JP2008040270A - Carrier for electrostatic latent image development and developer for electrostatic latent image development - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier for electrostatic latent image development and a developer for electrostatic latent image development that are stable against mechanical stress applied to the carrier and excellent in image characteristics. <P>SOLUTION: The carrier for electrostatic latent image development has a core particle and a resin coating layer coating the surface of the core particle, and the developer for electrostatic latent image development contains the carrier, wherein an average interval Sm and an arithmetic average roughness Ra representing the surface roughness of the core particle are set in a predetermined range and the lowermost layer of the resin coating layer comprising at least two layers contains at least one of a novolac resin and a novolac resin derivative. Therefore, the present invention can provide the carrier for electrostatic latent image development and the developer for electrostatic latent image development that are stable against mechanical stress applied to the carrier and excellent in image characteristics. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrostatic latent image developing carrier (hereinafter sometimes simply referred to as “carrier”) and an electrostatic latent image developing developer (hereinafter simply referred to as “carrier”) used in electrophotography and electrostatic recording. It may also be referred to as “developer”).

  In electrophotography, an electrostatic latent image is formed on a latent image holding member (photoreceptor) by charging and exposure processes, developed with toner, the developed image is transferred onto a transfer member, and fixed by heating or the like to obtain an image. Developers used in such an electrophotographic method are roughly classified into a one-component developer using a toner in which a colorant is dispersed in a binder resin and a two-component developer composed of the toner and a carrier. Can do. Two-component developers are currently widely used because of their high controllability because the carrier has a charging / conveying function. The two-component developer has a feature such that the carrier has functions such as stirring, transporting, and charging of the developer, and the function as the developer is separated, so that the controllability is good.

  In recent years, digitization processing has been adopted as a means for achieving high image quality, and high-speed processing of complex images has become possible through digitization processing. Further, a laser beam is used in the process of forming an electrostatic latent image on the latent image carrier, and the electrostatic latent image has been made finer by the development of the exposure technique using a small laser beam. With such an image processing technique, electrophotography is being developed for light printing and the like. Furthermore, recent electrophotographic apparatuses are required to be faster and smaller. In particular, with regard to full-color image quality, high-quality printing similar to high-quality printing and silver salt photography is desired. For this reason, it is important to maintain the developer charge in order to visualize the finer latent image faithfully over a long period of time. That is, further improvement in charging stability of a carrier having a charging function is desired.

  In order to obtain high image quality, the toner has a smaller particle size, and a toner containing a low-melting point wax or the like is used for writing a fixed image with a pen or the like. In particular, a full color toner uses a toner in which a binder resin contains a resin having a low softening point, a low melting point wax and the like in order to improve color reproducibility and color developability. The developer is charged by obtaining a desired charge amount by frictional charging between the toner and the carrier. When such toner is used, the toner component is caused by friction between the toner carrier, collision of the carrier, stirring in the developing machine, and temperature rise in the developing machine. Becomes easier to spend on the carrier surface. For this reason, there is a problem in that the charge imparting ability of the carrier with respect to the toner is reduced and the low-charged toner is increased, so that the toner stain (fogging) on the non-image portion and the in-machine stain are deteriorated with use. In addition, in the case of a toner containing a wax or a resin having a low softening point, an additive added to the toner due to stress is buried on the toner surface and cannot perform its original function. For example, there is a problem that image quality deterioration due to image roughness due to a decrease in fluidity, a decrease in developability, or a decrease in transferability occurs.

  In order to improve such charging stability and long life, various studies have been made on the carrier coating layer.

  As one of them, it is considered that two or more kinds of different types of resins are coated in multiple layers to separate functions from each other and to make a more highly functional carrier. For example, the coating layer in contact with the core particle (core material) includes functions such as adhesion, protection and resistance control with the core particle, and the top layer includes functions such as contamination resistance, fluidity and surface resistance control. Thus, a highly functional carrier can be obtained. However, at the interface between resins having different functions, the adhesion is weak, and when there is a strong mechanical stress, it often peels from the interlayer.

  As a method for increasing the adhesion between the resin-coated layers, for example, Patent Document 1 proposes a method in which a coupling agent is contained in the intermediate layer. Patent Document 2 proposes a method in which an intermediate layer contains a resol type phenol resin.

JP-A-2-051167 JP 2005-49478 A

  However, in the method of Patent Document 1, there is a problem of uneven adhesion strength due to uneven distribution of the coupling agent and environmental dependency due to the presence of the coupling agent. This is particularly noticeable when the resin coating layer deteriorates, and is unstable to mechanical stress on the carrier. Further, in the method of Patent Document 2, the adhesion changes depending on the surface state of the core particles. In particular, the thicker the resin coating layer is due to the multilayer structure, the more easily the resin coating layer is peeled off. Under such conditions, sufficient performance cannot be obtained.

  The present invention is an electrostatic latent image developing carrier and an electrostatic latent image developing developer that are stable against mechanical stress on the carrier and excellent in image characteristics.

  The present invention relates to a carrier for developing an electrostatic latent image having core particles and a resin coating layer covering the surface of the core particles, wherein the roughness of the surface of the core particles is 1.0 μm as an average interval Sm of unevenness. In the range of ~ 3.5 μm and arithmetic mean roughness Ra in the range of 0.2 μm to 0.7 μm, the resin coating layer is composed of at least two layers, and the lowermost resin coating layer has a novolak structure. A curable resin that is at least one of a novolak resin and a derivatized novolak resin derived from the novolak resin.

  The present invention also relates to a developer for developing an electrostatic latent image including a toner and a carrier, wherein the carrier is the carrier for developing an electrostatic latent image.

  In the present invention, in the electrostatic latent image developing carrier having the core particles and the resin coating layer covering the surface of the core particles, and the electrostatic latent image developing developer containing the carrier, the surface roughness of the core particles is reduced. When the average interval Sm and the arithmetic average roughness Ra shown are within a predetermined range, and the lowermost layer of the resin coating layer composed of at least two layers includes a curable resin that is at least one of a novolac resin and a derivatized novolac resin, An electrostatic latent image developing carrier and an electrostatic latent image developing developer that are stable against mechanical stress on the carrier and excellent in image characteristics can be provided.

  Embodiments of the present invention will be described below.

<Electrostatic latent image developing carrier>
The carrier for developing an electrostatic latent image according to this embodiment has core particles and a resin coating layer that covers the surface of the core particles. The roughness of the surface of the core particles has an average interval Sm of unevenness of 1.0 μm. It is in the range of ~ 3.5 μm, the arithmetic average roughness Ra is in the range of 0.2 μm to 0.7 μm, the resin coating layer is composed of at least two layers, and the lowermost resin coating layer has a novolac structure A curable resin that is at least one of a novolak resin and a derivatized novolak resin derived from the novolak resin (hereinafter, both may be referred to as “novolak resin or the like”).

  When the resin coating layer is composed of at least two layers, the functions are separated from each other, and a higher-performance carrier can be obtained. And the strength of the resin coating layer is increased by using a curable resin obtained by crosslinking a novolac resin or the like in the lowermost layer of the resin coating layer, and the adhesion (adhesiveness) between the core particles and the lowermost layer by containing the novolac resin, And the adhesiveness of the said lowermost layer and its upper layer can be improved, and a stable multilayer structure is attained. Furthermore, by making the core particle surface moderately rough, the resin is embedded in the recesses of the core particle, improving the physical adhesion due to the anchoring effect between the core particle and the lowermost layer, and improving the adhesion by increasing the contact area Can be obtained. In particular, the anchoring effect is more strongly exhibited when the lowermost layer contains a curable resin. This combination provides a carrier that is strong against mechanical stress on the carrier and stress on the external environment. In addition, the outermost resin coating layer is considered to provide charge controllability, resistance controllability, etc. without considering adhesiveness to the core particles, when the resin coating layer is formed as a single layer. Well, it is possible to obtain a highly functional carrier in which the resin coating layer is difficult to peel off with an easy resin design, and a long life can be achieved with high image quality.

  If the surface of the core particle is small and has a smooth surface, the contact area between the coating resin and the core particle surface will be small, the interface will be smooth, and part of the peeling will directly lead to peeling of the surface. It tends to appear as delamination. Therefore, low density and background fogging are likely to occur during printing in a long-term or stressful state. For this reason, if the surface of the core particles has moderate irregularities, the contact area increases, and the effect of throwing the coating resin on the irregularities occurs, and the adhesive force is synergistically improved. For this reason, low density and background fogging are unlikely to occur even in printing for a long period of time or in a stressful state. On the other hand, if the surface roughness of the core particles is too rough, the covering resin is not sufficiently embedded, and the adhesive force may be reduced due to the formation of voids. Furthermore, more coating resin is required to coat the core particles, a portion having a high film thickness is locally generated, and peeling due to external stress is likely to occur.

