JP2008257026A - Carrier for electrostatic charge image development, developer for electrostatic charge image development and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier for electrostatic charge image development capable of reducing a defect in picture quality caused by deposition of an isolated resin powder included in a resin coated carrier onto a charging member or the like. <P>SOLUTION: The carrier for electrostatic charge image development comprises a carrier core material and a resin coating layer, wherein the resin coating layer contains a foam suppressor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a carrier for developing an electrostatic image, a developer for developing an electrostatic image, and an image forming apparatus.

  A method for visualizing image information through an electrostatic latent image (electrostatic image) such as electrophotography is currently used in various fields. In electrophotography, an electrostatic latent image formed on a photoreceptor by charging and exposure processes contains an electrostatic charge image developing toner (hereinafter sometimes referred to simply as “toner”). It is developed with an agent (hereinafter sometimes simply referred to as “developer”), and visualized through a transfer and fixing process. As a developer used for development, a two-component developer including a toner and a carrier for developing an electrostatic image (hereinafter sometimes simply referred to as “carrier”) and a toner used alone such as a magnetic toner are used. There are component developers, but the two-component developer has characteristics such as good controllability because the carrier shares functions such as stirring, transport and charging of the developer and is separated as a developer. Is currently widely used.

  Carriers are generally divided into resin-coated carriers that have a resin coating layer on the surface of the magnetic core material (carrier core material) and uncoated carriers that do not have a coating layer on the surface. Since resin-coated carriers are superior, various types of resin-coated carriers have been developed and put into practical use. There are various properties required for resin-coated carriers, but it is possible to stably impart appropriate chargeability (charge amount, charge distribution, etc.) to the toner, and to maintain the appropriate and stable chargeability over a long period of time. Desired. For this purpose, the carrier has suitable electrical properties, and has high resistance to environmental changes such as humidity and temperature, impact resistance, friction resistance, contamination resistance, etc., and it should have long-term chargeability. It is important not to change.

  In order to obtain these characteristics, various resin-coated carriers have been proposed. For example, in the resin coating layer of these resin-coated carriers, inorganic particles such as carbon black, titanium oxide, and silica, charge control agents, and additives such as resin particles are used for the purpose of adjusting the electrical characteristics and chargeability of the carrier. Has been practiced. Further, as a typical method for forming these resin coating layers on the surface of the carrier core material, a dry coating method in which the carrier core material and the resin coating material are mixed and heat-kneaded by a kneader or an extruder, a coating resin is used. A dipping method in which the powder of the carrier core material is immersed in a resin solution dissolved in an organic solvent to form a resin coating layer, a spray method in which the resin solution is sprayed on the surface of the carrier core material, a carrier core material and a resin in a kneader coater Examples include a kneader coater method that mixes the solution and removes the solvent, but in a system where an additive is added to the resin coating layer, the dispersibility of the additive and the uniformity of the resin coating layer are improved. In order to obtain carrier characteristics, the kneader coater method is particularly preferably used.

  In this kneader coater method, in the stage of removing the organic solvent, the dispersion of the additive is improved by increasing the viscosity of the resin solution and a strong shearing force acting between the carrier core material and the coating resin. Easy to coat the material uniformly.

  In addition, for example, in Patent Documents 1 to 3, inorganic / organic systems such as curing catalysts, wettability improvers, plasticizers, antifoaming agents, thickeners, etc., within the range that does not impair the effects of the invention in the carrier coating agent. It is described that various additives can be added as needed.

JP 2001-100144 A JP-A-10-83099 JP 2001-27829 A

  The present invention relates to an electrostatic charge image developing carrier, an electrostatic charge image developing developer, and image formation that can reduce image quality defects caused by free resin powder contained in a resin-coated carrier adhering to a charging member or the like. Device.

  The present invention is an electrostatic charge image developing carrier comprising a carrier core material and a resin coating layer, wherein the resin coating layer contains a foam inhibitor.

  In the electrostatic charge image developing carrier, it is preferable that the antifoaming agent is at least one of a vinyl antifoaming agent, an acrylic antifoaming agent, and a fluorine antifoaming agent.

  The present invention also provides an electrostatic charge image developing developer comprising the electrostatic charge image developing carrier and the electrostatic charge image developing toner.

  Furthermore, the present invention provides an image carrier, latent image forming means for forming an electrostatic latent image on the surface of the image carrier, and developing the electrostatic latent image using a developer to form a toner image. An image forming apparatus comprising: a developing unit; and a transfer unit that transfers the developed toner image to a transfer target, wherein the developer is the developer for developing an electrostatic image.

  According to claim 1 of the present invention, it is possible to provide a carrier for developing an electrostatic image capable of reducing image quality defects caused by free resin powder contained in a resin-coated carrier adhering to a charging member or the like. .

  According to claim 2 of the present invention, it is possible to manufacture a carrier for developing an electrostatic charge image that can further reduce image quality defects caused by free resin powder contained in a resin-coated carrier adhering to a charging member or the like. it can.

  According to claim 3 of the present invention, it is possible to provide a developer for developing an electrostatic charge image capable of reducing image quality defects caused by free resin powder contained in a resin-coated carrier adhering to a charging member or the like. it can.

  According to claim 4 of the present invention, it is possible to provide an image forming apparatus capable of reducing image quality defects caused by free resin powder contained in a resin-coated carrier adhering to a charging member or the like.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

<Carrier for developing electrostatic image>
As described above, for example, in the kneader coater method, in the step of removing the organic solvent, the dispersion of the additive is improved by the action of a strong shearing force between the carrier core material and the coating resin as the viscosity of the resin solution increases. Easy to coat the layer uniformly on the carrier core. On the other hand, resin powder released from the carrier core due to uneven coating of the resin coating layer, surface roughness, etc. is likely to occur, and by adhering to the charging member, transfer member, photoreceptor, etc. in the image forming apparatus, It tends to cause image quality defects such as color spots and white spots. Further, if resin powder is mixed in the toner image, the fixability is hindered and problems such as hot offset are likely to occur. In particular, in a small-sized image forming apparatus that has a contact-type charger that applies a charge to the photosensitive member and that does not have a cleaning system such as a cleaning blade, the photosensitive member is charged with a polarity opposite to that of the toner. Since the free resin powder that adheres to and accumulates on the charging member via the photoreceptor, image quality defects due to poor charging are likely to occur along with the number of image outputs, so a regular member cleaning process is required in the image forming apparatus As a result, the number of images that can be continuously output has been reduced and the speed has been hindered. In addition, regardless of the method of forming the resin coating layer, the compatibility between the resin and additives such as a resistance adjusting agent and a charge adjusting agent may be low, and good carrier characteristics may not be obtained.

