JP2009186655A - Carrier for hybrid development, developer for hybrid development, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier for hybrid development, a developer for hybrid development and an image forming apparatus for sufficiently preventing occurrence of an image memory phenomenon for a long period of time. <P>SOLUTION: The carrier for hybrid development includes a resin coat layer on the surface of a core material, wherein the core material has an SF1 value of from 100 to 120 and an SF2 value of 120 to 130 and the carrier has an average particle diameter D50 of 20 to 80 μm and a dynamic current of 0.1 to 0.8 μA. The SF1 value is defined by SF1=(MXLNG)<SP>2</SP>/AREA×π/4×100, wherein MXLNG represents the absolute maximum length of the core material on an image and AREA represents the projected area of the core material; and the SF2 value is defined by SF2=(PERIME)<SP>2</SP>/AREA×π/4×100, wherein PERIME is the perimeter length of a projected image of the core material on the image and AREA represents the projected area of the core material. The developer for hybrid development contains the above carrier for hybrid development and toner. The image forming apparatus includes the above developer for hybrid development. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus, a developer for hybrid development used in the image forming apparatus, and a carrier for hybrid development used in the developer.

  As a developing method employed in an electrophotographic image forming apparatus, a one-component developing method using only toner as a main component of a developer and a two-component developing method using toner and a carrier as main components of a developer are known. ing.

  The developing device of the one-component development system includes a toner carrier that carries and conveys toner, and a friction charging member that contacts the toner carrying surface of the toner carrier. When the toner carried on the toner carrying member passes through the contact position of the frictional charging member, the toner is brought into frictional contact with the frictional charging member to be thinned and charged to a predetermined polarity. As described above, the one-component developing device has an advantage that the configuration is simple, small, and inexpensive because the toner is charged by frictional contact with the frictional charging member. However, since the toner is subject to strong stress at the contact position of the frictional charging member, the toner is liable to deteriorate, so that the chargeability of the toner is impaired relatively early. In addition, the contact pressure between the toner carrier and the frictional charging member reduces the ability of the toner to adhere to and charge the toner, resulting in a relatively short life of the developing device.

  In the developing device of the two-component developing method, the toner and the carrier are charged to a predetermined polarity by frictional contact between the toner and the carrier, so that the toner receives less stress than the one-component developing device. Since the surface area of the carrier is larger than that of the toner, the toner is less likely to adhere and become dirty. However, since the carrier exists in the development region, the carrier moves to the latent image carrier, and image deterioration due to the carrier is likely to occur on the image.

  In view of this, a hybrid development system has been proposed that can be used in combination with the advantages of these development systems (for example, Patent Document 1). In the hybrid developing system, only toner is selectively supplied to the outer peripheral surface of the developing roller from the developer including the toner and carrier held on the outer peripheral surface of the magnetic roller, and the toner held on the outer peripheral surface of the developing roller is used. The electrostatic latent image (electrostatic latent image portion) on the photosensitive member is developed. As the carrier, magnetic particles such as ferrite, a coated carrier in which a resin film is simply provided on the surface of the magnetic particles, and a binder carrier in which magnetic powder is dispersed in a binder resin are usually used.

  In the hybrid developing system, the carrier must supply toner and collect residual toner on the developing roller in the toner supply / collection region between the magnetic roller and the developing roller. However, there has been a problem that residual toner is not sufficiently collected by the carrier. If the residual toner is insufficiently collected, there will be a difference in toner amount or toner charge amount between the area where the toner remains without being developed on the developing roller and the area where new toner is supplied after development. As a result, image memory was generated on the image. The image memory is a phenomenon in which a density difference occurs in an image that should be originally printed under the influence of the image printed immediately before. For example, when there is a toner consumption area due to image printing and an area where toner is not consumed on the developing roller, a density difference occurs when a solid image or a halftone image is printed after one round of the developing roller.

In view of this, a technique has been proposed in which a toner supply roller for supplying toner to the developing roller and a toner collecting roller for collecting toner from the developing roller are provided separately, and the toner remaining on the developing roller is collected by the toner collecting roller. (Patent Document 2). As a result, the toner that has not been used for development is always peeled off from the developing roller, so that the image memory can be suppressed. However, the structure of the device is complicated and large, and the manufacturing cost increases.
JP 2003-167441 A JP 2000-8178 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a carrier for hybrid development, a developer for hybrid development, and an image forming apparatus that can sufficiently prevent generation of an image memory over a long period of time without causing the apparatus to become complicated or large.

The present invention is a carrier for hybrid development having a resin coat layer on the surface of a core material,
The SF1 value represented by the formula (I) is 100 to 120, and the SF2 value represented by the formula (II) is 120 to 130,
A carrier for hybrid development having an average particle diameter D50 of the carrier of 20 to 80 μm and a dynamic current value of 0.1 to 0.8 μA;
SF1 = (MXLNG) ² / AREA × π / 4 × 100 (I)
[Where MXLNG indicates the absolute maximum length of the core material on the image; AREA indicates the projected area of the core material]
SF2 = (PERIME) ² / AREA × π / 4 × 100 (II)
[Where PELME indicates the peripheral length of the projected image of the core material on the image; AREA indicates the projected area of the core material].

  The present invention also relates to a developer for hybrid development including the carrier for hybrid development and a toner.

  The present invention also relates to an image forming apparatus comprising the developer for hybrid development.

The developing device included in the image forming apparatus of the present invention is particularly
A developing device that visualizes an electrostatic latent image on an electrostatic latent image carrier using a developer including toner and a carrier,
A developer containing toner and the carrier for hybrid development;
A first conveying member disposed in an opening of a developing tank that contains the developer;
A second conveying member facing the first conveying member via the first region and facing the electrostatic latent image carrier via the second region;
A first electric field is formed between the first conveying member and the second conveying member, and the toner in the developer held by the first conveying member is moved to the second conveying member. A second electric field is formed between the second transport member and the electrostatic latent image carrier, and the toner held by the second transport member is transferred to the electrostatic latent image carrier. The hybrid developing apparatus includes a second electric field forming unit that moves the electrostatic latent image to make the electrostatic latent image visible.

  Since the carrier for hybrid development of the present invention has a resin coating layer on the surface of the core material and the core material has moderate irregularities on the surface and has a relatively high sphericity, the carrier can be developed over a long period of time. After supplying the toner to the roller, a relatively large charge having a polarity opposite to the toner charging polarity can be held. Therefore, the residual toner on the developing roller can be sufficiently collected, and the generation of the image memory can be prevented for a long time.

[Carrier for hybrid development]
The carrier for hybrid development (hereinafter simply referred to as “carrier”) of the present invention has a resin coating layer on the surface of a core material.

  The core material has moderate unevenness on the surface and has a relatively high sphericity. Specifically, the SF1 value represented by the formula (I) is 100 to 120, preferably 107 to 113, and the formula (II). The represented SF2 value is 120 to 130, preferably 122 to 128. Thereby, the film thickness of the coat layer of the carrier is made uniform, and a partial leak portion is eliminated, so that the resistance of the carrier can be increased. As a result, charges having a polarity opposite to that of the toner at the time of supplying the toner to the developing roller can be effectively accumulated, so that the residual toner on the developing roller can be more efficiently collected with the opposite polarity charge. In addition, the stress applied to the carrier is equalized, the wear of the coat layer during durable printing progresses uniformly, and the adhesion of the coat layer improves, so there is no partial exposure of the core material for a long time. A stable high resistance can be maintained. As a result, since the residual toner on the developing roller can be sufficiently collected even during durable printing, the occurrence of image memory can be prevented over a long period of time.

