JP2011070075A - Positively-charged two-component developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positively-charged two-component developer that prevents reduction of the charged amount of toner and suppresses occurrence or the like of fogging even when image forming is performed for a long time, and forms a high definition image for a long time. <P>SOLUTION: The positively-charged two-component developer includes a toner and a carrier. The toner contains toner mother particles containing a binding resin and colorant, and an external additive added to the toner mother particles. The external additive contains surface treated particles produced by treating the surfaces of metal oxide fine particles with a first surface treating agent containing a positively-charged treating agent and then treating them with a second surface treating agent containing a negatively-charged treating agent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a positively charged two-component developer containing a toner and a carrier.

  An image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile machine, and a multi-function machine of these is developed by a developing device on the surface of a photosensitive drum on which an electrostatic latent image based on image data is formed. A toner image is formed by supplying the toner. Then, the toner image formed on the photosensitive drum is transferred onto a predetermined sheet by a transfer device or the like. Then, the transferred toner image is fixed on a sheet by being pressed and heated by a fixing device, and an image based on the image data is formed on the sheet.

  Examples of the developing device provided in such an image forming apparatus include one using a one-component developer containing toner and not containing a carrier, and one using a two-component developer containing toner and a carrier. Such a developing device charges the toner by stirring the developer in advance before supplying the toner to the surface of the photosensitive drum. In the case of a developing device using a two-component developer, when the developer is stirred, the toner is stirred in the presence of the carrier. Therefore, a developing device using a two-component developer is preferably used as compared with a developing device using a one-component developer because it is easier to secure the charge amount of the toner.

  However, in the case of a developing device using a two-component developer, it is easy to secure the charge amount of the toner, and it is easy to obtain a high-quality image as an image to be formed. It is known that the image quality tends to decrease, fogging due to the toner of the developer tends to occur, and a good image tends to be difficult to form.

  Examples of such a two-component developer include those described in Patent Documents 1 to 3.

  Patent Document 1 discloses that positively charged host particles having a volume average particle diameter of 5 to 10 μm mainly composed of a binder resin, a colorant, a desorbed fatty acid type carnauba wax, and a quaternary ammonium salt, A toner in which an additive that reduces the charge amount of the base particles when mixed with another additive that increases the charge amount of the base particles when mixed with the base particles, and a silicone resin on the surface A two-component dry developer composed of a carrier provided with a coating layer containing a conductive substance and an alkoxysilane coupling agent having a chlorine group therein is described.

  Further, in Patent Document 2, in a two-component developer containing at least a binder resin, a colorant, a toner containing a release agent and a carrier, (i) the binder resin contains at least a polyester unit, ii) The transmittance B (%) of the toner in a 45 volume% methanol aqueous solution is in the range of 10 ≦ B ≦ 70, and (iii) the endothermic curve in the differential thermal analysis (DSC) measurement of the toner has a temperature of 30 to One or a plurality of endothermic peaks in the range of 110 ° C., and the temperature Tsc of the maximum endothermic peak in the endothermic peak is 65 ° C. <Tsc <105 ° C. (iv) the carrier is a resin coating layer and a resin A two-component developer containing fine particles is described.

  In Patent Document 3, in a developer for developing an electrostatic charge image containing a carrier having a resin coating layer on a carrier core material and a toner, the carrier contains 7 to 35 silica or carbon black in the resin coating layer. An electrostatic charge image comprising, in mass%, an external additive fine particle having a weight average molecular weight (Mw) of 300 to 600,000 and a number average particle diameter of 70 to 300 nm. Developers for development are described.

  Note that the developers described in Patent Document 2 and Patent Document 3 are not positively charged developers but negatively charged developers.

Japanese Patent Laid-Open No. 5-232740 JP 2005-24580 A JP 2008-304745 A

  When the present inventor reaches the present invention and forms an image over a long period in a developing device using a two-component developer, the charge amount of the toner is reduced and the developer is likely to be fogged by the toner. The reason for the difficulty in forming a good image was presumed as follows.

  When a developing device using a two-component developer, for example, a two-component developing device, forms an image, first, the two-component developer is brought into contact with a developing roller that is disposed facing the photosensitive drum and includes a magnet. Let By doing so, a magnetic brush made of a two-component developer is formed on the developing roller, where the carrier is continuous in a spike shape and the toner is attached to the carrier. Then, by bringing the magnetic brush into contact with the photosensitive drum, toner is supplied to the surface of the photosensitive drum on which the electrostatic latent image based on the image data is formed, and a toner image based on the image data is formed. For this reason, when the two-component developing device forms an image, the toner is used and a new toner is replenished to form an image over a long period of time. On the other hand, the same carrier is repeatedly used even if image formation is performed over a long period of time. From this, for example, it is considered that the toner component adheres to the surface of the carrier, carrier spent, etc. occur, and the charge imparting performance (charge imparting ability) of the carrier gradually decreases.

  Further, as a developing device using a two-component developer, for example, a two-component developer that is provided in the developing device is temporarily held by a magnetic roller including a magnet, and the two-component developer held by the magnetic roller is used. Examples include a so-called hybrid development type developing device that forms a toner image on the photosensitive drum by transferring only the toner to the developing roller and causing the toner transferred to the surface of the developing roller to fly to the photosensitive drum. Even in such a developing device of the hybrid developing system, since the same carrier is repeatedly used, it is considered that the same problem as the above two-component developing device occurs.

  According to Patent Documents 1 to 3, it is described that carrier spent can be suppressed. However, even with these developers, it is difficult to maintain the charge amount of the toner, fogging of the developer with the toner tends to occur, and it may be difficult to form a high-quality image over a long period of time. It was. Specifically, for example, when toner particles having a small particle size are used as toner base particles in order to form a high-quality image, it is difficult to form a high-quality image over a long period of time. It was. In particular, when high density printing with a high printing rate is performed, that is, when the amount of toner used per unit driving time is large and the amount of toner replenishment is large, the toner charge amount tends to decrease, and the developer toner There was a strong tendency for fogging and the like to occur.

  This is presumed by the inventors as follows.

  When using toner base particles having a reduced particle size, the amount of the external additive added to the toner base particles is often increased in order to ensure the fluidity and developability of the toner. As the external additive, one having the same polarity as the toner base particles and the opposite polarity to the carrier is generally used. For this reason, it is considered that when the amount of the external additive is increased, the external additive is detached from the toner base particles and easily moves to the carrier, and the carrier spent as described above is likely to occur.

  The present invention has been made in view of such circumstances, and even when image formation is performed over a long period of time, the toner charge amount is unlikely to decrease, and occurrence of fogging can be suppressed. An object of the present invention is to provide a positively charged two-component developer capable of forming a clear image.