  Therefore, the present inventors suppress the amount of free resin powder generated from the carrier in the resin-coated carrier for developing an electrostatic charge image, and the free resin powder adheres to the photoreceptor, charging member, transfer member, etc. in the image forming apparatus. We studied to improve the problem of image quality defects such as color spots and white spots caused by this. As a result, in the carrier including the carrier core material and the resin coating layer, the resin coating layer contains a foam suppressant, thereby suppressing uneven coating of the resin coating layer, surface roughness, etc., and free resin powder from the carrier. Can reduce image quality defects due to adhesion of free resin powder to the photosensitive member, charging member, transfer member, etc., and also contain a foam suppressor to provide a coating resin and a resistance modifier, It has been found that the compatibility with additives such as a charge control agent can be improved and good carrier characteristics can be obtained. In particular, it is possible to improve the number of continuous image outputs and increase the speed of an image forming apparatus that employs a cleanerless system. Furthermore, it is possible to contribute to speeding up of the image forming apparatus and reduction of waste toner.

  Generally used antifoaming agents can be broadly categorized according to their action, and the defoaming agent that breaks the foam film of the generated foam and the suppression that breaks the foam to be generated and hardly exists as foam. Although it is classified into two types, foaming agents, in order to reduce the free resin powder of the resin-coated carrier, generally used solvent-based foam breakers such as acetone and ethanol, surfactants, etc. The effect of suppressing the generation of bubbles is small and undesirable.

  That is, the foam suppressor used in the present embodiment breaks bubbles to be generated so that they hardly exist as bubbles. A specific method for measuring the volume of foam is as follows. In a 100 mL glass or plastic lidded container, 50 g of a toluene solution containing 10% by weight of a coating resin is added, 10 mg of a foam inhibitor is added, and the mixture is stirred at 90 rpm using a turbula mixer at 25 ° C. for 1 minute. Transfer to a 100 mL graduated cylinder and measure the volume of foam generated within 10 seconds. The above is the method for measuring the foam volume, and the foam suppressor can suppress the foam volume to 10 mL, preferably 5 mL or less.

Examples of such antifoaming agents include oil-type silicone antifoaming agents such as silicone oils and oil compounds, vinyl antifoaming agents such as vinyl ether polymers, acrylic antifoaming agents such as acrylic polymers, and fluorine-based antifoaming agents. Fluorine-based antifoaming agents such as alcohol can be used, but at least one of vinyl-based antifoaming agents, acrylic-based antifoaming agents, and fluorine-based antifoaming agents is preferably used in terms of carrier charging stability. . Examples of vinyl foam suppressants include n-butyl vinyl ether, 2-ethylhexyl vinyl ether, alkyl vinyl ethers such as octadecyl vinyl ether, hydroxyalkyl vinyl ethers such as hydroxybutyl vinyl ether, vinyl ether polymers such as allyl vinyl ether, polycarboxylic acid vinyl esters, polystyrene Examples thereof include sulfonates and copolymers thereof. Acrylic foam inhibitors include polyacrylic acid or polyacrylate, polymers of (meth) acrylic acid long chain alkyl esters having 3 to 18 carbon atoms, polyacrylic acid or polyalkyl acrylate partial alkyl ester heavy polymers. Examples thereof include copolymers and copolymers thereof. Examples of the fluorine-based foam suppressor include fluorine-based alcohols such as H (CF ₂ CF ₂ ) _n CH ₂ OH (where n is an integer of 1 to 5).

  Specific examples thereof include, for example, commercially available products such as Floren AC-1190 (manufactured by Kyoeisha Chemical Co., Ltd.), Dispalon 1950 (manufactured by Enomoto Kasei Co., Ltd.), Floren AC-300 (manufactured by Kyoeisha Chemical Co., Ltd.), Dispalon Examples include acrylic foam suppressors such as OX-883 (manufactured by Enomoto Kasei), and fluorine foam suppressors such as telomeric alcohol (2,2,3,3-tetrafluoro-1-propanol, Showa Denko). .

  Moreover, it is preferable to select the kind of foam suppressant according to the kind of coating resin used for a resin coating layer. For example, fluorine-based foam inhibitors for fluorine-based resins such as perfluoroalkyl acrylate, and vinyl-based foam inhibitors for styrene / acrylic resins such as styrene and methyl methacrylate (MMA) and their copolymers. Agents and acrylic antifoaming agents are preferred from the viewpoint of compatibility with the resin and influence on the chargeability of the carrier.

  The amount of these antifoaming agents added is preferably 0.1% by weight or more and 5% by weight or less, and preferably 0.2% by weight or more and 1% by weight or less with respect to the coating resin in the coating resin layer. More preferred. If the added amount of the foam suppressor is less than 0.1% by weight with respect to the coating resin, the effect of reducing the amount of free resin powder generated may not be exhibited. If it is 5% by weight or more, there will be no significant difference in the effect. In some cases, the coating effect of the coating resin may be hindered.

  Examples of the coating resin used for the resin coating 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, and polyvinyl carbazole. , Polyvinyl ether and polyvinyl ketone; vinyl chloride / vinyl acetate copolymer; styrene / acrylic copolymer; straight silicone resin composed of organosiloxane bond or modified product thereof; fluororesin such as polytetrafluoroethylene, polyvinyl fluoride, Polyvinylidene fluoride, polychlorotrifluoroethylene; polyester; polyurethane; polycarbonate, amino resin such as urea-formaldehyde Fats; epoxy resins; perfluoroalkyl (meth) acrylate / (meth) acrylate copolymer, and the like. These may be used alone or in combination with a plurality of resins. Of these, styrene / acrylic copolymers and perfluoroalkyl (meth) acrylate / (meth) acrylate copolymers are preferred from the viewpoints of carrier charge imparting property and charge maintaining property.

  The resin coating layer may contain a negative charge control agent. Negative charge control agents include trimethylethane dyes, metal complexes of salicylic acid, metal complexes of benzyl acid, copper phthalocyanine, perylene, quinacridone, azo pigments, metal complex azo dyes, azochrome complexes, and other heavy metal-containing acids. Examples thereof include dyes, calixarene type phenolic condensates, cyclic polysaccharides, resins containing a carboxyl group and / or a sulfonyl group.