SF1 = (MXLNG) ² / AREA × π / 4 × 100 (I)
[Where MXLNG indicates the absolute maximum length of the core material on the image; AREA indicates the projected area of the core material]
SF2 = (PERIME) ² / AREA × π / 4 × 100 (II)
[Where PELME indicates the peripheral length of the projected image of the core material on the image; AREA indicates the projected area of the core material].

  “MXLNG”, “AREA”, and “PERIME” can be measured from photographic images of core particles. Specifically, using a SEM, a photographic image magnified 2000 times is obtained, and 100 core particles having a maximum length within an average diameter of ± 5 μm are randomly sampled. The image information can be introduced into an image analysis apparatus (LUZEX AP) manufactured by Nicole via an interface and analyzed to obtain “MXLNG”, “AREA”, and “PERIME”.

SF1 indicates the degree of roundness of the core particles, and when the value is 100, it is a perfect circle. As the value increases, it becomes less round and becomes indefinite.
SF2 indicates the degree of unevenness on the surface of the core particle, and when the value is 100, the surface is smooth, and the larger the value, the larger the surface irregularity (the surface area increases).

If SF1 is too large, the film thickness of the coat layer becomes non-uniform, so that the core material is exposed during durable printing, and the effect of preventing image memory cannot be obtained.
If SF2 is too large or too small, the adhesiveness of the coat layer is lowered, so that the core material is exposed during durable printing, and the effect of preventing image memory cannot be obtained.

  The core material is not particularly limited as long as it has the above-described SF1 and SF2, and may be a magnetic material conventionally used in the field of carriers contained in an electrophotographic developer. Specific examples of preferable core material include various soft magnetic materials such as manganese ferrite, magnesium ferrite, and manganese magnesium ferrite, and particularly soft ferrite.

Hereinafter, the manufacturing method will be described mainly using manganese ferrite as an example. However, it is apparent that the described method can be applied to the manufacture of other magnetic core materials.
First, raw material powder is prepared. For details, when raw material preparation of the components constituting the soft ferrite, to prepare the _Mn 3 _{O 4} and MnCO _{3, Fe} 2 _{O 3} as the Fe source as Mn source. Each raw material is weighed so that the composition ratio of Mn and Fe in the soft ferrite corresponds to the intended composition ratio of soft ferrite. Further, a predetermined amount of CaCO ₃ is added as a Ca source to be added if desired, and carbon black (hereinafter referred to as CB) is measured as a C source. When mixing these raw materials sufficiently and preparing them, the mixing method may be normal mixing by using a mortar or the like. It is considered that the blended CaCO ₃ is decomposed and oxidized into a Ca oxide in the firing step described later, and CB is converted to CO ₂ . The C source is not particularly limited as long as it is an organic compound containing carbon, and besides CB, for example, polyvinyl alcohol (PVA), graphite, polyacrylamide, acetylene and the like can be suitably used.

For example, when magnesium ferrite is selected as the ferrite as another method, MgO, Mg (OH) ₂ , MgCO ₃ , or Fe ₂ O ₃ may be used as the Mg source. For example, when manganese magnesium ferrite is selected as another method, Mn ₃ O ₄ or MnO is used as the Mn source, MgO, Mg (OH) ₂ , MgCO _{3 is} used as the Mg source, and Fe ₂ O ₃ is used as the Fe source. . Subsequent steps can be produced in the same manner as in the case of manganese ferrite. In addition to CaCO ₃ , CaO or the like can be suitably used as the Ca source. And even if any raw material is used, each ferrite can be manufactured with the manufacturing process similar to the manufacturing process of the manganese ferrite demonstrated below.

  Next, pulverization and granulation are performed. Specifically, the prepared raw material is mixed with water, and further, if necessary, a dispersant such as polycarboxylic acid is mixed to obtain a slurry having a raw material mixing ratio of about 60 to 90% by mass, and this is wet pulverized with a ball mill or the like. To do. A finely pulverized raw material slurry is obtained by wet pulverization. The slurry of this raw material is spray-dried with a spray dryer or the like, or granulated with a pelletizer, and dried into spherical pellets having a diameter of 10 to 500 μm.

Next, the spherical pellet is fired. In that case, a baking process is performed at a temperature of 1000 to 1500 ° C., particularly 1000 to 1300 ° C. in a nitrogen gas atmosphere in an electric furnace. In the firing, the C compound in the raw material becomes CO ₂ . If the addition ratio of the C compound is 0.5% by mass or more in terms of C element, the sinterability is improved.
Finally, sieving is performed. The fired soft ferrite is crushed by a pulverizer to obtain a pulverized powder, and the pulverized powder is classified or sieved to collect a powder having a predetermined particle size to obtain a carrier core material. The average particle diameter of the core material is usually 10 to 100 μm, preferably 20 to 80 μm.

In the core material manufacturing method, SF1 and SF2 can be controlled by adjusting the addition ratio of the C compound and the sintering temperature.
For example, as the addition ratio of the C compound is larger, the sinterability is improved as described above, but the sphericity of the core material is lowered. From the viewpoint of the balance between the spherical shape and the sinterability of the core material, the addition ratio of the C compound is 0.5 to 1.0 mass%, particularly 0.6 to 0.8 mass%, in terms of C element. This is because, while improving the sinterability, it is possible to avoid the difficulty of maintaining the spherical shape of the particles due to the progress of the sinterability. When the addition ratio is too large, SF1 becomes too large.
For example, SF2 can be controlled by adjusting the firing temperature. Specifically, when the firing temperature is increased, SF2 is increased, and when the firing temperature is decreased, SF2 is decreased. Therefore, the firing temperature is within the above range. If the firing temperature is too high, SF2 becomes too large, and if it is too low, SF2 becomes too small.

  The resin constituting the resin coat layer may be a resin conventionally used for a coat layer in the field of a coat type carrier contained in an electrophotographic developer. For example, polyolefin resins such as polyethylene, polypropylene, chlorinated polyethylene and chlorosulfonated polyethylene; polyacrylates such as polystyrene and polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl Polyvinyl and polyvinylidene resins such as ethers and polybiliketones; Copolymers such as vinyl chloride-vinyl acetate copolymers and styrene-acrylic acid copolymers; Silicone resins composed of organosiloxane bonds or modified resins thereof (for example, alkyd resins) , Polyester resins, epoxy resins, modified resins made of polyurethane, etc.); polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene Polyamides; fluororesin emissions such Poruesuteru; polyurethane; polycarbonates; - urea amino resins such as formaldehyde resins, epoxy resins and the like.

  Other additives may be contained in the resin coat layer as long as the carrier achieves the dynamic current value described later, but it is usually composed of only the resin.

Examples of the method for forming the resin coating layer include a wet coating method and a dry coating method.
Specific examples of the wet coating method include a fluidized bed spray coating method, a dip coating method, and a polymerization method. In the fluidized bed spray coating method, a coating solution in which a coating resin is dissolved in a solvent is spray-coated on the surface of the core material particles using a fluidized bed, and then dried to form a coating layer. In the dip coating method, core material particles are immersed in a coating solution in which a coating resin is dissolved in a solvent, followed by coating treatment, and then dried to form a coating layer. In the polymerization method, the core material particles are immersed in a coating solution in which a reactive compound is dissolved in a solvent for coating treatment, and then a polymerization reaction is performed by applying heat or the like to form a coat layer.

