Toner

Abstract

To provide a toner having high charging characteristics and capable of achieving high image quality.SOLUTION: In the toner, the work functions of the strontium titanate fine particles are 5. 65eV or more and 7. 00eV or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a toner used in an electrophotographic system, an electrostatic recording system, an electrostatic printing system, and a toner jet system. [Background technology]

[0002] As copiers and printers have become more widespread, the performance requirements for toner have become more advanced. In recent years, print-on-demand (POD), a digital printing technology that prints directly without going through the plate-making process, has been attracting attention. POD has advantages over conventional offset printing in that it can handle short-run printing, printing with different content on each sheet, and distributed printing. When considering the application of toner-based image formation methods to the POD market, it is necessary to consistently obtain high-quality print results even when printing large quantities at high speed over long periods of time. Toner that can maintain high electrostatic properties in various environments is required in order to obtain high-quality print products even when outputting a large amount of material at high speed for a long period of time. To improve cleaning performance, inorganic particles are added to toner particles, and silica particles have been widely used as the external additive. Strontium titanate particles, in particular, are attracting attention because their crystal structure, shape, and charging properties are significantly different from those of silica particles. Patent Document 1 proposes a toner containing, as an external additive, strontium titanate-based fine particles having a cubic or rectangular parallelepiped shape, an SrO / TiO2 molar ratio of 0.80 or more but less than 0.95, and a narrow primary particle size distribution. Furthermore, like other external additives, strontium titanate is often subjected to a hydrophobic treatment. Patent Document 1 also proposes strontium titanate whose surface has been treated with silane coupling or silicone oil. Patent Document 2 also proposes a combination of silane coupling treatment and silicone oil treatment on titanium oxide fine particles. From the viewpoint of improving charging properties, one possible approach is to increase the work function of the external additive. Increasing the work function makes it difficult for electrons to be released during contact charging between different materials, making it easier to maintain negative charging. Patent Document 3 proposes strontium titanate, which has a high work function of 5.6 eV. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-137208 [Patent Document 2] JP 2005-173208 Public Relations [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-93732 Summary of the Invention [Problem to be solved by the invention]

[0004] Among the above-mentioned prior art documents, Patent Documents 2 and 3 include evaluations based on durable image reproduction, but even toners using the technologies described in the prior art documents have not been able to achieve the high target values ​​for chargeability that have become common in recent years, and improvements have been required. In other words, in order to stably obtain high-quality print products even when outputting a large amount of images at high speed over a long period of time, a toner that maintains high chargeability regardless of the environment is required. SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to obtain a toner that has excellent charging properties even when outputting a large amount of material at high speed for a long period of time. [Means for solving the problem]

[0005] The present invention relates to a toner comprising toner particles containing a binder resin and a colorant, and strontium titanate fine particles, wherein the work function of the strontium titanate fine particles is 5.65 eV or more and 7.00 eV or less. [Effects of the Invention]

[0006] The present invention provides a toner that has excellent charging characteristics and can achieve high image quality, and can stably produce high-quality print products even when outputting a large amount at high speed over a long period of time. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a cell for powder measurement. [Figure 2] FIG. 1 is a schematic diagram illustrating a surface analysis method. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Meaning and Features of the Present Invention] As a result of extensive research, the present inventors have found that by using a toner having toner particles containing a binder resin and a colorant and strontium titanate microparticles, in which the work function of the strontium titanate microparticles is 5.65 eV or more and 7.00 eV or less, a toner having excellent charging properties and capable of achieving high image quality can be obtained.

[0009] The reason why the effects of the present invention are obtained is not clear, but the present inventors assume the mechanism as follows.

[0010] It is important that the strontium titanate fine particles used in the present invention have a work function of 5.65 eV to 7.00 eV. The work function of strontium titanate fine particles indicates the ease with which they emit electrons, and when the work function value is in a specific range, the function of adjusting the charge amount of the toner is enhanced.

