JP2020181124A - Developer, method for manufacturing the same, image forming apparatus, developer storage unit, and image forming method - Google Patents

Abstract

To provide a developer that allows sufficient charge control even after a long period of running, can maintain sufficient storage stability even under a high-temperature and high-humidity environment, does not generate soil spots after a long period of running, and allows continuous paper feed with a printing density at a low image area ratio even in a high-speed machine using a low-temperature fixing toner.SOLUTION: A developer contains toner and carrier. The toner includes silica particles and toner base bodies. The ratio of the silica particles based on 100 parts by mass of the toner base body is 1.5 parts by mass or more and less than 5 parts by mass. The carrier has a resin layer including barium sulfate fine particles. The amount of Ba in the carrier detected by XPS is 0.3 atomic% or more. The equivalent circle diameter of the barium sulfate fine particles is 400 nm or more and 900 nm or less. The charge reduction ratio of the carrier, with an image area ratio of 40% and after the running of 1,000,000 sheets, is 20% to 30%.SELECTED DRAWING: Figure 2

Description

The present invention relates to a developer, a method for producing the same, an image forming apparatus, a developing agent accommodating unit, and an image forming method.

In image formation by the electrophotographic method, an electrostatic latent image is formed on an electrostatic latent image carrier such as a photoconductive substance, and a charged toner is adhered to the electrostatic latent image to form a toner image. After that, the toner image is transferred to a recording medium, fixed, and becomes an output image. In recent years, the technology of copiers and printers using electrophotographic methods has been rapidly expanding from monochrome to full color, and the full color market tends to expand.

In full-color image formation, additive fine particles are attached to the surface of the toner for the purpose of downsizing the fixing device and simplifying the configuration. However, this additive has a problem of causing image abnormality by desorbing from the toner and damaging the photoconductor. Further, there is a problem that toner filming occurs and the chargeability is lowered, so that the toner is scattered.

On the other hand, as carriers, prevention of toner filming, formation of uniform surface, prevention of surface oxidation, prevention of deterioration of humidity sensitivity, extension of developer life, prevention of adhesion of photoconductor to surface, exposure Carriers having a coating layer in which a resin containing carbon black is formed on the surface are known for the purpose of protecting the body from scratches or wear, controlling the polarity of charge, adjusting the amount of charge, and the like.
However, although a good image can be formed at the initial stage, there is a problem that the coating layer is scraped and the image quality deteriorates as the number of copies increases. Further, there is a problem that color stains occur due to scraping of the coating layer or desorption of carbon black from the coating layer. Titanium oxide, zinc oxide, and the like are generally known as alternative materials for carbon black, but the effect of reducing the volume intrinsic resistance is insufficient.
When these toners and carriers are mixed and used as a developing agent, there is a problem that the storage stability deteriorates as the temperature inside the machine rises.

Therefore, Patent Document 1 discloses a developer using a carrier having a toner containing titanium oxide as an additive and a resin layer containing fine particles of barium sulfate. Patent Document 2 discloses a developer in which a coating layer containing antimony-doped tin oxide (ATO) is formed as a needle-like conductive powder. Patent Document 3 discloses a developer using a carrier in which a coating layer containing conductive particles in which a tin dioxide layer and an indium oxide layer containing tin dioxide are laminated on the surface of base particles is formed. Patent Document 4 describes a coating layer containing a first conductive particle which is a metal oxide conductive particle and a second conductive particle whose surface is a conductive treatment of the metal oxide particle and / or the metal salt particle. A developer using a carrier having the above is disclosed. Further, Patent Document 5 discloses a developer using a toner containing only silica fine particles as an additive on the surface of the toner. Patent Document 6 discloses a developer using a carrier having a coating layer containing barium sulfate, and Patent Document 7 discloses a carrier having a coating layer containing a resin made of a specific copolymer and barium sulfate. Has been done. Further, Patent Documents 8 and 9 describe carriers having a coating layer containing barium sulfate, and have a Ba / Si ratio of 0.01 to 0.08 as measured by X-ray photoelectron spectroscopy (XPS). The carrier is disclosed. Furthermore, Patent Document 10 discloses a carrier using barium sulfate as a substrate for conductive particles contained in the carrier.

However, in the technique disclosed in Patent Document 1, there is a problem that titanium oxide used as a toner additive is spint on the carrier and the charging ability as a developer is lowered, so that toner is scattered. is there. In the technique disclosed in Patent Document 2, since the color tone of ATO is bluish, there is a problem that color stains occur as in carbon black. Since the technique disclosed in Patent Document 3 is a conductive particle containing a rare metal, there are problems in terms of cost, permanent usability, and the like. The technique disclosed in Patent Document 4 has a certain effect on a decrease in the charging ability of the carrier, but when a toner containing a large amount of an external additive is used and continuous paper is passed over a high image area, the paper is continuously passed. However, the charging ability is also lowered, and the charging effect cannot be said to be sufficient. Further, the techniques disclosed in Patent Documents 5 to 10 have a certain effect on a decrease in the charging ability of the carrier when the toner is balanced in a high image area. However, in recent years, toner tends to be fixed at a low temperature in order to reduce power consumption, and there is also a demand for higher printing speed. Spent formation in which a toner film is formed on the surface of carrier particles is more likely to occur. Further, the toner tends to contain a large amount of additives due to the demand for higher image quality, and these spint on the carrier, causing problems such as a decrease in the amount of toner charge, toner scattering, and background stains. Furthermore, since the amount of charged fine particles and the like is reduced to fix the toner at a low temperature, the toner at the time of replenishment is not sufficiently mixed with the developer, so that the toner is not charged and the toner scatters. There is. The developer using the carrier and the toner described in each of the above-mentioned patent documents cannot sufficiently exert the effect on such a new problem.

On the other hand, in the commercial printing market, which has been expanding in recent years, the so-called production printing field, higher image quality than ever is required. That is, density fluctuations and density unevenness within a single image, density fluctuations between images when printing tens of thousands of sheets, toner scattering, and detached external additives accumulate on the surface of the photoconductor, resulting in an abnormal image. It is technically extremely difficult to suppress the generation of so-called medaka, which is generated, only by the machine itself. Therefore, it is required more than ever to control the charge amount of the toner to be constant. However, the developing agent using the carrier and the toner described in each of the above-mentioned patent documents cannot satisfy the requirement.

INDUSTRIAL APPLICABILITY According to the present invention, with respect to the image quality required in the field of production printing, sufficient charge control is possible even after long-term running, sufficient storage stability can be maintained even in a high temperature and high humidity environment, and after long-term running. It is an object of the present invention to provide a developing agent that enables continuous paper passing at a printing density with a low image area ratio even in a high-speed machine using a low-temperature fixing toner without generating medaka.

The above problem is solved by the following configuration 1).
1) A developer containing at least toner and carriers.
The toner contains silica particles and a toner matrix.
The ratio of the silica particles to 100 parts by mass of the toner base is 1.5 parts by mass or more and less than 5 parts by mass.
The carrier is a carrier having a resin layer containing at least one kind of fine particles.
At least one of the fine particles is composed of barium sulfate fine particles.
The amount of Ba detected by X-ray photoelectron spectroscopy (XPS) of the carrier is 0.3 atomic% or more.
Development characterized in that the equivalent circle diameter of the barium sulfate fine particles is 400 nm or more and 900 nm or less, the image area ratio of the carrier is 40%, and the charge reduction rate after running 1 million sheets is 20% to 30%. Agent.

According to the present invention, with respect to the image quality required in the field of production printing, sufficient charge control is possible even after long-term running, sufficient storage stability can be maintained even in a high temperature and high humidity environment, and long-term storage is possible. It is possible to provide a developing agent that does not generate medaka after running and enables continuous paper passing at a print density with a low image area ratio even in a high-speed machine using a low-temperature fixing toner.

FIG. 1 is a diagram showing a cell used when measuring the volume specific resistance of the carrier of the present invention. FIG. 2 is a diagram showing an example of a process cartridge used in the present invention.

Hereinafter, embodiments of the present invention will be described in more detail.

The developer of the present invention contains at least toner and carriers and, if necessary, other components.
The present invention also includes the following forms <2> to <11>.
<2>
The silica particles are characterized by containing small particle size silica particles having a flat diameter of 5 nm or more and 30 nm or less, and large particle size silica particles having a flat diameter of 70 nm or more and 150 nm or less. The developer according to 1>.
<3>
The ratio of the large particle size silica particles to 100 parts by mass of the toner base is 2 parts by mass or more and 3 parts by mass or less, and the ratio of the small particle size silica particles to 100 parts by mass of the toner base is 1 part by mass or more and 2 parts by mass. The developer according to <2>, which is characterized by having a mass of parts or less.
<4>
The developer according to any one of <1> to <3>, wherein the toner has a crystalline resin.
<5>
The developer according to any one of <1> to <4>, wherein the rate of change in fluidity of the developer is 13% or less.
<6>
The developer according to any one of <1> to <5>, wherein the barium sulfate fine particles have Ba present on the surface of the fine particles.
<7>
Any of <1> to <6>, wherein the content of the barium sulfate fine particles in the resin layer is 50% by mass or more and less than 100% by mass with respect to the resin contained in the resin layer. The developer described.
<8>
A method for producing a developer containing at least toner and carriers.
The toner is configured to contain silica particles and a toner matrix.
The ratio of the silica particles to 100 parts by mass of the toner base is set to 1.5 parts by mass or more and less than 5 parts by mass.
The carrier is configured to be a carrier having a resin layer containing at least one kind of fine particles.
At least one of the fine particles is set to barium sulfate fine particles,
The amount of Ba detected by X-ray photoelectron spectroscopy (XPS) of the carrier is set to be 0.3 atomic% or more.
It is characterized in that the equivalent circle diameter of the barium sulfate fine particles is set to 400 nm or more and 900 nm or less, the image area ratio of the carrier is 40%, and the charge reduction rate after running 1 million sheets is 20% to 30%. How to manufacture the developer.
<9>
Electrostatic latent image carrier and
An electrostatic latent image forming means for forming an electrostatic latent image on the electrostatic latent image carrier,
Having a developing means for developing the electrostatic latent image formed on the electrostatic latent image carrier with the developing agent according to any one of <1> to <7> to form a toner image. An image forming apparatus characterized by.
<10>
A developer accommodating unit accommodating the developer according to any one of <1> to <7>.
<11>
An electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier,
A developing step of developing the electrostatic latent image formed on the electrostatic latent image carrier with the developer according to any one of <1> to <7> to form a toner image is included. An image forming method characterized by this.

