JP2016173518A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of preventing fusion of a toner component onto the surface of a developing sleeve.SOLUTION: A developing device 5 includes: a development sleeve 61 which is subjected to sand blast treatment and has a cylindrical shape; a magnet roller 62 having a plurality of magnetic poles; a regulation member 55 for adjusting a conveyance amount of a two-component developer; and a two-component developer containing toner base particles a capsule toner containing a coating layer formed by fusing resin fine particles onto the surface of the toner base particles, and a carrier. When an average particle size of abrasive grains used in the sand blast treatment is represented by A μm, a content of the carrier particles having a particle size of 0.7×A μm or more and A μm or less is less than 5 mass% of the whole carrier.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a developing device and an image forming apparatus, and more particularly, to a developing device capable of preventing fusion of a toner component to the surface of a developing sleeve.

  In an image forming apparatus using an electrophotographic system, an image is generally formed on a recording medium through a series of processes including a charging process, an exposure process, a development process, a transfer process, a cleaning process, and a fixing process. . In the developing process, the developer is supplied to the electrostatic image on the photosensitive drum formed through the charging process and the exposure process using a developing device that stores the developer, thereby forming a toner image. Specifically, the developer in the developing device is pumped up and conveyed toward the photosensitive drum using a developing roller including a cylindrical developing sleeve and a magnet roller having a magnetic pole.

  In order to stabilize the developer transport amount, the developing sleeve has irregularities formed on the surface thereof by a process such as a sandblast process. Japanese Patent Application Laid-Open No. 2011-8016 describes a developing device that includes a two-component developer containing toner and a carrier, and a developing sleeve whose surface roughness is adjusted.

  As for the developer, a one-component developer composed only of toner and a two-component developer composed of toner and carrier are known, but as a toner used in these developers, low-temperature fixability and blocking resistance are known. An excellent capsule toner has been proposed (see JP-A-2-208661).

JP 2011-8016 A JP-A-2-208661

  However, when a developing device comprising a sandblasted cylindrical developing sleeve and a two-component developer containing capsule toner and a carrier is used, toner component fusion occurs on the surface of the developing sleeve, resulting in uneven image density. There was a problem such as.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a developing device capable of solving the above-described problems of the prior art and preventing the toner component from being fused to the surface of the developing sleeve. Another object of the present invention is to provide an image forming apparatus provided with such a developing device.

The present inventor has examined the cause of fusing of the toner component to the surface of the developing sleeve when the developing device as described above is used. By the fusion of the toner component, a black film is finally formed on the surface of the developing sleeve. In the initial stage, the formation of the white film can be confirmed. Here, the black film is due to the color of the black toner, but the white film is considered to be due to the fusion of the resin fine particles constituting the capsule toner.
The capsule toner contains a coating layer formed by fusing resin fine particles on the surface of the toner base particles, but part of the resin fine particles are detached from the coating layer when the two-component developer is stirred and conveyed. It adheres to the recess on the surface of the developing sleeve.
Further, the two-component developer passes through the gap between the developing sleeve and the regulating member, and the conveyance amount thereof is adjusted, but at that time, it receives a compressive force. For this reason, it is presumed that the resin fine particles adhering to the recesses on the surface of the developing sleeve are crushed by the carrier particles, the resin fine particles are fused on the surface of the developing sleeve, and a white film is formed.
When a white film is formed, filming of toner components such as toner base particles is likely to occur, and as a result, a black film is formed over time, which causes image density unevenness.

  Under such circumstances, as a result of intensive studies to achieve the above object, the present inventor has developed by adjusting the particle size distribution of the carrier with respect to the average particle size of the abrasive particles used for the sandblasting treatment of the developing sleeve. The inventors have found that the toner component can be prevented from being fused to the sleeve surface, and have completed the present invention.

That is, the developing device of the present invention includes a sandblasted cylindrical developing sleeve,
A magnet roller having a plurality of magnetic poles;
A regulating member for adjusting the transport amount of the two-component developer;
A developing device including a toner base particle and a two-component developer including a capsule toner including a coating layer formed by fusing resin fine particles on the surface of the toner base particle and a carrier,
When the average particle size of the abrasive grains used in the sandblasting treatment is A μm, the content of carrier particles having a particle size of 0.7 × A μm or more and A μm or less is less than 5% by mass of the whole carrier. And

  In a preferred example of the developing device of the present invention, the content of carrier particles having a particle size of 0.2 × A μm or more and 0.4 × A μm or less is 20% by mass or more and 50% by mass or less of the entire carrier.

  An image forming apparatus according to the present invention includes the above developing device.

  According to the developing device of the present invention, the toner component can be prevented from being fused to the surface of the developing sleeve by adjusting the carrier particle size distribution with respect to the average particle size of the abrasive grains used for sandblasting of the developing sleeve. A possible developing device can be provided. In addition, according to the image forming apparatus of the present invention, it is possible to provide an image forming apparatus capable of preventing the toner component from being fused to the surface of the developing sleeve by using such a developing apparatus.

1 is a schematic cross-sectional view illustrating an overall configuration of an image forming apparatus 1 that is an embodiment of an image forming apparatus of the present invention. It is a schematic sectional drawing explaining the whole structure of one embodiment of the image development apparatus of this invention, and is an enlarged view of the image development apparatus 5 shown in FIG. FIG. 3 is a view taken along the line A-A ′ of the developing device shown in FIG. 2. FIG. 3 is a perspective view of a developing roller 52 shown in FIG. 2.

  The developing device of the present invention will be described in detail below. The developing device of the present invention includes a sandblasted cylindrical developing sleeve, a magnet roller having a plurality of magnetic poles, a regulating member for adjusting the transport amount of the two-component developer, toner base particles, and the surface of the toner base particles A developing device comprising a two-component developer including a capsule toner including a coating layer formed by fusing resin fine particles to a carrier and a carrier, and having an average particle diameter of Aμm used for the sandblasting process The content of carrier particles having a particle size of 0.7 × A μm or more and A μm or less is less than 5% by mass of the whole carrier.

  The developing sleeve used in the developing device of the present invention is a member constituting the developing roller together with a magnet roller, which will be described later, and is provided so as to be rotatable in the developing device. By rotating the developing sleeve, the two-component developer in the developing device can be pumped and conveyed toward the photosensitive drum.

As the developing sleeve, for example, a cylindrical developing sleeve formed of a nonmagnetic material such as aluminum or stainless steel can be used. On the surface thereof, the transport amount of the two-component developer is stabilized. , Sand blasting is applied to form irregularities. Sandblasting is a technology for surface treatment such as roughening by spraying abrasive grains on the surface using compressed air or steam. As abrasive grains, alumina, silicon carbide, spherical glass beads, etc. are used. it can. Moreover, a sand blaster is used as a device for spraying abrasive grains, and the size of the surface irregularities is adjusted by conditions such as the grain size of the abrasive grains, the nozzle diameter of the sand blaster, the air pressure, and the processing time. In particular, the influence of the grain size of the abrasive grains is the largest.
In this invention, it is preferable that the average particle diameter of the abrasive grain used for a sandblasting process is 70 micrometers or more and 100 micrometers or less. In the present invention, the grain size of the abrasive grains is represented by a sphere equivalent diameter by a laser diffraction / scattering method, and the average particle size (volume average particle size) is a particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., model: Microtrack MT3000). The other conditions are not particularly limited. For example, the sand blaster nozzle diameter is 2000 to 6000 μm, the air pressure is 0.2 to 0.35 MPa, and the treatment time is 3.15 to 3. 20 seconds.