  In the dry coating method, the coating resin particles are deposited on the surface of the core material particles, and then the mechanical impact force is applied so that the resin particles deposited on the surface of the core material particles are melted or softened and fixed. Form. For example, the core material, the resin, the charge control particles and the low resistance fine particles are stirred at a high speed with a high-speed stirring mixer capable of applying a mechanical impact force with or without heating, and the impact force is repeatedly applied to the mixture. Then, a carrier fixed by melting or softening a resin on the surface of the core particle is manufactured. When heating, 60-125 degreeC is preferable. This is because if the heating temperature is excessive, aggregation of carrier particles tends to occur.

  The dynamic current value of the carrier can be controlled by adjusting the coating amount of the resin coat layer. For example, when the coating amount is increased, the dynamic current value is decreased, and when the coating amount is decreased, the dynamic current value is increased. The coating amount is not particularly limited as long as the dynamic current value of the carrier is within the range described below, and is usually 1.1 to 4.5 parts by weight, particularly 2.0 to 4.0 parts by weight with respect to 100 parts by weight of the core material. Part by weight is preferred. If the coating amount is too large, the dynamic current value becomes too small, and if the coating amount is too small, the dynamic current value becomes too large.

The volume average particle diameter (D50) of the carrier is 20 to 80 μm, preferably 30 to 60 μm. If the average particle size is too small, the contact area of the ears of the magnetic brush will increase, but the squeezing strength of the ears will be weak and the recovery effect will be reduced, so the memory prevention effect will not be obtained, so the image memory prevention effect will be obtained. I can't. On the other hand, if the average particle size is too large, the contact area of the ear becomes small, and the image memory prevention effect cannot be obtained.
The volume average particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

  The dynamic current value of the carrier is 0.1 to 0.8 μA, preferably 0.15 to 0.5 μA. If the dynamic current value is too small, the toner charge amount tends to be high, and the toner with a high charge amount adheres strongly to the developing roller, resulting in poor recoverability. If the dynamic current value is too large, the reverse charge generated by friction with the toner cannot be effectively accumulated, and the toner remaining on the developing roller cannot be effectively collected, so that the effect of preventing the image memory cannot be obtained.

In this specification, the value measured by the following method using the apparatus which has the structure schematically shown in FIG. 7 is used for the dynamic current value (CDC value) of the carrier.
A carrier (210) is set on the aluminum sleeve (212), and a voltage is applied by a DC power source (214) while rotating the sleeve (212). The current flowing from the sleeve (212) to the ammeter (215) through the carrier (210) and the aluminum tube (213) is measured. The measurement conditions are as follows.
・ Sleeve rotation speed: 50rpm
・ Applied voltage: 500V
・ Sample amount: 5g
・ Sleeve (212)
Longitudinal length: 55 mm, diameter: 31 mm, magnet magnetic force: 1000 gauss, number of magnet magnetic poles: 8, aluminum tube (213)
Longitudinal length: 55 mm, diameter: 30 mm

  The mixing ratio of the carrier and the toner may be adjusted so as to obtain a desired toner charge amount. The toner mixing ratio is 3 to 20% by weight, preferably 6 to 10% by weight based on the total amount of the toner and the carrier. Is preferred.

[Developer for hybrid development]
The developer for hybrid development of the present invention contains the above carrier and toner.

  The mixing ratio of the carrier and the toner may be adjusted so as to obtain a desired toner charge amount. The toner mixing ratio is 3 to 20% by weight, preferably 6 to 10% by weight based on the total amount of the toner and the carrier. Is preferred.

  In the present invention, a toner that has been conventionally used as a toner in the field of electrophotographic developers can be used. However, the above-mentioned carrier has a specific average circularity and a sharp particle size distribution. In combination with a new toner, an even better image memory prevention effect can be obtained.

  The average circularity of the toner is preferably 0.92 to 0.98, more preferably 0.94 to 0.96.

The volume average particle diameter of the toner is usually 1 to 10 μm, preferably 2.5 to 8.5 μm.
The toner preferably has a glass transition temperature of 20 to 45 ° C. from the viewpoint of image fixability.

The degree of circularity is:
Circularity = (perimeter of a circle having the same projection area as the particle image) / (perimeter of the particle projection image)
Is a characteristic value related to the shape of the particle defined by. As the average value of such circularity (average circularity), a value measured by “FPIA-2100” (manufactured by Sysmex Corporation) is used.
Specifically, the average circularity is measured by the following procedure. The toner is blended with an aqueous solution containing a surfactant and dispersed by ultrasonic dispersion for 1 minute. Then, using “FPIA-2100”, the number of HPF detections is 3000 to 10,000 in the measurement condition HPF (high magnification imaging) mode. Measure at the appropriate concentration. Within this range, reproducible identical measurement values can be obtained.

Values measured by Coulter Multisizer III (manufactured by Beckman Coulter) are used as the volume average particle diameter, the small particle diameter, and the large particle content ratio.
Specifically, it is measured by the following method. Measurement and calculation are performed using a device in which a computer system (manufactured by Beckman Coulter) equipped with data processing software “Software V3.51” is connected to Coulter Multisizer III (manufactured by Beckman Coulter). As a measurement procedure, 0.02 g of toner is blended with 20 ml of a surfactant solution (for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant component 10 times with pure water for the purpose of dispersing the toner). After that, ultrasonic dispersion is performed for 1 minute to prepare a toner dispersion. This toner dispersion is poured into a beaker containing ISOTON II (manufactured by Beckman Coulter) in a sample stand with a pipette until the display density of the measuring instrument is 5% to 10%. By setting this concentration range, a reproducible measurement value can be obtained. In the measuring machine, the measurement particle count is set to 25000, the aperture diameter is set to 50 μm, and the frequency range is calculated by dividing the measurement range of 1 to 30 μm into 256 parts. The particle diameter of 50% from the larger volume integrated fraction is defined as the volume average particle diameter.

The glass transition temperature of the toner can be measured using a DSC-7 differential scanning calorimeter (manufactured by PerkinElmer) or a TAC7 / DX thermal analyzer controller (manufactured by PerkinElmer).
As a measurement procedure, toner 4.5 mg to 5.0 mg is precisely weighed to 2 digits after the decimal point, sealed in an aluminum pan (KIT NO. 0219-0041), and set in a DSC-7 sample holder. The reference used an empty aluminum pan. The measurement conditions were a measurement temperature of 0 ° C. to 200 ° C., a temperature increase rate of 10 ° C./min, a temperature decrease rate of 10 ° C./min, and heat-cool-heat temperature control. Analysis was performed based on the data in Heat. The glass transition temperature draws an extension of the baseline before the rise of the first endothermic peak and a tangent line indicating the maximum slope between the rise of the first peak and the peak apex, and the intersection is taken as the glass transition point. Show.

  The toner is negatively or positively charged by frictional contact with the carrier, and contains at least a colorant and optionally a negative or positive charge control agent or a release agent in the binder resin. It is.

  The binder resin contained in the toner is not particularly limited. For example, a styrene resin (monopolymer or copolymer containing styrene or a styrene substitution product, such as a styrene / acrylic resin), a polyester resin, an epoxy resin, Examples thereof include a vinyl chloride resin, a phenol resin, a polyethylene resin, a polypropylene resin, a polyurethane resin, a silicone resin, a nitrogen-containing acrylic resin, or a mixture of these resins. The binder resin preferably has a softening temperature in the range of about 80 to 160 ° C and a glass transition point in the range of about 50 to 75 ° C.