<Toner>
The toner in the present invention includes silica particles and a toner matrix. Preferably, the toner in the present invention contains small particle size silica particles having a flat diameter of 5 nm or more and 30 nm or less, and large particle size silica particles having a flat diameter of 70 nm or more and 150 nm or less. Hereinafter, a case where the silica particles are composed of the large particle size silica and the small particle size silica will be described as an example. With such a toner configuration, spent (adhesion to the carrier surface) due to other additives to the carrier can be suppressed, and a decrease in the charge amount of the developer can be suppressed. In addition, the toner in the present invention is characterized in that the ratio of the large particle size silica particles and the small particle size silica particles to 100 parts by mass of the toner base is 1.5 parts by mass or more and less than 5 parts by mass. The silica particles have a great influence on the fluidity, storage stability and chargeability of the developer, and further have a great influence on the medaka fish generated after long-term running as an image quality. When the ratio of the large particle size silica particles and the small particle size silica particles to 100 parts by mass of the toner base is 1.5 parts by mass or more, the fluidity of the developer is improved, and the storage stability and charging characteristics are improved. Further, when the ratio of the large particle size silica particles and the small particle size silica particles to 100 parts by mass of the toner base is less than 5 parts by mass, the amount of silica particles released from the toner base is suppressed and medaka is not generated in the image.

<Ratio of large particle size silica and small particle size silica>
As described above, the ratio of the large particle size silica particles and the small particle size silica particles to 100 parts by mass of the toner base is preferably 1.5 parts by mass or more and less than 5 parts by mass, but the flow of the developer. The ratio of the large particle size silica particles to 100 parts by mass of the toner base is 2 parts by mass or more and 3 parts by mass or less, and 100 parts by mass of the toner base is ensured. It is desirable that the ratio of the small particle size silica particles to the particle is 1 part by mass or more and 2 parts by mass or less. When the ratio of the large particle size silica particles to 100 parts by mass of the toner base is 2 parts by mass or more, the distance between the toners becomes wide, the toners are hard to stick to each other, and the storage stability is improved. Further, when the ratio of the large particle size silica particles to 100 parts by mass of the toner base is 3 parts by mass or less, nuclei that generate medaka are less likely to be generated after long-term running, and the generation of medaka is suppressed. Further, when the ratio of the small particle size silica particles to 100 parts by mass of the toner base is 1 part by mass or more, the fluidity of the toner is improved and the charging ability is improved. Further, when the ratio of the small particle size silica particles to 100 parts by mass of the toner base is 2 parts by mass or less, medaka does not grow after long-term running, and the amount of medaka generated can be suppressed.

<Average particle size of large particle size silica and small particle size silica>
In the present invention, the average particle size of the large particle size silica particles is 5 nm or more and 30 nm or less, and the average particle size of the small particle size silica particles is 70 n or more and 150 nm or less. When the average particle size of the large particle size silica is 5 nm or more, the distance between the toners becomes wide, the toners do not easily stick to each other, and the storage stability is improved. When the average particle size of the large-particle silica is 30 nm or less, nuclei that generate medaka are less likely to be generated after long-term running, and the generation of medaka is suppressed. When the average particle size of the small particle size silica is 70 nm or more, the distance between the toners becomes wide, the toners do not easily stick to each other, and the storage stability is improved. Further, when the average particle size of the small particle size silica is 150 nm or less, the fluidity of the toner is improved and the charging performance is improved.

<< Evaluation method of average particle size of large particle size silica and small particle size silica >>
The average particle size of large particle size silica and small particle size silica is measured by dispersing these silica in an appropriate solvent (tetrahydrofuran (THF), etc.), removing the solvent on the substrate, and drying the sample. The particle size in the visual field was measured with an electroradiating scanning electron microscope (FE-SEM, acceleration voltage: 5 kV to 8 kV, observation magnification: 8,000 to 10,000 times).

<Crystalline resin>
It is desirable that the toner base contains a crystalline resin. When a crystalline resin is contained, it is possible to maintain low temperature fixability while maintaining the storage stability of the toner.

The toner can contain at least a binder resin and a colorant, and may be either a monochrome toner or a color toner. Further, the toner may contain a release agent in order to be applied to an oilless system in which the fixing roller is not coated with the toner sticking prevention oil. Toners are generally prone to filming, but the carriers and toners of the present invention can suppress filming, so that the developer of the present invention can maintain good quality for a long period of time. it can.
Further, color toners, particularly yellow toners, generally have a problem that color stains occur due to scraping of the coating layer of the carrier. However, since the carrier of the present invention has high durability, the present invention has a problem. The developer can suppress the occurrence of color stains. If necessary, the toner may contain a charge control agent, an external additive, a fluidity improver, a cleanability improver, a magnetic material, and the like.

The toner can be produced by using a known method such as a pulverization method or a polymerization method. For example, when toner is produced by using a pulverization method, first, the melt-kneaded product obtained by kneading the toner material is cooled, then pulverized and classified to produce parent particles. Next, in order to further improve the transferability and durability, an external additive is added to the parent particles to prepare a toner.

The binder resin is not particularly limited, but is a homopolymer of styrene such as polystyrene, polyp-styrene, polyvinyltoluene and its substitution product; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, and the like. Styrene-vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer Combined, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene- Styrene-based copolymers such as butadiene copolymers, styrene-isoprene copolymers, and styrene-maleic acid ester copolymers; polymethylmethacrylate, butylpolymethacrylate, polyvinyl chloride, vinylacetate, polyethylene, polyester, Examples thereof include polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid, rosin, modified rosin, terpen resin, phenol resin, aliphatic or aromatic hydrocarbon resin, aromatic petroleum resin, and two or more thereof may be used in combination. ..
The binder resin for pressure fixing is not particularly limited, but is a polyolefin such as low molecular weight polyethylene and low molecular weight polypropylene; ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, and styrene-methacrylic acid copolymer. , Ethylene-methacrylic acid ester copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, olefin copolymer such as ionomer resin; epoxy resin, polyester, styrene-butadiene copolymer, polyvinylpyrrolidone, Examples thereof include a methyl vinyl ether-maleic anhydride copolymer, a maleic acid-modified phenol resin, and a phenol-modified terpene resin, and two or more of them may be used in combination.

The colorant (pigment or dye) is not particularly limited, but is limited to cadmium yellow, mineral fast yellow, nickel titanium yellow, navels yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow GR, and quinoline yellow rake. , Permanent Yellow NCG, Tartrazine Lake and other yellow pigments; Molybdenum Orange, Permanent Orange GTR, Pyrazolone Orange, Balkan Orange, Indance Rembrilliant Orange RK, Benzidine Orange G, Indance Rembrilliant Orange GK and other orange pigments; Red pigments such as cadmium red, permanent red 4R, resole red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B; fast violet B, methyl violet Purple pigments such as lake; cobalt blue, alkaline blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, indanslen blue BC and other blue pigments; chrome green, chromium oxide, Green pigments such as Pigment Green B and Malakite Green Lake; azine pigments such as carbon black, oil furnace black, channel black, lamp black, acetylene black and allin black, metal salt azo pigments, metal oxides, composite metal oxides, etc. Black pigments and the like can be mentioned, and two or more of them may be used in combination.

The release agent is not particularly limited, and examples thereof include polyolefins such as polyethylene and polypropylene, fatty acid metal salts, fatty acid esters, paraffin wax, amide wax, polyhydric alcohol wax, silicone varnish, carnauba wax, and ester wax. However, two or more types may be used in combination.

When the developer of the present invention is used in an image forming apparatus that forms an image while discharging excess developing agent in the developing apparatus, stable image quality can be obtained for an extremely long period of time. That is, in an image apparatus in which a deteriorated carrier in a developing apparatus and a non-deteriorated carrier in a replenishing developing agent are replaced, the developing agent of the present invention keeps a stable charge amount for a long period of time and produces a stable image. Can contribute to the formation. It is particularly effective in the image method when printing a high image area. When printing a high image area, the carrier charge deterioration due to the toner spent on the carrier is the main carrier deterioration, but by using the carrier and the toner of the present invention, the influence of the spent and scraping can be suppressed.