  The developing sleeve used in the developing device of the present invention preferably has a 10-point average roughness Rz of 5 to 10 μm on the sandblasted surface. The ten-point average roughness Rz is measured according to JIS B 0601-1994, and for example, a surface roughness measuring device SJ-400 (manufactured by Mitutoyo Corporation) can be used.

  The magnet roller used in the developing device of the present invention is a member constituting the developing roller together with the developing sleeve, and is disposed inside the developing sleeve. The developing sleeve is provided so as to be able to rotate in the developing device, but the magnet roller is fixed so as not to rotate in the developing device. Further, the magnet roller has a plurality of magnetic poles, and is fixed to the magnet roller fixed shaft so that, for example, N poles and S poles are alternately arranged along the circumferential direction.

  The regulating member used in the developing device of the present invention is not particularly limited as long as it can adjust the transport amount of the two-component developer. For example, a plate-like member extending in parallel with the axial direction of the developing sleeve is used. Can be used. The regulating member is fixed to the developing device so as to maintain a constant gap with respect to the surface of the developing sleeve, and when the two-component developer pumped up by the developing sleeve passes through the gap, the two-component developer layer Adjust the transport amount with a constant thickness. As a material of the regulating member, for example, a nonmagnetic material such as aluminum or stainless steel can be used. However, the material is not limited to this, and a magnetic material may be used.

  The two-component developer used in the developing device of the present invention includes a toner base particle and a capsule toner including a coating layer formed by fusing resin fine particles on the surface of the toner base particle and a carrier. The two-component developer can be prepared by mixing capsule toner and carrier. Here, as the mixing device, for example, a powder mixer such as a V-type mixer (trade name: V-5, manufactured by Tokuju Kogakusho Co., Ltd.) can be used. The mixing ratio of the capsule toner and the carrier is preferably, for example, a mass ratio of 10:90 to 5:95.

  The carrier is composed of carrier particles having different sizes. In the developing device of the present invention, when the average particle size of the abrasive used for sandblasting the developing sleeve is A μm, the particle size is 0.7. It is required that the content of carrier particles of x Aμm or more and Aμm or less is less than 5% by mass of the entire carrier. As described above, the toner component is fused to the surface of the developing sleeve (formation of a black film) is a white color formed by the resin particles adhering to the concave portion of the developing sleeve surface being crushed and fused by the carrier particles. The membrane is the beginning. Therefore, the present inventor suppresses the fusion of the toner component to the surface of the developing sleeve by eliminating or significantly reducing the carrier particles having the defect of crushing the resin fine particles from the particle group, thereby causing uneven image density. It was found that the occurrence can be prevented. As a result of examination by the present inventors, carrier particles having a particle size of 0.7 × A μm or more and Aμm or less enter a recess on the surface of the developing sleeve that has been sandblasted with an abrasive having an average particle size of A μm, and It was found that the resin fine particles adhering to the recesses tend to be crushed. According to the developing device of the present invention, since the content of carrier particles having a particle size of 0.7 × A μm or more and Aμm or less is less than 5% by mass of the entire carrier, the toner component is prevented from being fused to the surface of the developing sleeve. can do.

  In the developing device of the present invention, the content of carrier particles having a particle size of 0.2 × A μm or more and 0.4 × A μm or less when the average particle size of the abrasive grains used for sandblasting of the developing sleeve is A μm. Is preferably 20% by mass or more and 50% by mass or less of the entire carrier. By making the content of carrier particles having a particle size of 0.2 × A μm or more and 0.4 × A μm or less 20% by mass or more and 50% by mass or less of the entire carrier, occurrence of fusion phenomenon over a long period of time (white Formation of a film and a black film) can be suppressed. Carrier particles having a particle size of 0.2 × A μm or more and 0.4 × A μm or less have a high effect of scraping resin fine particles adhering to the recesses on the surface of the developing sleeve, and can suppress the occurrence of the fusion phenomenon over a long period of time. Presumed to be possible. If the content of carrier particles having a particle size of 0.2 × A μm or more and 0.4 × A μm or less is less than 20% by mass, the effect of preventing the fusion phenomenon may not be maintained for a long time. It is estimated that this is because the scraping effect is low. Conversely, when the content of carrier particles having a particle size of 0.2 × A μm or more and 0.4 × A μm or less exceeds 50% by mass, the carrier particles having a particle size smaller than the size of the concave portion on the surface of the developing sleeve. Since the ratio becomes high, the carrying ability of the two-component developer by the developing sleeve is lowered, and image density unevenness is likely to occur.

  A method of adjusting the particle size distribution of the carrier (specifically, a method of adjusting the content of carrier particles having a particle size of 0.7 × A μm or more and A μm or less to less than 5% by mass of the entire carrier, preferably the particle size is 0 The content of carrier particles having a particle size of 0.2 × A μm or more and 0.4 × A μm or less is adjusted to be less than 5% by mass of the entire carrier. Examples of the method of adjusting to 20% by mass or more and 50% by mass or less include a method of classifying with a sieve or an air classifier.

  As the carrier, magnetic particles having a volume average particle diameter of 20 μm or more and 80 μm or less can be used. If the volume average particle diameter of the carrier is less than 20 μm, white spots may occur in the resulting image due to the carrier moving from the developing roller to the photoreceptor during development. On the other hand, if it exceeds 80 μm, the dot reproducibility deteriorates and the image becomes rough. In the present invention, the particle diameter of the carrier is represented by a sphere equivalent diameter by a laser diffraction / scattering method, and the volume average particle diameter is measured by a particle size distribution measuring apparatus (manufactured by Nikkiso Co., Ltd., model: Microtrac MT3000). it can.

  Regarding the saturation magnetization of the carrier, the lower the saturation magnetization, the softer the magnetic brush (formed on the surface of the developing roller) in contact with the photoconductor, so that an image faithful to the electrostatic latent image can be obtained, but the saturation magnetization is too low. As a result, carriers adhere to the surface of the photoreceptor, and white spots are likely to occur. On the other hand, if the saturation magnetization is too high, it becomes difficult to obtain an image faithful to the electrostatic latent image due to the stiffening of the magnetic brush. For this reason, it is preferable that the saturation magnetization of a carrier exists in the range of 30-100 emu / g.

  As such a carrier, a coated carrier in which a coating layer is provided on the surface of magnetic core particles is generally used. Known magnetic particles can be used as the core particles, but ferrite particles are preferred. When ferrite particles are used, carriers with high saturation magnetization can be obtained, and the amount of carriers attached to the photoreceptor can be reduced. Known ferrite particles can be used, such as zinc ferrite, nickel ferrite, copper ferrite, nickel-zinc ferrite, manganese-magnesium ferrite, copper-magnesium ferrite, manganese-zinc ferrite, Manganese-copper-zinc ferrite and the like can be mentioned.

These ferrite particles can be produced by a known method. For example, ferrite raw materials such as Fe ₂ O ₃ and Mg (OH) ₂ are mixed, and this mixed powder is heated in a heating furnace and calcined. After the obtained calcined product is cooled, it is pulverized with a vibration mill so as to have particles of approximately 1 μm, and a dispersant and water are added to the pulverized powder to prepare a slurry. The slurry is wet pulverized with a wet ball mill, and the resulting suspension is granulated and dried with a spray dryer to obtain ferrite particles.

  A known resin material can be used as the coating material constituting the coating layer of the carrier, and examples thereof include an acrylic resin and a silicone resin. In particular, a coated carrier coated with a silicone resin, that is, a coated carrier having a silicone resin coating layer is preferable. When a coated carrier having a silicone resin coating layer is used, toner components such as a crystalline polyester resin and a release agent are less likely to adhere to the surface of the carrier, thereby suppressing carrier contamination and excellent charging stability.