  As the colorant, a known material conventionally used as a colorant in the toner field is used. Specific examples of the colorant include, for example, carbon black, aniline black, activated carbon, magnetite, benzine yellow, permanent yellow, naphthol yellow, phthalocyanine blue, first sky blue, ultramarine blue, rose bengal, lake red and the like. In general, the addition amount of the colorant is preferably 2 to 20 parts by weight with respect to 100 parts by weight of the binder resin.

  As the release agent, a known release agent conventionally used as a release agent in the field of toner is used. Specific examples of the release agent include, for example, polyethylene, polypropylene, carnauba wax, sazol wax, or a mixture obtained by appropriately combining them. The release agent is preferably used at a ratio of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  As the charge control agent, a known material conventionally used as a charge control agent in the field of toner is used. Specifically, for the positively charged toner, for example, nigrosine dyes, quaternary ammonium salt compounds, triphenylmethane compounds, imidazole compounds, and polyamine resins can be used as positive charge control agents. For the negatively charged toner, metal-containing azo dyes such as Cr, Co, Al, and Fe, salicylic acid metal compounds, alkylsalicylic acid metal compounds, and curixarene compounds can be used as negative charge control agents. The charge control agent is preferably used at a ratio of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  The method for producing the toner is not particularly produced, and examples thereof include so-called pulverization methods and wet methods such as suspension polymerization methods, emulsion polymerization association methods, and dissolution suspension methods. In view of obtaining a toner having a sharp particle size distribution, the toner is preferably produced by an emulsion polymerization association method.

  A method for producing toner particles by the emulsion polymerization association method will be described. A method for producing toner particles by an emulsion polymerization association method is a method of forming toner particles in an aqueous medium, and is disclosed in, for example, JP-A-2002-351142. Also, a method for producing a toner particle dispersion by aggregating / fusing resin particles disclosed in JP-A-5-265252, JP-A-6-329947, and JP-A-9-15904 in an aqueous medium. Can be mentioned. Specifically, after dispersing resin particles in water using an emulsifier, a coagulant having a critical aggregation concentration or higher is added to cause salting out and aggregation, and at the same time, heating at a temperature higher than the glass transition temperature of the formed polymer itself. While fusing to form fused particles, the particle size grows gradually. When the desired particle size is reached, a large amount of water is added to stop particle size growth, and the particle surface is smoothed while heating and stirring. Thus, the shape is controlled to prepare a toner particle dispersion. A solvent that is infinitely soluble in water, such as alcohol, may be added simultaneously with the flocculant. Examples of the aqueous medium include, but are not particularly limited to, water, methanol, ethanol, isopropanol, butanol, 2-methyl-2-butanol, acetone, methyl ethyl ketone, tetrahydrofuran, or a mixture thereof. . A suitable toner particle can be selected from these. Another organic solvent may be further added to the aqueous medium. Examples of the organic solvent include toluene, xylene, or a mixture thereof, but are not particularly limited.

In general, the toner is externally added with an external additive such as a fluidizing agent.
As the fluidizing agent, for example, inorganic fine particles such as silica, titanium oxide, and aluminum oxide, and resin fine particles such as acrylic resin, styrene resin, silicone resin, and fluorine resin can be used. In particular, it is preferable to use a fluidizing agent hydrophobized with a silane coupling agent, a titanium coupling agent, or silicone oil. The fluidizing agent is preferably added at a ratio of 0.1 to 5 parts by weight with respect to 100 parts by weight of the toner particles. The average primary particle size of these additives is preferably 10 to 100 nm, particularly preferably 10 to 90 nm.

Charged particles may be further added to the toner for the purpose of improving chargeability.
The charged particles are appropriately selected according to the charging polarity of the toner, and particles that are charged to the opposite polarity to the charging polarity of the toner by frictional contact with the carrier are used. The average primary particle diameter of the charged particles is, for example, 100 to 850 nm.

  For example, when using a toner that is negatively charged by frictional contact with a carrier, charged particles are particles that are positively charged by frictional contact with the carrier. Such particles include, for example, inorganic particles such as strontium titanate, barium titanate, magnesium titanate, calcium titanate, and alumina, and thermoplastic resins such as acrylic resin, benzoguanamine resin, nylon resin, polyimide resin, and polyamide resin. Or the particle | grains comprised with the thermosetting resin can be used. You may use the particle | grains which made the resin which comprises a charged particle contain the positive charge control agent charged to positive polarity by contact with a toner. As the positive charge control agent, for example, nigrosine dye, quaternary ammonium salt and the like can be used. The charged particles may be composed of a copolymer of nitrogen-containing monomers.

  Further, for example, in the case of toner charged to positive polarity by frictional contact with a carrier, charged particles are particles charged to negative polarity by frictional contact with the carrier. As such particles, for example, inorganic particles such as silica and titanium oxide, and particles made of thermoplastic resin or thermosetting resin such as fluororesin, polyolefin resin, silicone resin, and polyester resin can be used. You may use the particle | grains which made the resin which comprises a charged particle the negative charge control agent electrically charged to negative polarity by contact with a toner. Examples of negative charge control agents include salicylic acid-based and naphthol-based chromium complexes, aluminum complexes, iron complexes, and zinc complexes. The charged particles may be copolymer particles of a fluorine-containing acrylic monomer or a fluorine-containing methacrylic monomer.

  The content of the charged particles is not particularly limited as long as the object of the present invention is achieved. For example, 0.1 to 3 weights is preferable with respect to 100 parts by weight of the toner particles.

[Image forming apparatus]
The developer of the present invention is used in a hybrid developing device and an image forming apparatus provided with the developing device. In the hybrid development system, the two-component developer is held on the outer peripheral surface of the first conveying member (conveying roller) and conveyed to the area facing the second conveying member (developing roller), and the toner is selectively selected. Supplying to the outer peripheral surface of the second conveying member, forming a toner thin layer on the outer peripheral surface of the second conveying member, and developing the electrostatic latent image on the electrostatic latent image carrier using the toner thin layer To do.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. In the following description, terms indicating a specific direction (for example, “up”, “down”, “left”, “right”, and other terms including them, “clockwise direction”, “counterclockwise” ”) Is used to facilitate understanding of the invention with reference to the drawings, and the present invention should not be construed as being limited by the meaning of these terms. Further, in the image forming apparatus and the developing apparatus described below, the same reference numerals are used for the same or similar components.

  FIG. 1 shows an example of a part related to image formation of an electrophotographic image forming apparatus according to the present invention. The image forming apparatus may be any of a copier, a printer, a facsimile machine, and a multi-function machine having a combination of these functions. The image forming apparatus 11 includes a photoreceptor 12 that is an electrostatic latent image carrier. In the embodiment, the photoconductor 12 is formed of a cylindrical body, but the present invention is not limited to such a form, and an endless belt type photoconductor can be used instead. The photoreceptor 12 is drivingly connected to a motor (not shown), and is rotated in the direction of arrow 14 based on the driving of the motor. Around the photoconductor 12, a charging station 16, an exposure station 18, a developing station 20, a transfer station 22, and a cleaning station 24 are arranged along the rotation direction of the photoconductor 12.