The mixing ratio of the carrier and the toner of the developer when used as a replenishing developer is preferably 2 parts by mass to 50 parts by mass of the toner with respect to 1 part by mass of the carrier. When the amount of toner is 2 parts by mass or more, it is possible to suppress an excessive amount of replenishment carriers, and it is possible to suppress an increase in the amount of charge of the developer due to an increase in the carrier concentration in the developing apparatus. Further, it is possible to prevent the problem that the developing ability is lowered and the image density is lowered by increasing the charge amount of the developer. Further, when the amount is 50 parts by mass or less, it is possible to prevent a decrease in the carrier ratio in the replenishing developer, and it is possible to prevent the problem of carrier deterioration due to less carrier replacement in the image forming apparatus. it can.
In addition, in a form other than the use of the replenishing developer, the mixing ratio of the carrier of the developer and the toner can be 2 parts by mass to 12 parts by mass of the toner with respect to 1 part by mass of the carrier.

(Career)
The carrier of the present invention has a resin layer. Preferably, the carrier of the present invention comprises a core material and a resin layer covering the core material.
At least one kind of fine particles is contained in the resin layer, and in the present invention, at least one kind of the fine particles is barium sulfate fine particles.
The carrier of the present invention shows a Ba detection amount of 0.3 atomic% or more in the Ba analysis by X-ray photoelectron spectroscopy (XPS).
The equivalent circle diameter of the barium sulfate fine particles is 400 nm or more and 900 nm or less.
The carrier of the present invention that satisfies the above requirements can sufficiently control charging for a desired image quality, can supply a stable amount of a developer to a developing region, and uses a low-temperature fixing toner. It is a carrier that enables continuous paper transfer with a print density of low image area ratio even in high-speed machines.

In the present invention, it is important that the resin layer contains at least fine particles of barium sulfate, and the amount of Ba detected on the surface of the resin layer is 0.3 atomic% or more in the XPS analysis. Barium sulfate can increase the chargeability of the toner, and barium sulfate on the surface layer can maintain the chargeability even after output in a high image area for a long time. In addition, it is also important that the equivalent circle diameter of barium sulfate is 400 nm or more and 900 nm or less. By setting the particle size of barium sulfate as described above, barium sulfate is present in a convex state with respect to the surface of the resin layer of the carrier. The surface of the carrier on which the convex portion is formed by barium sulfate is constantly stressed by friction with the toner, carrier, developing screw, etc. in the developing device, so that toner resin, wax, additives, etc. are temporarily applied. Even if it is spun, the film spuned by the above stress is immediately scraped. Therefore, barium sulfate can be kept exposed at all times.
On the other hand, toner resin, wax, additives, etc. are spinted in the recesses existing between the convex parts of barium sulfate, but since they are electrically charged with the same charge as the toner by being covered with these, it is more than that. Spent material does not accumulate. The carrier surface layer, which becomes a recess due to these spents, cannot be charged with toner, but since it is a recess, the probability of friction with the toner is low, and the contribution to toner charging is small. Therefore, since the portion where barium sulfate forms a convex portion determines the charging ability of the carrier, it is possible to maintain a stable charging ability for a long period of time.
Further, by setting the particle size of barium sulfate in the above range, an uneven shape can be formed on the surface layer of the carrier, thereby stabilizing the bulk density of the carrier. Normally, the bulk density of the carrier fluctuates due to the scraping of the carrier surface or the toner component spinting on the carrier surface layer, and the amount of the developer pumped onto the developing sleeve changes, so that the amount of the developing agent supplied to the developing region changes. As a result, there is a problem that the developing capacity fluctuates. However, by containing barium sulfate having a circle-equivalent diameter of 400 nm or more and 900 nm or less in the resin layer, it is possible to obtain the effect that the bulk density of carriers is less likely to fluctuate because the spent material accumulates in the recesses. In addition, by dispersing the fine particles of barium sulfate in the resin layer, the film strength of the resin layer can be increased, so that the amount of scraping of the resin layer can be reduced. For this reason, fluctuations in bulk density due to either spending or scraping are unlikely to occur, and stable developing ability can be ensured over a long period of time.

<Resin layer>
The resin layer contains a resin and fine particles of barium sulfate. Further, the resin layer may contain various conductive fine particles in addition to the fine particles of barium sulfate, and further, in order to improve the stability and durability of the carrier over time, silane coupling is performed. The agent may be contained.
The resin layer preferably has no film defects and an average film thickness of 0.80 μm to 1.50 μm. When the average film thickness is 0.80 μm or more, the fine particles of barium sulfate can be sufficiently retained, and the fine particles of barium sulfate can be prevented from detaching from the resin layer. Further, if it is 1.50 μm or less, it is possible to prevent a problem that fine particles of barium sulfate are taken into the resin layer and a sufficient charging ability cannot be exhibited.

<< Fine particles of barium sulfate >>
It is important that the equivalent circle diameter of the barium sulfate fine particles is 400 nm or more and 900 nm or less for the reason described above, but the equivalent circle diameter is 600 nm or more in order to secure stable charging ability and developing ability. Is more preferable. If the equivalent circle diameter of barium sulfate exceeds 900 nm, the size of the fine particles of barium sulfate is too large with respect to the thickness of the resin layer, and the particles are easily separated from the resin layer. Therefore, 900 nm or less is preferable.

It is preferable that Ba is present on the surface of the fine particles of barium sulfate. It is preferable that the fine particles of barium sulfate are contained in the resin layer in a manner in which Ba is present on the surface. As described above, barium sulfate exposed on the surface layer contributes to stable charging ability. Therefore, if the surface layer of barium sulfate is covered with a substance such as tin, sufficient charging ability is secured so that barium sulfate is not exposed on the surface layer. I can't. Therefore, it is difficult to exhibit a stable charging ability. In addition, the exposure of barium sulfate to the surface layer has the effect of facilitating the uptake of the replenished toner. It is considered that this is because barium sulfate is easily triboelectrically charged with the toner, and it has a particularly remarkable effect on the toner in which the charged particles are reduced due to low temperature fixing. The mode in which barium is present on the surface here means that barium sulfate is not covered with a substance such as tin, and 90% or more of the surface of the fine particles is barium sulfate. It may be a single particle of barium sulphate.

The content of the fine particles of barium sulfate is preferably 50% by mass or more and less than 100% by mass with respect to the resin contained in the resin layer.
If it is 50% by mass or more, it is possible to prevent the problem that the toner cannot be sufficiently charged due to the small number of exposed parts of barium sulfate. Further, if it is less than 100% by mass, it is possible to prevent the problem that the initial charge adjustment becomes difficult because the charging capacity of the carrier is too high.

<< Resin >>
The resin is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the copolymer containing the following monomer A component (also referred to as A component) and the following monomer B component (also referred to as B component). Examples thereof include a resin obtained by heat-treating the coalescence.

(In the formula, R ¹ , m, R ² , R ³ , X, and Y indicate the following.)
R ¹ is a hydrogen atom, or methyl group m is an integer of 1 to 8, and therefore (CH ₂ ) _m is an alkylene such as a methylene group, an ethylene group, a propylene group, and a butylene group having 1 to 8 carbon atoms. R ² representing a group is a methyl group having 1 to 4 carbon atoms, an ethyl group, a propyl group, an isopropyl group, and an alkyl group such as a butyl group. R ³ is a methyl group having 1 to 8 carbon atoms, an ethyl group, and propyl. Alkyl groups such as groups, isopropyl groups, and butyl groups, or alkoxy groups such as methoxy groups, ethoxy groups, propoxy groups, and butoxy groups having 1 to 4 carbon atoms X = 10 mol% to 90 mol%, more preferably. Is 30-70 mol%.
Y = 10 mol% to 90 mol%, more preferably 30 to 70 mol%.

The component A has an atomic group tris (trimethylsiloxy) silane in which a large number of methyl groups are present in the side chain, and the surface energy decreases as the ratio of the component A to the entire resin increases, and the toner resin Adhesion of components, wax components, etc. is reduced. If the A component is 10 mol% or more, a sufficient effect can be obtained, and a rapid increase in adhesion of the toner component can be prevented. Further, if it is 90 mol% or less, the component B and the component C described later are reduced, so that the cross-linking does not proceed, the toughness is insufficient, and the adhesiveness between the core material and the resin layer is lowered, so that the carrier coating is formed. It is possible to prevent problems such as deterioration of durability.
R ² is an alkyl group having 1 to 4 carbon atoms, and examples of such A component include a tris (trialkylsiloxy) silane compound represented by the following formula.
In the following formula, Me is a methyl group, Et is an ethyl group, and Pr is a propyl group.
CH ₂ = CMe-COO-C ₃ H _6- Si (OSiMe ₃ ) ₃
CH ₂ = CH-COO-C ₃ H _6- Si (OSiMe ₃ ) ₃
CH ₂ = CMe-COO-C ₄ H _8- Si (OSiMe ₃ ) ₃
CH ₂ = CMe-COO-C ₃ H _6- Si (OSiEt ₃ ) ₃
CH ₂ = CH-COO-C ₃ H _6- Si (OSiEt ₃ ) ₃
CH ₂ = CME-COO-C ₄ H _8- Si (OSiEt ₃ ) ₃
CH ₂ = CMe-COO-C ₃ H _6- Si (OSiPr ₃ ) ₃
CH ₂ = CH-COO-C ₃ H _6- Si (OSiPr ₃ ) ₃
CH ₂ = CMe-COO-C ₄ H _8- Si (OSiPr ₃ ) ₃
The method for producing the component A is not particularly limited, but a method for reacting tris (trialkylsiloxy) silane with allyl acrylate or allyl methacrylate in the presence of a platinum catalyst, and as described in JP-A-11-217389. In addition, it can be obtained by a method of reacting a methacryloxyalkyltrialkoxysilane with a hexaalkyldisiloxane in the presence of a carboxylic acid and an acid catalyst.