  A well-known thing can be used as a silicone resin. Moreover, the silicone resin is marketed, for example with the form of a varnish, and these can be used conveniently. Specific examples include silicone varnish (manufactured by Toshiba Corporation: TSR115, TSR114, TSR102, TSR103, YR3061, TSR110, TSR116, TSR117, TSR108, TSR109, TSR180, TSR181, TSR187, TSR144, TSR165, manufactured by Shin-Etsu Chemical Co., Ltd .: KR271, KR272, KR275, KR280, KR282, KR267, KR269, KR211, KR212), alkyd-modified silicone varnish (manufactured by Toshiba Corporation: TSR184, TSR185), epoxy-modified silicone varnish (manufactured by Toshiba Corporation: TSR194, YS54), polyester Resin-modified silicone varnish (Toshiba Corporation: TSR187), acrylic-modified silicone varnish (Toshiba Corporation: TSR) 70, TSR171), urethane-modified silicone varnish (manufactured by Toshiba Corporation: TSR175), reactive silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd .: KA1008, KBE1003, KBC1003, KBM303, KBM403, KBM503, KBM602, KBM603) and the like. .

  In order to control the volume resistivity value of the carrier, a conductive material is preferably added to the covering material. Examples of the conductive material include silicon oxide, alumina, carbon black, graphite, zinc oxide, titanium black, iron oxide, titanium oxide, tin oxide, potassium titanate, calcium titanate, aluminum borate, magnesium oxide, barium sulfate, Examples thereof include calcium carbonate. Among these conductive materials, carbon black is preferable from the viewpoint of production stability, cost, and low electrical resistance. The type of carbon black is not particularly limited, but a carbon black having a DBP (dibutyl phthalate) oil absorption in the range of 90 to 170 ml / 100 g is preferable in terms of excellent production stability. In addition, particles having a primary particle size of 100 nm or less are particularly preferable because of excellent dispersibility. These conductive materials may be used alone or in combination of two or more. It is preferable that the addition amount of a electrically conductive material is 0.1-20 mass parts with respect to 100 mass parts of coating | covering materials.

  In order to coat the carrier particles with the coating material, a known method can be employed. For example, an immersion method in which carrier particles are immersed in an organic solvent solution of the coating material, a spray method in which the organic solvent solution of the coating material is sprayed on the carrier particles, an organic solvent solution of the coating material in a state where the carrier particles are suspended by flowing air And a kneader coater method in which carrier particles and an organic solvent solution of a coating material are mixed in a kneader coater to remove a solvent such as an organic solvent. Here, the organic solvent solution of the covering material preferably contains a conductive material.

  The capsule toner constituting the two-component developer preferably has a circularity of 0.950 or more and 0.960 or less. If the capsule toner has a circularity of 0.960 or less, the occurrence of poor cleaning can be suppressed. On the other hand, when the circularity of the capsule toner is less than 0.950, the charging stability may be lowered.

In the present invention, the circularity of the capsule toner or toner base particles described later can be measured using, for example, a flow type particle image analyzer “FPIA-3000” (manufactured by Malvern). The measuring principle of this apparatus is to take a still image of particles in a dispersion medium with a CCD camera and perform calculation such as circularity calculation from the image. The sample put in from the chamber is sent to the flat sheath flow cell and sandwiched between sheath liquids to form a flat flow. A still image is taken with a CCD camera while irradiating the sample passing through the cell with strobe light. The contour of each particle is extracted by image processing of the captured image, and the projected area S, the peripheral length L, and the like of the particle image are measured. From this, the equivalent circle diameter and circularity are calculated.
The equivalent circle diameter is the diameter of a circle having the same area as the projected area of the particle image, and the circularity is defined as the circumference of the circle calculated from the equivalent circle diameter divided by the circumference of the projected particle image. Is calculated by the following equation.
Circularity = 2 × (π × S) ^1/2 / L
As the sheath liquid, a particle sheath “PSE-900A” (manufactured by Malvern) is used, as a dispersant, a commercially available 5% by weight aqueous dispersion of household detergent, and as a disperser, the autosampler apparatus of the apparatus is used. Then, the sample is dispersed and introduced into the flow type particle image analyzer, and 10000 capsule toners or toner base particles are measured in a total count in the HPF measurement mode. Then, the binarization threshold at the time of particle analysis is set to 85%, and the average circularity of the capsule toner or toner base particles is obtained as the total particle size range.

  The capsule toner preferably has a volume average particle size of 4.0 μm or more and 8.0 μm or less, and the content of the capsule toner having a particle size of 3.0 μm or less is 2% by mass or more of the whole capsule toner. Is preferred. As a method of adjusting the particle size distribution of the capsule toner, there is a method of classifying the capsule toner or toner base particles with an air classifier.

  The toner base particles constituting the capsule toner usually contain a binder resin and a colorant. The binder resin is not particularly limited, and a known binder resin for black toner or color toner can be used. For example, polystyrene, styrene monomer and (meth) acrylic acid monomer and / or Examples include styrene-acrylic resins copolymerized with (meth) acrylic acid ester monomers, (meth) acrylic acid ester resins such as polymethyl methacrylate, polyolefin resins such as polyethylene, polyesters, polyurethanes, and epoxy resins. Moreover, you may use resin obtained by mixing a raw material monomer mixture with a mold release agent and performing a polymerization reaction. Binder resin can be used individually by 1 type, or can use 2 or more types together.

  The monomer constituting the styrene-based resin preferably contains a styrene monomer as an essential monomer and, if necessary, a (meth) acryl monomer and / or a carboxyl group-containing vinyl monomer. Here, the styrene resin means a homopolymer of a styrene monomer or a copolymer of a styrene monomer and another monomer. Moreover, (meth) acryl means acryl and / or methacryl. Examples of the styrene monomer include styrene and alkyl styrene having an alkyl group having 1 to 3 carbon atoms (for example, α-methyl styrene, p-methyl styrene) and the like. Styrene is preferred. Examples of (meth) acrylic monomers include alkyl groups such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate. C1-C18 alkyl (meth) acrylate; Hydroxyethyl (meth) acrylate etc. Alkyl group C1-C18 hydroxylalkyl (meth) acrylate; Dimethylaminoethyl (meth) acrylate, Diethylaminoethyl (meth) Examples thereof include alkylamino group-containing (meth) acrylates having 1 to 18 carbon atoms in the alkyl group such as acrylate; nitrile group-containing vinyl monomers such as acrylonitrile and methacrylonitrile. Examples of the carboxyl group-containing vinyl monomer include monocarboxylic acids [having 3 to 15 carbon atoms such as (meth) acrylic acid, crotonic acid and cinnamic acid], dicarboxylic acids [having 4 to 15 carbon atoms such as (anhydrous) maleic acid and fumaric acid. , Itaconic acid, citraconic acid], dicarboxylic acid monoester [monoalkyl (carbon number 1 to 18) ester of the above dicarboxylic acid, such as maleic acid monoalkyl ester, fumaric acid monoalkyl ester, itaconic acid monoalkyl ester, citraconic acid monoester Alkyl ester] and the like. Among these (meth) acrylic monomers and carboxyl group-containing vinyl monomers, alkyl (meth) acrylates having 1 to 18 carbon atoms, acrylonitrile, methacrylonitrile, (meth) acrylic acid, dicarboxylic acid monoesters, and two or more kinds thereof Mixtures are preferred.

  A known monomer can be used as the monomer constituting the polyester resin, and examples thereof include a polycondensate of a polybasic acid and a polyhydric alcohol.

  As the polybasic acid, those known as polyester monomers can be used. Examples thereof include aliphatic carboxylic acids such as fumaric acid, succinic acid, alkenyl succinic anhydride, and adipic acid, and methyl esterified products of these polybasic acids. A polybasic acid can be used individually by 1 type, or can use 2 or more types together.

