1. The components and physical properties of the obtained carrier core are shown in Table 1.

(Example of manufacturing carrier cores 13 and 14)
Carrier cores 13 and 14 were obtained in the same manner as carrier core 1 except that the conditions for adjusting the particle size were changed. The components and physical properties of the obtained carrier core are shown in Table 1.

(Example of manufacturing carrier core 15)
A carrier core 15 was obtained in the same manner as the carrier core 1 except that the carrier composition was changed as shown in Table 1 and the amount of heavy metal oxide was changed as shown in Table 1. The components and physical properties of the obtained carrier core are shown in Table 1.

  The amount of magnetization of the carrier core 15 increased due to the difference in the amount of heavy metal oxide.

(Example of manufacturing carrier 1)
Straight silicone (KR255 manufactured by Shin-Etsu Chemical Co., Ltd. (solid content conversion)) 100 parts by mass Silane coupling agent (γ-aminopropylethoxysilane) 10 parts by mass polymethyl methacrylate resin (1) (volume average particle size 100 nm) 20 masses Part The above components were mixed with 300 parts by mass of xylene to obtain a carrier resin coating solution. While stirring using a fluidized bed heated to 70 ° C. using this resin coating solution, coating and solvent removal operations were performed on the carrier core 1 so that the resin coating solid content was 1.5 mass%. Furthermore, using an oven, treatment was performed at 230 ° C. for 2.5 hours, and pulverization and classification using a sieve were performed. Finally, the carrier was put into a Nauter mixer and mixed at 100 rpm for 30 minutes to obtain carrier 1.

(Production example of carriers 2 to 4)
Carriers 2 to 4 were obtained in the same manner as Carrier 1 except that the carrier core was changed as described in Table 2. Table 2 shows the components and physical properties of the obtained carrier.

(Example of manufacturing carriers 5 and 6)
Carrier 1 except that the carrier core was changed as described in Table 2 and that polymethyl methacrylate resin (2) (volume average particle size 55 nm) was used instead of polymethyl methacrylate resin (1). Carriers 5 and 6 were obtained in the same manner as in the production method. Table 2 shows the components and physical properties of the obtained carrier.

(Example of manufacturing carrier 7)
Fluorine-acrylic resin (perfluorooctylethyl acrylate-methyl methacrylate) 100 parts by mass melamine resin fine particles (volume average particle size 350 nm) 30 parts by mass The above components were mixed with 300 parts by mass of xylene to obtain a carrier resin coating solution. While stirring using a fluidized bed heated to 70 ° C. using this resin coating solution, coating and solvent removal operations were performed on the carrier core 5 so that the resin coating solid content was 0.6 mass%. Furthermore, the carrier 7 was obtained by performing the process for 2.5 hours at 230 degreeC using the oven, and performing the crushing and the classification process by a sieve.

(Example of manufacturing carrier 8)
Fluorine-acrylic resin (perfluorooctylethyl acrylate-methyl methacrylate) 100 parts by mass melamine resin fine particles (volume average particle size 350 nm) 30 parts by mass The above components were mixed with 300 parts by mass of xylene to obtain a carrier resin coating solution. While stirring using a fluidized bed heated to 70 ° C. using this resin coating solution, coating and solvent removal operations were performed on the carrier core 6 so that the resin coating solid content was 0.6 mass%. Furthermore, using an oven, treatment was performed at 230 ° C. for 2.5 hours, and pulverization and classification using a sieve were performed. Finally, the carrier was put into a Nauter mixer and mixed at 100 rpm for 30 minutes to obtain carrier 8.

(Production example of carriers 9 to 12)
Carriers 9 to 12 were obtained in the same manner as the carrier 8 production method except that the carrier core was changed as described in Table 2. Table 2 shows the components and physical properties of the obtained carrier.

(Example of manufacturing carrier 13)
Carrier 13 was obtained in the same manner as Carrier 1 except that polymethyl methacrylate resin (3) (volume average particle size 9 nm) was used instead of polymethyl methacrylate resin (1). Table 2 shows the components and physical properties of the obtained carrier.

(Example of manufacturing carrier 14)
Carrier 14 was obtained in the same manner as Carrier 1 except that polymethyl methacrylate resin (4) (volume average particle size 520 nm) was used instead of polymethyl methacrylate resin (1). Table 2 shows the components and physical properties of the obtained carrier.

(Example of production of carriers 15 to 19)
Carriers 15 to 19 were obtained in the same manner as Carrier 1 except that the carrier core was changed as described in Table 2. Table 2 shows the components and physical properties of the obtained carrier.