[0011] It is speculated that the work function of the strontium titanate particles attached to the toner falls within this range, making it difficult to bind electrons, which makes it easier for the toner to retain electrons, leading to improved charging properties of the toner. The work function of the strontium titanate particles is preferably 5.70 eV or more, and more preferably 5.75 eV or more.

[0012] A work function of 5.65 eV or higher makes it easier to retain electrons, allowing the toner's charge to be maintained at a constant level. This makes it possible to maintain a high toner charge, especially in situations where the toner's charge is likely to decrease, such as in high-humidity environments or when printing a large number of images with a high print ratio. Furthermore, maintaining high charge improves transferability, preventing the phenomenon of transfer defects, in which part of the toner image in the center of a character is not transferred during the transfer process.

[0013] A work function of 7.00 eV or less allows electrons to be released appropriately, preventing the toner from becoming excessively charged. This makes it possible to maintain an appropriate toner charge even in situations where the toner tends to become excessively charged, such as in low-humidity environments or when printing a large number of images with a low print ratio. Maintaining an appropriate toner charge prevents excessive adhesion to the photoconductor, making it possible to maintain good cleaning properties.

[0014] [Preferred embodiment of the present invention] The strontium titanate fine particles of the present invention are preferably surface-treated from the viewpoint of hydrophobicity and chargeability.

[0015] The surface treatment of the strontium titanate microparticles of the present invention may be carried out using a silane compound. The silane compound is not particularly limited, but examples thereof include alkoxysilanes such as methoxysilane, ethoxysilane, and propoxysilane, halosilanes such as chlorosilane, bromosilane, and iodosilane, hydrosilanes, alkylsilanes, arylsilanes, vinylsilanes, acrylicsilanes, epoxysilanes, silyl compounds, siloxanes, silylureas, silylacetamides, and silane compounds having the same different substituents as those of the silane compounds.

[0016] Specific examples include trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, trialkoxyalkylsilane, allyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, dimethyldiethoxysilane, dimethyldimethoxysilane, and hexamethyldisiloxane.

[0017] In particular, alkyltrialkoxysilanes are preferred from the viewpoint of hydrophobicity and chargeability. Among these, methyltriethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyltriethoxysilane, etc. are preferably used. More preferably, the alkyl group has 3 to 6 carbon atoms, and isobutyltrimethoxysilane is even more preferred.

[0018] The method of treatment with a silane coupling agent is not particularly limited, but examples include spraying the coupling agent onto the surface of strontium titanate microparticles, or mixing a vaporized coupling agent with strontium titanate microparticles and then heat-treating. Water, amines, or other catalysts may also be used. The surface modification with the coupling agent is preferably carried out under an inert gas atmosphere such as nitrogen. Alternatively, a method may be used in which the coupling agent, strontium titanate microparticles, and a solvent are mixed together, and the resulting mixture is heated and dried. Either the coupling agent or the strontium titanate microparticles may be dispersed in the solvent first, or all components may be mixed simultaneously.

[0019] In the case of a primary particle diameter of 0.02 μm or more and 0.3 μm or less, it is preferable to coat the strontium titanate with a hydrophobizing agent in an aqueous system, since this provides better dispersibility. The method for treating the strontium titanate in an aqueous system is not particularly limited, but a method in which a silane coupling agent is adsorbed onto a strontium titanate slurry in water is preferred.

[0020] Silicone oil may be used for the surface treatment of the strontium titanate microparticles of the present invention. Silicone oil is not particularly limited, but examples include dimethyl silicone oil, alkyl-modified silicone oil, α-methylstyrene-modified silicone oil, chlorophenyl silicone oil, and fluorine-modified silicone oil. The silicone oil has a viscosity of 1.0×10 at 25° C. -7 m 2 / s or more 0.1m 2 / s or less is preferred.