  In the effect due to such surface roughness, the surface roughness of the core particles is such that the average interval Sm of the irregularities is in the range of 1.0 μm to 3.5 μm, and the arithmetic average roughness Ra is 0.2 μm to 0. The range is 7 μm. In addition, it is preferable that the average interval Sm between the irregularities is in the range of 1.2 μm to 2.5 μm and the arithmetic average roughness Ra is in the range of 0.3 μm to 0.6 μm because the adhesion becomes better.

  Here, the average interval Sm and the arithmetic average roughness Ra of the irregularities on the surface of the core particles can be measured with an ultra-depth color 3D shape measuring microscope (VK-9500, manufactured by Keyence Corporation) in accordance with JIS B0601. As the measurement sample, a sample in which the toner is detached from the developer and the resin coating layer is separated from the carrier with a solvent can be used. When the resin coating layer is difficult to dissolve in a solvent, a method such as heating, ultrasonic treatment, or using a solvent after carrying out mechanical treatment of the carrier in advance, such as a crusher, can be used.

  The carrier can be highly functionalized by forming the core particle coating into at least two layers and separating the functions of the respective layers. For example, it is possible to design a carrier function such as charging and resistance without considering the adhesiveness with the core particle in the upper layer by specializing the layer in contact with the core particle with the adhesive force. As the resin used for the lowermost layer, it is desirable to use a curable resin from the viewpoints of adhesion to the core particles and the strength of the resin coating film. However, it is necessary to consider the adhesiveness with the upper layer, and it is difficult to use a silicone resin or a fluororesin from the viewpoints of wettability, surface tension, adhesion, and the like. The present inventors have found that a novolak resin having a novolak structure as a curable resin and a derivatized novolak resin derived from the novolak resin are favorable in consideration of the adhesion to the core particles and the adhesion to the upper layer. It was. With such a structure, the adhesion with the core particles is good, and the adhesion with a thermoplastic resin having a low adhesion strength is also good.

  The novolak resin and derivatives thereof that can be used for the lowermost layer are not particularly limited as long as they have a novolak structure, but examples include novolac-type epoxy resins and phenol novolac resins. It may be modified by a component or the like. Examples of novolak type epoxy resins include phenol novolac type epoxy resins and o-cresol type epoxy resins. Examples of the phenol novolac resin include phenol novolac resins derived from phenol, cresol and the like.

  A curing agent is required to cure the novolac type epoxy resin. Examples of the curing agent include aromatic amines, aliphatic amines, alicyclic amines, polyamides, dicyandiamide, trimellitic anhydride, Examples thereof include pyromellitic anhydride, benzophenone tetracarboxylic acid anhydride, acid anhydrides such as a reaction product of trimellitic anhydride and glycol, dihydrazides such as adipic acid dihydrazide, sebacic acid dihydrazide, and isophthalic acid dihydrazide, and phenol resins.

  Examples of the curing agent for the phenol novolac resin include aliphatic amine curing agents such as hexamethylenetetramine. Further, isocyanates such as tolylene diisocyanate, xylene diisocyanate, and polyisocyanate may be used.

  Furthermore, a combination of phenol novolac resin and epoxy resin is also possible. Examples of the epoxy resin include epoxy resins derived from bisphenol A, bisphenol F, and the like, glycidylamine, glycidyl ether, glycidyl esters and modified products thereof such as acrylic modification, polyester modification, and urethane modification.

  Among the above-mentioned novolac resins, novolac-type epoxy resins are preferable because they have high adhesiveness with thermoplastic resins such as styrene, acrylic, and polyester, and increase the choice of upper layers.

  In the carrier according to this embodiment, at least one resin coating layer is provided as an upper layer on the lowermost resin coating layer containing a novolak resin or the like. Usually, one upper layer may be provided, but two or more upper layers may be provided. The upper layer is preferably one layer, that is, the resin coating layer is preferably two layers, from the viewpoint of ease of production, deterioration during long-term use, and the like.

  Examples of the coating resin used for the upper layer include polyolefin resins such as polyethylene, polypropylene; polyvinyl and polyvinylidene resins such as polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, Polyvinyl ether and polyvinyl ketone; vinyl chloride-vinyl acetate copolymer; styrene-acrylic copolymer; straight silicone resin composed of an organosiloxane bond or a modified product thereof; fluororesin such as polytetrafluoroethylene, polyvinyl fluoride, polyfluoride Polyvinyl chloride, Polychlorotrifluoroethylene; Polyester; Polyurethane; Polycarbonate, Amino resin, eg urea-formaldehyde resin ; Epoxy resins. These may be used alone or in combination with a plurality of resins.

  Among these, polyester resins are preferable from the viewpoint of easy charge control and the like, and styrene acrylic resins are preferable from the viewpoint of high strength and low contamination, and may be selected according to the characteristics of the intended carrier. .

  Examples of polyester resins include aromatic polyesters composed of bisphenol A and terephthalic acid, aliphatic polyesters composed of nonanediol and dodecanedioic acid, and polyesters having a thioether structure in which the methylene group of alcohol or carboxylic acid is replaced with a sulfur atom. , Modified products such as maleic acid and α-olefin, and the like, and aromatic polyester resins are preferred from the standpoint of chargeability to the environment.

  Styrene acrylic resins include methyl acrylate, methyl ethacrylate, ethyl methacrylate, butyl methacrylate, lauryl methacrylate, stearyl methacrylate, alkyl acrylates such as behenyl methacrylate, cycloalkyl acrylates such as cyclopentyl methacrylate, cyclohexyl methacrylate, and aromatics such as phenyl methacrylate. Acrylic and styrene, such as aromatic acrylates, copolymers of these with acrylic acid, copolymers of epoxy compounds such as glycidyl methacrylate, copolymers of alcoholic compounds such as glycerin monomethacrylate and 2-hydroxyethyl methacrylate, etc. Examples include copolymers, methyl methacrylate, ethyl ethacrylate from the point of environmental dependency when used as a carrier. Copolymers of short-chain alkyl acrylate and styrene are preferred.

  The resin coating layer is formed on the surface of the core particle by dipping the core particle in the resin coating layer forming solution, spraying the resin coating layer forming solution on the core particle surface, and flowing the core particle. Examples thereof include a fluidized bed method in which the resin coating layer forming solution is sprayed in a state of being suspended by air, and a kneader coater method in which the core particles and the resin coating layer forming solution are mixed in a kneader coater to remove the solvent. In view of the influence on the first resin coating layer and the uniform coating property of the second resin coating layer, etc., it is preferable to use a fluidized bed type coating apparatus in the second layer coating.

  The solvent used in the resin coating layer forming solution is not particularly limited as long as it dissolves the coating resin. For example, aromatic hydrocarbons such as toluene and xylene, ketones such as acetone and methyl ethyl ketone, and the like. And ethers such as tetrahydrofuran and dioxane can be used. Further, a resin dispersion using water, alcohol or the like may be used. In this case, those using a surfactant may cause charging deterioration due to residual surfactant after being used as a carrier, and it is necessary to sufficiently remove the surfactant. As a method for removing the surfactant, after the resin coating is completed, the surfactant can be removed by stirring in ion-exchanged water at a temperature 5 to 15 ° C. higher than the Tg of the resin.

  The resin coating layer of the carrier may be used in combination with conductive powder (conductive particles) for further carrier resistance adjustment. Examples of the conductive particles include metal powder, carbon black, titanium oxide, tin oxide, and zinc oxide. These conductive particles preferably have a volume average particle diameter of 1 μm or less. When the volume average particle diameter is larger than 1 μm, it is difficult to control the dispersion of the powder in the resin coating layer, and it may be difficult to control the electric resistance. The addition amount of the conductive particles is preferably less than 20% by volume of the resin coating layer. When 20 volume% or more is added, it is difficult to control the dispersion of the powder in the resin coating layer, and it may be difficult to control the electric resistance. Examples of the method for dispersing the conductive particles include a sand mill, a dyno mill, and a homomixer.

  The conductive particles are preferably contained in at least the upper layer of the two or more resin coating layers, but are more preferably contained in all the resin coating layers. When the resin coating layer is two layers, it is preferable that conductive particles are contained in the upper layer and the lower layer. When conductive particles are contained in the resin coating layer, the film strength and adhesiveness may be slightly lowered. However, in order to control the resistance, it is preferable to contain conductive particles in at least the upper layer. In the present embodiment, the average interval Sm and the arithmetic average roughness Ra of the core particles are set in the predetermined range, and the lowermost layer of the resin coating layer includes the novolak resin or the like as a curable resin. The resistance of the carrier can be controlled with almost no decrease in adhesiveness.