  As polyhydric alcohols, those known as monomers for polyesters can be used. For example, aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, glycerin, cyclohexanediol, cyclohexanedi Examples include alicyclic polyhydric alcohols such as methanol and hydrogenated bisphenol A, aromatic diols such as an ethylene oxide adduct of bisphenol A, and a propylene oxide adduct of bisphenol A. A polyhydric alcohol can be used individually by 1 type, or can use 2 or more types together.

  The polycondensation reaction between the polybasic acid and the polyhydric alcohol can be carried out according to a conventional method. For example, the polybasic acid and the polyhydric alcohol are contacted in the presence or absence of an organic solvent and in the presence of a polycondensation catalyst. The process is terminated when the acid value, softening temperature, and the like of the resulting polyester reach desired values. Thereby, polyester is obtained. When a methyl esterified product of a polybasic acid is used as a part of the polybasic acid, a demethanol polycondensation reaction is performed. In this polycondensation reaction, by appropriately changing the compounding ratio of polybasic acid and polyhydric alcohol, the reaction rate, etc., for example, the carboxyl group content at the end of the polyester can be adjusted, and thus the properties of the resulting polyester Can be denatured. Even when trimellitic anhydride is used as the polybasic acid, a carboxyl group can be easily introduced into the main chain of the polyester, thereby obtaining a modified polyester. A self-dispersible polyester in water in which a hydrophilic group such as a carboxyl group or a sulfonic acid group is bonded to the main chain and / or side chain of the polyester can also be used. Further, polyester and acrylic resin may be grafted.

  The binder resin preferably has a glass transition point of 30 ° C. or higher and 80 ° C. or lower, and more preferably 30 ° C. or higher and 50 ° C. or lower. If the glass transition point of the binder resin is less than 30 ° C., blocking in which the toner thermally aggregates easily occurs in the image forming apparatus, and storage stability may be lowered. When the glass transition point of the binder resin exceeds 80 ° C., the fixability of the toner to the recording medium is lowered, and there is a possibility that fixing failure occurs.

  The binder resin preferably has a softening temperature of 80 ° C. or higher and 150 ° C. or lower, and more preferably 100 ° C. or higher and 150 ° C. or lower. Furthermore, the binder resin preferably has an acid value of 0 KOHmg / g or more and 30 KOHmg / g or less.

  As the colorant, organic dyes, organic pigments, inorganic dyes, inorganic pigments and the like commonly used in the electrophotographic field can be used. Although the usage-amount of a coloring agent is not restrict | limited in particular, Preferably it is 5 mass parts or more and 10 mass parts or less with respect to 100 mass parts of binder resin.

  The toner base particles may contain a charge control agent in addition to the binder resin and the colorant. As the charge control agent, a charge control agent for positive charge control and negative charge control commonly used in this field can be used. The amount of the charge control agent used is not particularly limited, but is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the binder resin.

  Further, the toner base particles may contain a release agent in addition to the binder resin and the colorant. As the release agent, those commonly used in this field can be used. For example, petroleum wax such as paraffin wax and derivatives thereof, microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin wax (polyethylene wax, polypropylene Wax, etc.) and derivatives thereof, low molecular weight polypropylin wax and derivatives thereof, polyolefin polymer wax (low molecular weight polyethylene wax etc.) and derivatives thereof, hydrocarbon synthetic wax, carnauba wax and the like. The amount of the release agent used is not particularly limited, but is preferably 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The toner base particles preferably have a volume average particle size of 4 μm or more and 8 μm or less. The toner base particles usually have a circularity of 0.96 or less, preferably 0.940 or more and 0.960 or less.

  The coating layer constituting the capsule toner is formed as a film by fusing resin fine particles on the surface of the toner base particles. Examples of a method for coating resin fine particles on the surface of toner base particles include, for example, a method in which resin fine particles are attached to the surface of the toner base particles in an aqueous medium and heating, or a method in which resin fine particles are attached to the surface of the toner base particles and mechanical impact is applied. There are known methods of applying force, methods of attaching resin fine particles to the surface of toner base particles and heating in a high temperature air flow of 300 ° C. or higher, methods of spraying resin fine particle emulsion while stirring toner base particles, etc. A method of applying a mechanical impact force by attaching resin fine particles to the surface of the toner base particles is preferable.

  The resin fine particles used for forming the coating layer can be obtained by, for example, an emulsion polymerization reaction of a monomer component that is a resin raw material, or can be obtained by emulsifying and dispersing the resin with a homogenizer or the like to obtain fine particles. Can do.

  As the resin used as the resin fine particle raw material, for example, a resin used for a toner material can be used. For example, polystyrene, styrene monomer, (meth) acrylic acid monomer and / or (meth) acrylic acid ester monomer can be used. Examples thereof include copolymerized styrene-acrylic resins, (meth) acrylic ester resins such as polymethyl methacrylate, and polyester resins. The resin fine particles preferably include a styrene-acrylic resin or a polyester resin among the resins exemplified above. Styrene-acrylic resins have many advantages such as light weight, high strength, high transparency, low cost, and easy to obtain materials with uniform particle diameters.

  The resin used as the resin fine particle raw material may be the same type of resin as the binder resin contained in the toner base particles or a different type of resin. Therefore, it is preferable to use a different type of resin. When a resin different from the binder resin contained in the toner mother particles is used as the resin used as the resin fine particle raw material, the softening temperature of the resin used as the resin fine particle raw material is the binder resin contained in the toner mother particles, or It is preferably higher than the softening temperature of the component contained in the toner base particles such as a release agent. As a result, the toner can be prevented from fusing during storage, and storage stability can be improved. The softening temperature of the resin used as the resin fine particle raw material is preferably 80 ° C. or more and 140 ° C. or less, although it depends on the image forming apparatus in which the toner is used. By using a resin having a softening temperature in such a range, a toner having both storage stability and fixability can be obtained.

  The resin fine particles are required to have a volume average particle size sufficiently smaller than the average particle size of the toner base particles, and preferably 0.1 μm or more and 0.5 μm or less. When the volume average particle diameter of the resin fine particles is 0.1 μm or more and 0.5 μm or less, it is excellent in plasticity and easily deforms, and a uniform coating layer is formed on the surface of the toner base particles. The particle diameter of the resin fine particles represents a volume average particle diameter measured by a dynamic light scattering method.

  The resin fine particles preferably have a glass transition point of 50 ° C. or higher and 80 ° C. or lower. The resin fine particles preferably have a softening temperature of 80 ° C. or higher and 140 ° C. or lower.

  The capsule toner may have an external additive. The external additive has a function of imparting fluidity to the toner and controlling the charge amount of the toner, and examples thereof include silica, titanium oxide, silicon carbide, aluminum oxide, barium titanate, and the like. Those that have been surface treated (hydrophobized) with a silane coupling agent or the like are preferred.

  As a method of coating resin fine particles on the surface of toner base particles, when a method of applying mechanical impact force by attaching resin fine particles to the surface of toner base particles is employed, the above-described capsule toner manufacturing method produces toner base particles. Toner base particle preparation step, resin fine particle preparation step for obtaining dried resin fine particles, composite particle formation step for coating resin fine particles on the surface of the toner base particles, and capsule toner particles for imparting mechanical impact force to the composite particles A forming step, a classification step of adjusting the particle size distribution of the capsule toner, and an external addition step of adding an external additive as necessary.

(1) Toner base particle preparation step In the toner base particle preparation step, toner base particles are prepared. Examples of the method for producing the toner base particles include dry methods such as a kneading and pulverization method, and wet methods such as a suspension polymerization method, an emulsion aggregation method, a dispersion polymerization method, a dissolution suspension method, and a melt emulsification method. Hereinafter, a method for producing toner base particles by a kneading and pulverizing method will be described.