  The charging station 16 includes a charging device 26 that charges a photosensitive layer, which is the outer peripheral surface of the photosensitive member 12, to a predetermined potential. In the embodiment, the charging device 26 is represented as a cylindrical roller. However, instead of this, other types of charging devices (for example, a rotary or fixed brush-type charging device or a wire-discharge-type charging device) may be used. Can be used. In the exposure station 18, the image light 30 emitted from the exposure device 28 disposed in the vicinity of the photosensitive member 12 or away from the photosensitive member 12 travels toward the outer peripheral surface of the charged photosensitive member 12. A passage 32 is provided. On the outer peripheral surface of the photoconductor 12 that has passed through the exposure station 18, an electrostatic latent image is formed that includes a portion where the image light is projected and the potential is attenuated and a portion where the charged potential is substantially maintained. In the embodiment, the portion where the potential is attenuated is the electrostatic latent image portion, and the portion where the charged potential is substantially maintained is the electrostatic latent image non-image portion. The developing station 20 includes a developing device 34 that visualizes the electrostatic latent image using a powder developer. Details of the developing device 34 will be described later. The transfer station 22 includes a transfer device 36 that transfers a visible image formed on the outer peripheral surface of the photoreceptor 12 to a sheet 38 such as paper or film. In the embodiment, the transfer device 36 is represented as a cylindrical roller, but other types of transfer devices (for example, wire discharge transfer devices) can also be used. The cleaning station 24 includes a cleaning device 40 that collects untransferred toner remaining on the outer peripheral surface of the photoconductor 12 without being transferred to the sheet 38 at the transfer station 22 from the outer peripheral surface of the photoconductor 12. In the embodiment, the cleaning device 40 is shown as a plate-like blade, but other types of cleaning devices (for example, a rotary type or a fixed type brush type cleaning device) may be used instead.

  When the image forming apparatus 11 having such a configuration forms an image, the photoconductor 12 rotates clockwise based on the driving of a motor (not shown). At this time, the outer peripheral portion of the photoreceptor passing through the charging station 16 is charged to a predetermined potential by the charging device 26. The charged outer periphery of the photoreceptor is exposed to image light 30 at the exposure station 18 to form an electrostatic latent image. The electrostatic latent image is conveyed to the developing station 20 along with the rotation of the photosensitive member 12, where it is visualized as a developer image by the developing device 34. The visualized developer image is conveyed to the transfer station 22 along with the rotation of the photosensitive member 12, and is transferred to the sheet 38 by the transfer device 36 there. The sheet 38 to which the developer image has been transferred is conveyed to a fixing station (not shown), where the developer image is fixed to the sheet 38. The outer peripheral portion of the photosensitive member that has passed through the transfer station 22 is conveyed to the cleaning station 24 where the developer remaining on the outer peripheral surface of the photosensitive member 12 without being transferred to the sheet 38 is recovered.

[Development equipment]
The developing device 34 includes a developing tank (housing) 42 that accommodates the developer 10 of the present invention and various members described below. In order to facilitate understanding of the invention by simplifying the drawing, a part of the developing tank 42 is omitted. The developing tank 42 includes a series of openings (44, 52) opened toward the photosensitive member 12, and a toner conveying member (second conveying member) is formed in a space 46 formed in the vicinity of the opening 44. A developing roller 48 is provided. The developing roller 48 is a cylindrical member (second rotating cylindrical body), and is arranged in parallel to the photosensitive member 12 and rotatably via the outer peripheral surface of the photosensitive member 12 and a predetermined developing gap 50. .

  Behind the developing roller 48, another space 52 is formed as an opening. In the space 52, a transport roller 54 that is a developer transport member (first transport member) is disposed in parallel with the developing roller 48 and through an outer peripheral surface of the developing roller 48 and a predetermined supply / recovery gap 56. . The conveyance roller 54 includes a magnet body 58 that is fixed so as not to rotate, and a cylindrical sleeve 60 (first rotating cylinder body) that is rotatably supported around the magnet body 58. Above the sleeve 60, a restricting plate 62 fixed to the developing tank 42 and extending in parallel with the central axis of the sleeve 60 is disposed so as to oppose a predetermined restricting gap 64.

  The magnet body 58 has a plurality of magnetic poles facing the inner surface of the transport roller 54 and extending in the direction of the central axis of the transport roller 54. In the embodiment, the plurality of magnetic poles are opposed to the magnetic pole S <b> 1 facing the upper inner peripheral surface portion of the transport roller 54 near the regulating plate 62 and the left inner peripheral surface portion of the transport roller 54 near the supply and recovery gap 56. Magnetic pole N1, magnetic pole S2 facing the lower inner peripheral surface portion of the transport roller 54, and two adjacent magnetic poles N2, N3 of the same polarity facing the right inner peripheral surface portion of the transport roller 54.

  A developer stirring chamber 66 is formed behind the transport roller 54. The stirring chamber 66 has a front chamber 68 formed in the vicinity of the transport roller 54 and a rear chamber 70 separated from the transport roller 54. A front screw 72 that is a pre-stirring and conveying member that conveys the developer while stirring the developer from the front surface to the back surface of the drawing is rotatably disposed in the front chamber 68, and the rear chamber 70 is rotated from the back surface to the front surface of the drawing. A rear screw 74 that is a rear stirring member transporting member that transports the developer while stirring is disposed rotatably. As shown in the figure, the front chamber 68 and the rear chamber 70 may be separated by a partition wall 76 provided therebetween. In this case, the partition portions near both ends of the front chamber 68 and the rear chamber 70 are removed to form a communication passage, and the developer that has reached the downstream end of the front chamber 68 passes through the communication passage. The developer that has been fed to 70 and reaches the downstream end of the rear chamber 70 is fed to the front chamber 68 via a communication passage.

  The operation of the developing device 34 configured as described above will be described. During image formation, the developing roller 48 and the sleeve 60 rotate in the directions of arrows 78 and 80, respectively, based on driving of a motor (not shown). The front screw 72 rotates in the direction of arrow 82 and the rear screw 74 rotates in the direction of arrow 84. Thereby, the developer 10 accommodated in the developer stirring chamber 66 is stirred while being circulated and conveyed through the front chamber 68 and the rear chamber 70. As a result, the toner and the carrier contained in the developer come into frictional contact with each other and are charged with opposite polarities.

  The charged developer 10 is supplied to the transport roller 54 in the process of being transported through the front chamber 68 by the front screw 72. The developer 10 supplied from the front screw 72 to the conveyance roller 54 is held on the outer peripheral surface of the sleeve 60 by the magnetic force of the magnetic pole N3 in the vicinity of the magnetic pole N3. The developer 10 held by the sleeve 60 forms a magnetic brush along the magnetic field lines formed by the magnet body 58, and is conveyed in the counterclockwise direction based on the rotation of the sleeve 60. The amount of developer 10 held by the magnetic pole S <b> 1 in the area facing the restriction plate 62 (restriction area 86) is restricted to a predetermined amount by the restriction plate 62 through the restriction gap 64. The developer 10 that has passed through the regulation gap 64 is transported to a region (supply / recovery region) 88 where the developing roller 48 and the transporting roller 54 are opposed, where the magnetic pole N1 is opposed. Of the supply / recovery region 88, an upstream region (supply region) 90 mainly with respect to the rotation direction of the sleeve 60 adheres to the carrier due to the presence of an electric field formed between the developing roller 48 and the sleeve 60. Toner is electrically supplied to the developing roller 48. Further, in the supply / recovery area 88, the area on the downstream side (recovery area) 92 mainly with respect to the rotation direction of the sleeve 60, the toner on the developing roller 48 sent back to the supply / recovery area 88 without contributing to the development. The magnetic brush formed along the magnetic field lines of the magnetic pole N1 is scraped off and collected by the sleeve 60. The carrier is held on the outer peripheral surface of the sleeve 60 by the magnetic force of the magnet body 58 and does not move from the sleeve 60 to the developing roller 48. The charged particles behave together with the carrier to suppress a decrease in the toner charging ability of the carrier.