  Although it does not specifically limit as a method of forming a resin coating layer in a core particle, For example, it can produce with the following method. A novolac resin and a curing agent are dissolved and mixed in a solvent such as toluene to prepare a lower layer forming solution. Also, a styrene acrylic resin or a polyester resin is dissolved and mixed in a solvent such as toluene to prepare an upper layer forming solution. Next, the core particles and the lower layer forming solution are put in a kneader so that the coating resin is 1.0 to 3.0% by weight with respect to the core particles, and the pressure is reduced under reduced pressure under the conditions of 60 ° C to 100 ° C. Stir and mix for 3 to 1.0 hours. After the solvent is volatilized, the reduced pressure is released and taken out as a lower layer coat carrier. Furthermore, the lower layer coat carrier and the upper layer forming solution are put in a kneader so that the coating resin is 1.0 to 3.0% by weight with respect to the lower layer coat carrier, and the pressure is reduced under a condition of 60 ° C to 100 ° C. At 0.3 to 1.0 hours with stirring. After the solvent is volatilized, the decompression is released and the coated carrier is taken out. Further, the conductive particles or the like may be added to the upper layer forming solution, or the upper layer forming solution and the lower layer forming solution. In addition, when the lower layer resin is coated, after being taken out as a lower layer coat carrier, heat treatment may be performed under normal pressure under a condition of 100 to 200 ° C. for 0.5 to 2.0 hours in order to proceed with curing.

It can be confirmed by ¹ H-NMR, ¹³ C-NMR, and FT-IR that the coating resin contains novolak resin or the like. NMR can be measured using JNM-AL400 manufactured by JEOL Ltd. under the conditions of a 5 mm glass tube, a 3 wt% deuterated chloroform solution, and a measurement temperature of 25 ° C. FT-IR can be measured by KBr method using FT / IR-410 manufactured by JASCO Corporation. The structure can be identified from the proton and carbon peaks obtained from NMR and the infrared absorption spectrum by FT-IR. In addition, as the measurement sample, it is possible to use a sample in which the toner is detached from the developer and the resin coating layer is peeled off from the carrier by ultrasonic treatment, a pulverizer, or the like. Further, the resin coating layer soluble in the solvent may be recovered by dissolving it directly from the carrier with the solvent.

  The total thickness of the resin coating layer is 0.1 μm to 5 μm, preferably 0.3 μm to 3 μm. If the thickness of the entire resin coating layer is smaller than 0.1 μm, it may be difficult to form a uniform and flat resin coating layer on the core particle surface. On the other hand, if the thickness is larger than 5 μm, carriers may be aggregated and it may be difficult to obtain a uniform carrier. At this time, the thickness of the lower layer is preferably 0.3 μm to 2.0 μm, preferably 0.5 μm to 1.0 μm, and the thickness of the upper layer is 0.5 μm to 3.0 μm, preferably 1. It is preferably in the range of 0 μm to 2.0 μm. The thickness of the resin coating layer can be measured by image analysis by cutting the carrier particles with a diamond knife, capturing a cross-sectional image with a transmission electron microscope or the like.

  As the core particles, any conventionally known particles can be used, and ferrite and magnetite are particularly preferably selected. For example, iron powder is known as another core particle. In the case of iron powder, since the specific gravity is large and the toner is likely to be deteriorated, ferrite and magnetite are more stable. An example of ferrite is generally represented by the following formula.

(MO) _X (Fe ₂ O ₃ ) _Y
(In the formula, M contains at least one selected from Cu, Zn, Fe, Mg, Mn, Ca, Li, Ti, Ni, Sn, Sr, Al, Ba, Co, Mo, etc. X, Y represents a weight mol ratio and satisfies the condition X + Y = 100).

The M is preferably a ferrite particle which is one or a combination of Li, Mg, Ca, Mn, Sr and Sn, and the content of other components is 1% by weight or less. By adding Cu, Zn, and Ni elements, the resistance tends to be low and charge leakage is likely to occur. In addition, the resin tends to be difficult to coat, and the environmental dependency tends to deteriorate. Furthermore, since it is a heavy metal, the stress given to a carrier becomes strong because it is heavy, and it may have a bad influence on life property. In recent years, from the viewpoint of safety, an element containing Mn element or Mg element has been widely used. Ferrite core material is preferable. As raw material for core particles, Fe ₂ O ₃ is an essential component, and as magnetic particles used, ferromagnetic iron oxide particles such as magnetite and maghemite, metals other than iron (Mn, Ni, Zn, Mg, Cu, etc.) containing spinel ferrite particle powder containing one or more types, magnet plumbite type ferrite particle powder such as barium ferrite, and iron or iron alloy fine particle powder having an oxide film on its surface be able to.

  Specific examples of the core particles include iron oxides such as magnetite, γ iron oxide, Mn—Zn ferrite, Ni—Zn ferrite, Mn—Mg ferrite, Li ferrite and Cu—Zn ferrite. Can be mentioned. Among these, inexpensive magnetite can be more preferably used.

  When using a ferrite core material as the core particle, as an example of a method for producing a ferrite core material, first, an appropriate amount of each oxide is blended, pulverized and mixed for 8 to 35 hours with a wet ball mill or the like, and granulated with a spray dryer or the like. After drying, calcination is performed at 800 ° C. to 1000 ° C. for 8 to 10 hours using a rotary kiln or the like. Temporary baking is performed 0 to 3 times as necessary. Thereafter, the calcined product is dispersed in water and pulverized with a wet ball mill or the like until the volume average particle size becomes 0.3 to 1.2 μm. This slurry is granulated and dried using a spray dryer, etc., and for the purpose of adjusting the magnetic properties and resistance, this slurry is calcined for 6 to 10 hours at 800 to 1300 ° C. while controlling the oxygen concentration, and then pulverized to obtain a desired particle size. It can be obtained by classification into distributions. In the present embodiment, it is preferable to use a rotary electric furnace in order to make the core surface shape uniform.

  In order to set the average interval Sm and the arithmetic average roughness Ra of the surface irregularities of the core particles within the above ranges, the core particles may be temporarily fired, the wet pulverization time before the main firing and the main firing conditions may be adjusted. For example, by increasing the wet pulverization time, Sm and Ra are reduced. As the main baking time is increased or the temperature is increased, crystal growth proceeds, Sm and Ra increase, and as the process proceeds further, the surface becomes smooth and the roughness disappears. The wet pulverization and main firing conditions may be determined according to the material used for the core particles with respect to the target Sm and Ra.

  The core particles may be resin-dispersed core particles in which the magnetic particles (magnetic material) are dispersed in a binder resin.

  As the binder resin, phenolic resin, melamine resin, epoxy resin, urethane resin, polyester resin, silicone resin, etc. are used, but it should contain phenolic resin from the viewpoint of wetting with coating resin, etc. Is preferred.

  The core particles may have a resin dispersed core in which the magnetic particles (magnetic material) are dispersed in a binder resin, and a core coating layer that covers the surface of the resin dispersed core. . Since the core particle surface is covered with the core coating layer, the influence of the magnetic substance exposure of the core (core material) is small.

  The circularity of the carrier is preferably 0.975 or more. The closer the circularity is to 1, the closer the shape is to a true sphere, and the larger the surface roughness, the finer the surface is. Become. By adjusting the circularity of the core particle to 0.975 or more and making it close to a true sphere, it is possible to improve the fluidity of the carrier, enable the coating of a uniform resin coating layer, and suppress the aggregation of the core particles. The rate can be further improved. The circularity can be measured in the LPF measurement mode using FPIA-3000 (manufactured by Sysmex Corporation). As for the sample, 200 mg of carrier particles are added to 30 ml of an ethylene glycol aqueous solution and stirred, the supernatant aqueous solution is removed, and the residue is used as a measuring machine sample. The average circularity is determined by cutting and analyzing particles having a particle size of less than 10 μm and exceeding 50 μm.

  The core exposure rate on the surface of the carrier is preferably 4% or less. When core particles having irregularities on the surface are used as in this embodiment, the exposed portion of the carrier surface is often a convex portion of the core. When the carrier resin coating layer is detached due to developing machine stress or the like, the resin coating layer is detached using the core exposed portion on the carrier surface as a nucleus. As described above, when the exposure rate of the core exceeds 4%, there are many places where the resin coating layer is detached. Therefore, the resin coating layer is easily detached after long-term use. That is, there is a problem that the carrier charging function is lowered.

  The amount of core exposure on the surface of the carrier is measured with an X-ray photoelectron spectrometer (JPS-9000MX) manufactured by JASCO Corporation at an X-ray source MgKα, an output of 10 kV, and an analysis region of 10 × 10 mm. It can be obtained by calculating the surface atom concentration. The surface atom concentration is calculated using the relative photosensitivity factor provided by JASCO. The peak intensity of each element measured is proportional to the abundance in the analysis region for each atom. By taking the ratio of the peak intensity derived from iron atoms on the carrier surface to the peak intensity derived from iron atoms on the core particle surface, the amount of core exposure on the carrier surface can be estimated.