  When the toner base particles are prepared by a pulverization method, the toner base particle raw materials containing a binder resin, a colorant and other additives are dry-mixed in a mixer and then melt-kneaded by melting and kneading in a kneader. Get things. The melt-kneaded product is cooled and solidified, and the solidified product is pulverized with a pulverizer to obtain a finely pulverized product. Thereafter, if necessary, the particle size is adjusted by classification or the like to obtain toner mother particles.

A known mixer can be used, and examples thereof include a Henschel mixer (trade name, manufactured by Mitsui Mining Co., Ltd.) and a super mixer (trade name, manufactured by Kawata Co., Ltd.).
As the kneader, known ones can be used. For example, a twin-screw kneader such as PCM-65 / 87 and PCM-30 (all of which are trade names, manufactured by Ikegai Co., Ltd.), and kneedex (trade name, Mitsui Mine). Open roll kneaders, etc.).
Examples of the pulverizer include a counter jet mill AFG (trade name, manufactured by Hosokawa Micron Corporation) that pulverizes using a supersonic jet stream.
Examples of the classifier include a rotary classifier TSP separator (trade name, manufactured by Hosokawa Micron Corporation).

(2) Resin fine particle preparation step In the resin fine particle production step, dried resin fine particles are produced. For example, a resin having a volume average particle size of 0.05 μm or more and 1 μm or less by a method of emulsifying and dispersing a resin fine particle raw material with a homogenizer or a method of polymerizing monomers by a method such as emulsion polymerization or soap-free emulsion polymerization It can be obtained by forming fine particles and drying the resin fine particles by a method such as spray drying.

(3) Composite Particle Formation Step The composite particle formation step is a step of forming composite particles by coating resin fine particles on the surface of toner base particles. For example, toner mother particles and resin fine particles are placed in a Henschel mixer (trade name: FM20C, manufactured by Mitsui Mining Co., Ltd.), and the peripheral speed of the tip of the stirring blade is 20 to 30 m / sec. A method of stirring for 5 minutes can be used. The mixing ratio between the toner base particles and the resin fine particles is preferably such that the surface of the toner base particles is completely and thinly covered with the resin fine particles, and 2 to 5 parts by weight of the resin fine particles with respect to 100 parts by weight of the toner base particles. It is preferable to mix by ratio. Note that the composite particle forming step can be omitted by directly feeding the toner base particles and the resin fine particles to an apparatus for applying a mechanical impact force.

(4) Capsule toner particle forming step In the capsule toner particle forming step, by applying mechanical impact force to the composite particles, the resin fine particles are fused to the surface of the toner base particles to form a coating layer, This is a step of forming capsule toner particles. As an apparatus for applying a mechanical impact force to the composite particles, for example, a hybridization system (trade name: NHS-1 type, manufactured by Nara Machinery Co., Ltd.) can be used.

(5) Classification process The classification process is a process of adjusting the particle size distribution of the capsule toner, and performs classification using an air classifier. Examples of the classifier include a rotary classifier TSP separator (trade name, manufactured by Hosokawa Micron Corporation).

(6) External Addition Step The external addition step is a step of adhering the external additive to the particle surface of the capsule toner by mixing the capsule toner and the external additive with a mixer. As the external additive, silica fine particles having a primary particle diameter of 7 nm to 20 nm, titanium oxide fine particles, and the like, which have been subjected to a hydrophobization treatment with a silane coupling agent can be suitably used. A known mixer can be used, and examples thereof include a Henschel mixer (trade name, manufactured by Mitsui Mining Co., Ltd.) and a super mixer (trade name, manufactured by Kawata Co., Ltd.).

  Next, the image forming apparatus of the present invention will be described in detail. The image forming apparatus of the present invention includes the above-described developing device of the present invention. The image forming apparatus of the present invention is not particularly limited except that such a developing device is used, and can be produced by a known method.

  Hereinafter, an image forming apparatus and a developing apparatus of the present invention will be described in detail with reference to the drawings.

(Image forming device)
FIG. 1 is a schematic cross-sectional view illustrating the entire configuration of an image forming apparatus 1 that is one embodiment (first embodiment) of the image forming apparatus of the present invention. The image forming apparatus 1 is a printer that forms an image on a recording medium such as paper according to image data transmitted from the outside.

  The image forming apparatus 1 includes a cylindrical photosensitive drum 2 that is rotatably provided, a charging device 3 that charges the surface of the photosensitive drum 2, an exposure device 4 that irradiates the surface of the photosensitive drum 2 with laser light, and a photosensitive member. A developing device 5 that develops an electrostatic latent image on the surface of the drum 2 to form a toner image, a paper feed tray 6 that stores a recording medium such as paper, and a toner image formed on the surface of the photosensitive drum 2 A transfer device 7 for transferring the toner image; a fixing device 8 for fixing the toner image transferred onto the recording medium; a toner supply device 9 for supplying toner to the developing device 5 and supplying toner to the developing device 5; 2 is provided. On the upper surface of the image forming apparatus 1, a paper discharge tray 11 for receiving the recording medium after fixing the toner image is provided. The recording medium accommodated in the paper feeding tray 6 is sheeted by a plurality of conveying rollers 12a to 12h. After being transported on the transport path S and passing through the transfer device 7 and the fixing device 8, the paper is discharged onto the paper discharge tray 11.

  The photosensitive drum 2 is a photoconductive member provided with a photosensitive layer on the surface of a cylindrical aluminum base tube, and an electrostatic latent image is formed by charging and exposure.

  The charging device 3 is a corona discharge type saw blade charger including a saw blade electrode, and charges the surface of the photosensitive drum 2 to a predetermined potential. A corona charger using a wire electrode or the like can be used as a corona discharge charging device, and a charging roller or a charging brush can be used as a charging device other than the corona discharge method.

  The exposure device 4 is a laser scanning unit (LSU) including a laser irradiation unit, a polygon mirror, and a reflection mirror. The exposure device 4 irradiates (exposes) a laser beam according to image data onto the surface of the photosensitive drum 2, thereby causing an electrostatic latent image. Form an image.

  The developing device 5 contains a two-component developer composed of toner and carrier, and develops the electrostatic latent image on the photosensitive drum 2 to form a toner image on the surface of the photosensitive drum 2. Here, the developing device of the present invention is used as the developing device 5. Details of the developing device 5 will be described later.

  The transfer device 7 includes a transfer roller and a transfer bias applying device (not shown), and a transfer bias (+) having a polarity opposite to the charging polarity (−) of the toner is applied to the transfer roller. The toner image carried on the surface 2 is transferred onto the recording medium conveyed from the paper feed tray 6.

  The fixing device 8 includes a heating roller 8a and a pressure roller 8b that can rotate while being pressed against each other, and heats an unfixed toner image by passing a recording medium between the heating roller 8a and the pressure roller 8b. It is melted and fixed on the recording medium.

  The toner replenishing device 9 includes a container 9a that stores replenishing toner, a stirring blade 9b, and a replenishing member 9c including an auger screw, and supplies the replenishing toner to the developing device 5 by rotating the replenishing member 9c.

  The cleaning device 10 includes a urethane blade, and removes toner remaining on the surface of the photosensitive drum 2 by pressing the urethane blade against the surface of the photosensitive drum 2.

(Developer)
FIG. 2 is a schematic cross-sectional view illustrating the overall configuration of one embodiment (second embodiment) of the developing device of the present invention, and is an enlarged view of the developing device 5 shown in FIG. FIG. 3 is a view taken along the line AA ′ of the developing device shown in FIG. FIG. 4 is a perspective view of the developing roller 52 shown in FIG. Although the developing device of the present invention includes a two-component developer, the two-component developer accommodated in the developing device 5 is not shown in these drawings.