  The positively charged two-component developer according to one aspect of the present invention is a positively charged two-component developer including a toner and a carrier, wherein the toner includes toner base particles containing a binder resin and a colorant, An external additive externally added to the toner base particles, and the external additive treats the surface of the metal oxide fine particles with a first surface treatment agent containing a positive charge treatment agent, and then a negative charge treatment agent. It contains surface-treated particles treated with a second surface treating agent containing

  According to the above configuration, even when image formation is performed over a long period of time, the toner charge amount is unlikely to decrease, and the occurrence of fogging can be suppressed. Therefore, a high-quality image can be formed over a long period of time. A positively charged two-component developer can be provided.

  This is considered to be due to the following.

  In the toner constituting the positively charged two-component developer, an external additive is externally added to the toner base particles. This external additive is not so much embedded in the toner base particles in the so-called initial state, such as before stirring the positively charged two-component developer or immediately after the start of stirring, and is released from the toner base particles. It is considered easy.

  Further, as the external additive, the surface of the metal oxide fine particles is not only treated with the first surface treatment agent containing the positive charge treatment agent, but then the second surface treatment agent containing the negative charge treatment agent. Therefore, it is considered that the positive chargeability of the external additive is lowered by the treatment with the negative charge treatment agent.

  Therefore, when the positively charged two-component developer is in the initial state, the positive chargeability of the external additive is lowered, but the external additive is difficult to separate from the positively charged toner base particles and is negatively charged. It is thought that it becomes difficult to shift to the career that has been.

  On the other hand, as the positively charged two-component developer is stirred, the coating formed on the surface of the external additive by the treatment with the second surface treating agent containing the negatively charged treating agent is peeled off. It is considered that the film formed by the treatment with the first surface treating agent containing selenium is exposed. Therefore, when the toner constituting the positively charged two-component developer is used for image formation, the positive chargeability of the external additive externally added to the toner base particles increases, and the external additive is suitable for positive charging. It is thought that it will be possible to demonstrate sex.

  At that time, it is considered that the external additive is embedded in the toner base particles by stirring of the positively charged two-component developer and is not easily detached from the toner base particles.

  Therefore, it is considered that the external additive is in a state where the external additive has a low positive chargeability and is difficult to separate in an initial state in which the external additive is easily detached. Further, when the positively charged two-component developer is agitated and the toner constituting the positively charged two-component developer is used for image formation, the external additive is difficult to be separated, and the external additive is also an external additive. It is thought that it is in the state which can exhibit suitable positive chargeability as. Therefore, it is considered that the occurrence of carrier spent can be suppressed while providing positive chargeability suitable as an external additive, and the decrease in charge imparting performance of the carrier is suppressed.

  For these reasons, it is considered that even when image formation is performed over a long period of time, the charge amount of the toner is less likely to be reduced and the occurrence of fogging can be suppressed, and thus a high-quality image can be formed over a long period of time. .

  In addition, when the positively charged two-component developer is used, high density printing with a high printing rate is performed, that is, the amount of toner used per unit driving time is large and the amount of toner replenishment is large. However, it is difficult for the charge amount of the toner to decrease, and the occurrence of fogging can be suppressed, so that a high-quality image can be formed over a long period of time.

  Moreover, it is preferable that ratio of the said positive charge processing agent and the said negative charge processing agent is 3: 2-9: 1 by mass ratio. According to such a configuration, even when image formation is performed over a long period of time, the charge amount of the toner is less likely to decrease, and the occurrence of fogging and the like can be further suppressed. Accordingly, a higher quality image can be formed over a long period of time. A positively charged two-component developer that can be provided can be provided.

  This means that when the positively charged two-component developer is in the initial state, the mass ratio is a state in which the external additive is less likely to be separated from the toner base particles. When the toner to be used is used for image formation, it is considered that the ratio is such that an external additive capable of exhibiting the positive chargeability of the external additive more appropriately is obtained.

  Moreover, it is preferable that the said positive charge processing agent is a silane coupling agent which has an amino group in a molecule | numerator. According to such a configuration, it is possible to provide a positively charged two-component developer capable of forming a higher quality image over a long period of time. This is considered due to the fact that an external additive capable of exhibiting positive chargeability more suitable as an external additive is obtained.

  Moreover, it is preferable that the said negative charge processing agent is a silane coupling agent which has a fluorine in a molecule | numerator. According to such a configuration, even when image formation is performed over a long period of time, the charge amount of the toner is less likely to decrease, and the occurrence of fogging and the like can be further suppressed. Accordingly, a higher quality image can be formed over a long period of time. A positively charged two-component developer that can be provided can be provided. This is presumably because the external additive is less likely to be transferred by the carrier by containing surface-treated particles treated with a silane coupling agent having fluorine in the molecule as the external additive.

  Moreover, it is preferable that the first surface treatment agent contains a hydrophobic treatment agent. According to such a configuration, even when image formation is performed over a long period of time, the charge amount of the toner is less likely to decrease, and the occurrence of fogging and the like can be further suppressed. Accordingly, a higher quality image can be formed over a long period of time. A positively charged two-component developer that can be provided can be provided.

  This means that many of the positive charge treatment agents have low hydrophobicity. Specifically, for example, a silane coupling agent having an amino group in the molecule, which is an example of the positive charge treatment agent, is hydrophobic. Is thought to be due to the low. It is considered that the external additive treated with such a low-hydrophobic positively charged treating agent has low hydrophobicity. Therefore, when such an external additive having low hydrophobicity is externally added, the charge amount of the toner tends to decrease in a high temperature and high humidity environment. For this reason, when the first surface treatment agent is treated with the one containing the hydrophobic treatment agent, a highly hydrophobic external additive can be obtained. By adding, it is considered that a decrease in the charge amount of the toner can be suppressed.

  The hydrophobizing agent is preferably a silane coupling agent having a hydrophobic group in the molecule.

  According to the present invention, even when an image is formed over a long period of time, the charge amount of the toner is less likely to be reduced, and the occurrence of fogging can be suppressed. Thus, a positive charge capable of forming a high-quality image over a long period of time. A two-component developer can be provided.

2 is a schematic diagram illustrating the periphery of an image forming unit of the image forming apparatus 100. FIG. FIG. 2 is a cross-sectional view illustrating a developing device that is an example of a developing device provided in the image forming apparatus. 4 is a cross-sectional view showing a developing device 35 as another example of a developing device provided in the image forming apparatus 100. FIG.

  Hereinafter, although the embodiment concerning the present invention is described, the present invention is not limited to these.

[Positively charged two-component developer]
The positively charged two-component developer according to one aspect of the present invention is a positively charged two-component developer including a toner and a carrier, and the toner includes toner base particles containing at least a binder resin and a colorant; An external additive externally added to the toner base particles, and the external additive treats the surface of the metal oxide fine particles with a first surface treatment agent containing a positive charge treatment agent, and then performs a negative charge treatment. It contains surface-treated particles treated with a second surface treatment agent containing an agent.