The B component is a radically polymerizable bifunctional (when R ³ is an alkyl group) or trifunctional (when R ³ is also an alkoxy group) silane compound, and if the B component is 10 mol% or more, Sufficient toughness can be obtained. On the other hand, if it is 90 mol% or less, the problem that the film becomes hard and brittle and the film scraping is likely to occur can be prevented. In addition, deterioration of environmental characteristics can be prevented. This is because if a large number of hydrolyzed crosslinked components remain as silanol groups, the environmental characteristics (humidity dependence) may be deteriorated.
Examples of such B component include 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltriethoxysilane, and 3-methacryloxypropylmethyl. Examples thereof include dimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacrythoxypropyltri (isopropoxy) silane, and 3-acryloxypropyltri (isopropoxy) silane.

In the present invention, a crosslinked product obtained by hydrolyzing the following copolymer obtained by radical copolymerization of the monomer A component and the monomer B component to generate a silanol group and condensing with a catalyst. Is preferably coated on the core material and then heat-treated to form a resin layer.

Here, in the formula, R ¹ , m, R ² , R ³ , X, and Y are as described above.

Furthermore, in the present invention, an acrylic compound (monomer) may be added as the C component to the A component and the B component.
Examples of the one to which such a monomer C component (also referred to as C component) is added include the following copolymers.

Here, in the formula, R ¹ , m, R ² , and R ³ are as described above.
In the above copolymer, X = 10 mol% to 40 mol%, Y = 10 mol% to 40 mol%, Z = 30 mol% to 80 mol%, and 60 mol% <Y + Z <90 mol. %.

The C component is represented by the following formula. In the formula, R ¹ and R ² are as described above.

The C component imparts flexibility to the resin layer and improves the adhesiveness between the core material and the resin layer. However, if the C component is 30 mol% or more, sufficient adhesiveness is obtained. If it is 80 mol% or less, it is possible to prevent either the A component or the B component from being 10 mol% or less, and achieve both water repellency, hardness and flexibility (film scraping) of the carrier film. Can be made to.
As the acrylic compound (monomer) of the C component, an acrylic acid ester or a methacrylic acid ester is preferable, and specifically, methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, butyl methacrylate, butyl acrylate, 2- (dimethylamino). ) Ethyl methacrylate, 2- (dimethylamino) ethyl acrylate, 3- (dimethylamino) propyl methacrylate, 3- (dimethylamino) propyl acrylate are exemplified.
Of these, alkyl methacrylates are more preferred, and methyl methacrylates are particularly preferred. Further, one kind of these compounds may be used alone, or a mixture of two or more kinds may be used.

As a high durability technique by cross-linking a resin layer, for example, there is Japanese Patent No. 36911515. Patent No. 369115 has an organopolysiloxane having a vinyl group at least at the end of the magnetic particle surface and at least one functional group selected from the group consisting of a hydroxyl group, an amino group, an amide group, and an imide group. A carrier for developing an electrostatic charge image in which a copolymer with a radical copolymerizable monomer is crosslinked with an isocyanate-based compound and coated with a thermosetting resin is described. However, in the disclosed technique, the resin layer is peeled off. It cannot be said that sufficient durability is obtained in shaving. Although the reason has not been clarified, in the case of a thermosetting resin in which the above copolymer is crosslinked with an isocyanate-based compound, as can be seen from the structural formula, it reacts (crosslinks) with the isocyanate compound in the copolymer resin. ) There are few functional groups (active hydrogen-containing groups such as amino group, hydroxy group, carboxyl group, and mercapto group) per unit weight, and a two-dimensional or three-dimensional dense crosslinked structure is formed at the crosslinking point. I can't. Therefore, if it is used for a long time, the film is likely to be peeled off or scraped (the resin layer has low wear resistance), and it is presumed that sufficient durability is not obtained.
When the resin layer is peeled off or scraped, the image quality changes due to a decrease in carrier resistance and carrier adhesion occurs. In addition, peeling / scraping of the resin layer lowers the fluidity of the developer, causes a decrease in the pumping amount, and causes a decrease in image density, stains when TC is increased, and toner scattering.
On the other hand, the resin layer of the present invention formed of the above resin has a large number of bifunctional or trifunctional crosslinkable functional groups (points) (2 to 3 times per unit weight) even when viewed per unit weight of the resin. Since it is formed based on the copolymerized resin (often), and further, it is formed by cross-linking this by polycondensation, the resin layer is extremely tough and difficult to scrape, and high durability can be achieved. It is thought that it is.
Further, since the crosslinking by the siloxane bond of the present invention has a larger binding energy and is more stable against thermal stress than the crosslinking by the isocyanate compound, it is considered that the stability of the resin layer with time is maintained.

As described above, it is a preferable embodiment that the copolymer is hydrolyzed to generate a silanol group and polycondensated to form a resin layer, but titanium is used as a catalyst for the polycondensation. Examples thereof include system catalysts, tin catalysts, zirconium catalysts, and aluminum catalysts.
In the present invention, among these catalysts, it is preferable to use a titanium-based catalyst, and it is particularly preferable to use titanium diisopropoxybis (ethylacetacetate). It is considered that this is because the effect of promoting the condensation reaction of the silanol group is large and the catalyst is not easily deactivated.

As the resin used for forming the resin layer, in addition to the above-mentioned resin, a silicon resin, an acrylic resin, or a combination thereof can be used. Acrylic resin has strong adhesiveness and low brittleness, so it has excellent wear resistance. On the other hand, it has high surface energy, so when combined with toner that is easy to spent, toner component spent accumulates. This may cause problems such as a decrease in the amount of charge. In that case, this problem can be solved by using a silicon resin which has an effect that it is difficult to spent the toner component because the surface energy is low and it is difficult for the accumulation of the spent component to proceed due to film scraping. On the other hand, since silicone resin has weak adhesiveness and high brittleness, it is inferior in abrasion resistance. Therefore, when these two types of resins are used in combination, it is advisable to consider the balance between the two resins so that a resin layer that is difficult to spent and has wear resistance can be formed.
The silicone resin generally refers to generally known silicone resins, and examples thereof include straight silicones consisting only of organoshirosan bonds, silicone resins modified with alkyds, polyesters, epoxies, acrylics, urethanes, and the like. Be done. Examples of commercially available straight silicone resins include KR271, KR255, and KR152 manufactured by Shin-Etsu Chemical, and SR2400, SR2406, and SR2410 manufactured by Toray Dow Corning Silicone. In this case, it is possible to use the silicon resin alone, but it is also possible to use other components that undergo a cross-linking reaction, a charge amount adjusting component, and the like at the same time. Further, as the modified silicone resin, KR206 (alkyd modified), KR5208 (acrylic modified), ES1001N (epoxy modified), KR305 (urethane modified) manufactured by Shin-Etsu Chemical Co., Ltd., SR2115 (epoxy modified) manufactured by Toray Dow Corning Silicon Co., Ltd. , SR2110 (alkyd modification) and the like.

Examples of the method for forming the resin layer include the following methods.
In addition to the copolymer and the barium sulfate fine particles, the resin layer contains a silicone resin having a silanol group and / or a hydrolyzable functional group, a catalyst, and if necessary, a silanol group and / or a hydrolyzable functional group. It can be formed by using a resin layer composition containing a resin other than the silicon resin, a solvent, and the like. Specifically, it may be formed by condensing silanol groups while coating the core material with the resin layer composition, or after coating the core material with the resin layer composition, the silanol groups are condensed. It may be formed by making it. The method for condensing silanol groups while coating the core material particles with the resin layer composition is not particularly limited, but is a method of coating the core material with the resin layer composition while applying heat, light, or the like. Can be mentioned. The method for condensing silanol groups after coating the core material with the resin layer composition is not particularly limited, and examples thereof include a method of coating the core material with the resin layer composition and then heating the core material.

<< Other ingredients >>
As a component constituting the resin layer, in addition to the above-mentioned resin and the component of the fine particles of barium sulfate, other components such as conductive fine particles and a silane coupling agent may be contained.
The resin layer may contain conductive fine particles in order to adjust the volume specific resistance of the carrier.
The conductive fine particles are not particularly limited, and examples thereof include conductive polymers such as carbon black, ITO, PTO, WTO, tin oxide, zinc oxide, and polyaniline. These may be used in combination of two or more.