  As shown in FIG. 2, the developing device 5 includes a developing tank 51 that contains a two-component developer composed of toner and a carrier, a developing roller 52 that conveys the two-component developer toward the photosensitive drum 2, and a developing tank 51. The first developer transport member 53 and the second developer transport member 54 that transport the internal two-component developer while stirring, and a regulating member that adjusts the transport amount of the two-component developer transported toward the photosensitive drum 2. 55, a toner density detection sensor 56 for detecting the toner density of the two-component developer.

  As shown in FIG. 3, a partition plate 51 c is provided inside the developing tank 51 in parallel with the axis of the developing roller 52, and the inside of the developing tank 51 is partitioned into two transport paths. The first developer transport path P is on the developing roller 52 side of the partition plate 51c, and the second developer transport path Q is on the other side. At both ends of the partition plate 51c, a first communication path V and a second communication path W that connect the first developer transport path P and the second developer transport path Q are provided, and the first developer transport path P and the second developer transport path W are provided. An annular conveyance path including a developer conveyance path Q, a first communication path V, and a second communication path W is formed.

  The first developer transport member 53 and the second developer transport member 54 are auger screws having spiral blades, and are rotatably provided in the first developer transport path P and the second developer transport path Q, respectively. . When the first developer transport member 53 and the second developer transport member 54 are rotationally driven via a drive motor and a drive gear (not shown), the two-component developer and the second developer in the first developer transport path P The two-component developer in the transport path Q moves in the X direction and the Y direction, respectively, and circulates in the annular transport path.

  A developer tank upper lid 51a that constitutes an upper wall is provided on the upper portion of the developer tank 51, and a toner receiving port that receives replenishing toner from the toner replenishing device 9 on the second developer transport path Q side of the developer tank upper lid 51a. 51b is formed.

  The developing roller 52 includes a developing sleeve 61 formed of a cylindrical aluminum material that is rotatably provided, and a magnet roller 62 having a plurality of magnetic poles fixed so as not to rotate. The developing sleeve 61 rotates. As a result, the two-component developer in the first developer transport path P is pumped up and transported toward the photosensitive drum 2.

  As shown in FIG. 4, a developing sleeve rotating shaft 61a that rotates integrally with the developing sleeve 61 is provided at one end (right end in the figure) of the developing roller 52, and the other end (left end in the figure) of the developing roller 52. Is provided with a magnet roller fixing shaft 62a fixed integrally with the magnet roller 62, and only the developing sleeve rotating shaft 61a is rotationally driven via a driving motor and a driving gear (not shown). The magnet roller 62 is formed by integrating five magnetic poles, and N poles and S poles are alternately arranged along the circumferential direction.

  The restricting member 55 is a plate-like member extending in parallel with the axial direction of the developing roller 52, and is fixed to the developing tank 51 so as to maintain a certain gap with respect to the surface of the developing roller 52.

  The toner concentration detection sensor 56 is a magnetic permeability sensor that detects the magnetic permeability of the two-component developer, and is provided on the bottom wall portion at the center of the first developer conveyance path P. When the toner concentration of the two-component developer is decreased, the magnetic permeability detected by the toner concentration detection sensor 56 is increased, so that the replenishment toner is replenished from the toner replenishing device 9 into the developing device 5 according to the magnetic permeability value. To do. The toner supply is performed by a toner density control device (not shown).

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples. First, a method for measuring each physical property value will be described.

(Physical property measurement)
[Average grain size of abrasive grains]
Measurement was performed using a laser diffraction / scattering particle size distribution measuring apparatus (trade name: Microtrack MT3000, manufactured by Nikkiso Co., Ltd.). In order to prevent the sample from aggregating, a dispersion in which the measurement sample was dispersed in an aqueous solution of Family Fresh (manufactured by Kao Corporation) was charged and stirred, and then injected into the apparatus. The measurement was performed twice to obtain an average. The measurement conditions were: measurement time: 30 seconds, particle refractive index: 1.4, particle shape: non-spherical, solvent: water, solvent refractive index: 1.33. The volume particle size distribution of the measurement sample was measured, and the particle size at which the cumulative volume from the small particle size side in the cumulative volume distribution was 50% was calculated as the volume average particle size (μm) of the sample.

[Ten point average roughness Rz]
Rz was measured using a surface roughness measuring instrument SJ-400 (manufactured by Mitutoyo Corporation). Specifically, according to JIS B 0601-1994, Rz was measured at three locations along the axial direction of the developing sleeve, and the average value was obtained.

[Volume average particle diameter of carrier]
Measurement was performed using a laser diffraction / scattering particle size distribution measuring apparatus (trade name: Microtrack MT3000, manufactured by Nikkiso Co., Ltd.). In order to prevent the sample from aggregating, a dispersion in which the measurement sample was dispersed in an aqueous solution of Family Fresh (manufactured by Kao Corporation) was charged and stirred, and then injected into the apparatus. The measurement was performed twice to obtain an average. The measurement conditions were: measurement time: 30 seconds, particle refractive index: 1.4, particle shape: non-spherical, solvent: water, solvent refractive index: 1.33. The volume particle size distribution of the measurement sample was measured, and the particle size at which the cumulative volume from the small particle size side in the cumulative volume distribution was 50% was calculated as the volume average particle size (μm) of the sample.

[Volume average particle size, particle size distribution and coefficient of variation of toner base particles and capsule toner]
20 ml of a sample and 1 ml of sodium alkyl ether sulfate are added to 50 ml of an electrolytic solution (trade name: ISOTON-II, manufactured by Beckman Coulter, Inc.), and an ultrasonic disperser (trade name: tabletop type dual frequency ultrasonic cleaner VS- D100 (manufactured by ASONE Co., Ltd.) was used for dispersion treatment at a frequency of 20 kHz for 3 minutes to obtain a measurement sample. This sample for measurement was measured using a particle size distribution measuring apparatus (trade name: Multisizer 3, manufactured by Beckman Coulter, Inc.) under the conditions of aperture diameter: 100 μm, number of measured particles: 50000 count, and volume particle size of sample particles From the distribution, a volume average particle size, a particle size distribution, and a coefficient of variation were obtained.

[Volume average particle diameter of resin fine particles]
Measurement was performed using a laser diffraction / scattering particle size distribution measuring apparatus (trade name: Microtrack MT3000, manufactured by Nikkiso Co., Ltd.). In order to prevent the sample from aggregating, a dispersion in which the measurement sample was dispersed in an aqueous solution of Family Fresh (manufactured by Kao Corporation) was charged and stirred, and then injected into the apparatus. The measurement was performed twice to obtain an average. The measurement conditions were: measurement time: 30 seconds, particle refractive index: 1.4, particle shape: non-spherical, solvent: water, solvent refractive index: 1.33. The volume particle size distribution of the measurement sample was measured, and the particle size at which the cumulative volume from the small particle size side in the cumulative volume distribution was 50% was calculated as the volume average particle size (μm) of the sample.

[Glass transition point]
Using a differential scanning calorimeter (trade name: DSC220, manufactured by Seiko Denshi Kogyo Co., Ltd.), according to Japanese Industrial Standard (JIS) K7121-1987, 1 g of a sample was heated at a heating rate of 10 ° C. per minute and a DSC curve was measured. did. Draw the endothermic peak corresponding to the glass transition of the obtained DSC curve at a point where the slope is maximum with respect to the straight line that extends the base line on the high temperature side to the low temperature side and the curve from the rising part of the peak to the vertex. The glass transition point (Tg) was determined from the intersection with the tangent.