  Further, in order to measure the carrier surface core exposure amount in the developer, put the developer in a container such as a beaker, add an appropriate amount of a surfactant aqueous solution (for example, polyoxyethylene octyl phenyl ether 0.2 wt% aqueous solution), The carrier is held by a magnet from the bottom of the container, and only the toner is washed away. Do this until the supernatant is clear and colorless. Further, an appropriate amount of ethanol is added to remove the surfactant adhering to the carrier surface. The carrier from which the toner has been removed can be dried with a dryer, and then the core exposure amount on the surface of the carrier can be measured by the above method.

The magnetic susceptibility σ of the core particle of this embodiment is measured by the BH tracer method using a VSM (vibration sample method) measuring device in a magnetic field of 1 kOe, and the magnetization value σ1000 is 50 to 90 Am ² / kg (emu / g), preferably in the range of 55 to 70 Am ² / kg (emu / g). When σ1000 is less than 50 Am ² / kg (emu / g), the magnetic attraction force to the developing roll becomes weak and adheres to the photoreceptor, causing image defects, which is not preferable. On the other hand, when σ1000 exceeds 90 Am ² / kg (emu / g), the magnetic brush becomes too hard, and the photoreceptor is easily rubbed and easily damaged.

  The volume average particle size of the core particles of this embodiment is 10 μm to 100 μm, preferably 20 μm to 50 μm. If the volume average particle size is less than 10 μm, the developer tends to scatter from the developing device, and if it is more than 100 μm, it may be difficult to obtain a sufficient image density.

The electric resistance of the carrier on which the resin coating layer is formed is in the range of 1 × 10 ⁵ to 1 × 10 ¹⁴ Ω · cm, preferably 1 × 10 ⁹ to 1 × 10 ¹² Ω · cm when the measurement electric field is 10000 V / cm. Is appropriate.

  The chargeability of the carrier on which the resin coating layer is formed is preferably 15 to 50 μC / g. When the chargeability of the carrier is less than 15 μC / g, there is a high possibility that non-image area toner stains (fogging occurs) and a high-quality color image cannot be obtained, while the carrier chargeability is high. When it exceeds 50 μC / g, it becomes difficult to obtain a sufficient image density.

If the electric resistance of the carrier on which the resin coating layer is formed is less than 1 × 10 ⁵ Ω · cm, the charge easily moves on the surface of the carrier, and image defects such as brush marks are likely to occur, and the printing operation is not performed for a while. If left unattended, the chargeability becomes too low, and there may be cases where the first print of the first sheet is soiled. In addition, if the electric resistance of the carrier on which the resin coating layer is formed is greater than 1 × 10 ¹⁴ Ω · cm, a good solid image cannot be obtained, and if continuous printing is repeated many times, the toner charge becomes too large and the image density becomes too high. May go down.

The electrokinetic resistance when measured in the form of a carrier magnetic brush is 1 × 10 to 1 × 10 ⁹ Ω · cm, preferably 1 × 10 ³ to 1 × 10 ⁸ Ω, under an electric field of 10 ⁴ V / cm. A range of cm is appropriate. If the dynamic electrical resistance is less than 1 × 10 Ω · cm, image defects such as brush marks are likely to occur, and if it is greater than 1 × 10 ⁸ Ω · cm, it may be difficult to obtain a good solid image. The electric field of 10 ⁴ V / cm is close to the developing electric field in an actual machine, and the dynamic electric resistance is a value under this electric field.

From the above, the electrokinetic resistance when the carrier and the toner are mixed is suitably in the range of 1 × 10 ⁵ to 1 × 10 ⁹ Ω · cm under an electric field of 10 ⁴ V / cm. On the other hand, if it is less than 1 × 10 ⁵ Ω · cm, the resolution may be deteriorated due to background stains due to a decrease in toner chargeability after standing after printing, or thickening of line images due to over-development. If it exceeds 1 × 10 ⁹ Ω · cm, there may be a problem that a high-quality image cannot be obtained due to a decrease in developability at the edge of the solid image.

The dynamic electrical resistance of the carrier can be obtained as follows. A magnetic brush is formed by placing a carrier of about 30 cm ³ on the developing roll (the magnetic field of the sleeve surface of the developing roll is 1 kOe), and a plate electrode having an area of 3 cm ² is placed on the developing roll at intervals of 2.5 mm. Make them face each other. A voltage is applied between the developing roll and the plate electrode while rotating the developing roll at a rotation speed of 120 rpm, and the current flowing at that time is measured. The dynamic electric resistance is obtained from the obtained current-voltage characteristics using Ohm's law equation. It is well known that there is generally a relationship of ln (I / V) ∝V × 1/2 between the applied voltage V and the current I at this time. When the dynamic electrical resistance is quite low like the carrier used in this embodiment, measurement may not be possible because a large current flows in a high electric field of 10 ³ V / cm or more. In such a case, three or more points are measured in a low electric field, and an electric field of 10 ⁴ V / cm is extrapolated by the least square method using the above relational expression.

  The electrostatic latent image developing carrier according to this embodiment is stable against mechanical stress on the carrier and has excellent image characteristics. That is, it is stable against mechanical stress on the carrier and stress due to the external environment, excellent in resistance controllability and charge controllability, and excellent in high image quality and long life suitability.

<Developer for developing electrostatic latent image>
The developer for developing an electrostatic latent image according to the present embodiment includes a toner for developing an electrostatic latent image and a carrier, and the carrier is the carrier for developing an electrostatic latent image. That is, the developer for developing an electrostatic latent image according to the present embodiment is a two-component developer including a toner and a carrier. However, the toner described below may be a magnetic toner or a non-magnetic toner.

  The toner is not particularly limited, and a known toner containing a binder resin and a colorant as main components and containing a release agent or the like as necessary can be used. The toner may be produced by a dry production method such as a kneading and pulverization method, or may be produced by a wet production method such as an emulsion polymerization aggregation method, a dissolution suspension method, or a suspension polymerization method. . A toner produced by an emulsion polymerization aggregation method is preferred from the standpoint that the surface exposure of the colorant and the release agent is small and the stability of the image is good.

  Such a toner has a relatively round particle shape, a narrow particle size distribution, a relatively uniform toner surface, high chargeability, and a narrow charge distribution. Since this toner has a sharp particle size distribution, the occurrence of fogging is small.

  Therefore, the developer obtained by mixing with the carrier has extremely high fluidity and good developability, and therefore, a good high-quality color developer can be obtained. The developer according to the exemplary embodiment is stable against mechanical stress on the carrier and has excellent image characteristics. That is, it is stable against mechanical stress on the carrier and stress due to the external environment, excellent in resistance controllability and charge controllability, and excellent in high image quality and long life suitability.

  As the binder resin for the toner, styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, methyl acrylate, acrylic acid Esters of α-methylene aliphatic monocarboxylic acids such as ethyl, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl methyl ether, Examples include vinyl ethers such as vinyl ethyl ether and vinyl butyl ether; homopolymers or copolymers such as vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone. Examples of binder resins include polystyrene, styrene / alkyl acrylate copolymers, styrene / alkyl methacrylate copolymers, styrene / acrylonitrile copolymers, styrene / butadiene copolymers, styrene / maleic anhydride copolymers, Examples thereof include polyethylene and polypropylene. Further examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin waxes and the like.

  Examples of the colorant include carbon black, chrome yellow, hansa yellow, benzidine yellow, selenium yellow, quinoline yellow, permanent orange GTR, pyrazolone orange, vulcan orange, watch young red, permanent red, brillianthamine 3B, and brillianthamine. 6B, DuPont Oil Red, Pyrazolone Red, Resol Red, Rhodamine B Lake, Lake Red C, Rose Bengal, Aniline Blue, Ultramarine Blue, Calco Oil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Phthalocyanine Green, Malachite Green Oxalate, etc. Or acridine, xanthene, azo, benzoquinone, azine, anthraquinone, thio Various dyes such as Ndico, Dioxazine, Thiazine, Azomethine, Indico, Thioindico, Phthalocyanine, Aniline Black, Polymethine, Triphenylmethane, Diphenylmethane, Thiazine, Thiazole, and Xanthene Or in combination of two or more.

  In the toner according to the exemplary embodiment, the content of the colorant is preferably in the range of 1 to 30 parts by weight with respect to 100 parts by weight of the binder resin. It is also effective to use a colorant or a pigment dispersant. By appropriately selecting the type of the colorant, yellow toner, magenta toner, cyan toner, black toner and the like can be obtained.