<Toner base particles>
The toner base particles are not particularly limited as long as they contain at least a binder resin and a colorant and can be used as toner base particles. The toner base particles preferably have a volume average particle size of 3 to 9 μm. Here, the volume average diameter can be measured, for example, by measurement using a laser diffraction scattering method or the like, or measurement using a general particle size meter.

(Binder resin)
The binder resin can be used without particular limitation as long as it is conventionally used as a binder resin for toner base particles. Specifically, for example, polystyrene resins such as styrene-acrylic copolymers and styrene-butadiene resins; acrylic resins; polyethylene resins; polypropylene resins; vinyl chloride resins; polyester resins; Examples include polyurethane resins; polyvinyl alcohol resins; vinyl ether resins; N-vinyl resins. Among these, polyester resins are preferably used because they are excellent in low-temperature fixability and have a wide non-offset temperature range. Moreover, as said binder resin, each said binder resin may be used independently, and may be used in combination of 2 or more type.

  Examples of the polyester-based resin include those obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component. Moreover, the following are mentioned as a component used when synthesize | combining a polyester-type resin.

  The alcohol component is not particularly limited as long as it can be used as an alcohol for synthesizing a polyester resin. In addition, the alcohol component needs to contain an alcohol having 2 or more hydroxyl groups (divalent or higher alcohol) in the molecule. Specific examples of the divalent alcohol among those used as the alcohol component include, for example, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4- Butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol Diols such as bisphenol A, hydrogenated bisphenol A, bisphenols such as polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A, and the like. Further, among the alcohols used as the alcohol component, as the trivalent or higher alcohol, specifically, for example, sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dithiol Pentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, tri Examples include methylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene and the like. Moreover, as said alcohol component, said each component may be used independently and may be used in combination of 2 or more type.

  The carboxylic acid component is not particularly limited as long as it can be used as a carboxylic acid for synthesizing a polyester resin. The carboxylic acid component includes not only carboxylic acids but also acid anhydrides and lower alkyl esters of carboxylic acids. And as said carboxylic acid component, the carboxylic acid needs to contain what has two or more hydroxyl groups in a molecule | numerator (carboxylic acid more than bivalence). Specific examples of the divalent carboxylic acid used as the carboxylic acid include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and cyclohexanedicarboxylic acid. Examples include acids, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, alkyl succinic acid, and alkenyl succinic acid. Examples of the alkyl succinic acid include n-butyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid, isododecyl succinic acid and the like. Examples of the alkenyl succinic acid include n-butenyl succinic acid and isobutyl succinic acid. , Isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, isododecenyl succinic acid and the like. Further, among the carboxylic acids used as the carboxylic acid, the trivalent or higher carboxylic acid specifically includes, for example, 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid. Acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2 -Methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empole trimer acid, etc. Can be mentioned. Moreover, as said carboxylic acid component, said each component may be used independently and may be used in combination of 2 or more type.

  The polystyrene resin may be a styrene homopolymer or a copolymer with another copolymerizable monomer copolymerizable with styrene. Examples of the copolymerizable monomer include p-chlorostyrene; vinyl naphthalene; olefinic hydrocarbons (alkene) such as ethylene, propylene, butylene, and isobutylene; vinyl halides such as vinyl chloride, vinyl bromide, and vinyl fluoride; vinyl acetate. Vinyl esters such as vinyl propionate, vinyl benzoate, vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate Acrylic esters such as phenyl acrylate and methyl α-chloroacrylate; methacrylic esters such as methyl methacrylate, ethyl methacrylate and butyl methacrylate; acrylics such as acrylonitrile, methacrylonitrile and acrylamide Derivatives; Vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrole N-vinyl compounds, such as den, etc. are mentioned. Among these, acrylic ester is preferable and n-butyl acrylate is more preferable from the viewpoint of excellent low-temperature fixability, charging stability, and environmental stability. Moreover, as said copolymerization monomer, said each monomer may be used independently and may be used in combination of 2 or more type. The polystyrene resin preferably has two weight average molecular weight peaks (a low molecular weight peak and a high molecular weight peak). Specifically, for example, the low molecular weight peak is preferably in the range of 3000 to 20000, and the other high molecular weight peak is preferably in the range of 300000 to 1500,000. Furthermore, it is preferable that Mw / Mn is 10 or more for the weight average molecular weight (Mw) and the number average molecular weight (Mn). If the weight average molecular weight peak is within such a range, the toner can be easily fixed, and offset resistance can be improved.

  As the binder resin, it is preferable to use the thermoplastic resin as described above from the viewpoint of fixability, but it is not necessary to use only the thermoplastic resin, and a crosslinking agent or a thermosetting resin is combined with the thermoplastic resin. May be used. Thus, by introducing a partially crosslinked structure into the binder resin, it is possible to improve the storage stability, shape retention, durability, and the like of the toner while suppressing a decrease in fixability.

(Coloring agent)
As the colorant, a known pigment or dye can be used so as to obtain a desired color as the toner. Specifically, for example, the following colorants may be mentioned depending on the color. Examples of the black pigment include carbon black such as acetylene black, run black, and aniline black. Examples of yellow pigments include yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, and Benzidine Yellow. GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. And CI Pigment Yellow 180. Examples of the orange pigment include reddish yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK and the like. Red pigments include Bengala, cadmium red, red lead, mercury cadmium sulfide, permanent red 4R, risor red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, Brilliant Carmine 3B, C.I. I. Pigment red 238 and the like. Examples of purple pigments include manganese purple, fast violet B, and methyl violet lake. Examples of blue pigments include bitumen, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, fast sky blue, induslen blue BC, C.I. I. And CI Pigment Blue 15: 3 (copper phthalocyanine blue pigment). Examples of the green pigment include chrome green, chromium oxide, pigment green B, malachite green lake, and final yellow green G. Examples of white pigments include zinc white, titanium oxide, antimony white, zinc sulfide, barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white. For example, as a colorant for cyan toner, C.I. I. Pigment Blue 15: 3 (copper phthalocyanine blue pigment) is preferred.

  The addition amount of the colorant is generally 1 to 10 parts by mass with respect to 100 parts by mass of the binder resin in order to achieve a suitable image density, and 3 to 7 parts by mass. Preferably there is.