[0021] As the method of silicone oil treatment, known techniques can be used.For example, strontium titanate powder and silicone oil are mixed using a mixer.Similarly, silicone oil is sprayed into strontium titanate powder using a sprayer; or silicone oil is dissolved in a solvent and then mixed.The treatment method is not limited to these.

[0022] As mentioned above, when the primary particle diameter is 0.02 μm or more and 0.3 μm or less, those coated with a hydrophobizing agent in an aqueous system have even better dispersibility, and in the case of silicone oil, a preferred method is to emulsify the silicone oil in water using an emulsifier and then adsorb it onto a strontium titanate slurry.

[0023] In addition, with regard to the above surface treatment, it is preferable to carry out a silane coupling treatment and then a silicone oil treatment.

[0024] It has been discovered that the top surface of strontium titanate has irregularities at the molecular level, with some voids in the top TiO2 layer. In other words, the SrO layer underneath can be seen through the voids in the top TiO2 layer. It is speculated that the silane coupling agent easily bonds to the top TiO2 layer during silane coupling treatment, and that the subsequent silicone oil treatment fills the voids, treating the surface including the SrO layer. For these reasons, we believe that the maximum surface treatment can be achieved by combining these two types of treatment.

[0025] The strontium titanate fine particles of the present invention preferably have a number average particle diameter of 5 nm to 50 nm, more preferably 10 nm to 40 nm, since this enhances the function of adjusting the charge amount of the toner.

[0026] The strontium titanate fine particles of the present invention are preferably contained in the toner in an amount of 0.1% by mass to 5.0% by mass, more preferably 0.3% by mass to 4.0% by mass, since this enhances the function of adjusting the charge amount of the toner.

[0027] The strontium titanate fine particles of the present invention may be contained inside toner particles, and by containing the strontium titanate fine particles of the present invention in the toner particles, the toner particles can exhibit even better chargeability.

[0028] [Toner raw materials] Next, the raw materials of the toner used in the present invention will be described.

[0029] <Strontium titanate nanoparticles> The method for producing strontium titanate fine particles is not particularly limited, but examples include a wet method and a sintering method, with the wet method being more preferred due to its high surface treatment efficiency.

[0030] The titanate compound particles may contain a dopant. The dopant for the strontium titanate particles is not particularly limited, but is preferably lanthanoid, silica, aluminum, magnesium, calcium, barium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, niobium, molybdenum, ruthenium, palladium, indium, antimony, tantalum, tungsten, rhenium, iridium, platinum, bismuth, yttrium, zirconium, niobium, silver, or tin. As the lanthanoid, lanthanum and cerium are preferred. Among these, lanthanum and silica are more preferred because they have a size that makes them easy to incorporate into the crystal structure.

[0031] The strontium titanate microparticles of the present invention can be obtained, for example, by a normal pressure heating reaction method. In this method, a mineral acid peptized product of a titanium compound hydrolyzate is used as the titanium oxide source, and a water-soluble acidic metal compound is used as the strontium metal source. The mixture is reacted with an aqueous alkali solution at 60°C or higher, followed by acid treatment.

[0032] (Normal pressure heating reaction method) The titanium oxide source is a mineral acid peptized product of a titanium compound hydrolyzate. Metatitanic acid with an SO3 content of 1.0 mass% or less, preferably 0.5 mass% or less, obtained by a sulfuric acid method, is preferably peptized by adjusting the pH to 0.8 to 1.5 with hydrochloric acid. Metatitanic acid with an SO3 content of more than 1.0 mass% is not preferred because it does not peptize well.

[0033] As the source of the metal other than titanium, nitrates, hydrochlorides, etc. of the metal can be used.

[0034] As the nitrate, for example, strontium nitrate can be used. As the hydrochloride, for example, strontium chloride can be used. Among these, when strontium nitrate or hydrochloride is used for production, the resulting strontium titanate particles have a perovskite crystal structure, which is preferable in that the environmental stability of charging is further improved.