  Examples of mold release agents include low molecular weight polyolefins such as polyethylene, polypropylene and polybutene; silicones having a softening point upon heating; fatty acid amides such as oleic acid amide, erucic acid amide, ricinoleic acid amide and stearic acid amide; Plant waxes such as ester wax, carnauba wax, rice wax, candelilla wax, tree wax, jojoba oil, etc .; animal waxes such as beeswax; montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, fisher Mineral waxes such as Tropsch wax, petroleum waxes, and modified products thereof can be used. The addition amount of the release agent can be added in the range of 50% by weight or less with respect to the toner.

  As other internal additives, magnetic materials such as metals such as ferrite, magnetite, reduced iron, cobalt, nickel and manganese, alloys thereof, and compounds containing these metals can be used. As the charge control agent, various commonly used charge control agents such as quaternary ammonium salts, nigrosine compounds, dyes composed of complexes of aluminum, iron, chromium, and triphenylmethane pigments can be used. In order to control the ionic strength that affects the stability at the time of aggregation and fusion integration and to reduce wastewater contamination, a charge control agent that is difficult to dissolve in water is preferable.

  Examples of inorganic fine particles to be wet-added include silica, alumina, titania, calcium carbonate, magnesium carbonate, and tricalcium phosphate, all of which are usually used as external additives on the toner surface, such as ionic surfactants and It can be dispersed in a polymer acid or a polymer base and added wet.

  Surfactants used for emulsion polymerization, seed polymerization, pigment dispersion, resin particle dispersion, release agent dispersion, aggregation, or stabilization in the toner manufacturing process by a wet manufacturing method include sulfate ester salts, sulfonate salts, phosphorus Anionic surfactants such as acid esters and soaps, cationic surfactants such as amine salts and quaternary ammonium salts, and non-polyethylene glycols, alkylphenol ethylene oxide adducts, polyhydric alcohols, etc. It is also effective to use an ionic surfactant in combination.

  Further, the external additive used in the present embodiment is not particularly limited, and known external additives such as inorganic particles and organic particles can be used. Among them, silica, titania, alumina, cerium oxide, titanium, and the like can be used. Organic particles such as inorganic particles such as strontium acid, calcium carbonate, magnesium carbonate and calcium phosphate, metal soap such as zinc stearate, fluorine-containing resin particles, silica-containing resin particles and nitrogen-containing resin particles are preferred. Moreover, you may surface-treat on the surface of an external additive according to the objective. Examples of the surface treatment agent include a silane compound, a silane coupling agent, and a silicone oil for performing a hydrophobic treatment.

  The volume average particle size of the toner according to the exemplary embodiment is preferably in the range of 4 μm to 8 μm, more preferably in the range of 5 μm to 7 μm, and the number average particle size is preferably in the range of 3 μm to 7 μm. The range of 6 μm is more preferable.

  The volume average particle size and the number average particle size can be measured by measuring with a 100 μm aperture diameter using a Coulter Multisizer II type (manufactured by Beckman-Coulter). At this time, the measurement is performed after the toner is dispersed in an electrolyte aqueous solution (Isoton aqueous solution) and dispersed by ultrasonic waves for 30 seconds or more.

  In addition, the volume average particle size distribution index GSDv of the toner according to the exemplary embodiment is preferably 1.27 or less, and more preferably 1.25 or less. When GSDv exceeds 1.27, the particle size distribution is not sharp, resolution is deteriorated, and image defects such as toner scattering and fogging are caused.

The volume average particle diameter D50v and the volume average particle size distribution index GSDv can be obtained as follows. Draw cumulative distributions from the small diameter side for the particle size range (channel) divided based on the particle size distribution of the toner measured by the above-mentioned Coulter Multisizer II type (manufactured by Beckman-Coulter). In addition, the particle diameter that is accumulated 16% is defined as volume D16v and several D16p, the particle diameter that is accumulated 50% is defined as volume D50v and several D50p, and the particle diameter that is accumulated 84% is defined as volume D84v and several D84p. At this time, D50v represents the volume average particle diameter, and the volume average particle size distribution index (GSDv) is determined as (D84v / D16v) ^1/2 . In addition, (D84p / D16p) ^1/2 represents a number average particle size distribution index (GSDp).

Further, the shape factor SF1 represented by the following formula of the toner according to the present embodiment is in the range of 110 to 140, preferably in the range of 115 to 130.
SF1 = (ML ² / A) × (π / 4) × 100
[In the above formula, ML represents the maximum toner length (μm), and A represents the projected area (μm ² ) of the toner. ]
If the toner shape factor SF1 is less than 110 or exceeds 140, it may be impossible to obtain excellent chargeability, cleanability, and transferability over a long period of time.

In addition, shape factor SF1 was measured as follows using a Luzex image analyzer (manufactured by Nireco Corporation, FT). First, an optical microscopic image of toner spread on a slide glass is taken into a Luzex image analyzer through a video camera, and the maximum length (ML) and projection area (A) of 50 toners are measured. ML ² / A) × (π / 4) × 100 was calculated, and the average value was calculated as the shape factor SF1.

  The ratio of the toner in preparing the developer by mixing the toner and the carrier is 1 to 15% by weight, preferably 3 to 12% by weight of the whole developer.

If the toner ratio is less than 1% by weight, it is difficult to obtain a sufficient image density, and a solid image is difficult to be uniform. On the other hand, if the amount exceeds 15% by weight, the toner coverage on the carrier surface exceeds 100%, and the charge amount decreases (when the average value of the average charge amount is less than 15 μC / g). Fog) A high-quality color image cannot be obtained. For example, when the amount exceeds 15% by weight, the toner coverage on the carrier surface approaches 100%, and the resistance value as a developer is extremely increased, and is in the range of 1 × 10 ⁵ to 1 × 10 ⁸ Ω · cm. Therefore, it is difficult to obtain a good and high-quality color image such as blurring of the image edge portion.

  However, in a low-humidity environment, if the toner ratio is less than 1% by weight, a high charge amount (the absolute value of the average charge amount exceeds 25 μC / g) tends to occur, and it may be difficult to obtain a sufficient image density. Therefore, it is preferable to select the toner ratio so that the absolute value of the charging property is in the range of 15 to 50 μC / g depending on the environment.

<Image forming method>
The image forming method according to the present embodiment uses a latent image forming step of forming an electrostatic latent image on the surface of the latent image carrier and a developer carried on the developer carrier, and is formed on the surface of the latent image carrier. A development process for developing the electrostatic latent image to form a toner image, a transfer process for transferring the toner image formed on the surface of the latent image holding body to the surface of the transfer target, and a toner transferred to the surface of the transfer target In the image forming method including the fixing step of fixing the image, a developer containing the above-mentioned electrostatic latent image developing carrier is used as the developer. The image forming method according to the present embodiment may include steps other than the steps described above.

  As the latent image holding member, for example, an electrophotographic photosensitive member and a dielectric recording member can be used. In the case of an electrophotographic photosensitive member, the surface of the electrophotographic photosensitive member is uniformly charged by a corotron charger, a contact charger or the like and then exposed to form an electrostatic latent image (latent image forming step). Next, the toner particles are attached to the electrostatic latent image by contacting or approaching a developing roll having a developer layer formed on the surface, thereby forming a toner image on the electrophotographic photosensitive member (developing step). The formed toner image is transferred onto the surface of a transfer medium such as paper using a corotron charger or the like (transfer process). Further, the toner image transferred to the surface of the transfer target is heat-fixed by a fixing machine (fixing step) to form a final toner image.

  Examples of the transfer target (recording material) to which the toner image is transferred include plain paper, OHP sheet, and the like used for electrophotographic copying machines and printers. In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the transfer object is as smooth as possible. For example, coated paper in which the surface of plain paper is coated with a resin or the like, art paper for printing Etc. can be used suitably.

  Since the image forming method according to the present embodiment uses the developer containing the carrier for developing an electrostatic latent image, the image forming method is stable against mechanical stress on the carrier and can realize good color reproducibility. .

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

(Preparation of core particle 1)
After mixing 74 parts by weight of Fe ₂ O ₃ , 20 parts by weight of MnO ₂ , 5 parts by weight of Mg (OH) ₂ , and 1 part by weight of ZnO, the mixture is mixed and pulverized in a wet ball mill for 25 hours, and granulated and dried by a spray dryer. Then, calcination 1 was performed at 800 ° C. for 7 hours using a rotary kiln. The pre-fired product thus obtained was pulverized for 2 hours with a wet ball mill to a volume average particle size of 2.0 μm, further granulated and dried with a spray dryer, and then at 900 ° C. for 6 hours using a rotary kiln. Pre-baking 2 was performed. The two calcined products thus obtained were pulverized with a wet ball mill for 5 hours to a volume average particle size of 5.6 μm, further granulated and dried with a spray dryer, and then used in an electric furnace at a temperature of 900 ° C. The main firing for an hour was performed. Core particles (Mn—Mg ferrite particles) 1 having a volume average particle size of 36 μm were prepared through a crushing step and a classification step. Sm = 2.0 μm and Ra = 0.5 μm.