  When the developer 10 that has passed through the supply / recovery region 88 is held by the magnetic force of the magnet body 58 and passes through the opposing portion of the magnetic pole S2 along with the rotation of the sleeve 60, it reaches the opposing region (discharge region 94) of the magnetic poles N2 and N3. The repulsive magnetic field formed by the magnetic poles N2 and N3 is discharged from the outer peripheral surface of the sleeve 60 to the front chamber 68 and mixed with the developer 10 being conveyed through the front chamber 68.

The toner held on the developing roller 48 in the supply area 90 is conveyed counterclockwise with the rotation of the developing roller 48, and is an area (developing area) 96 where the photoconductor 12 and the developing roller 48 face each other. It adheres to the electrostatic latent image portion formed on the outer peripheral surface. In the image forming apparatus according to the embodiment, a predetermined negative potential V _H is applied to the outer peripheral surface of the photoreceptor 12 by the charging device 26, and the electrostatic latent image image portion on which the image light 30 is projected by the exposure device 28 is predetermined. attenuated until the potential V _L, an electrostatic latent image non-image portion of the image light 30 is not projected by the exposing device 28 maintains a substantially charge potential V _H. Accordingly, in the developing region 96, the negatively charged toner adheres to the electrostatic latent image portion due to the action of the electric field formed between the photosensitive member 12 and the developing roller 48, and this electrostatic latent image is displayed. The image is visualized as a developer image.

  When the toner is consumed from the developer 10 in this manner, it is preferable that an amount of toner corresponding to the consumed amount is supplied to the developer 10. For this purpose, the developing device 34 includes means for measuring the mixing ratio of the toner and the carrier stored in the developing tank 42. In addition, a toner replenishment section 98 is provided above the rear chamber 70. The toner supply unit 98 includes a container 100 for storing toner. An opening 102 is formed at the bottom of the container 100, and a supply roller 104 is disposed in the opening 102. The replenishing roller 104 is drivingly connected to a motor (not shown), and the motor is driven based on the output of the means for measuring the mixing ratio of toner and carrier so that the toner drops and replenishes the rear chamber 70. Since charged particles behave with carriers, consumption of charged particles is suppressed. Therefore, the replenishment toner can be set by reducing the ratio of charged particles to the content ratio of charged particles to toner particles in the initially filled developer.

[Electric field forming means]
In order to efficiently move the toner from the sleeve 60 to the developing roller 48 in the supply region 90, the developing roller 48 and the sleeve 60 are electrically connected to the electric field forming device 110. Specific examples of power supplies are shown in FIGS.

The electric field forming apparatus 110 according to the first exemplary embodiment illustrated in FIG. 2A includes a first power source 112 (corresponding to a second electric field forming unit) connected to the developing roller 48 and a second power source 114 (corresponding to the second electric field forming unit). Corresponding to first electric field forming means). The first power supply 112 has a DC power supply 118 connected between the developing roller 48 and the ground 116, and supplies a first DC voltage V _DC1 (for example, −200 volts) having the same polarity as the charging polarity of the toner. It is applied to the developing roller 48. The second power source 114 has a DC power source 120 connected between the sleeve 60 and the ground 116, and has the same polarity as the charging polarity of the toner and a second DC voltage V higher than the first DC voltage. _DC2 (eg, −400 volts) is applied to the sleeve 60. As a result, in the supply region 90, the negatively charged toner is electrically attracted from the sleeve 60 to the developing roller 48 under the action of a DC electric field formed between the developing roller 48 and the sleeve 60. The At this time, the positively charged carrier is not attracted to the developing roller 48 from the sleeve 60. In the developing region 96, the negative toner held on the developing roller 48 is, as shown in FIG. 2B, the developing roller 48 (V _DC1 : −200 volts) and the electrostatic latent image portion (V _L :−). It adheres to the electrostatic latent image portion based on the potential difference of 80 volts). At this time, the negative polarity toner adheres to the electrostatic latent image non-image portion due to a potential difference between the developing roller 48 (V _DC1 : −200 volts) and the electrostatic latent image non-image portion (V _H : −600 volts). There is nothing.

In the electric field forming apparatus 122 of FIG. 3A according to the second embodiment, the first power supply 124 (corresponding to the second electric field forming means) is provided between the developing roller 48 and the ground 126, similarly to the power supply of the first embodiment. The first DC voltage V _DC1 (for example, −200 volts) having the same polarity as the charging polarity of the toner is applied to the developing roller 48. The second power supply 130 (corresponding to the first electric field forming means) has a DC power supply 132 and an AC power supply 134 between the sleeve 60 and the ground 126. The DC power supply 132 applies a second DC voltage V _DC2 (for example, −400 volts) having the same polarity as the toner charging polarity and higher than the first DC voltage to the sleeve 60. As shown in FIG. 3B, the AC power supply 134 applies an _AC voltage VAC having a peak-to-peak voltage V _PP of, for example, 300 volts between the sleeve 60 and the ground 126. As a result, in the supply region 90, the negatively charged toner is electrically attracted from the sleeve 60 to the developing roller 48 due to the action of the pulsating electric field formed between the developing roller 48 and the sleeve 60. Is done. At this time, the positively charged carrier is held by the sleeve 60 by the magnetic force of the fixed magnet inside the sleeve 60 and is not supplied to the developing roller 48. In the developing region 96, the negative toner held on the developing roller 48 is caused by a potential difference between the developing roller 48 (V _DC1 : −200 volts) and the electrostatic latent image portion (V _L : −80 volts). Based on the electrostatic latent image portion.

In the electric field forming device 136 shown in FIG. 4A, the first power supply 138 includes a DC power supply 142 and an AC power supply 144 between the developing roller 48 and the ground 140. The DC power supply 142 applies a first DC voltage V _DC1 (for example, −200 volts) having the same polarity as the toner charging polarity to the sleeve 60 and the developing roller 48. The AC power supply 144 applies an _AC voltage VAC having an amplitude (peak-to-peak voltage) _VP-P of, for example, 1,600 volts between the sleeve 60 and the developing roller 48 and the ground 146. The second power source 146 (corresponding to the first electric field forming means) has a DC power source 150 connected between the terminal 148 between the developing roller 48 and the AC power source 144 and the sleeve 60. The DC power supply 150 can output a predetermined DC voltage V _DC2 , and the anode is connected to the terminal 148 and the cathode is connected to the sleeve 60, whereby the sleeve 60 is biased to the negative polarity with respect to the developing roller 48. (See FIG. 4B). Accordingly, in the supply region 90, the negatively charged toner is electrically attracted from the sleeve 60 to the developing roller 48 due to the action of the pulsating electric field formed between the developing roller 48 and the sleeve 60. The In the developing region 96, the negative toner on the developing roller 48 is statically charged based on the potential difference between the developing roller 48 (V _DC1 : −200 volts) and the electrostatic latent image portion (V _L : −80 volts). It adheres to the electrostatic latent image portion.