A silane coupling agent may be contained in the resin layer in order to stably disperse the fine particles.
The silane coupling agent is not particularly limited, but r- (2-aminoethyl) aminopropyltrimethoxysilane, r- (2-aminoethyl) aminopropylmethyldimethoxysilane, r-methacryloxypropyltrimethoxysilane, N-β- (N-vinylbenzylaminoethyl) -r-aminopropyltrimethoxysilane hydrochloride, r-glycidoxypropyltrimethoxysilane, r-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane , Vinyltriacetoxysilane, r-chloropropyltrimethoxysilane, hexamethyldisilazane, r-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride, r- Chlorpropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, allyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, dimethyldiethoxysilane, 1,3-divinyltetra Examples thereof include methyldisilazane and methacryloxyethyldimethyl (3-trimethoxysilylpropyl) ammonium chloride. These may be used in combination of two or more.
Commercially available products of the silane coupling agent include, for example, AY43-059, SR6020, SZ6023, SH6026, SZ6032, SZ6050, AY43-310M, SZ6030, SH6040, AY43-026, AY43-031, sh6062, Z-6911, sz6300. , Sz6075, sz6079, sz6083, sz6070, sz6072, Z-6721, AY43-004, Z-6187, AY43-021, AY43-043, AY43-040, AY43-047, Z-6265, AY43-204M, AY43-048. , Z-6403, AY43-206M, AY43-206E, Z6341, AY43-210MC, AY43-083, AY43-101, AY43-013, AY43-158E, Z-6920, Z-6940 (manufactured by Toray Silicone), etc. Can be mentioned.
The amount of the silane coupling agent added is preferably 0.1% by mass to 10% by mass with respect to the resin. When the amount of the silane coupling agent added is 0.1% by mass or more, the adhesiveness between the core material or the conductive fine particles and the resin is lowered, and the problem that the resin layer falls off during long-term use is prevented. If it is 10% by mass or less, the problem that toner filming occurs during long-term use can be prevented.

<Core material>
The core material is not particularly limited as long as it is a magnetic material; ferromagnetic metals such as iron and cobalt; iron oxides such as magnetite, hematite and ferrite; various alloys and compounds; these magnetic materials are dispersed in a resin. Examples thereof include the made resin particles. Among them, Mn-based ferrite, Mn-Mg-based ferrite, Mn-Mg-Sr ferrite and the like are preferable from the viewpoint of the environment.

<Characteristics of carrier>
As described above, the carrier of the present invention shows a Ba detection amount of 0.3 atomic% or more in the Ba analysis by X-ray photoelectron spectroscopy (XPS).
The Ba detection amount is more preferably 0.3 atomic% to 2.0 atomic%, and further preferably 0.3 atomic% to 1.5 atomic%.

The carrier of the present invention preferably has a volume average particle diameter of 28 μm or more and 40 μm or less. When the volume average particle size of the carrier particles is 28 μm or more, the occurrence of carrier adhesion can be prevented, and when it is 40 μm or less, problems such as deterioration of image detail reproducibility and inability to form a fine image are suppressed. be able to.

The carrier of the present invention preferably has a volume specific resistance of 8 to 16 (LogΩ · cm). When the volume specific resistance is 8 (LogΩ · cm) or more, the occurrence of carrier adhesion in the non-image portion can be prevented, and when it is 16 (LogΩ · cm) or less, the edge effect can be ensured.

<Measuring method of various carrier characteristics>
Each of the above characteristics of the carrier can be measured by the following method.

<< Ba analysis by X-ray photoelectron spectroscopy (XPS) >>
The amount of Ba detected on the carrier surface can be measured by AXIS ULTRA (Shimadzu Corporation / KRATOS).
The beam irradiation region is approximately 900 μm × 600 μm, and a range of 25 carriers × 17 is detected. Further, the penetration depth is 0 nm to 10 nm, and the state near the surface of the carrier can be measured.
Specific measurement conditions are measurement mode: Al: 1486.6 eV, excitation source: monochrome (Al), detection method: spectrum mode, magnet lens: OFF.
Then, the detected elements are identified by a wide area scan, and then peaks are detected by a narrow scan for each detected element. After that, Ba (atomic%) for all detected elements is calculated with the attached peak analysis software.

<< Measuring method of equivalent circle diameter >>
The equivalent circle diameter of the fine particles of barium sulfate is measured by the following method.
The carrier is mixed with an embedded resin (manufactured by Devcon, a two-component mixture, a 30-minute curable epoxy resin), left overnight or longer to cure, and a rough cross-sectional sample is prepared by mechanical polishing. A cross section polisher (SM-09010 manufactured by JEOL) is used for this, and the cross section is finished under the conditions of an accelerating voltage of 5.0 kV and a beam current of 120 μA. This is photographed using a scanning electron microscope (Merlin manufactured by Carl Zeiss) under the conditions of an accelerating voltage of 0.8 kV and a magnification of 30,000 times. The captured image is incorporated into a TIFF image, and the equivalent circle diameter of 100 particles of barium sulfate is measured using Image-Pro Plus manufactured by Media Cybernetics, and the average value is obtained.

<< Method for measuring the volume average particle size of carriers >>
The volume average particle size of the carrier can be measured using, for example, the Microtrack particle size distribution meter model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.).

<< Measurement method of carrier volume specific resistance >>
The volume specific resistance of the carrier can be measured using the cell shown in FIG. Specifically, first, the carrier (3) is placed in a cell composed of a fluororesin container (2) in which an electrode (1a) having a surface area of 2.5 cm × 4 cm and an electrode (1b) are housed at a distance of 0.2 cm. ) Is filled, and tapping is performed 10 times with a drop height of 1 cm and a tapping speed of 30 times / minute. Next, a DC voltage of 1000 V was applied between the electrodes (1a) and (1b), and the resistance value r [Ω] 30 seconds later was measured using a high resistance meter 4329A (manufactured by Hewlett-Packard Co., Ltd.). Then, the volume specific resistance [Ω · cm] can be calculated from the following formula.

The volume specific resistance (LogΩ · cm) of the carrier is a common logarithmic value of the volume specific resistance [Ω · cm] obtained by the above measurement.

The carrier in the present invention needs to have an image area ratio of 40% (using A4 size paper) and a charge reduction rate of 20% to 30% after running 1 million sheets, which is 25% to 30%. Is more preferable. The charge reduction rate can be calculated from the following formula, where Qs is the initial charge amount before running, 40% image area ratio, and Qe is the charge amount of the developer after 1 million sheets of running. When the charge reduction rate is 30% or less, the charge amount of the developer does not decrease after long-term running, and toner scattering can be suppressed.
The amount of charge on the carrier can be measured by mixing the carrier and toner at a mass ratio of 95: 5 for 10 minutes and using a triboelectric device (TB-200: manufactured by Toshiba Chemical Co., Ltd.) to measure a triboelectrically charged sample.

In order to control the charge reduction rate to 20% to 30%, means such as using only silica fine particles as the toner additive can be mentioned.

The developer of the present invention preferably has a fluidity change rate of 13% or less.
The rate of change in fluidity was determined by setting 80 g of a developer with a toner concentration of 10% by mass in a funnel supported by a funnel support in a fluidity measuring device (manufactured by Kuramochi Scientific Instruments Manufacturing Co., Ltd.) used in JIS Z2502, and having a diameter of 3 mm. It can be calculated by dropping the developer from the hole into the receiver by its own weight and measuring the time (seconds) from the start to the end of the outflow.
Specifically, it is calculated from the following formula, where Ts is the time when 80 g of the developer before running falls, and Te is the time when 80 g of the developer after running 1 million sheets falls with a 40% image area ratio. be able to. When the rate of change in fluidity is 13% or less, the amount of charge of the developer does not decrease after long-term running, and toner scattering can be suppressed.

In the method for producing a developer of the present invention, the toner is configured to contain silica particles and a toner base, and the ratio of the silica particles to 100 parts by mass of the toner base is 1.5 parts by mass or more and less than 5 parts by mass. The carrier is configured to have a resin layer containing at least one kind of fine particles, and at least one kind of the fine particles is set to barium sulfate fine particles, and X-ray photoelectron spectroscopic analysis of the carrier is performed. The amount of Ba detected by (XPS) is set to 0.3 atomic% or more, the equivalent circle diameter of the barium sulfate fine particles is set to 400 nm or more and 900 nm or less, and the image area ratio of the carrier is 40% and 1 million. It is characterized in that the charge reduction rate after running the sheet is 20% to 30%. Each requirement in the manufacturing method is the same as each requirement in the description of the developer of the present invention.

(Image forming apparatus and image forming method)
The image forming apparatus of the present invention forms an electrostatic latent image carrier, an electrostatic latent image forming means for forming an electrostatic latent image on the electrostatic latent image carrier, and an electrostatic latent image carrier. It has a developing means for developing the generated electrostatic latent image with the developer of the present invention to form a toner image, and further, if necessary, other means, for example, a transfer means, a fixing means, a cleaning means. , Static electricity elimination means, recycling means, control means, etc.
The image forming method of the present invention comprises an electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier, and the electrostatic latent image formed on the electrostatic latent image carrier. It has a developing step of developing with the developer of the present invention to form a toner image, and further, if necessary, other steps such as transfer step, fixing step, cleaning step, static elimination step, recycling step, control. Including processes and the like.
The image forming method of the present invention can be preferably carried out by the image forming apparatus of the present invention.
The electrostatic latent image forming means may have a charging means for charging the electrostatic latent image carrier and an exposure means for exposing the surface of the electrostatic latent image carrier in an image manner.
Further, the image forming apparatus of the present invention includes a transfer means for transferring the toner image formed on the electrostatic latent image carrier to a recording medium, a fixing means for fixing the toner image transferred to the recording medium, and the like. It is preferable to further have a cleaning means for cleaning the electrostatic latent image carrier.