  The content of the negative charge control agent is preferably in the range of 0.001 wt% to 1.0 wt% with respect to the weight of the carrier core material, 0.01 wt% to 0.8 wt%. The following range is more preferable. If the content of the negative charge control agent is less than 0.001% by weight with respect to the weight of the carrier core material, there may be no effect on the toner charge rising property. May inhibit the charging ability.

  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.

  Further, the resin coating layer of the carrier may contain a wax. Waxes are hydrophobic, are relatively soft at room temperature, and have low film strength. This originates from the molecular structure of the wax. However, if wax is present in the resin coating layer for this property, toner components such as external additives added to the toner surface or toner bulk components are present on the carrier surface. Hard to adhere. Even if it adheres, the surface of the carrier is renewed by peeling off the wax at the adhesion level at the molecular level, and the carrier surface is not easily contaminated.

  The wax is not particularly limited, and examples thereof include paraffin wax and derivatives thereof, montan wax and derivatives thereof, microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, and polyolefin wax and derivatives thereof. Derivatives include oxides, polymers with vinyl monomers, and graft modified products. In addition, alcohols, fatty acids, plant waxes, animal waxes, mineral waxes, ester waxes, acid amides, and the like can be used. Other known materials can also be used. The melting point of the wax is preferably 60 ° C. or higher and 200 ° C. or lower. More preferably, the melting point of the wax is 80 ° C. or higher and 150 ° C. or lower. If it is less than 60 degreeC, the fluidity | liquidity as a carrier will deteriorate.

  The thickness of the resin coating layer is preferably in the range of 0.1 μm to 5 μm, and more preferably in the range of 0.2 μm to 3 μm. If the thickness of the resin coating layer is smaller than 0.1 μm, it may be difficult to form a uniform and flat resin coating layer on the surface of the carrier core material. 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.

  As the carrier core material, any conventionally known carrier material can be used, and ferrite or magnetite is particularly preferably selected. For example, iron powder is known as another carrier core material. 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 tends 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 and 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 a raw material for carrier core material, 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.) spinel ferrite particle powder containing one or more types, magnet plumbite type ferrite particle powder such as barium ferrite, iron or iron alloy particle powder having an oxide film on its surface Can be used.

  Specific examples of the carrier core material 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 a carrier core material, as an example of a method for producing a ferrite core material, an appropriate amount of each oxide is first blended, pulverized and mixed for 2 to 12 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 hours to 10 hours using a rotary kiln or the like. Temporary baking is performed once or more and three times or less as necessary. Thereafter, the temporarily fired product is dispersed in water and pulverized with a wet ball mill or the like until the volume average particle size becomes 0.3 μm or more and 1.2 μm or less. This slurry is granulated and dried using a spray dryer, etc., and for the purpose of adjusting the magnetic properties and resistance, the slurry is baked at 800 ° C. or more and 1200 ° C. or less for 4 hours or more and 12 hours or less while controlling the oxygen concentration and then pulverized. Further, it can be obtained by classification into a desired particle size distribution.

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

  As the binder resin, a phenol resin, a crosslinked styrene resin, an acrylic resin, a styrene / acrylic copolymer resin, or the like is used.

The magnetic susceptibility σ of the carrier core material of this embodiment is measured by a 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 Am ² / kg (emu / g). ) To 90 Am ² / kg (emu / g), preferably 55 Am ² / kg (emu / g) 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 carrier core material of this embodiment is preferably in the range of 10 μm to 100 μm, and more preferably in the range of 20 μm to 50 μm. If the volume average particle diameter of the carrier core material is smaller than 10 μm, the developer is likely to be scattered from the developing device, and if it is larger than 100 μm, it may be difficult to obtain a sufficient image density.

1 × 10 ⁵ Ω · cm or more 1 × ^{10 14} Ω · cm more preferably in the range when the electrical resistance of the carrier to form a resin coating layer field measurement field ^{10000V / cm, 1 × 10 9} Ω · cm or more The range of 1 × 10 ¹² Ω · cm or less is more preferable.

  The chargeability of the carrier on which the resin coating layer is formed is preferably in the range of 15 μC / g or more and 50 μC / g or less in absolute amount. 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 smaller than 1 × 10 ⁵ Ω · cm, the charge easily moves on the surface of the carrier, and image defects such as the image surface being swept away are likely to occur. If the image output operation is left unattended for a while, the charging property becomes too low, and there may be a case where the first image output of the first sheet is soiled. Further, if the electric resistance of the carrier on which the resin coating layer is formed is larger than 1 × 10 ¹⁴ Ω · cm, not only a solid image can be obtained, but if the continuous image output is repeated many times, the toner charge becomes too large and the image becomes too large. Concentration may decrease.

The electrokinetic resistance when measured in the form of a carrier magnetic brush is preferably in the range of 1 × 10 Ω · cm to 1 × 10 ⁹ Ω · cm under an electric field of 10 ⁴ V / cm. A range of 10 ³ Ω · cm to 1 × 10 ⁸ Ω · cm is more preferable. If the dynamic electrical resistance is less than 1 × 10 Ω · cm, image defects such as the image surface being swept away are likely to occur, and if it is greater than 1 × 10 ⁸ Ω · cm, it is difficult to obtain a good solid image. May be. 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 Ω · cm 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 contamination due to a decrease in toner chargeability after leaving after image output or due to over-development of the line image. 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.

<Method for producing carrier for developing electrostatic image>
The method of forming the resin coating layer on the surface of the carrier core material is to add a coating resin, conductive particles, etc. into a solvent in which the coating resin is soluble to obtain a resin coating layer forming liquid (dispersion or solution). Immersion method in which carrier core material powder is immersed in layer forming liquid, spray method in which resin coating layer forming liquid is sprayed on the surface of carrier core material, and resin coating layer is formed with carrier core material suspended in flowing air Examples thereof include a fluidized bed method in which a working solution is sprayed, a kneader coater method in which a carrier core material and a resin coating layer forming solution are mixed in a kneader coater, and then the solvent is removed.