[Softening temperature (Tm)]
Using a flow characteristic evaluation apparatus (trade name: Flow Tester CFT-100C, manufactured by Shimadzu Corporation), 1 g of a sample was heated at a heating rate of 6 ° C. per minute, and a load of 20 kgf / cm ² (9.8 × 10 ⁵ Pa). The sample was allowed to flow out of the die (nozzle diameter 1 mm, length 1 mm). The temperature at which the sample began to flow was defined as the flow-out start temperature (Tfb), and the temperature at which half the sample flowed out was defined as the softening temperature (Tm).

(Sand blasting)
The sandblasting process is generally performed by causing an abrasive particle having a certain size and hardness to be injected and collided with an object at a certain pressure and speed from an injection nozzle while rotating the object around its central axis. The processing time, air pressure, nozzle diameter, etc. are adjusted as appropriate.
In this example, Fuji glass beads manufactured by Fuji Seisakusho Co., Ltd., adjusted to a predetermined particle size, are used as abrasive grains, and the air pressure is 0.2 to 0.35 MPa, the processing time is 3.15 to 20.00 sec, and the nozzle diameter is 4 mm. Under the conditions, sandblasting was performed on the cylindrical developing sleeve (material aluminum).
Table 1 below shows the average particle diameter of the abrasive grains used in the sandblasting process and the ten-point average roughness Rz of the developing sleeve after the sandblasting process.

<Example 1>
(Carrier production)
Finely pulverized Fe ₂ O ₃ , MnCO ₃ and MgCO ₃ were prepared as raw materials for the carrier core material. Then, the carrier core material is weighed so as to have a ferrite composition represented by the composition formula MnO · MgO · Fe ₂ O ₃ . On the other hand, polyethylene resin particles (LE-1080 manufactured by Sumitomo Seika Co., Ltd.) having an average particle diameter of 5 μm corresponding to 10% by mass with respect to all raw materials in water, and 1.5% by mass of an ammonium polycarboxylate dispersant as a dispersant. Prepared by adding 0.05% by weight of San Nopco SN wet 980 as a wetting agent and 0.02% by weight of polyvinyl alcohol as a binder, and adding previously weighed Fe ₂ O ₃ and MgCO ₃ Stirring to obtain a slurry having a concentration of 75% by mass. The slurry was wet pulverized with a wet ball mill, stirred for a while, and then sprayed with a spray dryer to produce a dry granulated product (10 kg) having a particle size of 10 μm to 200 μm.
From this granulated product, coarse particles were separated using a sieve mesh having a mesh size of 61 μm, and then heated to 900 ° C. in the atmosphere and calcined to decompose the resin particle components. Thereafter, the main calcination was performed at 1160 ° C. in a nitrogen atmosphere for 5 hours to form a ferrite. This ferritized fired product was crushed with a hammer mill, fine powder was removed using an air classifier, and the particle size was adjusted with a vibrating screen having a mesh size of 54 μm to obtain a carrier core material (5 kg) having a volume average particle size of 40 μm. .
Next, 0.75 parts by mass of silicone resin (trade name: KR240, manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.75 parts by mass of silicone resin (trade name: KR251, manufactured by Shin-Etsu Chemical Co., Ltd.) are dissolved in 12 parts by mass of toluene. And 0.075 parts by mass of conductive particles (trade name: VULCAN XC-72, manufactured by Cabot Corporation) and 0.075 parts by mass of a coupling agent (trade name: Z6011, manufactured by Toray Dow Corning Co., Ltd.). 273 g of a coating resin solution was prepared by internal addition or dispersion.
Next, the surface of 100 parts by mass of the carrier core material was coated by a fluidized bed method using 30 parts by mass of the obtained coating resin solution. Thereafter, the resin coating of Example 1 having a particle size distribution shown in Table 1 and a volume average particle size of 42 μm by passing through a sieve having an opening of 150 μm through a curing process at a curing temperature of 260 ° C. and a curing time of 90 minutes. A carrier (2 kg) was obtained.

(Manufacture of capsule toner)
Toner mother particle production process / polyester resin (trade name: Toughton, manufactured by Kao Corporation, glass transition point 60 ° C., softening temperature 138 ° C.) 85 parts by mass, colorant (CI Pigment Blue 15: 3) 5 parts by mass 8 parts by weight of wax (trade name: Carnauba wax, manufactured by Toa Kasei Co., Ltd., melting point 82 ° C.) 2 parts by weight of charge control agent (trade name: Bontron E84, Orient Chemical Co., Ltd.) After premixing for a minute, the mixture was melt kneaded using a twin screw extruder (trade name: PCM-30, manufactured by Ikegai Co., Ltd.). The melt-kneaded product is cooled by a cooling belt, coarsely pulverized by a speed mill having a φ2 mm screen, finely pulverized by a jet type pulverizer (trade name: IDS-2, manufactured by Nippon Pneumatic Industry Co., Ltd.), and Classifying with an elbow jet classifier (trade name, manufactured by Nippon Steel & Mining Co., Ltd.), toner base particles (5 kg) having a volume average particle size of 6.5 μm, a coefficient of variation of 22%, a glass transition point of 60 ° C., and a softening temperature of 120 ° C. Produced.

Resin fine particle preparation step: Styrene-butyl acrylate-acrylic acid copolymer resin having a glass transition point (Tg) of 57 ° C., a softening temperature of 106 ° C. and an acid value of 23 mg KOH / g, 250 parts by mass, anionic surfactant (first Kogyo Seiyaku Co., Ltd. 5 parts by mass / ion exchanged water 4500 parts by mass The above raw materials were heated to 90 ° C. and dispersed using a homogenizer (manufactured by IKA: Ultra Tarrax T50). Manufactured by Gorin Co., Ltd.) to prepare a resin fine particle dispersion (5000 g) having a volume average particle size of 0.20 μm and a solid particle size distribution peak of 1% by mass.
The resin fine particle dispersion (5000 g) was dried with a spray dryer to obtain resin fine particles (500 g).

Capsule toner particle formation process A total of 110 parts by weight of toner base particles and 10 parts by weight of resin fine particles is attached to a device in which a two-fluid nozzle is attached to a hybridization system (trade name: NHS-1 type, manufactured by Nara Machinery Co., Ltd.) ) And was allowed to stay at a rotational speed of 8000 rpm for 1 minute.
As the spray unit of the above apparatus, a unit in which a liquid feed pump (trade name: SP11-12, manufactured by FROM Co., Ltd.) and a two-fluid nozzle were connected was used so that the quantitative liquid feeding of ethanol was possible. The spraying speed and the discharging speed of the vaporized spray liquid can be observed using a commercially available gas detector (trade name: XP-3110, manufactured by Shin Cosmos Electric Co., Ltd.).
A temperature adjusting jacket is provided on the entire surface of the powder flow section and the stirring section wall of the above apparatus, and a temperature sensor is attached to the powder flow path. The temperature of the powder flow section and the stirring section is 45 ° C. It adjusted so that it might become. In the above apparatus, the peripheral speed at the outermost periphery of the rotating stirring means of the hybridization system was 100 m / sec. The mounting angle of the two-fluid nozzle was set so that the angle formed by the spray direction of the spray liquid and the powder flow direction (hereinafter referred to as “spray angle”) was parallel (0 °).
Ethanol was sprayed at a spray rate of 0.5 g / min and an air flow rate of 5 L / min for 40 minutes, and the resin fine particles were fused on the surface of the toner base particles to form a coating layer. After stopping the ethanol spraying, the mixture was stirred for 5 minutes to obtain a capsule toner of Example 1. At this time, the discharge concentration of the spray liquid discharged through the through hole and the gas discharge portion of the apparatus was stable at about 1.4% by volume.