An electric field forming apparatus 152 shown in FIG. 5 is obtained by adding AC power supplies 154 and 156 to the first power supply 112 and the second power supply 114, respectively, in the electric field forming apparatus 110 of Embodiment 1 shown in FIG. 2A. The output voltages of the AC power supplies 154 and 156 are V _AC1 and V _AC2 . The voltages V _AC1 and V _AC2 may be the same or different. An electric field forming device 158 shown in FIG. 6 is obtained by adding an AC power source 160 to the first power source 112 in the power source of the embodiment shown in FIG. 2A. The output voltage of the AC power supply 160 is _{V AC.} Similarly to the electric field forming devices 110, 122, and 136, the electric field forming devices 152 and 158 of these forms also receive the action of the pulsating electric field formed between the developing roller 48 and the sleeve 60, and in the supply region 90. The negatively charged toner is supplied from the sleeve 60 to the developing roller 48, and the negatively charged toner is supplied from the developing roller 48 to the electrostatic latent image portion (V _L : −80 volts) in the developing region 96. Is supplied to the electrostatic latent image portion.

EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, it is clear that this invention should not be construed limited to an Example. “Parts” shall mean “parts by weight”.
Example 1
<Manufacture of carriers>
The core material was manufactured according to the following method.
(Raw material crushing process)
0.01% by mass of MgCl ₂ was mixed with the compounding ratio of Fe ₂ O ₃ = 60 mol% and MgO = 40 mol%, and the raw materials were pulverized with a pulverizer / mixer.
(Slurry process and granulation process)
An adhesive (polyvinyl alcohol (compound C)) and water were added to the pulverized product obtained above to form a 60% by mass slurry, which was further pulverized by a wet ball mill to form a slurry. The slurry dispersion was sprayed and dried using a spray dryer to produce granulated particles having a number average particle size of about 38 μm. The addition ratio of the C compound was 0.7% by mass in terms of C element.

(Baking process)
The above granulated particles were fired at 1230 ° C. in an air atmosphere in a drying furnace to produce ferrite particles.
(Disintegration / classification process)
The fired ferrite particles were pulverized and sieved to obtain ferrite particles having a volume average particle size of about 35 μm except for those having large and small particle sizes.
(Magnetic separation process)
The ferrite particles were passed through a magnetic separator to remove non-magnetic or weak magnetic particles to produce ferrite particles (core material). Table 1 shows SF1 and SF2 of the core material.

A coating layer was formed on the core material according to the following method.
Polymerization is carried out by a known emulsion polymerization method using CHMA (cyclohexyl methacrylate) / MMA (methyl methacrylate) / ST (styrene) = 45/45/10 (monomer weight ratio), and then washed with water and dried to obtain an average particle diameter. 100 nm styrene acrylic resin fine particles (Tg; 102 ° C., Tm; 220 ° C.) were obtained.
A carrier was obtained by coating 100 parts of the core material with styrene acrylic resin particles by a dry coating method so that the coating amount (after drying) was 2.4 parts. Table 1 shows the dynamic current value D50 of the carrier.

<Manufacture of toner>
(First stage polymerization; miniemulsion polymerization)
175 g of styrene
60 g of n-butyl acrylate
Methacrylic acid 15g
n-octyl-3-mercaptopropionate 7 g
A monomer mixed solution consisting of the above was placed in a reaction vessel equipped with a stirrer, and 100 g of pentaerythritol tetrabehenate was added thereto, heated to 70 ° C. and dissolved to prepare a monomer solution.

  On the other hand, a surfactant solution in which 2 g of polyoxyethylene (2) sodium dodecyl ether sulfate is dissolved in 1350 g of ion-exchanged water is heated to 70 ° C., added to and mixed with the monomer solution, and then a machine having a circulation path. Dispersion was carried out at 70 ° C. for 30 minutes using an expression disperser “Clearmix” (manufactured by M Technique Co., Ltd.) to prepare an emulsified dispersion.

  Next, an initiator solution prepared by dissolving 7.5 g of potassium persulfate in 150 g of ion-exchanged water was added to this dispersion, and polymerization was performed by heating and stirring the system at 78 ° C. for 1.5 hours. A dispersion of resin particles was obtained. This is referred to as “dispersion of resin particles 1”.

(Second stage polymerization; formation of outer layer)
An initiator solution prepared by dissolving 12 g of potassium persulfate in 220 g of ion-exchanged water was added to the “dispersion of resin particles 1” obtained as described above, and 320 g of styrene under a temperature condition of 80 ° C.
n-Butyl acrylate 100g
Methacrylic acid 35g
n-octyl-3-mercaptopropionate 7.5 g
A monomer mixture consisting of was added dropwise over 1 hour. After completion of the dropping, polymerization was carried out by heating and stirring for 2 hours. Then, it cooled to 28 degreeC and obtained "the dispersion liquid of the resin particle 2."

(Colorant particle dispersion)
A solution was prepared by stirring and dissolving 90 g of sodium dodecyl sulfate in 1600 g of ion-exchanged water. While stirring this solution, 400.0 g of carbon black “Regal 330R” (Cabot) is gradually added, and then dispersed using a mechanical disperser “Clearmix” (M Technique). Thus, a colorant particle dispersion was prepared. The particle diameter of the colorant particles in this dispersion was measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.) and found to be 110 nm.

((Aggregation / fusion) meeting process)
Resin particle 2 dispersion 2000 g
670 g of ion exchange water
Colorant particle dispersion 400g
The above solution is put into a 5 L reaction vessel equipped with a temperature sensor, a cooling pipe, a nitrogen introducing device, and a stirring device, stirred, and adjusted to a temperature of 30 ° C. Then, a 5N sodium hydroxide aqueous solution is added to this solution. The pH was adjusted to 10.

  Next, an aqueous solution in which 60 g of magnesium chloride hexahydrate was dissolved in 60 g of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After standing for 3 minutes, the temperature was started to rise, and the temperature of the system was raised to 90 ° C. over 60 minutes to grow the particle size and perform an association reaction. In this state, the particle size of the associated particles was measured with “Coulter Multisizer III” (manufactured by Beckman Coulter), and 8.5 g of sodium chloride was ion exchanged when the median particle size on the volume basis reached 6 μm. An aqueous solution dissolved in 35 g of water was added to stop particle growth, and then heating and stirring were continued for 3 hours for fusion.

  Then, it cooled to 30 degreeC, hydrochloric acid was added, pH was adjusted to 2.0, and stirring was stopped. The grown associated particles were filtered, washed repeatedly with ion exchange water at 35 ° C., and then dried with hot air at 40 ° C. to obtain toner particles.

  With respect to 100 parts by weight of the toner particles, 0.2 parts by weight of the first hydrophobic silica, 0.5 parts by weight of the second hydrophobic silica, 0.5 parts by weight of the hydrophobic titanium oxide, and a number average particle diameter of 350 nm 2 parts by weight of strontium titanate was subjected to a surface treatment for 3 minutes at a speed of 40 m / s using a Henschel mixer (manufactured by Mitsui Kinzoku Mining Co., Ltd.) to obtain a negatively chargeable toner. Table 1 shows the average particle diameter and average circularity of the toner.

The first hydrophobic silica used here is a silica (# 130: manufactured by Nippon Aerosil Co., Ltd.) having a number average primary particle size of 16 nm and surface-treated with hexamethyldisilazane (HMDS) as a hydrophobizing agent. is there.
The second hydrophobic silica is obtained by surface-treating silica having a number average primary particle size of 20 nm (# 90: manufactured by Nippon Aerosil Co., Ltd.) with HMDS.
Hydrophobic titanium oxide is obtained by surface-treating anatase-type titanium oxide having a number average primary particle size of 30 nm with isobutyltrimethoxysilane as a hydrophobizing agent in an aqueous wet process.