(Example of manufacturing carrier 20)
Carrier 20 was obtained in the same manner as Carrier 1 except that polymethyl methacrylate resin (1) was not added. Table 2 shows the components and physical properties of the obtained carrier.

(Toner Production Example 1)
To 710 parts by mass of ion-exchanged water, 450 parts by mass of 0.1 M Na ₃ PO ₄ aqueous solution was added and heated to 60 ° C., and then at 12000 rpm using a TK homomixer (made by Tokushu Kika Kogyo). Stir. To this, 68 parts by mass of 1.0 M CaCl ₂ aqueous solution was gradually added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .

on the other hand,
Styrene 165 parts by mass n-butyl acrylate 35 parts by mass C.I. I. Pigment Blue 15: 3 (colorant) 12 parts by mass, 2,5-ditertiary butylsalicylate aluminum compound (charge control agent)
3 parts by mass / saturated polyester (weight average molecular weight: 17000, glass transition temperature: 54 ° C., acid value: 19.9, hydroxyl value: 7.5) 10 parts by mass / ester wax (total carbon number: 36, melting point 70 ° C. ) 20 parts by mass The above material was heated to 60 ° C. and uniformly dissolved and dispersed at 11000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). In this, 10 parts by mass of a polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.

The polymerizable monomer composition was put into an aqueous medium, and stirred at 11000 rpm for 10 minutes with a TK homomixer in an N ₂ atmosphere at 60 ° C. to granulate the polymerizable monomer composition. Then, while stirring with a paddle stirring blade, the temperature was raised to 80 ° C. and reacted for 10 hours. After completion of the polymerization reaction, the residual monomer was distilled off under reduced pressure. After cooling, hydrochloric acid was added to dissolve Ca ₃ (PO ₄ ) _{2 and the} like, followed by filtration, washing with water and drying to obtain cyan toner particles. .

  0.5 parts by mass of hydrophobized silica fine powder (number average particle size of primary particles: 0.03 μm) and hydrophobized titania fine powder (number of primary particles) with respect to 100 parts by mass of the obtained cyan toner particles. 0.5 part by mass of (average particle size: 0.03 μm) was externally added to obtain cyan toner 1 having a weight average particle size of 6.8 μm. The average circularity of the toner 1 was 0.973.

(Toner Production Example 2)
・ 100 parts by mass of polyester resin (condensation polymer of propoxylated bisphenol A, fumaric acid and trimellitic acid)
・ C. I. Pigment Blue 15: 3 5 parts by mass / aluminum compound of dialkyl salicylic acid 3 parts by mass / polyolefin wax 5 parts by mass The above materials are mixed by a Henschel mixer, and the vent port is connected to a suction pump and sucked with a twin screw extruder. Melt kneading was performed. This melt-kneaded product was roughly crushed with a hammer mill to obtain a 1 mm mesh pass crushed product. Furthermore, after finely pulverizing with a jet mill, classification is performed with a multi-division classifier (elbow jet), and then thermal spheronization is performed with a surffusion system (manufactured by Nippon Pneumatic Industry Co., Ltd.) to obtain cyan toner particles. Got.

  0.8 parts by mass of hydrophobized titanium oxide fine powder (number average particle size of primary particles: 0.05 μm) and hydrophobized silica oxide fine powder (number of primary particles) with respect to 100 parts by mass of the cyan toner particles (Average particle size: 0.03 μm) was mixed by a 0.8 part by mass Henschel mixer to obtain cyan toner 2 having a weight average particle size of 6.6 μm. The average circularity of the toner 2 was 0.940.

[ Reference Example A ]
The carrier 1 (93 parts by mass) obtained above and cyan toner 1 (7 parts by mass) were mixed with a V-type mixer at 38 rpm for 3 minutes to obtain developer 1.

  Next, this developer 1 was evaluated as follows. As an evaluation machine, iRC3200 (manufactured by Canon Inc.) was used. CLC80g paper (Canon Sales Co., Ltd.) was tested for 8000 sheets using an original document with a low image area ratio of 3% in a single color mode under normal temperature and humidity conditions (23 ° C / 60% RH, hereinafter also referred to as N / N). Then, an image was tested and evaluated using an original document with a high image area ratio of 20% and 2000 sheets. The same evaluation was performed under a high temperature and high humidity environment (32.5 ° C./90% RH, hereinafter also referred to as H / H). Moreover, it evaluated based on the following evaluation methods. The results are shown in Table 3. Durability was good, and the triboelectric charge difference in a specific environment was also good.