  The volume average particle size of the core particles is a particle size range (channel) obtained by dividing the particle size distribution obtained by a laser diffraction / scattering particle size distribution analyzer (LS Particle Size Analyzer: LS13 320, manufactured by BECKMAN COULTER). On the other hand, the volume cumulative distribution was subtracted from the small particle diameter side, and the particle diameter at 50% accumulation was defined as the volume average particle diameter. The average interval Sm and arithmetic mean roughness Ra of the core particle surface irregularities were measured with an ultra-depth color 3D shape measuring microscope (VK-9500, manufactured by Keyence Corporation) in accordance with JIS B0601.

(Preparation of core particle 2)
Mixed pulverization: 25 hours, calcination 1: 800 ° C., 7 hours, wet pulverization 1: 2 hours, calcination 2: 900 ° C., 6 hours, wet pulverization 2: 8 hours, main calcination: 900 ° C., 8 hours Except for the above, a core particle (Mn—Mg ferrite particle) 2 having a volume average particle diameter of 38 μm was prepared in the same manner as the core particle 1. Sm = 1.2 μm and Ra = 0.6 μm.

(Preparation of core particle 3)
Mixed pulverization: 10 hours, calcination 1: 800 ° C., 7 hours, wet pulverization 1: none, calcination 2: none, wet pulverization 2: 12 hours, main calcination: 900 ° C., 12 hours except for core particle 1 In the same manner, core particles (Mn—Mg ferrite particles) 3 having a volume average of 38 μm were prepared. Sm = 2.5 μm and Ra = 0.3 μm.

(Preparation of core particle 4)
Mixed pulverization: 25 hours, calcination 1: 800 ° C., 7 hours, wet pulverization 1: 8 hours, calcination 2: 900 ° C., 6 hours, wet pulverization 2:10 hours, main calcination: 900 ° C., 8 hours Except for the above, a core particle (Mn—Mg ferrite particle) 4 having a volume average particle size of 38 μm was prepared in the same manner as the core particle 1. Sm = 0.5 μm and Ra = 0.8 μm.

(Preparation of core particle 5)
Mixed pulverization: 25 hours, calcination 1: 800 ° C., 7 hours, wet pulverization 1: 7 hours, calcination 2: 900 ° C., 6 hours, wet pulverization 2: 8 hours, main calcination: 900 ° C., 8 hours Except for the above, a core particle (Mn—Mg ferrite particle) 5 having a volume average particle size of 38 μm was prepared in the same manner as the core particle 1. Sm = 1.8 μm and Ra = 0.8 μm.

(Preparation of core particle 6)
Mixed pulverization: 25 hours, calcination 1: 800 ° C., 7 hours, wet pulverization 1: none, calcination 2: none, wet pulverization 2: 2 hours, main calcination: 900 ° C., 14 hours, except for 14 hours In the same manner, core particles (Mn—Mg ferrite particles) 6 having a volume average particle diameter of 35 μm were prepared. Sm = 4.4 μm and Ra = 0.8 μm.

(Preparation of core particle 7)
Mixed pulverization: 25 hours, calcination 1: 800 ° C., 7 hours, wet pulverization 1: 9 hours, calcination 2: 900 ° C., 5 hours, wet pulverization 2:14 hours, main calcination: 900 ° C., 7 hours Except for the above, a core particle (Mn—Mg ferrite particle) 7 having a volume average particle diameter of 38 μm was prepared in the same manner as the core particle 1. Sm = 0.5 μm and Ra = 0.1 μm.

(Preparation of core particle 8)
Mixed pulverization: 25 hours, calcination 1: 800 ° C., 7 hours, wet pulverization 1: 9 hours, calcination 2: 900 ° C., 7 hours, wet pulverization 2: 9 hours, main calcination: 800 ° C., 9 hours Except for the above, a core particle (Mn—Mg ferrite particle) 8 having a volume average particle size of 38 μm was prepared in the same manner as the core particle 1. Sm = 1.0 μm and Ra = 0.4 μm.

(Preparation of core particle 9)
Mixed pulverization: 25 hours, calcination 1: 800 ° C., 7 hours, wet pulverization 1: 9 hours, calcination 2: 900 ° C., 7 hours, wet pulverization 2: 2 hours, main calcination: 1000 ° C., 10 hours Except for the above, a core particle (Mn—Mg ferrite particle) 9 having a volume average particle diameter of 38 μm was prepared in the same manner as the core particle 1. Sm = 3.5 μm and Ra = 0.7 μm.

(Preparation of core particle 10)
Mixed pulverization: 25 hours, calcination 1: 800 ° C., 7 hours, wet pulverization 1: 9 hours, calcination 2: 900 ° C., 7 hours, wet pulverization 2: 2 hours, main calcination: 1200 ° C., 10 hours Except for the above, a core particle (Mn—Mg ferrite particle) 10 having a volume average particle size of 38 μm was prepared in the same manner as the core particle 1. Sm = 3.6 μm and Ra = 0.8 μm.

(Preparation of resin coating layer forming solution 1)
Novolac type epoxy resin (YDCN700-10, manufactured by Tohto Kasei) 100 parts by weight Amine-based curing agent (Adeka Hardener EH4602, manufactured by Adeka) 10 parts by weight Toluene 200 parts by weight Methyl ethyl ketone 600 parts by weight Resin coating layer forming solution 1 was prepared.

(Preparation of resin coating layer forming solution 2)
Bisphenol A type epoxy resin (YD-014, manufactured by Tohto Kasei) 10 parts by weight Glycidylamine (YH-434, manufactured by Tohto Kasei) 1 part by weight 2-Phenylimidazole 0.1 parts by weight Phenol novolac (PR-HF-6, Sumitomo) 100 parts by weight Methyl ethyl ketone 700 parts by weight Ethyl acetate 110 parts by weight The above was stirred to prepare a resin coating layer forming solution 2 having a solid content of 12% by weight.

(Preparation of resin coating layer forming solution 3)
Styrene acrylic resin (styrene: methyl methacrylate = 2 mol: 8 mol)
30 parts by weight Carbon black (VXC72, manufactured by Cabot) 4 parts by weight Toluene (manufactured by Wako Pure Chemical Industries) 300 parts by weight The above components and glass beads (particle size: 1 mm, the same amount as toluene) are put into a sand mill manufactured by Kansai Paint Co., Ltd. Then, the mixture was stirred at a rotational speed of 1200 rpm for 30 minutes to prepare a resin coating layer forming solution 3 having a solid content of 10% by weight.

(Preparation of resin coating layer forming solution 4)
Polyester resin (bisphenol A: dodecenyl succinic acid: terephthalic acid = 10 mol: 2 mol: 8 mol) 30 parts by weight Carbon black (VXC72, manufactured by Cabot) 4 parts by weight Toluene (manufactured by Wako Pure Chemical Industries) 300 parts by weight The above components and glass beads (Particle size: 1 mm, the same amount as toluene) was charged into a sand mill manufactured by Kansai Paint Co., Ltd., and stirred at a rotational speed of 1200 rpm for 30 minutes to prepare a resin coating layer forming solution 4 having a solid content of 10% by weight.

(Preparation of resin coating layer forming solution 5)
Novolac type epoxy resin (YDCN700-10, manufactured by Toto Kasei) 30 parts by weight Carbon black (VXC72, manufactured by Cabot) 3 parts by weight Toluene (manufactured by Wako Pure Chemical Industries) 200 parts by weight Methyl ethyl ketone 65 parts by weight The above components and glass beads (particle size) 1 mm, the same amount as toluene) was put into a sand mill manufactured by Kansai Paint Co., Ltd., and stirred at a rotational speed of 1200 rpm for 30 minutes to prepare a resin solution having a solid content of 10% by weight. Next, 3 parts by weight of Adeka Hardener EH4602 was added while stirring the resin solution to prepare a resin coating layer forming solution 5 having a solid content of 12% by weight.

(Preparation of resin coating layer forming solution 6)
Styrene acrylic resin (styrene: methyl methacrylate = 2 mol: 8 mol)
30 parts by weight Toluene (manufactured by Wako Pure Chemical Industries, Ltd.) 300 parts by weight The above components and glass beads (particle size: 1 mm, equivalent to toluene) were put into a sand mill manufactured by Kansai Paint Co., Ltd., and stirred for 30 minutes at a rotation speed of 1200 rpm. A resin coating layer forming solution 6 having a solid content of 10% by weight was prepared.