(Charge control agent)
The toner base particles generally contain a charge control agent in order to improve chargeability and the like. Further, since the toner is a toner constituting the positively charged two-component developer, that is, a positively chargeable toner, the charge control agent has conventionally been positively charged among the charge control agents of toner base particles. As long as it is used as the charge control agent shown, it can be used without particular limitation. Specific examples thereof include a nigrosine compound, a quaternary ammonium salt compound, and a charge control agent exhibiting positive charge, such as a resin type charge control agent in which an amine compound is bonded to a resin. Further, the amount of the charge control agent added is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, with respect to 100 parts by mass of the binder resin. When the amount of the charge control agent added is too small, it becomes difficult to stably charge the toner to a predetermined polarity, and fog tends to occur. On the other hand, when the amount of the charge control agent added is too large, there is a tendency that defects such as contamination of the photoconductor tend to occur due to environmental resistance, in particular, poor charging under high temperature and high humidity, and defective images.

(wax)
The toner base particles generally contain a wax in order to improve fixability and offset property. The wax is not particularly limited as long as it is conventionally used as a wax for toner base particles. Specific examples include, for example, plant waxes such as carnauba wax, sugarcane wax, and wood wax; animal waxes such as beeswax, insect wax, whale wax, and wool wax; Fischer-Tropsch (hereinafter referred to as “FT”) And synthetic hydrocarbon waxes such as wax, polyethylene wax and polypropylene wax. Among these, synthetic hydrocarbon waxes such as FT wax and carnauba wax are preferable, and carnauba wax is more preferable because of excellent dispersibility in the binder resin. The added amount of the wax is preferably 0.5 to 10 parts by mass, and more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the binder resin. When the addition amount is too small, there is a tendency that sufficient wax effect cannot be obtained. When the addition amount is too large, the blocking resistance is lowered and the toner may be detached.

(Production method)
The method for producing the toner base particles is not particularly limited, but can be produced, for example, as follows.

  First, the components of the toner base particles such as the binder resin and the colorant are mixed with a mixer or the like. As the mixer, a known one can be used, and examples thereof include a Henschel type mixing device such as a Henschel mixer, a super mixer, and a mechano mill, an ang mill, a hybridization system, and a cosmo system.

  Next, the obtained mixture is melt-kneaded with a kneader or the like. A well-known thing can be used as said kneading machine, For example, a twin-screw extruder, a three roll mill, a lab blast mill etc. are mentioned, A twin-screw extruder is used suitably. Further, the temperature at the time of melt kneading is preferably a temperature that is not lower than the softening point of the binder resin and lower than the thermal decomposition temperature of the binder resin.

  Next, the obtained melt-kneaded product is cooled to form a solid, and the solid is pulverized by a pulverizer or the like. As the pulverizer, known pulverizers can be used. For example, an air pulverizer such as a jet pulverizer (jet mill) that pulverizes using a supersonic jet stream, a mechanical pulverizer such as a turbo mill, or an impact pulverizer. Examples thereof include a pulverizer, and a mechanical pulverizer, particularly a turbo mill, is preferably used.

  Finally, the obtained pulverized product is classified with a classifier or the like. By classification, excessively pulverized material and coarse powder can be removed, and desired toner base particles can be obtained. As the classifier, known ones can be used, for example, a wind classifier such as a swirl wind classifier (rotary wind classifier) such as an elbow jet, a centrifugal classifier, and the like. In particular, an elbow jet is preferably used.

<External additive>
As the external additive, the surface of the metal oxide fine particles is treated with a first surface treatment agent containing a positive charge treatment agent and then treated with a second surface treatment agent containing a negative charge treatment agent. Containing.

  The surface treatment particles are not particularly limited as long as they are treated with the first surface treatment agent containing a positive charge treatment agent and then treated with a second surface treatment agent containing a negative charge treatment agent. Specifically, what was obtained as follows is mentioned, for example. First, a first surface treatment agent containing a positive charge treatment agent is added to metal oxide fine particles and heated and stirred, and then a second surface treatment agent containing a negative charge treatment agent is added and heated and stirred. The obtained particles and the like are exemplified as the surface-treated particles. In addition, the manufacturing method of the said surface treatment particle | grain is mentioned later.

  Examples of the metal oxide fine particles before the treatment with the first surface treatment agent include silica particles, alumina particles, titanium oxide particles, zinc oxide particles, magnesium oxide particles, and strontium titanate particles. Among these, silica particles are preferable from the viewpoint of high fluidity. Moreover, as said metal oxide fine particle, said each metal oxide fine particle may be used independently, and may be used in combination of 2 or more type.

  The metal oxide fine particles are preferably spherical, and the particle diameter is preferably 7 to 100 nm, more preferably 15 to 50 nm in terms of volume average diameter. Here, the volume average diameter can be measured, for example, by measurement using a laser diffraction scattering method or the like, or measurement using a general particle size meter. If the particle diameter of the metal oxide fine particles is too small, the metal oxide particles tend to be embedded in the toner base particles, and when the toner is stressed (during low density printing), the image density tends to decrease. Further, if the particle diameter of the metal oxide fine particles is too large, the fluidity of the toner tends to decrease.

  The first surface treatment agent is not particularly limited as long as it contains a positive charge treatment agent. Specifically, it is preferable that a hydrophobizing agent is contained. Moreover, the solvent (diluent) for diluting the said positive charge processing agent may contain.

The positive charging agent is not particularly limited as long as it can introduce positively charged polar groups into the metal oxide fine particles. Examples of the positively charged polar group include an amino group. Examples of the positive charging agent include a silane coupling agent having a hydrolyzable group such as an alkoxy group or a halogen group in the molecule. Therefore, specific examples of the positive charging agent include a silane coupling agent having an amino group in the molecule. More specifically, for example, H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (OCH ₃ ) ₃ , H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (CH ₃ ) (OCH ₃ ) ₂ , H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (OCH ₃ ) ₃ , H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (OCH ₃ ) ₃ , H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ , and C ₆ H ₅ NH (CH ₂ ) ₃ Si (OCH ₃ ) ₃ . Moreover, as said positive charge processing agent, said each positive charge processing agent may be used independently, and may be used in combination of 2 or more type.

  The amount of the positive charging agent introduced is preferably 5 to 25 parts by mass and more preferably 10 to 20 parts by mass with respect to 100 parts by mass of the metal oxide fine particles. If the introduction amount of the positive charging agent is too small, the positive chargeability of the external additive tends to be insufficient. In addition, if the amount of the positive charge treatment agent introduced is too large, the external additive is detached from the toner base particles even if the treatment with the negative charge treatment agent is performed after the treatment with the positive charge treatment agent. There is a tendency that the so-called carrier spent that shifts to cannot be sufficiently suppressed.