Further, the developer accommodating unit of the present invention accommodates the developer of the present invention.
Here, as an embodiment of the developer accommodating unit, there are a container containing a developer, a developer, and a process cartridge.
The container containing a developer means a container containing a developer.
The developer has a means for accommodating and developing a developer.
The process cartridge means a cartridge in which at least an electrostatic latent image carrier and a developing means having the developer of the present invention are integrated and can be attached to and detached from an image forming apparatus. Further, the process cartridge may be integrally formed with at least one of a charging means, an exposure means, and a cleaning means in addition to the electrostatic latent image carrier and the developing means.

FIG. 2 shows an example of a process cartridge.
The process cartridge (10) uses the developer of the present invention to form a photoconductor (11), a charging device (12) for charging the photoconductor (11), and an electrostatic latent image formed on the photoconductor (11). A developing device that develops to form a toner image and a cleaning device (14) that removes the toner remaining on the photoconductor (11) after transferring the toner image formed on the photoconductor (11) to a recording medium. It is integrally supported, and the process cartridge (10) is removable from the main body of an image forming apparatus such as a copying machine or a printer.

Hereinafter, a method of forming an image using an image forming apparatus equipped with a process cartridge (10) will be described. First, the photoconductor (11) is rotationally driven at a predetermined peripheral speed, and the peripheral surface of the photoconductor (11) is uniformly charged to a predetermined positive or negative potential by the charging device (12). Next, exposure light is irradiated to the peripheral surface of the photoconductor (11) from an exposure device (not shown) such as a slit exposure type exposure device or an exposure device that scans and exposes with a laser beam, and an electrostatic latent image is sequentially formed. To. Further, the electrostatic latent image formed on the peripheral surface of the photoconductor (11) is developed by the developing apparatus (13) using the developing agent of the present invention to form a toner image. Next, the toner image formed on the peripheral surface of the photoconductor (11) is synchronized with the rotation of the photoconductor (11), and the paper feed unit (not shown) transfers the toner image to the photoconductor (11) and the transfer device (not shown). ), It is sequentially transferred to the transfer paper fed during. Further, the transfer paper on which the toner image is transferred is separated from the peripheral surface of the photoconductor (11), introduced into a fixing device (not shown), fixed, and then used as a copy of the image forming device. It is printed out to the outside. On the other hand, the surface of the photoconductor (11) after the toner image is transferred is cleaned by removing the residual toner by the cleaning device (14), and then statically removed by the static eliminator (not shown), and repeated. Used for image formation.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In addition, "part" represents a mass part.

(Toner Manufacturing Example 1)
-Synthesis of polyester resin A-
65 parts of ethylene oxide 2 mol adduct of bisphenol A, 86 parts of propion oxide 3 mol adduct of bisphenol A, 274 parts of terephthalic acid and 2 parts of dibutyltin oxide are put into a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube. Then, the reaction was carried out at 230 ° C. for 15 hours under normal pressure. Next, the polyester resin A was synthesized by reacting under reduced pressure of 5 mmHg to 10 mmHg for 6 hours. The obtained polyester resin A has a number average molecular weight (Mn) of 2,300, a weight average molecular weight (Mw) of 8,000, a glass transition temperature (Tg) of 58 ° C., an acid value of 25 mgKOH / g, and a hydroxyl value. It was 35 mgKOH / g.

-Synthesis of prepolymers (polymers that can react with active hydrogen group-containing compounds)-
682 parts of bisphenol A ethylene oxide 2 mol adduct, 81 parts of bisphenol A propylene oxide 2 mol adduct, 283 parts of terephthalic acid, 22 parts of trimellitic anhydride in a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube. And 2 parts of dibutyltin oxide were charged and reacted at 230 ° C. for 8 hours under normal pressure. Then, the reaction was carried out under reduced pressure of 10 mmHg to 15 mmHg for 5 hours to synthesize an intermediate polyester.
The obtained intermediate polyester has a number average molecular weight (Mn) of 2,100, a weight average molecular weight (Mw) of 9,600, a glass transition temperature (Tg) of 55 ° C., an acid value of 0.5, and a hydroxyl value. It was 49.
Next, 411 parts of the intermediate polyester, 89 parts of isophorone diisocyanate, and 500 parts of ethyl acetate were charged in a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen introduction tube, and reacted at 100 ° C. for 5 hours to pre-form. A polymer (a polymer capable of reacting with the active hydrogen group-containing compound) was synthesized.
The free isocyanate content of the obtained prepolymer was 1.60% by mass, and the solid content concentration of the prepolymer (after standing at 150 ° C. for 45 minutes) was 50% by mass.

-Synthesis of ketimine (the active hydrogen group-containing compound)-
30 parts of isophorone diamine and 70 parts of methyl ethyl ketone were charged in a reaction vessel in which a stirring rod and a thermometer were set, and the reaction was carried out at 50 ° C. for 5 hours to synthesize a ketimine compound (the active hydrogen group-containing compound). The amine value of the obtained ketimine compound (the active hydrogen machine-containing compound) was 423.

-Making a masterbatch-
Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) with 1,000 parts of water, 540 parts of carbon black Printex35 (manufactured by Degussa) with DBP oil absorption of 42 mL / 100 g and pH of 9.5, and 1,200 parts of polyester resin A. Was mixed using. Next, using two rolls, the obtained mixture was kneaded at 150 ° C. for 30 minutes, rolled and cooled, and pulverized with a palperizer (manufactured by Hosokawa Micron) to prepare a master batch.

-Preparation of aqueous medium-
306 parts of ion-exchanged water, 265 parts of a 10 mass% suspension of tricalcium phosphate and 1.0 part of sodium dodecylbenzenesulfonate were mixed and stirred to uniformly dissolve them to prepare an aqueous medium.

-Measurement of critical micelle concentration-
The critical micelle concentration of the surfactant was measured by the following method. Analysis was performed using an analysis program in the Sigma system using a surface tension meter Sigma (manufactured by KSV Instruments). The surfactant was added dropwise to the aqueous medium in an amount of 0.01% by mass, and the interfacial tension after stirring and standing was measured. From the obtained surface tension curve, the concentration of the surfactant at which the surfactant does not decrease even when the surfactant is dropped was calculated as the critical micelle concentration. When the critical micelle concentration of sodium dodecylbenzenesulfonate with respect to the aqueous medium was measured with a surface tension meter Sigma, it was 0.05% by mass with respect to the mass of the aqueous medium.

-Preparation of toner material solution-
70 parts of polyester resin A, 10 parts of prepolymer and 100 parts of ethyl acetate were placed in a beaker and dissolved by stirring. Add 5 parts of paraffin wax (HNP-9 manufactured by Nippon Seiko Co., Ltd., melting point 75 ° C.), 2 parts of MEK-ST (manufactured by Nissan Chemical Industries, Ltd.), and 10 parts of masterbatch as a mold release agent, and add an ultra viscomill (bead mill). Using a liquid feed rate of 1 kg / hour, a disk peripheral speed of 6 m / sec, and 3 passes under the condition that 80% by volume of zirconia beads having a particle size of 0.5 mm was filled, the ketimin 2.7 was used. Parts were added and dissolved to prepare a toner material solution.

-Emulsification or preparation of dispersion-
150 parts of the aqueous medium was placed in a container, and the mixture was stirred at a rotation speed of 12,000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), and 100 parts of the dissolution or dispersion of the toner material was added thereto. The mixture was mixed for 10 minutes to prepare an emulsified or dispersion (emulsified slurry).

-Removal of organic solvent-
100 parts of the emulsified slurry was charged into a corben set with a stirrer and a thermometer, and the solvent was removed at 30 ° C. for 12 hours while stirring at a stirring peripheral speed of 20 m / min.

-Washing-
After 100 parts of the desolvated emulsified slurry was filtered under reduced pressure, 100 parts of ion-exchanged water was added to the filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered. 300 parts of ion-exchanged water was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered twice. Twenty parts of a 10 mass% sodium hydroxide aqueous solution was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 30 minutes), and then filtered under reduced pressure. 300 parts of ion-exchanged water was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered. 300 parts of ion-exchanged water was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered twice. Further, 20 parts of 10% by mass hydrochloric acid was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered.

-Adjusting the amount of surfactant-
300 parts of ion-exchanged water was added to the filtered cake obtained by the above washing, and the electric conductivity of the toner dispersion liquid when mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes) was measured. The surfactant concentration of the toner dispersion was calculated from the calibration curve of the surfactant concentration prepared in advance. From that value, ion-exchanged water was added so that the surfactant concentration became the target surfactant concentration of 0.05% by mass, and a toner dispersion was obtained.

-Surface treatment process-
The toner dispersion liquid adjusted to the predetermined surfactant concentration was heated in a water bath at a heating temperature of T1 = 55 ° C. for 10 hours while mixing with a TK homomixer at 5000 rpm. Then, the toner dispersion was cooled to 25 ° C. and filtered. Further, 300 parts of ion-exchanged water was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered.

− Drying −
The obtained final filtered cake was dried at 45 ° C. for 48 hours in a circulation dryer and sieved with a mesh having a mesh size of 75 μm to obtain toner matrix particles 1.