  By containing a foam suppressor in the resin coating layer forming solution, uneven coating of the resin coating layer, surface roughness, etc. are suppressed, the amount of free resin powder generated from the carrier is reduced, and the photoreceptor, charging member, transfer Image quality defects due to adhesion of free resin powder to members and the like can be improved. In addition, by including a foam suppressor in the resin coating layer forming liquid, it is possible to obtain good carrier characteristics by increasing the compatibility between the coating resin and additives such as a resistance modifier and a charge modifier. .

  In particular, when the kneader coater method is used, in the conventional method, the adhesion of the resin coating to the carrier core material is hindered by bubbles generated when the organic solvent is removed from the resin coating layer forming liquid, and the carrier surface Uneven coating and surface roughness are likely to occur on the resin coating layer, and the coating resin is peeled off from the carrier core material due to the strong shearing force when the residual solvent is reduced and the resin solution viscosity is increased, and free resin powder is generated. End up. Application of the resin coating layer by foaming when the organic solvent is removed from the resin solution under reduced pressure or the like when the resin coating layer is formed on the carrier core material by including a foam inhibitor in the resin coating layer forming liquid Unevenness, surface roughness, and the like can be suppressed, the amount of free resin powder generated from the carrier can be reduced, and image quality defects due to free resin powder adhering to the photoreceptor, charging member, transfer member, and the like can be improved. Also, good carrier characteristics can be obtained by increasing the compatibility between the coating resin and additives such as a resistance adjusting agent and a charge adjusting agent. In particular, it is possible to improve the number of continuous image outputs and increase the speed of an image forming apparatus that employs a cleanerless system. Furthermore, it is possible to contribute to speeding up of the image forming apparatus and reduction of waste toner.

  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.

  The method for forming the resin coating layer on the carrier core material is not particularly limited, and a mixing step of mixing the carrier core material with a resin coating layer forming liquid containing a coating resin, a foam inhibitor and a solvent, and mixed mixing And a solvent removal step of removing the solvent from the liquid. In this method, it is preferable that the carrier core material and the resin coating layer forming liquid are mixed in a kneader coater, and then the above kneader coater method is used in which the solvent is removed.

  Usually, when manufacturing by a kneader coater method, the carrier core material and the resin coating layer forming liquid in which conductive particles and the like are dispersed are mixed, and the solvent is removed by heating and reducing pressure while stirring.

<Developer for developing electrostatic image>
The developer for developing an electrostatic charge image according to the exemplary embodiment includes a toner and a carrier, and the carrier is the carrier for developing an electrostatic charge image. That is, the developer for developing an electrostatic charge image according to the exemplary embodiment is a two-component developer including a toner and a carrier.

  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 narrow particle size distribution, it is preferable because it causes less fog.

  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 the binder resin include polystyrene, styrene / alkyl acrylate copolymer, styrene / alkyl methacrylate copolymer, styrene / acrylonitrile copolymer, styrene / butadiene copolymer, styrene / maleic anhydride copolymer, 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 part by weight to 30 parts by weight with respect to 100 parts by weight of the binder resin. It is also effective to use a surface-treated 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 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 wet-added.

  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 Examples thereof include anionic surfactants such as acid esters and soaps, and cationic surfactants such as amine salts and quaternary ammonium salts, and also polyethylene glycols, alkylphenol ethylene oxide adducts, polyhydric alcohols. It is also effective to use a nonionic surfactant such as a system together.

  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 10 μm, and more preferably in the range of 5 μm to 9 μm. If the volume average particle diameter of the toner is less than 4 μm, the amount of fine powder increases, so that toner fog and poor cleaning are likely to occur.

  In addition, the volume average particle size distribution index GSDv of the toner according to the exemplary embodiment is preferably in the range of 1.0 to 1.3, more preferably in the range of 1.1 to 1.3. More preferably, it is in the range of 1.15 or more and 1.24 or less. When the GSDv exceeds 1.3, the presence of coarse particles and fine powder particles increases, so that the aggregation of the toners becomes intense, and it becomes easy to cause charging failure and transfer failure. Moreover, when GSDv is less than 1.1, it will be quite difficult to manufacture.

The volume average particle size D50v and the volume average particle size distribution index GSDv can be obtained by measuring with an aperture diameter of 100 μm using a Coulter Multisizer II type (manufactured by Beckman Coulter, Inc.). At this time, the measurement is performed after the toner is dispersed in an electrolyte aqueous solution (Isoton II aqueous solution) and dispersed by ultrasonic waves for 30 seconds or more. For the particle size range (channel) divided based on the measured particle size distribution of the toner, a cumulative distribution is drawn from the small diameter side for each of the volume and number, and the particle size that becomes 16% is the volume D16v and the cumulative is 50%. The particle diameter to be defined is defined as volume D50v, and the particle diameter to be accumulated 84% is defined as volume D84v. 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 .

  The ratio of the toner in preparing the developer by mixing the toner and the carrier is in the range of 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) High-quality color images cannot be obtained. For example, when the amount exceeds 15% by weight, the toner coverage on the carrier surface approaches 100%, so that the resistance value as a developer is extremely increased, and is 1 × 10 ⁵ Ω · cm or more and 1 × 10 ⁸ Ω · cm or less. This makes it difficult to fit within the range, and 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 apparatus>
The image forming apparatus according to the present embodiment includes an image carrier, latent image forming means for forming an electrostatic latent image on the surface of the image carrier, and developing the electrostatic latent image with a developer to form a toner image. A developing unit that forms the toner image, and a transfer unit that transfers the developed toner image to the transfer target. The developer for developing an electrostatic charge image is used as the developer. In addition, the image forming apparatus according to the present embodiment includes means other than those described above, for example, charging means for charging the image holding member, fixing means for fixing the toner image transferred to the surface of the transfer target, and the surface of the image holding member. It may also include a cleaning means for removing the remaining toner.

  An example of the image forming apparatus according to the present embodiment is schematically shown in FIG. The image forming apparatus 500 includes a charging unit 502, an exposure unit 504, an electrophotographic photosensitive member 506 that is an image holding member, a developing unit 508, a transfer unit 510, a cleaning unit 512, and a fixing unit 514.

  In the image forming apparatus 500, around the electrophotographic photosensitive member 506, a charging unit 502 that is a charging unit that charges the surface of the electrophotographic photosensitive member 506 and the charged electrophotographic photosensitive member 506 are exposed and according to image information. An exposure unit 504 that is a latent image forming unit that forms an electrostatic latent image, a developing unit 508 that is a developing unit that develops the electrostatic latent image with toner to form a toner image, and the surface of the electrophotographic photosensitive member 506 A transfer unit 510 that is a transfer unit that transfers the toner image formed on the surface of the transfer object 516, and a cleaning unit 512 that is a cleaning unit that removes toner remaining on the surface of the electrophotographic photosensitive member 506 after transfer. Are arranged in this order. A fixing unit 514 that is a fixing unit that fixes the toner image transferred to the transfer target 516 is disposed on the left side of the transfer unit 510.