The hydrophobizing agent is not particularly limited as long as it can introduce a hydrophobic group into the metal oxide fine particles. Examples of the hydrophobic group include an alkyl group and an alkoxy group. Examples of the hydrophobic treatment agent include a silane coupling agent having a hydrolyzable group such as an alkoxy group or a halogen group in the molecule. Therefore, specific examples of the hydrophobizing agent include a silane coupling agent having the hydrophobic group in the molecule. The hydrophobic group and the hydrolyzable group may be the same functional group. More specifically, for example, CH ₃ SiCl ₃ , (CH ₃ ) ₂ SiCl ₂ , (CH ₃ ) ₃ SiCl, CH ₃ Si (OCH ₃ ) ₃ , CH ₃ Si (OCH ₂ CH ₃ ) ₃ , (CH ₃ ) ₃ Si (OCH ₃ ), (CH ₃ ) ₂ Si (OCH ₃ ) ₂ , (CH ₃ ) ₂ Si (OCH ₂ CH ₃ ) ₂ , (CH ₃ CH ₂ O) Si (OCH ₂ CH ₃ ) ₃ , (CH ₃ O) Si (OCH ₃ ) ₃ , CH ₃ (H) Si (OCH ₃ ) ₂ , CH ₃ (H) Si (OCH ₂ CH ₃ ) ₂ , (CH ₃ ) ₂ (H) Si (OCH ₂ CH ₃ ) and the like. Moreover, as said hydrophobic treatment agent, said each hydrophobic treatment agent may be used independently, and may be used in combination of 2 or more type.

  The introduction amount of the hydrophobizing agent is preferably 10 to 30 parts by mass, and more preferably 15 to 25 parts by mass with respect to 100 parts by mass of the metal oxide fine particles. If the introduction amount of the hydrophobizing agent is too small, the external additive is not sufficiently hydrophobic, and the charge amount of the toner tends to decrease in a high temperature and high humidity environment. Further, if the amount of the hydrophobic treatment agent introduced is too large, the metal oxide fine particles tend to aggregate during the hydrophobic treatment.

  In addition, the solvent contained in the first surface treatment agent is not particularly limited as long as it dissolves the positive charge treatment agent and does not inhibit the treatment with the positive charge treatment agent. Specific examples include tetrahydrofuran, toluene, ethyl acetate, methyl ethyl ketone, and acetone.

  The second surface treatment agent is not particularly limited as long as it contains a negative charge treatment agent. The second surface treatment agent may contain components other than the negative charge treatment agent. For example, the second surface treatment agent may contain a solvent (diluent) for diluting the negative charge treatment agent.

The negative charge treating agent is not particularly limited as long as the negatively charged polar group can be introduced into the metal oxide fine particles into which the positively charged polar group is introduced. Examples of the negatively charged polar group include a group having a fluorine atom such as a fluoroalkyl group. Examples of the negative charging agent include a silane coupling agent having a hydrolyzable group such as an alkoxy group or a halogen group in the molecule. Therefore, specific examples of the negative charging agent include a silane coupling agent having fluorine in the molecule. More specifically, for example, CF ₃ (CH ₂ ) ₂ SiCl ₃ , CF ₃ (CH ₂ ) ₅ SiCl ₃ , CF ₃ (CF ₂ ) ₅ (CH ₂ ) ₂ SiCl ₃ , CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ SiCl ₃ , CF ₃ (CF ₂ ) ₇ CH ₂ CH ₂ Si (OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ Si (CH ₃ ) Cl ₃ , CF ₃ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ , CF ₃ (CH ₂ ) ₂ Si (CH ₃ ) (OCH ₃ ) ₂ , CF ₃ (CF ₂ ) ₃ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₅ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₆ CONH (CH ₂ ) ₂ Si (OC ₂ H ₅ ) ₃ , CF ₃ (CF ₂ ) ₆ COO (CH ₂ ) ₂ Si (OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ , CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ Si (CH ₃ ) (OCH ₃ ) ₂ , CF ₃ (CF _{2) 7 SO 2 NH (CH2} ) 3 Si (OC 2 H 5) 3, CF 3 (CF 2) 8 (CH 2) 2 Si (OCH 3) 3 and the like. Moreover, as said negative charge processing agent, said each negative charge processing agent may be used independently, and may be used in combination of 2 or more type.

  The introduction amount of the negative charge treatment agent is preferably such an introduction amount that the ratio of the positive charge treatment agent to the negative charge treatment agent is 3: 2 to 9: 1 by mass ratio. If the introduction amount of the negative charging agent is too small, the so-called carrier spent, which is the external additive is detached from the toner base particles and transferred to the carrier, cannot be sufficiently suppressed. On the other hand, if the introduction amount of the negative charging agent is too large, the positive chargeability of the external additive becomes too low, and the image quality of the formed image tends to be lowered.

  The solvent contained in the second surface treatment agent is not particularly limited as long as it dissolves the negative charge treatment agent and does not inhibit the treatment with the negative charge treatment agent. Specific examples include tetrahydrofuran, toluene, ethyl acetate, methyl ethyl ketone, and acetone.

  The method for producing the surface-treated particles is not particularly limited as long as the metal oxide fine particles are treated with the first surface treatment agent and then treated with the second surface treatment agent. Specific examples of the treatment with each surface treatment agent include treatment by the following method. In addition, although it demonstrates by the case where a 1st surface treating agent is used, even if it uses a 2nd surface treating agent, it can carry out by the same method.

  First, the first surface treatment agent is added dropwise or sprayed to the metal oxide fine particles that are forcibly stirred by a mixer or the like, and sufficiently mixed. The resulting mixture is then placed in an oven, heated and dried thoroughly. Then, the dried mixture is forcibly stirred again with a mixer or the like to be crushed. By doing so, metal oxide fine particles treated with the first surface treating agent are obtained. As described above, the first surface treatment agent may contain a solvent (diluent).

  As another method, as the first surface treatment agent, a solution in which the positive charge treatment agent is dissolved in an organic solvent is used, and the metal oxide fine particles are immersed in the solution. Thereafter, the mixture obtained by dipping is placed in an oven, heated and sufficiently dried. Then, the dried mixture is forcibly stirred with a mixer or the like to be crushed. By doing so, metal oxide fine particles treated with the first surface treating agent are obtained.

  In addition, each introduction amount of the positive charge treatment agent, the negative charge treatment agent, and the hydrophobic treatment agent is the amount of each treatment agent charged with respect to 100 parts by mass of the metal oxide fine particles at the time of manufacturing the surface treatment particles. It is.

  Further, the surface-treated particles are preferably contained in an amount of 0.1 to 4 parts by mass, and more preferably 0.5 to 3 parts by mass with respect to 100 parts by mass of the toner base particles. When the content of the surface-treated particles with respect to the toner base particles is too small, there is a tendency that the fluidity of the toner cannot be ensured. In addition, when the content of the surface treatment particles in the toner base particles is too large, the surface treatment particles tend to be separated from the toner base particles and contaminate the carrier.