-External processing-
Further, with respect to 100 parts of the toner base particles 1, 1.9 parts of hydrophobic silica having an average particle size of 100 nm as a large particle size silica and hydrophobic silica fine powder having an average particle size of 20 nm as a small particle size silica are used. 0.9 part and 0.9 parts were mixed with a Henshell mixer to obtain toner 1. Each characteristic of the obtained toner 1 was evaluated using the above-mentioned measuring method. The measurement results are shown in Table 1 below (the measurement results of the toners 2 to 15 described below are also shown in Table 1).

(Toner Manufacturing Example 2)
Toner 2 corresponding to Toner Production Example 2 was obtained in the same manner as in Toner Production Example 1 except that the prescription amount of hydrophobic silica was changed to 2.5 parts.

(Toner Manufacturing Example 3)
Toner 3 corresponding to Toner Production Example 3 was obtained in the same manner as in Toner Production Example 1 except that the prescription amount of the hydrophobic silica fine powder was changed to 1.5 parts.

(Toner Manufacturing Example 4)
Toner production is carried out in the same manner as in Toner Production Example 1 except that the prescription amount of the hydrophobic silica fine powder is changed to 2.0 parts and the prescription amount of the hydrophobic silica fine powder is changed to 2.1 parts. Toner 4 corresponding to Example 4 was obtained.

(Toner Manufacturing Example 5)
Toner Production Example 5 in the same manner as in Toner Production Example 1 except that the prescription amount of hydrophobic silica was changed to 3.1 parts and the prescription amount of hydrophobic silica fine powder was changed to 1.0 part. The corresponding toner 5 was obtained.

(Toner Manufacturing Example 6)
Toner except that the prescription amount of hydrophobic silica was changed to 2.5 parts, the prescription amount of hydrophobic silica fine powder was changed to 1.5 parts, and the average particle size of hydrophobic silica fine powder was changed to 31 nm. Toner 6 corresponding to Toner Production Example 6 was obtained in the same manner as in Production Example 1.

(Toner Manufacturing Example 7)
Toner 7, which corresponds to Toner Production Example 7, was prepared in the same manner as in Toner Production Example 6 except that the average particle size of the hydrophobic silica was changed to 151 nm and the average particle size of the hydrophobic silica fine powder was changed to 20 nm. Obtained.

(Toner Manufacturing Example 8)
Toner 8 corresponding to Toner Production Example 8 was obtained in the same manner as in Toner Production Example 6 except that the average particle size of the hydrophobic silica fine powder was changed to 4 nm.

(Toner Manufacturing Example 9)
Toner 9 corresponding to Toner Production Example 9 was obtained in the same manner as in Toner Production Example 7 except that the average particle size of the hydrophobic silica was changed to 69 nm.

(Toner Manufacturing Example 10)
Toner 10 corresponding to Toner Production Example 10 was obtained in the same manner as in Toner Production Example 9 except that the particle size of the hydrophobic silica was changed to 100 nm.

(Toner Manufacturing Example 11)
Synthesis of crystalline polyester In a reaction vessel equipped with a nitrogen introduction tube, dehydration tube, stirrer and thermocouple, 2070 parts of 1,4-butanediol, 2535 parts of fumaric acid, 291 parts of trimellitic anhydride, hydroquinone 4. Nine parts were added and reacted at 160 ° C. for 5 hours, then heated to 200 ° C. for 1 hour, and further reacted at 8.3 kPa for 1 hour to obtain a crystalline polyester.

Preparation of Crystalline Polyester Dispersion Solution The crystalline polyester is added to 55 parts of ethyl acetate, melted by heating at 60 ° C. for 3 hours, and then cooled to 30 ° C. or lower with an external heat exchanger to prepare a crystallizing solution. The crystallization solution was circulated and pulverized for 20 hours using a bead mill device (LMZ60, manufactured by Ashizawa Finetech) to obtain a crystalline polyester dispersion having a dispersion particle size of 0.5 μm. The bead mill device was operated under the conditions of a zirconia bead filling rate of 70%, a bead diameter of 0.5 mm, an agitator peripheral speed of 7.0 m / s, and a circulation flow rate of 20 kg / min.

Toner 11 corresponding to Toner Production Example 11 was obtained in the same manner as in Toner Production Example 10 except that three parts of the crystalline polyester dispersion was added to the toner material solution.

(Toner Manufacturing Comparative Example 1)
Toner 13, which corresponds to a toner production comparative example, was obtained in the same manner as in Toner Production Example 11 except that 0.3 part of titanium oxide fine particles were added to the toner base 100 as a toner additive.

(Toner Manufacturing Comparative Example 2)
Toner Production Comparative Example 2 in the same manner as in Toner Production Example 11 except that the prescription amount of hydrophobic silica was changed to 1.0 part and the prescription amount of hydrophobic silica fine powder was changed to 0.4 part. The corresponding toner 14 was obtained.

(Toner Manufacturing Comparative Example 3)
Toner Production Comparative Example 2 in the same manner as in Toner Production Example 11 except that the prescription amount of hydrophobic silica was changed to 3.0 parts and the prescription amount of hydrophobic silica fine powder was changed to 2.1 parts. The corresponding toner 15 was obtained.

(Resin Synthesis Example 1)
300 g of toluene was put into a flask equipped with a stirrer, and the temperature was raised to 90 ° C. under a nitrogen gas stream. Next, 3-methacryloxypropyltris (trimethylsiloxy) silane represented by CH ₂ = CMe-COO-C ₃ H _6- Si (OSiMe ₃ ) ₃ (Me is a methyl group in the formula) 84. 4 g (200 mmol: Silaplane TM-0701T / manufactured by Chisso Co., Ltd.), 39 g (150 mmol) of 3-methacryloxypropylmethyldiethoxysilane, 65.0 g (650 mmol) of methyl methacrylate, and 2,2'-. A mixture of 0.58 g (3 mmol) of azobis-2-methylbutyronitrile was added dropwise over 1 hour. After completion of the dropping, a solution prepared by dissolving 0.06 g (0.3 mmol) of 2,2'-azobis-2-methylbutyronitrile in 15 g of toluene was further added (2,2'-azobis-2-methylbuty). A total amount of ronitrile (0.64 g = 3.3 mmol) was mixed at 90 ° C. to 100 ° C. for 3 hours and radical copolymerized to obtain a methacrylic copolymer R1.

(Carrier Manufacturing Example 1)
A methacrylic copolymer R1 [solid content 100% by mass] with a weight average molecular weight of 35,000 obtained in Synthesis Example 1: 20 parts, a solution of a silicone resin (SR2410 manufactured by Toray Dow Corning Silicone Co., Ltd.) [solid content 20 Mass%]: 100 parts, Aminosilane [Solid content 100% by mass]: 3.0 parts, Barium sulfate fine particles as fine particles (Sakai Chemical Co., Ltd., equivalent circle diameter 700 nm): 20 parts, Oxygen-deficient tin fine particles (Mitsui Metal Co., Ltd., Primary particle size 30 nm): 60 parts, 2 parts of titanium diisopropoxybis (ethylacetacetate) TC-750 (manufactured by Matsumoto Fine Chemical Co., Ltd.) as a catalyst is diluted with toluene to obtain a resin solution having a solid content of 20% by mass. It was.
Mn ferrite particles having a weight average particle diameter of 35 μm were used as the core material, and the above resin solution was applied to the surface of the core material using a atomizing nozzle in a fluidized bed coating device. The above resin solution was applied so that the average film thickness of the resin layer was 1.00 μm, and the application and the applied film were dried while the temperature in the flow tank was controlled to 60 ° C. The obtained carrier was calcined in an electric furnace at 210 ° C. for 1 hour to obtain carrier 1.
Each characteristic of the obtained carrier 1 was evaluated using the above-mentioned measuring method. The measurement results are shown in Table 1 below (the measurement results of carriers 2 to 6 described below are also shown in Table 1).

(Carrier Manufacturing Example 2)
Carrier 2, which corresponds to Carrier Production Example 2, was obtained in the same manner as in Carrier Production Example 1 except that the prescribed amount of barium sulfate fine particles was changed to 36 parts by mass.

(Carrier Manufacturing Comparative Example 1)
Carrier 3, which corresponds to Carrier Production Comparative Example 1, was obtained in the same manner as in Carrier Production Example 1 except that the barium sulfate fine particles were changed to alumina fine particles (circle equivalent diameter 600 nm).

(Comparative Example 2 of Carrier Manufacturing)
Carriers are carried in the same manner as in Example 1 of carrier production, except that the barium sulfate fine particles are changed to oxygen-deficient tin oxide-coated barium sulfate fine particles (circle equivalent diameter 400 nm) and oxygen-deficient tin fine particles are not used. Carrier 4, which corresponds to Production Comparative Example 2, was obtained.

(Carrier Manufacturing Comparative Example 3)
Carrier 5, which corresponds to Carrier Production Comparative Example 4, was obtained in the same manner as in Carrier Production Example 1 except that the equivalent circle diameter of the barium sulfate fine particles was changed to 910 nm.

(Carrier Manufacturing Comparative Example 4)
A carrier 6 corresponding to Carrier Production Comparative Example 5 was obtained in the same manner as in Carrier Production Example 1 except that the equivalent circle diameter of the barium sulfate fine particles was changed to 390 nm.