  An operation of the image forming apparatus 500 according to the present embodiment will be described. First, the surface of the electrophotographic photosensitive member 506 is uniformly charged by the charging unit 502 (charging process). Next, the surface of the electrophotographic photosensitive member 506 is exposed by the exposure unit 504, the charged charge in the exposed part is removed, and an electrostatic charge image (electrostatic latent image) is formed according to image information (latent image formation). Process). Thereafter, the electrostatic charge image is developed by the developing unit 508, and a toner image is formed on the surface of the electrophotographic photosensitive member 506 (developing step). For example, in the case of a digital electrophotographic copying machine using an organic photoconductor as the electrophotographic photoconductor 506 and using a laser beam as the exposure unit 504, the surface of the electrophotographic photoconductor 506 is given a negative charge by the charging unit 502. Then, a digital latent image is formed in a dot shape by the laser beam light, and a toner is applied to a portion irradiated with the laser beam light by the developing unit 508 to be visualized. In this case, a negative bias is applied to the developing unit 508. Next, in the transfer unit 510, a transfer object 516 such as paper is superimposed on the toner image, and a charge having a polarity opposite to that of the toner is applied to the transfer object 516 from the back side of the transfer object 516, and the toner image is generated by electrostatic force. Is transferred to the transfer object 516 (transfer process). The transferred toner image is heated and pressed by a fixing member in the fixing unit 514, and is fused and fixed to the transfer target 516 (fixing step). On the other hand, toner remaining on the surface of the electrophotographic photosensitive member 506 without being transferred is removed by a cleaning unit 512 (cleaning step). One cycle is completed in a series of processes from charging to cleaning. In FIG. 1, the toner image is directly transferred to the transfer target 516 such as paper by the transfer unit 510, but may be transferred via a transfer member such as an intermediate transfer member.

  Hereinafter, a charging unit, an image carrier, an exposure unit, a developing unit, a transfer unit, a cleaning unit, and a fixing unit in the image forming apparatus 500 of FIG. 1 will be described.

(Charging means)
As the charging unit 502 serving as a charging unit, for example, a charger such as a corotron as shown in FIG. 1 is used, but a conductive or semiconductive charging roll may be used. A contact charger using a conductive or semiconductive charging roll may apply a direct current to the electrophotographic photosensitive member 506 or superimpose an alternating current. For example, the charging unit 502 charges the surface of the electrophotographic photosensitive member 506 by generating a discharge in a minute space near the contact portion with the electrophotographic photosensitive member 506. Normally, it is charged to −300V or more and −1000V or less. The conductive or semiconductive charging roll may have a single layer structure or a multiple structure. Further, a mechanism for cleaning the surface of the charging roll may be provided.

(Image carrier)
The image carrier has a function of forming at least an electrostatic latent image (electrostatic charge image). As the image carrier, an electrophotographic photosensitive member is preferably exemplified. The electrophotographic photoreceptor 506 has a coating film containing an organic photoreceptor on the outer peripheral surface of a cylindrical conductive substrate. The coating film is a substrate in which a subbing layer and a photosensitive layer including a charge generating layer containing a charge generating material and a charge transporting layer containing a charge transporting material are formed in this order on the substrate as necessary. is there. The order of stacking the charge generation layer and the charge transport layer may be reversed. These are laminated photoconductors in which a charge generation material and a charge transport material are contained in separate layers (charge generation layer, charge transport layer), but both the charge generation material and the charge transport material are the same. A single-layer type photoreceptor included in the above layer may be used, and a laminated photoreceptor is preferable. Further, an intermediate layer may be provided between the undercoat layer and the photosensitive layer. In addition, other types of photosensitive layers such as an amorphous silicon photosensitive film may be used in addition to the organic photoreceptor.

(Exposure means)
The exposure unit 504 that is an exposure unit is not particularly limited. For example, an optical system device that can expose a light source such as semiconductor laser light, LED light, and liquid crystal shutter light on the surface of the image carrier in a desired image-like manner. Can be mentioned.

(Development means)
A developing unit 508 serving as a developing unit has a function of developing a latent image formed on the image carrier with a developer containing toner to form a toner image. Such a developing device is not particularly limited as long as it has the above-mentioned function, and can be appropriately selected according to the purpose. For example, toner for developing an electrostatic image is used using a brush, a roller, or the like. A known developing device having a function of adhering to the electrophotographic photosensitive member 506 may be used. The electrophotographic photosensitive member 506 normally uses a DC voltage, but may be used with an AC voltage superimposed thereon.

(Transfer means)
As the transfer unit 510 serving as a transfer unit, for example, a charge having a polarity opposite to that of the toner is applied to the transfer object 516 from the back side of the transfer object 516 as shown in FIG. A transfer roll and a transfer roll pressing device using a conductive or semiconductive roll that transfers directly to the surface of the transfer object 516 via the transfer object 516 can be used. . A direct current may be applied to the transfer roll as a transfer current applied to the image carrier, or an alternating current may be applied in a superimposed manner. The transfer roll can be arbitrarily set depending on the width of the image area to be charged, the shape of the transfer charger, the opening width, the process speed (circumferential speed), and the like. Further, a single layer foam roll or the like is suitably used as a transfer roll for cost reduction. The transfer method may be a method of transferring directly to a transfer target 516 such as paper or a method of transferring to a transfer target 516 via an intermediate transfer member.

  A known intermediate transfer member can be used as the intermediate transfer member. Materials used for the intermediate transfer member include polycarbonate resin (PC), polyvinylidene fluoride (PVDF), polyalkylene phthalate, PC / polyalkylene terephthalate (PAT) blend material, ethylene tetrafluoroethylene copolymer (ETFE) / PC, ETFE / PAT, PC / PAT blend materials, and the like can be mentioned. From the viewpoint of mechanical strength, an intermediate transfer belt using a thermosetting polyimide resin is preferable.