[Evaluation methods and standards]
1) Measuring method of triboelectric charge amount of toner FIG. 3 shows a schematic diagram of an apparatus for measuring the triboelectric charge amount. About 0.5 to 1.5 g of a two-component developer collected from the developing sleeve of a copying machine or printer is placed in a metal measuring container 52 having a 635 mesh screen 53 at the bottom, and a metal lid 54 is placed. . The total mass of the measurement container 52 at this time is weighed and is defined as W1 (g). Next, in the suction device 51 (at least the insulator is in contact with the measurement container 52), the suction is performed through the suction port 57 and the air volume control valve 56 is adjusted so that the pressure of the vacuum gauge 55 is 250 mmAq. In this state, the toner is removed by suction for 2 minutes. The potential of the electrometer 59 at this time is set to V (volt). Here, 58 is a capacitor, and the capacity is C (mF). Moreover, the weight of the whole measurement container after suction is weighed and is defined as W2 (g). The triboelectric charge amount (mC / kg) of this sample was calculated as follows.
Sample triboelectric charge (mC / kg) = C × V / (W1-W2)
(However, the measurement conditions are 23 ° C. and 60% RH)

2) Fog In a paper passing test under N / N and H / H environments, the fog at 10000 sheets was measured. As a method, the average reflectance Dr (%) of plain paper before image printing was measured by a reflection densitometer (“REFLECTOMETER MODEL TC-6DS” manufactured by Tokyo Denshoku Co., Ltd.) equipped with filters of complementary colors of each color. . On the other hand, a solid white image was drawn on plain paper, and then the reflectance Ds (%) of the solid white image was measured. The fog (%) was calculated from the following formula.
Fog (%) = Dr (%) − Ds (%)

Moreover, it evaluated according to the following standard.
A: Less than 0.4% Very good B: 0.4% to less than 1.0% Good C: 1.0% to less than 1.6% Practical level D: 1.6% to less than 2 Less than 2% Contamination occurred E: 2.2% or more Practical level

3) Carrier adhesion evaluation Using iRC3200 (Canon), the development contrast was adjusted so that the toner development amount on the drum was 0.3 mg / cm ² , and the A4 full solid halftone image was CLC80g paper (Canon Sales) 5) was output continuously. At this time, the number of white particles falling to the carrier particle size was counted and expressed as an average per A4 paper.
-Blank rank A: None is required.
B: Less than 0.5 is sufficient.
C: More than 0.5 and 1 or less.
D: More than 1 and 2 or less.
E: More than two.

4) Halftone image uniformity Image density was evaluated in an N / N environment using iRC3200 (manufactured by Canon Inc.) and adjusting the development contrast so that the toner development amount on the drum was 0.3 mg / cm ² . The A4 full solid halftone image was output on CLC 80g paper (manufactured by Canon Sales Co.). At this time, in the output image, the image density at five locations was measured using a reflection densitometer RD918 (manufactured by Macbeth).

For the evaluation of the halftone image uniformity, the difference between the maximum value and the minimum value of the image densities at the five positions measured in the above-described image density evaluation was obtained.
A: 0.04 or less B: More than 0.04 and 0.08 or less C: More than 0.08 and less than 0.12 D: More than 0.12 E: Image has uneven texture

5) Difference in triboelectric charge in specific environment The difference between initial triboelectric charge in N / N environment and initial triboelectric charge in H / H environment was measured.
A: The difference in triboelectric charge is 5 or less B: The triboelectric charge difference is 5 or more and less than 10 C: The triboelectric charge difference is 10 or more and less than 15 D: The triboelectric charge difference is 15 or more and less than 20 E: The triboelectric charge difference is 20 more than

[ Reference Example B , Reference Examples 1-6, Comparative Example A, Reference Example 7, Comparative Example B, Comparative Example C]
Developers 2 to 12 were prepared and evaluated in the same manner as Developer 1 except that the carrier was changed as shown in Table 3. The results are shown in Table 3.

[ Comparative Example D ]
A developer 13 was prepared and evaluated in the same manner as the developer 12 except that the toner was changed as shown in Table 3. The results are shown in Table 3.

[Comparative Examples 1-8]
Developers 14 to 21 were prepared and evaluated in the same manner as Developer 1 except that the carrier was changed as described in Table 3. The results are shown in Table 3.

( Example )
7.0 parts by mass of toner 1 was added to 1.0 part by mass of carrier 1 and mixed with a tumbler mixer to prepare developer 1 for replenishment.
Using this replenishment developer 1 and the developer 1 described above for the black station of a commercially available iRC3100 (manufactured by Canon Inc.), the development contrast so that the initial image density is 1.40 in an N / N, H / H environment. The original image with an image area ratio of 5% was evaluated using a CLC80g paper (manufactured by Canon Sales Co.).
As a result, the image density and charging were stabilized and good results were obtained.