<Evaluation>
The developer obtained by mixing the negatively chargeable toner and the carrier obtained in the example / comparative example at a weight mixing ratio (toner / carrier) of 8/92 is incorporated into the hybrid developing device having the form shown in FIG. The image forming apparatus (bizhub C350 modified machine; manufactured by Konica Minolta Business Technologies, Inc.) was mounted. Using this image forming apparatus, a predetermined image was printed and evaluated. The toner is controlled to be replenished based on the toner density detection result of the developer.

Development conditions are as follows. The electric field forming apparatus employs the form shown in FIG. 6, and a DC voltage V _{DC2 of} −500 volts is applied to the transport roller, and an AC voltage of DC voltage V _{DC1 of} −300 volts is applied to the developing roller. AC voltage frequency: 2 kHz, the amplitude _V P-P: 1,500 volts, minus the duty ratio (toner collecting duty ratio): 40%, plus a duty ratio (toner supply duty ratio): was 60% of the rectangular wave . The development gap 50 was set to 0.3 mm, the supply / recovery gap 56 was set to 0.6 mm, and the regulating portion was set so that the developer conveyance amount of the conveyance roller was 50 mg / cm ² . The charged potential (non-image portion) of the photoreceptor was −550 volts, and the potential of the electrostatic latent image (image portion) formed on the photoreceptor was −60 volts.

(Image memory)
90,000 image patterns 400 having a solid area 401 and a half area 402 as shown in FIG. 8 were output and printed, and evaluated based on the degree of occurrence of image memory in the printed image. Specifically, the evaluation was made according to the following criteria. The negative image is a relatively low density image portion that appears in the half area. A positive image is a half image portion that appears at an appropriate density. The density difference (ΔTD) was determined with a transmission densitometer.
A: Although some negative / positive images having a density difference of less than 0.04 were partially generated, the occurrence of the negative portion was hardly visually recognized;
○: Although there was some occurrence of a negative / positive image having a density difference of less than 0.07, there was no practical problem as a whole image;
Δ: Negative / positive image having a density difference of less than 0.10 was generated, but there was no practical problem;
X: A negative / positive image having a density difference of 0.10 or more is generated, which is problematic in practical use.

(Charge by carrier)
After printing 90,000 images with a printing rate of 5%, the carrier was taken out of the developing device. The new negatively chargeable toner and the carrier were mixed at a weight mixing ratio (toner / carrier) of 8/92 for a predetermined time, and the charge amount of the toner was measured by a blow-off method. Evaluation was made based on the absolute value (Qa) of the toner charge amount.
A: 30 ≦ Qa ≦ 40;
○: 20 ≦ Qa <30 or 40 <Qa ≦ 50;
Δ: 10 ≦ Qa <20 or 50 <Qa ≦ 60 (no problem in practical use);
X: Qa <10 or 60 <Qa (practical problem).

(Examples 2-15, Comparative Examples 1-7)
A carrier having the physical properties shown in Table 1 was produced in the same manner as in Example 1 except that the carrier production conditions were appropriately changed as shown in Table 1.
In the association process at the time of toner production, when the median particle diameter (D ₅₀ ) on the volume basis reaches a predetermined value, the particle growth is stopped, and the average circularity is adjusted by adjusting the stirring time for fusing. A toner having the physical properties shown in Table 1 was produced in the same manner as in Example 1 except that the control was performed.

  Evaluation was performed in the same manner as in Example 1 except that such carrier and toner were used.

In the table, acrylic means acrylic resin particles produced by the following method.
Polymerization is carried out by a known emulsion polymerization method using CHMA (cyclohexyl methacrylate) / MMA (methyl methacrylate) = 50/50 (monomer weight ratio), followed by washing with water and drying to obtain acrylic resin fine particles having an average particle diameter of 100 nm (Tg : 115 ° C, Tm: 230 ° C).
When silicone was used, the carrier was manufactured according to the following method.
A coating solution of 200 parts of a silicone resin liquid (Toray Silicone SR2406, solid content 20%) and 1500 parts of toluene was prepared. 5 kg of ferrite carrier with an average particle diameter of 50 μm is put into a rotating disk type fluidized bed particle coating device and the coating liquid of the above formulation is sprayed under heating at 80 ° C. while flowing, and the applied material is removed from the coating device. The silicone film was cured by heating at 200 ° C. for 2 hours.

1 is a diagram illustrating a schematic configuration of an example of an image forming apparatus according to the present invention and a cross section of a developing device according to the present invention. The figure which shows one Embodiment of an electric field formation apparatus. The figure which shows the relationship between the voltage supplied to the sleeve and the image development sleeve from the electric field formation apparatus shown to FIG. 2A. The figure which shows other embodiment of an electric field formation apparatus. The figure which shows the relationship between the voltage supplied to the sleeve and the image development sleeve from the electric field formation apparatus shown to FIG. 3A. The figure which shows other embodiment of an electric field formation apparatus. The figure which shows the relationship between the voltage supplied to the sleeve and the image development sleeve from the electric field formation apparatus shown to FIG. 4A. The figure which shows other embodiment of an electric field formation apparatus. The figure which shows other embodiment of an electric field formation apparatus. Schematic for demonstrating the measuring method of the dynamic current value of a carrier. The schematic of the image for evaluating in an Example.

Explanation of symbols

  10: Developer, 11: Image forming device, 12: Photoconductor, 16: Charging station, 18: Exposure station, 20: Development station, 22: Transfer station, 24: Cleaning station, 26: Charging device, 28: Exposure device , 30: image light, 32: passage, 34: developing device, 36: transfer device, 38: sheet, 40: cleaning device, 42: developing tank (housing), 44: opening, 46: second space, 48 : Development roller, 50: development gap, 52: opening (second space), 54: transport roller, 56: supply / recovery gap, 58: magnet body, 60: sleeve, 62: restriction plate, 64: restriction gap, 66: developer stirring chamber, 68: front chamber, 70: rear chamber, 72: front screw, 74: rear screw, 76: partition wall, 86: restriction area, 88: supply / recovery area 90: feed zone, 92: collection area, 94: emission region, 96: development region, 98: a toner supply unit, 100: a container, 102: opening, 104: supply roller, 110: electric field forming apparatus.

Claims (5)

A carrier for hybrid development having a resin coating layer on the surface of a core material,
The SF1 value represented by the formula (I) is 100 to 120, and the SF2 value represented by the formula (II) is 120 to 130,
A carrier for hybrid development having an average particle diameter D50 of the carrier of 20 to 80 μm and a dynamic current value of 0.1 to 0.8 μA;
SF1 = (MXLNG) ² / AREA × π / 4 × 100 (I)
[Where MXLNG indicates the absolute maximum length of the core material on the image; AREA indicates the projected area of the core material]
SF2 = (PERIME) ² / AREA × π / 4 × 100 (II)
[Where PELME indicates the peripheral length of the projected image of the core material on the image; AREA indicates the projected area of the core material].   The carrier for hybrid development according to claim 1, wherein the resin coat layer contains an acrylic resin.   A developer for hybrid development comprising the carrier according to claim 1 or 2 and a toner. The toner agglomerates and fuses the resin fine particles and the colorant,
The average circularity of the toner is 0.92 to 0.98,
The developer for hybrid development according to claim 3, wherein the toner has a volume average particle diameter of 3 to 8 μm.   An image forming apparatus comprising the developer for hybrid development according to claim 3.

Images