  The external additive may contain an external additive other than the surface-treated particles. Examples of the external additive other than the surface-treated particles include metal oxide fine particles that have not been surface-treated as described above. Examples of external additives other than the surface-treated particles include silica particles, titanium oxide particles, alumina particles, and magnetite particles.

(Career)
The positively charged two-component developer contains the toner and a carrier. The carrier is not particularly limited as long as it is used as a magnetic carrier for a two-component developer. Specifically, for example, magnetic particles such as ferrite carriers, and the like, in which the magnetic particles are used as a carrier core material and the surface thereof is coated with a resin can be used. Specific examples of the magnetic particles include magnetic metals such as iron, nickel, and cobalt, alloys thereof, alloys containing rare earths, hematite, magnetite, manganese-zinc ferrite, nickel-zinc Magnetic materials produced by sintering and atomizing magnetic materials such as ferrite, manganese-magnesium ferrite, soft ferrite such as lithium ferrite, iron-based oxides such as copper-zinc ferrite, and mixtures thereof. And body particles.

  As a surface coating agent for coating the surface of the carrier core material obtained as described above, for example, a silicone resin, an acrylic-modified silicone resin, a binder resin such as an acrylic resin, polytetrafluoroethylene, polychlorotrifluoroethylene, Examples thereof include fluorine resins such as polyvinylidene fluoride. Among these, a silicone resin is preferable from the viewpoint of excellent charging stability and durability. As the surface coating agent, each of the above surface coating agents may be used alone, or two or more kinds may be used in combination. Specifically, for example, a mixture of a binder resin such as a silicone resin or an acrylic resin and a fluorine resin such as polytetrafluoroethylene, polychlorotrifluoroethylene, or polyvinylidene fluoride can be used.

  The carrier may be, for example, particles made of a binder resin in which the magnetic particles are dispersed. Examples of the binder resin include vinyl resins, polyester resins, epoxy resins, phenol resins, urea resins, polyurethane resins, polyamide resins, polyimide resins, cellulose resins, and polyether resins. Moreover, as the said resin, each said binder resin may be used independently and may be used in combination of 2 or more type.

The particle diameter of the carrier is preferably a volume center diameter in the range of 20 to 200 μm, and more preferably in the range of 30 to 150 μm. Here, the volume center diameter can be measured by, for example, measurement using an electron microscope, measurement using a laser diffraction scattering method, or measurement using a general particle size meter. When the carrier material is mainly composed of a magnetic material, the apparent density of the carrier varies depending on the composition of the magnetic material, the surface structure, and the like, but is generally preferably in the range of 3-8 g / cm ³ .

  The toner concentration in the two-component developer containing the toner and the carrier is preferably 1 to 20% by mass, and more preferably 3 to 15% by mass. If the toner density is too low, the image density tends to be too thin. On the other hand, if the toner concentration is too high, the toner scatters in the developing device, and there is a tendency for the toner to adhere to the background portion such as in-machine dirt or transfer paper. Therefore, by setting the toner density within the above range, a high image density is obtained, and further, toner scattering occurs in the developing device, and the problem that the toner adheres to background portions such as in-machine dirt and transfer paper is suppressed. Can do.

  The developer of this embodiment is a two-component developer in which the toner is mixed with the carrier at an appropriate ratio, and can be used, for example, in an image forming apparatus described later.

[Image forming apparatus]
An image forming apparatus using a positively charged two-component developer according to this embodiment will be described. FIG. 1 is a schematic diagram illustrating the periphery of an image forming unit of the image forming apparatus 100. The image forming apparatus 100 is an apparatus that forms a predetermined image on a sheet 30 as a recording medium by an electrophotographic method. Further, as shown in FIG. 1, the image forming apparatus 100 includes a charging device 32, an exposure device 33, and a developing device around a photosensitive drum 31 having photosensitivity in order along the rotation direction A of the photosensitive drum 31. 34, 35, a transfer roller 36, a cleaner 37, a static elimination device 38, and the like. The cleaner 37 and the charge removal device 38 may be disposed in reverse.

  The photosensitive drum 31 uses an amorphous silicon photosensitive member. In this embodiment, a photosensitive drum, which is a drum-shaped photosensitive member, is described as an example of the image carrier. However, the present invention is not limited to this, and the belt-shaped photosensitive member and the sheet-shaped photosensitive member are not limited thereto. It can also be applied to the body.

  The charging device 32 applies a predetermined potential to the surface of the photosensitive drum 31 by generating corona discharge. The exposure device 33 forms an electrostatic latent image by selectively attenuating the surface potential of the photosensitive drum 31 by irradiating light based on image data. The developing devices 34 and 35 form a toner image by developing the electrostatic latent image formed on the surface of the photosensitive drum 31 with toner. For example, the developing devices 34 and 35, which will be described later, are provided. Can be mentioned. The transfer roller 36 transfers the toner image formed on the photosensitive drum 31 onto the paper 30. The cleaner 37 includes a rubber blade 39 for removing the toner remaining on the surface of the photosensitive drum 31 and a collection container 40 for collecting the toner removed by the rubber blade 39. The neutralizing device 38 neutralizes the surface charge of the photosensitive drum 31 with lamp light.

  Further, the image forming apparatus 100 includes a fixing device 41 (a heating roller 42 and a pressure roller 43) on the downstream side in the conveyance direction of the paper 30. The fixing device 41 applies heat and pressure to the paper 30 on which the toner image has been transferred to fix the toner image, thereby forming a predetermined image on the paper 30.

  Hereinafter, the developing devices 34 and 35 used in the image forming apparatus 100 will be described.

  First, the developing device 34 will be described. FIG. 2 is a cross-sectional view illustrating a developing device 34 which is an example of a developing device provided in the image forming apparatus 100. The developing device 34 includes a developer container 51 that stores a two-component developer including toner and a carrier (not shown), two stirring rollers 52 and 53 that stir the two-component developer, and photosensitive the toner. A developing roller 54 for shifting to the surface of the body drum 31 is provided. The developing roller 54 is provided with a blade 55, that is, a two-component developing type developing device.

  The agitation rollers 52 and 53 have helical blades and agitate the two-component developer while conveying the two-component developer in opposite directions to charge the toner of the two-component developer. Further, the agitation roller 53 supplies a two-component developer including charged toner and a carrier to the developing roller 54. The developing roller 54 adsorbs the two-component developer by a magnet disposed therein and conveys the two-component developer. At this time, the two-component developer becomes a magnetic brush by a magnet inside the developing roller 54, and the thickness of the magnetic brush is regulated when the magnetic brush passes between the blade 55 and the developing roller 54. The The portion of the photosensitive drum 31 exposed by the exposure device 34 due to the potential difference generated between the photosensitive drum 31 and the developing roller 54 by the toner of the magnetic brush conveyed to the vicinity of the photosensitive drum 31. Migrate to

  By the above image forming operation, the developing device 34 performs development based on the electrostatic latent image formed on the photosensitive drum 31.