(Cleaning means)
The cleaning unit 512, which is a cleaning unit, may be selected as appropriate as long as it cleans the residual toner on the image carrier, such as a blade cleaning method, a brush cleaning method, or a roll cleaning method. Among these, it is preferable to use a cleaning blade. Examples of the material for the cleaning blade include urethane rubber, neoprene rubber, and silicone rubber. Among them, it is particularly preferable to use a polyurethane elastic body because of its excellent wear resistance. However, there may be a mode in which the cleaning unit 512 is not used when toner having high transfer efficiency is used.

(Fixing means)
The fixing unit 514 serving as a fixing unit (image fixing device) fixes the toner image transferred to the transfer body 516 by heating, pressing, or heating and pressing, and includes a fixing member.

(Transfer)
Examples of the transfer target (paper) 24 to which the toner image is transferred include plain paper, OHP sheet, and the like used in electrophotographic copying machines, printers, and the like. In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the transfer target is as smooth as possible. For example, coated paper in which the surface of plain paper is coated with resin, art paper for printing, etc. Can be preferably used.

  Since the image forming apparatus and the image forming method according to the present embodiment use the electrostatic charge image developer (the carrier according to the present embodiment), the free resin powder contained in the resin-coated carrier adheres to the charging member or the like. As a result, image quality defects that occur can be reduced.

  Further, as the image forming apparatus according to the present embodiment, an image forming apparatus that employs a cleanerless system that does not have a cleaning unit for the photosensitive member can be exemplified.

  Such an image forming apparatus includes, for example, an image carrier, latent image forming means for forming an electrostatic latent image on the surface of the image carrier, and developing the electrostatic latent image with a developer to form a toner image. A secondary transfer unit, a developing unit to form, a primary intermediate transfer body that primarily transfers and holds the developed toner image, a secondary intermediate transfer body that secondary-transfers and holds the primary transferred toner image, and the secondary transferred image An image forming apparatus that employs a cleanerless system that does not have a cleaning system for an image carrier such as a cleaning blade, and that transfers a toner image to a transfer target. Developer is used.

  As an example of an image forming apparatus employing such a cleanerless system, FIG. 2 shows a tandem type full color printer. This apparatus is a system that transfers an image to a transfer medium via an intermediate transfer body. In addition, the arrow in FIG. 2 has shown the rotation direction of each rotation member. The basic configuration of the image forming apparatus and the operation of the image forming mode will be described below.

  As shown in FIG. 2, the full-color printer includes photosensitive drums (image carriers) 11, 12, 13, and 14 for cyan (C), magenta (M), yellow (Y), and black (K). Image forming units 1, 2, 3, 4, and charging rolls (contact type charging devices: charging means) 21, 22, 23, 24 for primary charging that are in contact with the photosensitive drums 11, 12, 13, 14; A laser optical unit (exposure device: latent image forming means) (not shown) that irradiates laser beams 31, 32, 33, and 34 of each color of cyan (C), magenta (M), yellow (Y), and black (K). , Developing devices (developing means) 41, 42, 43, 44, and a first primary intermediate transfer drum in contact with two of the four photosensitive drums 11, 12, 13, 14. (Primary intermediate transfer member 51 and the second primary intermediate transfer drum (primary intermediate transfer body) 52 in contact with the other two photosensitive drums 13 and 14, and the secondary in contact with the first and second primary intermediate transfer drums 51 and 52. An intermediate transfer drum (secondary intermediate transfer member) 53 and a final transfer roll (transfer means) 60 that contacts the secondary intermediate transfer drum 53 constitute the main part.

  The photosensitive drums 11, 12, 13, and 14 are arranged at a predetermined interval so as to have a common tangential plane M. Further, the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52 have respective rotation axes parallel to the axes of the photosensitive drums 11, 12, 13, and 14 and a predetermined target surface as a boundary. Arranged so as to have a surface object relationship. Further, the secondary intermediate transfer drum 53 is arranged so that the rotation axis is parallel to the photosensitive drums 11, 12, 13, and 14.

  Signals corresponding to image information for each color are rasterized by an image processing unit (not shown) and input to a laser optical unit (not shown). In this laser optical unit, the laser beams 31, 32, 33, and 34 of cyan (C), magenta (M), yellow (Y), and black (K) are modulated, and the corresponding photosensitive drums 11, Irradiates 12, 13, and 14.

  An image forming process for each color is performed around each of the photosensitive drums 11, 12, 13, and 14 by a known electrophotographic method. These photosensitive drums 11, 12, 13, and 14 are rotationally driven. The surfaces of the photosensitive drums 11, 12, 13, and 14 are charged, for example, by applying a DC voltage to charging rolls 12, 22, 32, and 42 as contact-type charging devices. The contact-type charging device may be a roll type, a film type, a brush type, or the like, but any type may be used. In this embodiment, a charging roll generally used in an electrophotographic apparatus in recent years is employed. Further, in order to charge the surfaces of the photosensitive drums 11, 12, 13, and 14, in this embodiment, a charging method in which only DC is applied is used, but a charging method in which AC + DC is applied may be used.

  Thereafter, the surfaces of the photosensitive drums 11, 12, 13, and 14 correspond to cyan (C), magenta (M), yellow (Y), and black (K) colors by a laser optical unit (not shown) as an exposure apparatus. The irradiated laser beams 31, 32, 33, and 34 are irradiated to form an electrostatic latent image corresponding to input image information for each color.

  In addition, electrostatic latent images corresponding to cyan (C), magenta (M), yellow (Y), and black (K) colors formed on the surfaces of the photosensitive drums 11, 12, 13, and 14 are compatible. Are developed by the developing devices 41, 42, 43, and 44, and the cyan (C), magenta (M), yellow (Y), and black (K) colors are formed on the photosensitive drums 11, 12, 13, and 14, respectively. Visualized as a toner image.

  The developing devices 41, 42, 43, and 44 include developments including cyan (C), magenta (M), yellow (Y), and black (K) toners of different colors and the carrier according to the present embodiment. The agent is filled.

  In the developing devices 41, 42, 43, and 44, when toner is supplied from a toner supply device (not shown), the supplied toner is sufficiently agitated with the carrier by the auger 404 and frictionally charged to a negative polarity. The Inside the developing roll 401, a magnet roll (not shown) having a plurality of magnetic poles arranged at a predetermined angle is arranged in a fixed state. The amount of developer conveyed to the vicinity of the surface of the developing roll 401 is regulated by the developer amount regulating member 402 by the paddle 403 that conveys the developer to the developing roll 401.