(Preparation of carrier 1)
Place 2000 parts by weight of core particle 1 in a vacuum degassing type 5L kneader, and further add 340 parts by weight of solution 1 for resin coating layer formation. While stirring, reduce the pressure to -200 mmHg at 60 ° C. and mix for 20 minutes. The resulting mixture was heated / depressurized and stirred at 90 ° C./−720 mmHg for 30 minutes and dried to obtain coated particles. Next, without applying a vacuum with the kneader, the temperature was set to 160 ° C. under atmospheric pressure, stirring was performed for 60 minutes, and sieving was performed with a 75 μm mesh sieving net to obtain coated particles 1.

  Next, 2000 parts by weight of the coated particles 1 was put into a vacuum degassing type 5 L kneader, and 400 parts by weight of the resin coating layer forming solution 3 was put into the vacuum degassing type 5 L kneader. Thereafter, the temperature was raised / depressurized, the mixture was stirred and dried at 90 ° C./−720 mHg for 20 minutes, and sieved with a 75 μm mesh sieve to obtain Carrier 1.

(Preparation of carrier 2)
Coated particles 2 were obtained in the same manner as the carrier 1 except that the core particles 1 and the resin coating layer forming solution 2 were used. Further, a carrier 2 was obtained in the same manner as the carrier 1 except that the coated particles 2 and the resin coating layer forming solution 3 were used.

(Preparation of carrier 3)
Coated particles 3 were obtained in the same manner as the carrier 1 except that the core particles 2 and the resin coating layer forming solution 1 were used. Further, a carrier 3 was obtained in the same manner as the carrier 1 except that the coated particles 3 and the resin coating layer forming solution 4 were used.

(Preparation of carrier 4)
Coated particles 4 were obtained in the same manner as the carrier 1 except that the core particles 3 and the resin coating layer forming solution 2 were used. Further, a carrier 4 was obtained in the same manner as the carrier 1 except that the coated particles 4 and the resin coating layer forming solution 3 were used.

(Preparation of carrier 5)
Coated particles 5 were obtained in the same manner as the carrier 1 except that the core particles 1 and the resin coating layer forming solution 5 were used. Further, a carrier 5 was obtained in the same manner as the carrier 1 except that the coated particles 5 and the resin coating layer forming solution 3 were used.

(Preparation of carrier 6)
Coated particles 6 were obtained in the same manner as the carrier 1 except that the core particles 4 and the resin coating layer forming solution 1 were used. Further, a carrier 6 was obtained in the same manner as the carrier 1 except that the coated particles 6 and the resin coating layer forming solution 3 were used.

(Preparation of carrier 7)
Coated particles 7 were obtained in the same manner as the carrier 1 except that the core particles 5 and the resin coating layer forming solution 1 were used. Further, carrier 7 was obtained in the same manner as carrier 1 except that coat particle 7 and resin coating layer forming solution 3 were used.

(Preparation of carrier 8)
Coated particles 8 were obtained in the same manner as the carrier 1 except that the core particles 6 and the resin coating layer forming solution 1 were used. Further, a carrier 8 was obtained in the same manner as the carrier 1 except that the coated particles 8 and the resin coating layer forming solution 3 were used.

(Preparation of carrier 9)
Coated particles 9 were obtained in the same manner as the carrier 1 except that the core particles 7 and the resin coating layer forming solution 1 were used. Further, a carrier 9 was obtained in the same manner as the carrier 1 except that the coated particles 9 and the resin coating layer forming solution 3 were used.

(Preparation of carrier 10)
Coated particles 10 were obtained in the same manner as the carrier 1 except that the core particles 7 and the resin coating layer forming solution 3 were used. Furthermore, 1000 parts by weight of the coated particles 10 are charged into a composite fluidized bed coating apparatus MP01-SFP (manufactured by Paulek), and the resin coating layer forming solution 4 is screen mesh 0.5 mm, rotating impeller 1000 rpm, exhaust air volume 1.2 m ^3. The coating was performed for 40 minutes under the conditions of / min, coating speed of 5 g / min, and temperature of 80 ° C. After taking out, the carrier 10 was obtained by sieving with a 75 μm mesh sieving net.

(Preparation of carrier 11)
Coated particles 11 were obtained in the same manner as the carrier 1 except that the core particles 8 and the resin coating layer forming solution 1 were used. Further, a carrier 11 was obtained in the same manner as the carrier 1 except that the coated particles 11 and the resin coating layer forming solution 3 were used.

(Preparation of carrier 12)
Coated particles 12 were obtained in the same manner as the carrier 1 except that the core particles 9 and the resin coating layer forming solution 1 were used. Further, a carrier 12 was obtained in the same manner as the carrier 1 except that the coated particles 12 and the resin coating layer forming solution 3 were used.

(Preparation of carrier 13)
Coated particles 13 were obtained in the same manner as the carrier 1 except that the core particles 1 and the resin coating layer forming solution 1 were used and the resin coating layer forming solution 1 was changed to 180 parts by weight. Further, a carrier 13 was obtained in the same manner as the carrier 1 except that the coated particles 13 and the resin coating layer forming solution 6 were used and the resin coating layer forming solution 6 was changed to 220 parts by weight.

(Preparation of carrier 14)
Coated particles 14 were obtained in the same manner as the carrier 1 except that the core particles 10 and the resin coating layer forming solution 1 were used. Further, a carrier 14 was obtained in the same manner as the carrier 1 except that the coated particles 14 and the resin coating layer forming solution 3 were used.

(Preparation of Colorant Dispersion 1)
Cyan pigment (copper phthalocyanine, CI Pigment Blue 15: 3, manufactured by Dainichi Seika) 50 parts by weight Anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku) 5 parts by weight Ion-exchanged water 200 parts by weight Then, the dispersion was dispersed for 5 minutes with an Ultra-Turrax manufactured by IKA and for 10 minutes with an ultrasonic bath to obtain a colorant dispersion 1 having a solid content of 21%. It was 160 nm when the volume average particle diameter was measured with a Horiba Seisakusho particle size measuring instrument LA-700.

(Preparation of release agent dispersion 1)
Paraffin wax (HNP-9, manufactured by Nippon Seiki) 19 parts by weight Anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 1 part by weight Ion-exchanged water 80 parts by weight The mixture was heated to 30 minutes and stirred. Next, the molten liquid is circulated from the bottom of the container to the gorin homogenizer, and under a pressure condition of 5 MPa, a circulation operation corresponding to 3 passes is performed. Then, the pressure is increased to 35 MPa, and further a circulation operation corresponding to 3 passes is performed. It was. The emulsion thus prepared was cooled in the heat-resistant solution to 40 ° C. or lower to obtain a release agent dispersion 1. It was 240 nm when the volume average particle diameter was measured with a Horiba Seisakusho particle size measuring instrument LA-700.

(Preparation of resin dispersion 1)
(Oil layer)
Styrene (manufactured by Wako Pure Chemical Industries, Ltd.) 30 parts by weight n-butyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd.) 10 parts by weight β-carboxyethyl acrylate (manufactured by Rhodia Nikka Co., Ltd.) 1.3 parts by weight Dodecane Thiol (Wako Pure Chemical Industries, Ltd.) 0.4 parts by weight (water layer 1)
17 parts by weight of ion-exchanged water Anionic surfactant (manufactured by Dowfax, Dow Chemical) 0.4 parts by weight (water layer 2)
Deionized water 40 parts by weight Anionic surfactant (Dowfax, manufactured by Dow Chemical) 0.05 part by weight Ammonium peroxodisulfate (manufactured by Wako Pure Chemical Industries, Ltd.) 0.4 part by weight The components were placed in a flask and mixed with stirring to obtain a monomer emulsified dispersion. The components of the aqueous layer 2 were put into a reaction vessel, the inside of the vessel was sufficiently replaced with nitrogen, and the reaction system was heated to 75 ° C. with an oil bath while stirring. The above monomer emulsified dispersion was gradually dropped into the reaction vessel over 3 hours to carry out emulsion polymerization. Polymerization was further continued at 75 ° C. after completion of the dropwise addition, and the polymerization was terminated after 3 hours to obtain a resin dispersion 1.

  The obtained resin particles were 250 nm when the volume average particle diameter D50v of the resin particles was measured with a laser diffraction particle size distribution measuring apparatus LA-700 (manufactured by Horiba, Ltd.). A differential scanning calorimeter (DSC- 50, manufactured by Shimadzu Corporation), and the glass transition point of the resin was measured at a temperature rising rate of 10 ° C./min. It was 53 ° C., and a molecular weight measuring device (HLC-8020, manufactured by Tosoh Corporation) was used with THF as the solvent. It was 13,000 when the number average molecular weight Mn (polystyrene conversion) was measured. As a result, a resin dispersion 1 having a volume average particle size of 250 nm, a solid content of 42% by weight, a glass transition point of 52 ° C., and a number average molecular weight Mn of 13,000 was obtained.