  Next, the developing device 35 will be described. FIG. 3 is a cross-sectional view showing a developing device 35 which is another example of the developing device provided in the image forming apparatus 100.

  The developing device 35 includes a developing roller 61, a magnetic roller 62, stirring rollers 63 and 64, a blade 65, a partition plate 66, and the like.

  The agitation rollers 63 and 64 have spiral blades and agitate the two-component developer while conveying the two-component developer in opposite directions to charge the toner of the two-component developer. Further, the stirring roller 63 supplies a two-component developer containing charged toner and a carrier to the magnetic roller 62.

  The magnetic roller 62 adsorbs the two-component developer by a magnet disposed therein and conveys the two-component developer. At this time, the two-component developer becomes a magnetic brush by a magnet inside the magnetic roller 62, and the thickness of the magnetic brush is regulated when the magnetic brush passes between the blade 65 and the magnetic roller 62. The Then, the toner of the two-component developer conveyed to the vicinity of the developing roller 61 shifts to the developing roller 61 due to the potential difference generated between the developing roller 61 and the magnetic roller 62.

  The developing roller 61 carries the toner transferred from the magnetic roller 62 while carrying it on the surface. Then, the toner conveyed to the vicinity of the photosensitive drum 31 is transferred to the photosensitive drum 31 due to a potential difference generated between the photosensitive drum 31 and the developing roller 61.

  Through the image forming operation described above, the developing device 35 performs development based on the electrostatic latent image formed on the photosensitive drum 31.

  In the developing devices 34 and 35, the carrier is not consumed by the development, but is collected in the device as it is and mixed with the toner again to be used.

  The image forming apparatus is an apparatus that directly transfers a toner image onto a sheet, but is not limited to such an image forming apparatus. For example, a so-called tandem image forming apparatus may be used in which a plurality of color toner images are temporarily transferred to an intermediate transfer belt, and the plurality of color toner images transferred to the intermediate transfer belt are transferred to a sheet. Although the tandem image forming apparatus has excellent high-speed performance, it has a drawback of increasing the size because a plurality of image forming units including a photosensitive drum and a developing device must be arranged side by side. As a countermeasure, there has been proposed a small tandem type image forming apparatus in which a downsized image forming unit is arranged so that the interval between the photosensitive drums is narrowed. In a small tandem type image forming apparatus, it is advantageous to make the developing device a vertical type in order to minimize the size of the image forming unit in the width direction. That is, it is desirable to arrange the developing device in the upper direction of the photosensitive drum.

  As a developing device applied to such a small tandem type image forming apparatus, there is a non-contact developing type developing device in which a gap is provided between the photosensitive drum and the developing roller and the magnetic brush does not contact the photosensitive drum. It is preferable in that the carrier does not adhere to the photoconductor, the photoconductor is not damaged by the magnetic brush, and the image quality can be improved. Therefore, the developing device applied to the small tandem type image forming apparatus is shown in FIG. 3 rather than the two-component developing type developing device 34 to which toner is supplied from the magnetic brush on the developing roller as shown in FIG. Such a developing device 35 is preferred.

  The image forming apparatus 100 forms an image on a sheet by the image forming operation as described above. And, by using the positively charged two-component developer, even when image formation is performed over a long period of time, in particular, even when high density printing with a high printing rate is performed, occurrence of fog and the like can be suppressed, Therefore, a high-quality image can be formed over a long period of time.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by the Example.

(Surface treatment particles A)
100 parts by mass of silica fine particles (Aerosil 90G manufactured by Nippon Aerosil Co., Ltd .: average primary particle size 20 nm) were put into a mixer and stirred in a nitrogen atmosphere. Then, with stirring in a nitrogen atmosphere, 15 parts by mass of H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (OCH ₃ ) ₃ as a positive charging agent with respect to 100 parts by mass of silica fine particles, The first surface treatment agent containing 20 parts by mass of CH ₃ Si (OCH ₂ CH3) ₃ as a hydrophobizing agent and toluene as a diluent is dropped, and heated until the liquid temperature reaches 150 ° C. did. Next, the liquid temperature was stirred for 1 hour. And the obtained mixture was dried. Next, the mixture obtained by drying was forcibly stirred with a mixer or the like to be crushed.

Thereafter, the mixture (crushed material) obtained by crushing was stirred under a nitrogen atmosphere. And while stirring in a nitrogen atmosphere, 5 parts by mass of CF ₃ (CF ₂ ) ₃ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ as a negative charge treatment agent (100 masses of silica fine particles) with respect to the crushed material. Second surface treatment agent containing 20 parts by mass of tetrahydrofuran as a diluent, and the mixture was heated until the liquid temperature reached 150 ° C. Next, the liquid temperature was stirred for 1 hour.

  And the obtained mixture was dried. Next, the mixture obtained by drying was forcibly stirred with a mixer or the like to be crushed. By doing so, the surface treatment particle | grains A processed by the 2nd surface treatment agent after being processed by the 1st surface treatment agent were obtained. The ratio of the positive charging agent to the negative charging agent is 3: 1 by mass ratio.

(Surface treatment particles B)
The surface-treated particles B were produced in the same manner as the method for producing the surface-treated particles A, except that 1.5 parts by mass was added instead of 5 parts by mass of the negatively charged treatment agent. In addition, the ratio of the said positive charge processing agent and the said negative charge processing agent is 10: 1 by mass ratio.

(Surface treatment particles C)
The surface-treated particles C were produced in the same manner as the method for producing the surface-treated particles A, except that 10 parts by mass was added instead of adding 5 parts by mass of the negative charging agent. In addition, the ratio of the said positive charge processing agent and the said negative charge processing agent is 3: 2 by mass ratio.

(Surface treatment particle D)
The surface-treated particles D were produced in the same manner as the method for producing the surface-treated particles A, except that 1 part by mass was added instead of 5 parts by mass of the negative charging agent. The ratio of the positive charging agent to the negative charging agent is 15: 1 by mass ratio.

(Surface treatment particles E)
The surface-treated particles E were produced in the same manner as the method for producing the surface-treated particles A, except that 12 parts by mass was added instead of 5 parts by mass of the negative charge treating agent. The ratio of the positive charge processing agent to the negative charge processing agent is 5: 4 in mass ratio.

(Surface treatment particles F)
The surface-treated particles F were produced in the same manner as the method for producing the surface-treated particles A except that the treatment with the negatively charged treatment agent was not performed.

  The above items for the surface-treated particles A to F are summarized in Table 1.