(Manufacture of two-component developer)
The two-component developer (500 g) of Example 1 was prepared by mixing the capsule toner of Example 1 and the resin-coated carrier of Example 1 so that the toner concentration was 7% by mass.

<Example 2>
(Carrier production)
Resin-coated carrier of Example 2 in the same manner as in Example 1 except that the volume average particle size of the carrier core material is adjusted to 30 μm and the resin-coated carrier is classified by sieving to have a predetermined particle size distribution and average particle size. Got.
(Manufacture of capsule toner)
In the toner base particle preparation step, a polyester resin (glass transition point 55 ° C., softening temperature 128 ° C.) is used instead of a polyester resin (trade name: Toughton, manufactured by Kao Corporation, transition point 60 ° C., softening temperature 138 ° C.). A capsule toner of Example 2 was obtained in the same manner as in Example 1 except that the toner base particles were pulverized so that the volume average diameter thereof was 4.3 μm.
(Manufacture of two-component developer)
A two-component developer of Example 2 was obtained in the same manner as Example 1.

<Example 3>
(Carrier production)
Resin-coated carrier of Example 3 in the same manner as in Example 1 except that the volume average particle size of the carrier core material is adjusted to 45 μm, and the resin-coated carrier is classified by sieving to have a predetermined particle size distribution and average particle size. Got.
(Manufacture of capsule toner)
In the toner base particle preparation process, a polyester resin (glass transition point 65 ° C., softening temperature 148 ° C.) is used instead of polyester resin (trade name: Toughton, manufactured by Kao Corporation, glass transition point 60 ° C., softening temperature 138 ° C.) Then, a capsule toner of Example 3 was obtained in the same manner as in Example 1 except that the toner base particles were pulverized so that the volume average diameter thereof was 7.4 μm.
(Manufacture of two-component developer)
The two-component developer of Example 3 was obtained in the same manner as Example 1.

<Example 4>
(Carrier production)
Resin-coated carrier of Example 4 in the same manner as in Example 1 except that the volume average particle size of the carrier core material is adjusted to 30 μm and the resin-coated carrier is classified by sieving so as to have a predetermined particle size distribution and average particle size. Got.
(Capsule toner)
The same capsule toner as in Example 1 was used.
(Manufacture of two-component developer)
A two-component developer of Example 4 was obtained in the same manner as Example 1.

<Example 5>
(Carrier production)
Resin-coated carrier of Example 5 in the same manner as in Example 1 except that the volume average particle size of the carrier core material is adjusted to 63 μm, and the resin-coated carrier is classified by sieving to have a predetermined particle size distribution and average particle size. Got.
(Capsule toner)
The same capsule toner as in Example 1 was used.
(Manufacture of two-component developer)
The two-component developer of Example 5 was obtained in the same manner as Example 1.

<Comparative Example 1>
(Carrier production)
The resin-coated carrier of Example 1 was classified with a sieve so as to obtain a predetermined particle size distribution and average particle size, whereby a resin-coated carrier of Comparative Example 1 was obtained.
(Capsule toner)
The same capsule toner as in Example 1 was used.
(Manufacture of two-component developer)
A two-component developer of Comparative Example 1 was obtained in the same manner as Example 1.

<Example 6>
(Carrier production)
The resin-coated carrier of Example 1 was classified with a sieve so as to obtain a predetermined particle size distribution and average particle size, and a resin-coated carrier of Example 6 was obtained.
(Capsule toner)
The same capsule toner as in Example 1 was used.
(Manufacture of two-component developer)
A two-component developer of Example 6 was obtained in the same manner as Example 1.

<Example 7>
(Carrier production)
The resin-coated carrier of Example 1 was classified with a sieve so as to have a predetermined particle size distribution and average particle size, and a resin-coated carrier of Example 7 was obtained.
(Capsule toner)
The same capsule toner as in Example 1 was used.
(Manufacture of two-component developer)
A two-component developer of Example 7 was obtained in the same manner as Example 1.

  Using the developed developing sleeve and the two-component developers of Examples 1 to 7 and Comparative Example 1, evaluation of image density unevenness, developer transport amount and toner component fusion was performed according to the following evaluation methods. It was. Table 1 shows combinations of the developing sleeve and the two-component developer, and Table 2 shows the evaluation results.

(Evaluation of uneven image density)
The two-component developers of Examples 1 to 7 and Comparative Example 1 were filled in the developing devices of a commercial copier (trade name: MX-M364FN, manufactured by Sharp Corporation) having the developing sleeve shown in Table 1, The surface potential of the photoreceptor and the developing bias were adjusted so that the toner adhesion amount on paper in a solid image (100% density) was 0.5 mg / cm ² and the toner adhesion amount in the non-image area was minimized. The test was performed in an environment of 25 ° C. and a humidity of 50%. A4 size electrophotographic paper (multi receiver: manufactured by Sharp Document System Co., Ltd.) was used as a test paper.
An image of 5% printing was printed on paper at 200K (200,000 sheets). Judgment from the solid image (100% density) at that time was made possible (◯) or impossible (×). In the case where there is a partial decrease in image density at a developing sleeve pitch in an area of 3 cm ² or more in a solid image, it is considered that the developability has decreased due to the fusion of the toner component to the developing sleeve, and its evaluation Was not possible (x), and when a partial decrease in image density was not observed, the evaluation was acceptable (◯).

(Evaluation of developer transport amount on the developing sleeve)
Before and after 200K (200,000 sheets) printing of the image density unevenness evaluation, if the developer transport amount on the developing sleeve is 55 mg / cm ² or more, the evaluation is acceptable (◯), and less than 55 mg / cm ² If so, the evaluation was impossible (x).

(Evaluation of fusion of toner component to developing sleeve surface)
After 200K (200,000 sheets) printing of the image density unevenness evaluation, the presence or absence of a black film on the developing sleeve was visually evaluated.
When there was no film formation, it was rated as (◯), when a white film was formed, it was marked with (Δ), and when a black film was formed, it was marked (x).

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photosensitive drum 3 Charging apparatus 4 Exposure apparatus 5 Developing apparatus 6 Paper feed tray 7 Transfer apparatus 8 Fixing apparatus 8a Heating roller 8b Pressure roller 9 Toner replenishing apparatus 9a Container 9b Stirring blade 9c Replenishing member 10 Cleaning apparatus DESCRIPTION OF SYMBOLS 11 Paper discharge tray 12a-12h Conveyance roller S Sheet conveyance path 51 Developing tank 51a Developing tank upper cover 51b Toner inlet 51c Partition plate 52 Developing roller 53 First developer conveying member 54 Second developer conveying member 55 Restriction member 56 Toner density Detection sensor 61 Developing sleeve 61a Developing sleeve rotating shaft 62 Magnet roller 62a Magnet roller fixed shaft P First developer conveying path Q Second developer conveying path V First communicating path W Second communicating path

Claims (3)

A sandblasted cylindrical developer sleeve;
A magnet roller having a plurality of magnetic poles;
A regulating member for adjusting the transport amount of the two-component developer;
A developing device including a toner base particle and a two-component developer including a capsule toner including a coating layer formed by fusing resin fine particles on the surface of the toner base particle and a carrier,
When the average particle size of the abrasive grains used in the sandblasting treatment is A μm, the content of carrier particles having a particle size of 0.7 × A μm or more and A μm or less is less than 5% by mass of the whole carrier. A developing device.   2. The developing device according to claim 1, wherein the content of carrier particles having a particle diameter of 0.2 × A μm to 0.4 × A μm is 20% by mass to 50% by mass of the entire carrier.   An image forming apparatus comprising the developing device according to claim 1.