<Preparation of developer>
Carrier Production [Carrier 1] (930 parts) and toner 1 (70 parts) obtained in Example 1 are mixed and stirred at 81 rpm for 5 minutes using a turbuler mixer, and the evaluation [Developer 1] is used. Was produced. Further, the replenishing developer was prepared by using the above carrier and the above toner so that the toner concentration was 95% by mass.

<Developer characteristic evaluation>
Using the obtained developer, image evaluation was performed using RICOH Pro C7110S manufactured by Ricoh Corporation (digital color copier / printer multifunction device manufactured by Ricoh Co., Ltd.). First, the machine was placed in an environmental evaluation room (low temperature and low humidity environment of 10 ° C. and 15%) and left for one day, and then the following characteristics were evaluated using the developer 1 of Example 1 and the toner 1.
The evaluation results of Example 1 are shown in Table 2.

-40% image area ratio, evaluation after running 1 million sheets-
Next, a running evaluation was carried out. Ricoh Co., Ltd. RICOH Pro C7110S (Ricoh Co., Ltd. digital color copier / printer multifunction device) uses the developer 1 and toner 1 of the example, and the initial and image area ratio is 40% (A4 size paper). The charge amount of the carrier after running 1 million sheets was measured, and the rate of change of the charge amount was calculated.

<< Toner scattering >>
After running 1 million sheets, the amount of toner accumulated in the lower part of the developer carrier was sucked and recovered, and the toner weight was measured. The evaluation criteria are shown below.
〔Evaluation criteria〕
⊚: 0 mg or more and less than 50 mg (very good)
〇: 50 mg or more and less than 100 mg (good)
Δ: 100 mg or more and less than 250 mg (usable)
X: 250 mg or more (defective)

<Evaluation method of medaka>
Seven parts of the toner 1 and 93 parts of the carrier 1 having a weight average particle diameter of 35 μm were uniformly mixed to prepare a two-component developer for evaluation. The developer was humidity-controlled for 2 hours or more in a high-temperature and high-humidity environment at 30 ° C. and 85% RH. Under the same environment, the medaka on the photoconductor and the image quality of the transferred image when 50,000 sheets were copied by a commercially available copier (imageo MP C4002, manufactured by Ricoh Co., Ltd.) using the developer were evaluated according to the following criteria.
⊚: There is no killifish on the photoconductor and the image quality is good.
◯: Although there is a small amount of killifish on the photoconductor, there is almost no medaka on the image.
Δ: There is medaka on the photoconductor, but there is almost no medaka on the image.
X: There are many killifish on the photoconductor, and the image quality is significantly degraded, such as killifish in the image.

<Preservation>
The developer was stored in an environment of 40 ° C. and 70% humidity for 2 weeks, then sieved for 1 minute using a 200 mesh sieve, and the residual rate of toner on the wire mesh was measured and evaluated according to the following criteria. The smaller the residual rate of toner, the better the storage stability. In addition, "◎", "○" and "△" were judged as pass, and "x" was judged as fail.
[Evaluation criteria]
⊚: Residual rate less than 0.1% ○: Residual rate 0.1% or more and less than 0.5% Δ: Residual rate 0.5% or more and less than 1.0% ×: Residual rate 1.0% or more

<Low temperature fixability>
A copy test was performed on recording paper (Type 6200, manufactured by Ricoh Co., Ltd.) using a device that was modified from the fixing part of a commercially available digital full-color printer (imagio MPC6000, A4 size horizontal color 50 sheets / minute, manufactured by Ricoh Co., Ltd.). It was. Specifically, the cold offset temperature (fixing lower limit temperature) was obtained by changing the fixing temperature. The evaluation conditions for the lower limit temperature of fixing were that the linear velocity of the paper feed was 260 mm / sec to 280 mm / sec, the surface pressure was 1.2 kgf / cm ² , and the nip width was 11 mm. The low temperature fixability was evaluated according to the following criteria. The lower the lower limit temperature for fixing, the better the low temperature fixing property.
[Evaluation criteria]
⊚: Very good, ○: Good, Δ: Allowable, ×: Level that cannot be used practically. ◎, ○, and △ were accepted, and × was rejected.
⊚: Lower limit temperature for fixing is less than 120 ° C ○: Lower limit temperature for fixing is 120 ° C or higher and lower than 130 ° C Δ: Lower limit temperature for fixing is 130 ° C or higher and lower than 140 ° C

(Examples 2 to 11)
In Example 1, the developing agents 2 to 11 were changed in the same manner as in Example 1 except that the toner 1 was changed to toners 2 to 11 and the developing agent 1 was changed to developing agents 2 to 11 respectively. Evaluation was performed. The evaluation results of Examples 2 to 11 are shown in Table 2.

(Example 12)
In Example 1, the developer 12 was evaluated in the same manner as in Example 1 except that the carrier 1 was changed to the carrier 2 and the developer 1 was changed to the developer 12 accordingly. The evaluation results of Example 12 are shown in Table 2.

(Comparative Examples 1 to 3)
In Example 12, the developing agents 13 to 15 were prepared in the same manner as in Example 12, except that the toner 11 was changed to toners 13 to 15 and the developing agent 1 was changed to developing agents 13 to 15, respectively. Evaluation was performed. The evaluation results of Comparative Examples 1 to 3 are shown in Table 2.

(Comparative Examples 4 to 7)
In Example 11, the developing agents 16 to 19 were changed in the same manner as in Example 11 except that the carriers 1 were changed from carriers 3 to 6 and the developing agents 1 were changed to the developing agents 16 to 19 respectively. Evaluation was performed. The evaluation results of Comparative Examples 4 to 7 are shown in Table 2.

From the results in each table, the developer of each example can sufficiently control the charge even after long-term running, has excellent storage stability, suppresses the generation of killifish after long-term running, and has excellent low-temperature fixability. Was recognized.

1a, 1b Electrode 2 Container 3 Carrier 10 Process cartridge 11 Photoreceptor 12 Charging device 13 Developing device 14 Cleaning device

JP-A-2016-212254 JP-A-11-202560 Japanese Unexamined Patent Publication No. 2006-39357 Japanese Unexamined Patent Publication No. 2010-117519 Japanese Patent No. 6127537 Japanese Unexamined Patent Publication No. 2011-145388 Japanese Patent No. 5626569 Japanese Patent No. 5534409 Japanese Unexamined Patent Publication No. 2011-209678 Japanese Unexamined Patent Publication No. 2006-079022

Claims (11)

A developer containing at least toner and carriers,
The toner contains silica particles and a toner matrix.
The ratio of the silica particles to 100 parts by mass of the toner base is 1.5 parts by mass or more and less than 5 parts by mass.
The carrier is a carrier having a resin layer containing at least one kind of fine particles.
At least one of the fine particles is composed of barium sulfate fine particles.
The amount of Ba detected by X-ray photoelectron spectroscopy (XPS) of the carrier is 0.3 atomic% or more.
Development characterized in that the equivalent circle diameter of the barium sulfate fine particles is 400 nm or more and 900 nm or less, the image area ratio of the carrier is 40%, and the charge reduction rate after running 1 million sheets is 20% to 30%. Agent. The silica particles are characterized by containing small particle size silica particles having a flat diameter of 5 nm or more and 30 nm or less and large particle size silica particles having a flat diameter of 70 nm or more and 150 nm or less. Item 2. The developer according to Item 1. The ratio of the large particle size silica particles to 100 parts by mass of the toner base is 2 parts by mass or more and 3 parts by mass or less, and the ratio of the small particle size silica particles to 100 parts by mass of the toner base is 1 part by mass or more and 2 parts by mass. The developer according to claim 2, wherein the amount is not more than parts by mass. The developer according to any one of claims 1 to 3, wherein the toner has a crystalline resin. The developer according to any one of claims 1 to 4, wherein the rate of change in fluidity of the developer is 13% or less. The developer according to any one of claims 1 to 5, wherein the barium sulfate fine particles have Ba present on the surface of the fine particles. The invention according to any one of claims 1 to 6, wherein the content of the barium sulfate fine particles in the resin layer is 50% by mass or more and less than 100% by mass with respect to the resin contained in the resin layer. Developer. A method for producing a developer containing at least toner and carriers.
The toner is configured to contain silica particles and a toner matrix.
The ratio of the silica particles to 100 parts by mass of the toner base is set to 1.5 parts by mass or more and less than 5 parts by mass.
The carrier is configured to be a carrier having a resin layer containing at least one kind of fine particles.
At least one of the fine particles is set to barium sulfate fine particles,
The amount of Ba detected by X-ray photoelectron spectroscopy (XPS) of the carrier is set to be 0.3 atomic% or more.
It is characterized in that the equivalent circle diameter of the barium sulfate fine particles is set to 400 nm or more and 900 nm or less, the image area ratio of the carrier is 40%, and the charge reduction rate after running 1 million sheets is 20% to 30%. How to manufacture the developer. Electrostatic latent image carrier and
An electrostatic latent image forming means for forming an electrostatic latent image on the electrostatic latent image carrier,
It is characterized by having a developing means for forming a toner image by developing the electrostatic latent image formed on the electrostatic latent image carrier with the developer according to any one of claims 1 to 7. Image forming apparatus. A developer accommodating unit accommodating the developer according to any one of claims 1 to 7. An electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier,
It includes a developing step of developing the electrostatic latent image formed on the electrostatic latent image carrier with the developer according to any one of claims 1 to 7 to form a toner image. Characteristic image forming method.