[Example 1]
(Manufacture of toner)
First, as a binder resin, 100 parts by mass of a polyester resin (acid value 5.6, melting point 120 ° C.), and as a colorant, copper phthalocyanine blue pigment (CI Pigment Blue 15: 3, manufactured by Clariant Japan Co., Ltd.) 4 parts by weight of Blue B4G, 1 part by weight of a quaternary ammonium salt compound (P51 made by Clariant) as a charge control agent, and 5 parts by weight of Carnauba wax (Carnauba No. 1 by Toa Kasei Co., Ltd.) as a wax The mixture was mixed for 5 minutes with a mixer (FM-10 manufactured by Nippon Coke Industries, Ltd.). Then, the obtained mixture was melt-kneaded with a twin screw extruder (PCM-30 manufactured by Ikegai Co., Ltd.). Then, the obtained melt-kneaded product was pulverized with a turbo mill (Turbo Industry Co., Ltd. turbo mill) and classified with an elbow jet classifier (Nitetsu Mining Co., Ltd. EJ-LABO). By doing so, toner mother particles having a volume average diameter of 6.8 μm were obtained. The volume average diameter of the toner base particles was measured with a particle size meter (Multisizer 3 manufactured by Beckman Coulter, Inc.).

  Next, 2 parts by mass of the surface-treated particles A are added as an external additive to 100 parts by mass of the obtained toner base particles, and 3500 rpm is obtained with a Henschel mixer (FM-10 type manufactured by Nippon Coke Industries, Ltd.). Mixed for 3 minutes. By doing so, toner (toner mother particles to which an external additive was externally added) was obtained.

(Manufacture of developer)
The toner obtained as described above was blended in a ferrite carrier (manufactured by Powder Tech Co., Ltd.) having a volume average particle diameter of 35 μm so that the toner concentration was 12% by mass. And it stirred for 30 minutes with the rocking mixer (RM-10 type | mold by Seiwa Giken Co., Ltd.). By doing so, the developer according to Example 1 was obtained.

[Example 2]
Example 1 is the same as Example 1 except that the surface-treated particles B were used instead of the surface-treated particles A.

[Example 3]
Example 1 is the same as Example 1 except that the surface-treated particles C were used instead of the surface-treated particles A.

[Example 4]
Example 1 is the same as Example 1 except that surface-treated particles D were used instead of surface-treated particles A.

[Example 5]
Example 1 is the same as Example 1 except that surface-treated particles E were used instead of surface-treated particles A.

[Comparative Example 1]
Example 1 is the same as Example 1 except that the surface-treated particles F were used instead of the surface-treated particles A.

[Evaluation]
The obtained toner and developer were evaluated by the following methods.

  First, a printer (FS-C5020N) manufactured by Kyocera Mita Co., Ltd. is used as an evaluation machine, each developer obtained is used as a start developer, each toner obtained is used as a replenishing toner, and the temperature is 28. Images were formed in an environment of ° C. and a relative humidity of 85% RH, and the following evaluation was performed.

  Specifically, first, the start developer was set in the evaluator, and the evaluator was turned on and stabilized. Thereafter, a sample image was output. This image was used as the initial image. Next, 50,000 sheets of images with a printing rate of 20% were printed while replenishing toner. Note that the same sample image as the initial image was output on the 50,000th sheet to obtain a printed image on the 50,000th sheet.

(Image density)
Reflection densitometers (Gretag Macbeth, Inc.) for the initial image and each image of the 50,000th print image at a position near the left end, the center, and the right end in the paper transport direction. The reflection density was measured using RD-19A (SpectroEyeLT) manufactured by KK. The average value was taken as the image density (ID) of the obtained image.

(Cover)
In the obtained image, the fog density (FD) is obtained by subtracting the image density value of the base paper (that is, the white paper before image output) from the image density value of the blank paper equivalent measured by the reflection densitometer. did.

(Charge amount)
The developer immediately after printing the initial image and the 50,000th print image was taken out, and 0.1 ± 0.01 g of the developer was weighed. The weighed developer was sucked by a suction part of a suction-type charge measuring device (q / m meter MODEL 210HS manufactured by Trek). By doing so, only the toner was sucked, and the sucked toner amount and charge amount were measured with a suction-type charge amount measuring device (q / m meter MODEL 210HS manufactured by Trek). From the measured toner amount and charge amount, the toner charge amount (μC / g) was calculated.

  The evaluation results are shown in Table 2.

  As can be seen from Table 2, after the surface of the metal oxide fine particles was treated with the first surface treatment agent containing the positive charge treatment agent, the surface treated particles were treated with the second surface treatment agent containing the negative charge treatment agent. In the case of the developer containing the toner added externally (Examples 1 to 5), compared with the case where the treatment with the second surface treatment agent containing the negatively charged treatment agent is not performed (Comparative Example 1). It can be seen that the decrease in the charge amount of the toner is suppressed, and the occurrence of fogging is suppressed even though the image density is not decreased.

  Further, when the ratio of the positive charging agent to the negative charging agent is 3: 2 to 9: 1 in terms of mass ratio (Example 1 and Example 3), other cases (Example 2). , 4, 5), it can be seen that the reduction in the charge amount of the toner is further suppressed, and the occurrence of fogging is further suppressed even though the image density is not reduced.

DESCRIPTION OF SYMBOLS 30 Paper 31 Photosensitive drum 32 Charging apparatus 33 Exposure apparatus 34,35 Development apparatus 36 Transfer roller 37 Cleaner 38 Static elimination apparatus 39 Rubber blade 40 Recovery container 41 Fixing apparatus 42 Heating roller 43 Pressure roller 51 Developer accommodating part 52,53, 63 Stirring roller 54, 61 Developing roller 55, 65 Blade 62 Magnetic roller 66 Partition plate

Claims (6)

A positively charged two-component developer comprising a toner and a carrier,
The toner includes toner base particles containing a binder resin and a colorant; and an external additive externally added to the toner base particles;
The external additive is obtained by treating the surface of the metal oxide fine particles with the first surface treatment agent containing a positive charge treatment agent and then treating with the second surface treatment agent containing a negative charge treatment agent. A positively charged two-component developer characterized by containing.   The positively charged two-component developer according to claim 1, wherein a ratio of the positively charged processing agent to the negatively charged processing agent is 3: 2 to 9: 1 in terms of mass ratio.   The positively charged two-component developer according to claim 1, wherein the positively charged processing agent is a silane coupling agent having an amino group in the molecule.   The positively charged two-component developer according to claim 1, wherein the negatively charged processing agent is a silane coupling agent having fluorine in the molecule.   The positively charged two-component developer according to claim 1, wherein the first surface treatment agent contains a hydrophobic treatment agent.   The positively charged two-component developer according to claim 5, wherein the hydrophobizing agent is a silane coupling agent having a hydrophobic group in the molecule.

Images