  The toner supplied onto the developing roll 401 is in the form of a magnetic brush composed of a carrier and toner by the magnetic force of the magnet roll, and this magnetic brush comes into contact with the photosensitive drums 11, 12, 13, and 14. Yes. A developing bias voltage of AC + DC is applied to the developing roll 401 to develop the toner on the developing roll 401 into an electrostatic latent image formed on the photosensitive drums 11, 12, 13, and 14, whereby a toner image is formed. It is formed.

  Next, the cyan (C), magenta (M), yellow (Y), and black (K) toner images formed on the photosensitive drums 11, 12, 13, and 14 are the first primary intermediate. The secondary transfer is electrostatically performed on the transfer drum 51 and the second primary intermediate transfer drum 52. Cyan (C) and magenta (M) toner images formed on the photosensitive drums 11 and 12 are yellow (on the first primary intermediate transfer drum 51 and the photosensitive drums 13 and 14). The toner images of Y) and black (K) are transferred onto the second primary intermediate transfer drum 52, respectively. Accordingly, on the first primary intermediate transfer drum 51, the single color image transferred from either the photosensitive drum 11 or 12 and the two color toner images transferred from both the photosensitive drums 11 and 12 are superimposed. A double color image is formed. In addition, similar single-color images and double-color images are formed on the second primary intermediate transfer drum 52 from the photosensitive drums 13 and 14.

  The single-color or double-color toner images formed on the first and second primary intermediate transfer drums 51 and 52 in this way are electrostatically and tertiary-transferred onto the secondary intermediate transfer drum 53. Accordingly, a final toner image from a single color image to a quadruple color image of cyan (C), magenta (M), yellow (Y), and black (K) is formed on the secondary intermediate transfer drum 53. Will be.

  Next, a final toner image from a single color image to a quadruple color image formed on the secondary intermediate transfer drum 53 is tertiary-transferred to a transfer medium passing through the paper conveyance path P by the final transfer roll 60. Is done. The transferred material passes through a paper transporting roll 90 through a paper feeding process (not shown), and is fed into the nip portion between the secondary intermediate transfer drum 53 and the final transfer roll 60. After this final transfer step, the final toner image formed on the transfer medium is fixed by the fixing device 70, and a series of image forming processes is completed. The toner or the like adhering to the final transfer roll 60 is collected by a cleaning device 80 including a final cleaning member 801 such as a blade provided in contact with the final transfer roll 60.

  In a small-sized image forming apparatus that employs a cleaner-less system that has a contact-type charger that contacts the photoreceptor and gives a charge and does not have a photoreceptor cleaning system such as a cleaning blade, the polarity is opposite to that of toner. Since the free resin powder that is charged to the toner adheres to and accumulates on the charging member via the photoconductor, image quality defects due to poor charging are likely to occur along with the number of image outputs, so conventionally, before the printing operation, after the printing operation, A member cleaning process is required at a certain predetermined timing, such as every predetermined number of sheets during continuous printing, which has been an obstacle to a decrease in the number of images that can be continuously output and an increase in speed. However, by using the carrier according to this embodiment, it is possible to improve the number of continuous image outputs, increase the speed, and the like.

  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.

<Production of resin-coated carrier>
Example 1
15 parts by weight toluene solution of styrene methacrylate resin (styrene: methyl methacrylate = 20: 80 (molar ratio)) 100 parts by weight Carbon black (manufactured by Cabot, VXC72) 1 part by weight Cross-linked melamine resin particles (0.3 μm) 2 parts by weight Vinyl Antifoaming agent (Dispalon 1950, manufactured by Enomoto Kasei) 0.05 parts by weight The above components were dispersed by a batch type sand grinder mill (manufactured by IMEX, BSG type) to obtain a dispersion for forming a resin coating layer.

  As a carrier core material, a resin core layer-forming dispersion liquid is added to a ferrite core having a volume average particle diameter of 35 μm (EFC35, manufactured by Powder Tech Co., Ltd.) so that the solid content is 2% by weight with respect to the carrier core material. A resin-coated carrier 1 was obtained by coating with KHO type manufactured by Inoue Seisakusho. It was 50 ppm when the free resin powder of the obtained resin-coated carrier 1 was measured by the following method.

[Measurement method of free resin powder]
(1) About 50 g (up to the fourth decimal place) of the sample is accurately weighed, recorded (Cw), and placed in a 250 mL polypropylene (PP) bottle.
(2) Place the aluminum pan on the METTLER electronic balance, adjust the zero point, place the filter paper on the aluminum pan, weigh precisely (W1), and record.
(3) About 200 mL of 0.1% triton (polyoxyethylene (10) phenyl ether) aqueous solution is put into a PP bottle with a lid, and shaken with a tumbler mixer for 2 minutes.
(4) Remove the PP bottle from the Turbula mixer as soon as possible after shaking the Turbula, and transfer the supernatant to a beaker while holding the carrier with a magnet from the outside of the PP bottle.
(5) Repeat (3) to (4) above once again.
(6) While holding the carrier from the outside of the PP bottle, rinse the carrier in the PP bottle with ion-exchanged water and add it to the supernatant.
(7) Attach a suction filter bottle / vacuum suction filter to the aspirator, place the filter paper precisely weighed in (2) on the vacuum suction filter, and attach a vacuum suction filter holder.
(8) Filter the supernatant. Since there is a possibility that the sample is slightly mixed in the supernatant, it is filtered from the outside of the beaker while holding the carrier with a magnet.
(9) After completion of the filtration, the filter paper is placed on an aluminum dish and dried at a temperature of 50 ° C. to 60 ° C. in a controlled temperature drier for 1 hour or longer.
(10) After taking out from the dryer, it is allowed to cool for about 10 minutes, and the weight of the filter paper is precisely weighed (to the fourth decimal place) with an electronic balance (W2).
(11) The amount of free resin powder is calculated by the following formula.
Free resin powder amount = (W2-W1) / Cw × 1000000 [ppm]

The evaluation criteria were as follows.
◎: Less than 100 ppm ○: 100 ppm or more and less than 300 ppm Δ: 300 ppm or more and less than 500 ppm ×: 500 ppm or more

  The foam volume measured by the method for measuring the foam volume was 3 mL.