Further, in order to evaluate the stability of the carrier concentration, 5 g of the replenishment developer was sampled from the replenishment port of the replenishment developer container every 1000 sheets, and the carrier concentration in the replenishment developer was measured. As a result, the carrier concentration was stable, and it was found that the carrier of the present invention can exhibit good dispersibility as a carrier for a replenishing developer.
The carrier concentration measurement method will be described in detail. After 5 g of the developer for replenishment is washed with ion-exchanged water containing 1% of Contaminone N (surfactant), the toner is separated from the carrier, and then dried, adjusted. Wet (25.0 ° C./60% RH). Thereafter, the carrier concentration in the supply developer was calculated by calculating the weight of the carrier contained in the supply developer. The toner concentration (T / C ratio) in the developing container at the start was 8% by mass. The amount of toner in the magnetic brush was 8 parts by mass with respect to 100 parts by mass of the carrier.

It is a partial schematic diagram showing an example of an image forming apparatus in which the image forming method of the present invention is suitably used. It is a schematic explanatory drawing which shows the other example of the image forming apparatus with which the image forming method of this invention is used suitably. FIG. 3 is a schematic view of an apparatus for measuring the triboelectric charge amount of toner. 1 is a configuration diagram of a tandem image forming apparatus. It is sectional drawing of an example of the developing device used for a tandem system.

Explanation of symbols

1, 61a Photosensitive member (photosensitive drum)
2 Charging means 2a Conductive support made of stainless steel 2e Charging roller pressure contact member (spring)
3 Exposure device 4, 63a Developing device 4a Developing container 4b, 11 Developer carrier (developing sleeve)
4c, 12 Magnet roller 4f, 13, 14 Developer conveying screw 4d, 15 Regulating blade 4g Developer storage chamber 5 Transfer roller 6 Fixing device 7 Charge amount control means 8 Non-contact thermistor 17 Partition 18 Replenishing developer 19 Developer 19a Toner 19b Carrier 20 Supply port 21 Magnet roller 22 Conveying sleeve 23 Magnetic brush 24, 67a, L Laser light 25, 92, P, S Transfer material (recording material)
26 Bias application means 27 Transfer blade 28 Toner density detection sensor R1 Developer chamber R2 Stir chamber R3 Developer storage chamber a Charging section b Exposure section c Development section d Transfer section e Charge amount control section S1, S2, S3, S4 Power supply 51 Suction machine 52 Measuring container 53 635 mesh screen 54 Metal lid 55 Vacuum gauge 56 Air flow control valve 57 Suction port 58 Condenser 59 Electrometer

Claims (1)

An electrostatic image is formed on the electrostatic image carrier, a magnetic brush is formed from the toner and carrier on the developer carrier that contains the magnetic field generating means, and the electrostatic charge is formed by the magnetic brush formed on the developer carrier. An image forming method of developing an image to form a toner image on the electrostatic charge image carrier,
The magnetic brush has 2 to 20 parts by mass of toner with respect to 100 parts by mass of the carrier,
Replenish the developer for replenishment to the developer, discharge the excess carrier inside the developer from the developer,
The replenishment developer is a two-component developer having a toner containing at least a binder resin and a colorant, and a carrier having at least a carrier core and a resin coating layer for coating the carrier core;
The coverage of the carrier with the resin is 0.5 mass% or more and 5.0 mass% or less,
The carrier core has a ferrite component;
The ferrite component contains a metal oxide having at least one metal element selected from the group consisting of Mg, Li and Ca, and the content of the metal oxide having at least one metal element of Mg, Li and Ca Is 15 mol% or more and 30 mol% or less with respect to the total ferrite component, and
Containing a metal oxide having Mn and Cu, the total content of the metal oxide having Mn and Cu is 50 ppm or more and 4000 ppm or less on a mass basis with respect to the total ferrite component;
The volume distribution standard 50% particle size (D50) of the carrier is 20.0 μm or more and 50.0 μm or less,
The unevenness of the carrier core is 1.10 or more and 1.35 or less,
The unevenness of the carrier is 1.10 or more and 1.25 or less,
[However, the unevenness of the carrier and the carrier core is a value obtained from the following formula (1).

Area: Area
Perimeter
It has particles in the coating layer, the primary number average particle diameter of the particles is 25 nm or more and 400 nm or less, and the addition amount of the particles is 5% by mass or more and 30% by mass or less with respect to the coat coating amount. An image forming method.

Images