(Production of Toner 1)
Resin dispersion 1 150 parts by weight Colorant dispersion 1 30 parts by weight Release agent dispersion 1 40 parts by weight Polyaluminum chloride 0.4 parts by weight Using the above-mentioned components in a stainless steel flask, Ultra Turrax made by IKA After sufficiently mixing and dispersing, the flask was heated to 48 ° C. with stirring in an oil bath for heating. After maintaining at 48 ° C. for 80 minutes, 70 parts by weight of the same resin dispersion 1 as above was gradually added thereto.

  Then, after adjusting the pH in the system to 6.0 using an aqueous solution of sodium hydroxide having a concentration of 0.5 mol / L, the stainless steel flask is sealed, and the stirring shaft seal is magnetically sealed while stirring is continued. Heat to 97 ° C. and hold for 3 hours. After completion of the reaction, the temperature lowering rate was cooled at 1 ° C./min, filtered and thoroughly washed with ion-exchanged water, and then solid-liquid separation was performed by Nutsche suction filtration. This was further redispersed with 3 L of ion exchanged water at 40 ° C., and stirred and washed at 300 rpm for 15 minutes. This washing operation was further repeated 5 times. When the pH of the filtrate was 6.54 and the electric conductivity was 6.5 μS / cm, No. 2 was obtained by Nutsche suction filtration. Solid-liquid separation was performed using 5A filter paper. Next, vacuum drying was continued for 12 hours to obtain toner mother particles.

The volume average particle diameter D50v of the toner base particles was measured with a Coulter counter. As a result, it was 6.2 μm and the volume average particle size distribution index GSDv was 1.20. When the shape was observed with a Luzex image analyzer manufactured by Luzex, the shape factor SF1 of the particles was 135, and it was observed that the particles had a potato shape. The glass transition point of the toner was 52 ° C. Further, this toner was mixed with silica (SiO ₂ ) particles having a primary particle volume average particle size of 40 nm, which was hydrophobized with hexamethyldisilazane (hereinafter sometimes abbreviated as “HMDS”), metatitanic acid and isobutyltrimethoxy. Add methacrylic acid compound particles with a primary particle volume average particle diameter of 20 nm, which is a reaction product of silane, so that the coverage of the surface of each colored particle is 40%, mix with a Henschel mixer, and add toner 1 Produced.

(Toner 2)
As the toner 2, a cyan toner for DCC1250 (manufactured by Fuji Xerox Co., Ltd., manufactured by a kneading pulverization method) was used.

<Example 1>
(Effect confirmation)
A DCC400 developing device (manufactured by Fuji Xerox Co., Ltd.) and an improved bench capable of rotating the developing device were prepared, and 200 g of carrier 1 alone was added and the device was rotated for 10 hours. Next, 12 g of Toner 1 was prepared, added little by little to the developer containing the carrier, and further spun for 3 hours. The developing device was attached to DCC400 (manufactured by Fuji Xerox Co., Ltd.), and printing was performed on 50 sheets under the conditions of TMA 0.6 g / m ² , 5 cm × 10 cm and Cin 50% in an environment of 24 ° C. and 50% RH. Next, 10 sheets were printed under the conditions of 30 ° C. and 85% RH. These printed materials were printed in the same manner in the developer 1 that was not spun and compared with the printed materials, but there was no difference in density at Cin 50%. The density was measured using a reflection densitometer X-rite 404 manufactured by X-rite, and the density difference before and after idling was 0% at 24 ° C. and 0% at 30 ° C. Also, toner fog on the background was not observed with a 25 magnification loupe. The results are summarized in Table 1.

The toner fog was evaluated according to the following criteria.
◎: Fog is not recognized with 25 magnifying loupe ○: Cannot be visually confirmed at 30 ° C., slightly confirmed with 25 magnifying loupe Δ: Fog is visually confirmed at 30 ° C. ×: 24 ° C. To the extent that fogging can be visually confirmed under both conditions at 30 ° C

<Example 2>
Evaluation was performed in the same manner as in Example 1 except that carrier 2 and toner 1 were used. 24 ° C. concentration difference = 0%, 30 ° C. concentration difference = 0%, and fogging at 30 ° C. could not be visually confirmed, but was slightly observable with a 25-fold loupe. The results are summarized in Table 1.

<Example 3>
Evaluation was performed in the same manner as in Example 1 except that carrier 3 and toner 1 were used. 24 ° C. density difference = 0%, 30 ° C. density difference = 0%, and no toner fog on the background was observed with a 25 × magnifier. The results are summarized in Table 1.

<Example 4>
Evaluation was performed in the same manner as in Example 1 except that carrier 4 and toner 1 were used. 24 ° C. concentration difference = 0%, 30 ° C. concentration difference = 2%, and fogging at 30 ° C. could not be visually confirmed, but was slightly observable with a 25-fold loupe. The results are summarized in Table 1.

<Example 5>
Evaluation was performed in the same manner as in Example 1 except that carrier 1 and toner 2 were used. 24 ° C. concentration difference = 2%, 30 ° C. concentration difference = 4%, and fogging at 30 ° C. could not be visually confirmed, but was slightly observable with a 25-fold loupe. The results are summarized in Table 1.

<Example 6>
Evaluation was performed in the same manner as in Example 1 except that carrier 5 and toner 1 were used. 24 ° C. density difference = 0%, 30 ° C. density difference = 0%, and no toner fog on the background was observed with a 25 × magnifier. The results are summarized in Table 1.

<Example 7>
Evaluation was performed in the same manner as in Example 1 except that carrier 11 and toner 1 were used. 24 ° C. concentration difference = 4%, 30 ° C. concentration difference = 6%, and fogging at 30 ° C. could not be visually confirmed, but could be slightly confirmed with a 25-fold loupe. The results are summarized in Table 1.

<Example 8>
Evaluation was performed in the same manner as in Example 1 except that carrier 12 and toner 1 were used. 24 ° C. concentration difference = 4%, 30 ° C. concentration difference = 8%, and fogging at 30 ° C. could not be visually confirmed, but only with a 25 times magnifier. The results are summarized in Table 1.

<Example 9>
Evaluation was performed in the same manner as in Example 1 except that carrier 13 and toner 1 were used. 24 ° C. concentration difference = 6%, 30 ° C. concentration difference = 10%, and fogging at 30 ° C. could not be visually confirmed, but could be confirmed with a 25-fold loupe. The results are summarized in Table 1.

<Comparative Example 1>
Evaluation was performed in the same manner as in Example 1 except that carrier 6 and toner 1 were used. 24 ° C. concentration difference = 4%, 30 ° C. concentration difference = 30%, and the fogging at 30 ° C. was of a level that could be visually confirmed. The results are summarized in Table 1.

<Comparative example 2>
Evaluation was performed in the same manner as in Example 1 except that carrier 7 and toner 1 were used. 24 ° C. concentration difference = 2%, 30 ° C. concentration difference = 30%, and the fogging at 30 ° C. was of a level that could be visually confirmed. The results are summarized in Table 1.

<Comparative Example 3>
Evaluation was performed in the same manner as in Example 1 except that carrier 8 and toner 1 were used. 24 ° C. concentration difference = 10%, 30 ° C. concentration difference = 60%, and under both conditions of 24 ° C. and 30 ° C., the fog could be visually confirmed. The results are summarized in Table 1.

<Comparative Example 4>
Evaluation was performed in the same manner as in Example 1 except that carrier 9 and toner 2 were used. 24 ° C. concentration difference = 20%, 30 ° C. concentration difference = 60%, and under both conditions of 24 ° C. and 30 ° C., the fog could be visually confirmed. The results are summarized in Table 1.

<Comparative Example 5>
Evaluation was performed in the same manner as in Example 1 except that carrier 10 and toner 2 were used. There was almost no concentration after idling. The results are summarized in Table 1.

<Comparative Example 6>
Evaluation was performed in the same manner as in Example 1 except that carrier 14 and toner 1 were used. 24 ° C. concentration difference = 8%, 30 ° C. concentration difference = 12%, and the fogging at 30 ° C. could be visually confirmed. The results are summarized in Table 1.

  As can be seen from Table 1, by using the developers of Examples 1 to 9, the developer was stable against mechanical stress on the carrier and had good image characteristics.

Claims (2)

An electrostatic latent image developing carrier having core particles and a resin coating layer covering the surface of the core particles,
The surface roughness of the core particles is such that the average interval Sm between the irregularities is in the range of 1.0 μm to 3.5 μm, and the arithmetic average roughness Ra is in the range of 0.2 μm to 0.7 μm,
The resin coating layer includes at least two layers, and the lowermost resin coating layer includes a curable resin that is at least one of a novolak resin having a novolak structure and a derivatized novolak resin derived from the novolak resin. A carrier for developing an electrostatic latent image. A developer for developing an electrostatic latent image including a toner and a carrier,
The electrostatic latent image developing developer, wherein the carrier is the electrostatic latent image developing carrier according to claim 1.