(Example 2)
Resin-coated carrier 2 was obtained in the same manner as in Example 1, except that the foam suppressor Disparon 1950 was replaced with an acrylic foam suppressor (Disparon OX-883, manufactured by Enomoto Kasei). It was 40 ppm when the free resin powder of the obtained resin coating carrier 2 was measured. Moreover, the foam volume measured by the said foam volume measuring method was 2 mL.

(Example 3)
Example 1 is the same as Example 1 except that the foam suppressor Disparon 1950 is replaced with a fluorine-based foam suppressor (telomeric alcohol (2,2,3,3-tetrafluoro-1-propanol), Showa Denko). Thus, a resin-coated carrier 3 was obtained. It was 150 ppm when the free resin powder of the obtained resin coating carrier 3 was measured. Moreover, the foam volume measured by the said foam volume measuring method was 5 mL.

Example 4
Resin-coated carrier 4 was obtained in the same manner as in Example 1 except that the foam suppressor Disparon 1950 was replaced with a silicone-based foam suppressor (Silicone Compound FS Antifoam DB-100, manufactured by Dow Corning) in Example 1. When the free resin powder of the obtained resin-coated carrier 4 was measured, it was 130 ppm. Moreover, the foam volume measured by the said foam volume measuring method was 3 mL.

(Example 5)
In Example 1, the styrene methacrylate resin was used as a perfluorooctylethyl methacrylate / methyl methacrylate copolymer (copolymerization ratio (molar ratio) 40/60), and the foam inhibitor Disparon 1950 was used as a fluorine foam inhibitor (telomeric alcohol (2 Resin-coated carrier 5 was obtained in the same manner as in Example 1 except that the product was changed to (2,2,3-tetrafluoro-1-propanol) and Showa Denko). It was 70 ppm when the free resin powder of the obtained resin coating carrier 5 was measured. Moreover, the foam volume measured by the said foam volume measuring method was 5 mL.

(Comparative Example 1)
Resin-coated carrier 6 was obtained in the same manner as in Example 1 except that no foam suppressor (Disparon 1950) was added. It was 450 ppm when the free resin powder of the obtained resin coating carrier 6 was measured.

(Comparative Example 2)
A resin-coated carrier 7 was obtained in the same manner as in Example 5 except that no foam suppressor (telomeric alcohol) was added. It was 800 ppm when the free resin powder of the obtained resin-coated carrier 7 was measured.

(Comparative Example 3)
A resin-coated carrier 8 was obtained in the same manner as in Example 1 except that the foam suppressor Disparon 1950 in Example 1 was replaced with ethanol (Wako Pure Chemicals), which is a foam breaker. It was 400 ppm when the free resin powder of the obtained resin coating carrier 8 was measured. Moreover, the foam volume measured by the said foam volume measuring method was 15 mL.

(Comparative Example 4)
A resin-coated carrier 9 was obtained in the same manner as in Example 1 except that the foam suppressor Disparon 1950 was replaced with a surfactant (Dowfax 2A1 manufactured by Dow Chemical Co., Ltd.) as a foam breaker. It was 700 ppm when the free resin powder of the obtained resin-coated carrier 9 was measured. Moreover, the foam volume measured by the said foam volume measuring method was 20 mL.

<Production of toner>
A toner was prepared by the method described in Japanese Patent No. 3661422. The volume average particle size of the toner was 6.0 μm.

<Production of developer>
Resin-coated carriers 1 to 9 were mixed with the toner and a V blender to obtain developers 1 to 9, respectively.

<Evaluation>
About the obtained developers 1 to 9, high temperature and high humidity environment conditions of 28 ° C./85% RH in an image forming apparatus (Fuji Xerox, DocuPrint C1616 type) adopting a cleanerless system that does not have a photoconductor cleaning device. Then, an image formation test was performed by outputting 100 images of CMYK color image area coverage of 5% and a total of 20% continuously. The results are shown in Table 1.

  As described above, the developers 1 to 5 of Examples 1 to 5 obtained good images continuously until the end. However, the developers 6 and 8 of Comparative Examples 1 and 3 started from around 50 sheets. A large number of density unevenness occurred in the solid portion, and color streaks occurred on the entire surface after exceeding 70 sheets. As a result of checking the image forming apparatus, dirt was adhered to the charger in contact with the photosensitive member, and when the charger was cleaned, a good image was obtained. Further, in Developers 7 and 9 of Comparative Examples 2 and 4, a large number of density unevenness occurred in the solid portion from around 30 sheets, and color streaks occurred on the entire surface from around 50 sheets. As a result of checking the image forming apparatus, dirt was adhered to the charger in contact with the photosensitive member, and when the charger was cleaned, a good image was obtained.

1 is a schematic diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. It is the schematic which shows the other example of the image forming apparatus which concerns on embodiment of this invention.

Explanation of symbols

  1, 2, 3, 4 Image forming unit 11, 12, 13, 14 Photosensitive drum (image carrier) 21, 22, 23, 24 Charging roll (contact type charging device) 31, 32, 33, 34 Laser light, 41, 42, 43, 44 Developing device (two-component developing means), 51, 52 Primary intermediate transfer drum (intermediate transfer member), 53 Secondary intermediate transfer drum (intermediate transfer member), 60 Final transfer roll (final) Transfer rotator), 70 fixing device, 80 cleaning device, 90 paper transport roll, 100 optical density sensor (detection means), 300 control circuit (process control means), 401 development roll, 402 developer amount regulating member, 403 paddle, 404 Auger, 500 Image forming apparatus, 502 Charging unit, 504 Exposure unit, 506 Electrophotographic photosensitive member, 508 Development unit, 510 Transfer unit, 512 Leaning unit, 514 a fixing unit, 516 a transfer member, 801 a final cleaning member.

Claims (4)

Including a carrier core material and a resin coating layer,
A carrier for developing an electrostatic charge image, wherein the resin coating layer contains a foam suppressant. The electrostatic charge image developing carrier according to claim 1,
The electrostatic charge image developing carrier, wherein the antifoaming agent is at least one of a vinyl antifoaming agent, an acrylic antifoaming agent and a fluorine antifoaming agent.   An electrostatic charge image developing developer comprising the electrostatic charge image developing carrier according to claim 1 and an electrostatic charge image developing toner. An image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the image carrier, a developing unit that develops the electrostatic latent image using a developer to form a toner image, and the development A transfer means for transferring the toner image thus transferred to a transfer medium,
An image forming apparatus, wherein the developer is the developer for developing an electrostatic image according to claim 3.

Images