[0035] As the alkaline aqueous solution, a caustic alkali can be used, but among these, an aqueous sodium hydroxide solution is preferred.

[0036] In the above-mentioned production method, factors that affect the particle size of the obtained strontium titanate microparticles include the mixing ratio of the titanium oxide source and the strontium source during the reaction, the concentration of the titanium oxide source at the beginning of the reaction, the temperature and addition rate when adding the alkaline aqueous solution, etc., and these can be appropriately adjusted to obtain the target particle size and particle size distribution. Note that, in order to prevent the formation of carbonate during the reaction process, it is preferable to prevent the inclusion of carbon dioxide gas, for example by carrying out the reaction under a nitrogen gas atmosphere.

[0037] In the above-mentioned production method, factors that affect the particle size distribution of the obtained strontium titanate microparticles include the pH when the metatitanic acid is peptized with hydrochloric acid, the concentration of the titanium oxide source at the beginning of the reaction, the addition rate and reaction time when the alkaline aqueous solution is added, and the stirring conditions. In particular, if the reaction is stopped by suddenly lowering the temperature of the system after the addition of the alkaline aqueous solution, for example by immersing the system in ice water, the reaction can be stopped forcibly before crystal growth reaches saturation, which makes it easier to broaden the particle size. In addition, the particle size distribution tends to become broader by making the reaction system non-uniform by lowering the stirring speed or changing the stirring method.

[0038] The mixing ratio of the titanium oxide source and strontium source during the reaction is preferably 0.90 to 1.40, more preferably 1.05 to 1.20, in terms of the molar ratio MxO / TiO2, where M represents a metal other than titanium and its oxide is MxO (where x is 1 when M is an alkaline earth metal and 2 when M is an alkali metal). When the MxO / TiO2 molar ratio is 1 or less, the reaction product is likely to contain not only metal titanate but also unreacted titanium oxide. Because metal sources other than titanium have relatively high solubility in water, while the titanium oxide source has low solubility in water, when the MxO / TiO2 molar ratio is 1 or less, the reaction product is likely to contain not only metal titanate but also unreacted titanium oxide. The concentration of the titanium oxide source at the start of the reaction is preferably 0.05 mol / L to 1.30 mol / L, more preferably 0.08 mol / L to 1.00 mol / L, in terms of TiO2.

[0039] The temperature at which the alkaline aqueous solution is added is preferably in the range of 60°C to 100°C, since a pressure vessel such as an autoclave is required if the temperature is above 100°C. Furthermore, the slower the rate of addition of the alkaline aqueous solution, the larger the particle size of the resulting strontium titanate particles, and the faster the rate of addition, the smaller the particle size of the resulting strontium titanate particles. The rate of addition of the alkaline aqueous solution is preferably 0.001 to 1.2 equivalents / h, and more preferably 0.002 to 1.1 equivalents / h, relative to the amount of raw material added, and can be adjusted appropriately depending on the particle size desired.

[0040] (acid treatment) In the above-described manufacturing method, it is preferable to further acid-treat the strontium titanate microparticles obtained by the atmospheric heating reaction. When synthesizing strontium titanate microparticles by the atmospheric heating reaction, if the mixing ratio of the titanium oxide source and the strontium source (MxO / TiO2) exceeds 1.0 in molar ratio, the unreacted strontium source remaining after the reaction reacts with carbon dioxide in the air to produce impurities such as metal carbonates. Furthermore, if impurities such as metal carbonates remain on the surface, the impurities will prevent uniform coating of the organic surface treatment agent during organic surface treatment to impart hydrophobicity. Therefore, it is preferable to perform an acid treatment to remove the unreacted metal source after adding an alkaline aqueous solution.

[0041] In the acid treatment, it is preferable to use hydrochloric acid to adjust the pH to 2.5 or more and 7.0 or less, more preferably 4.5 or more and 6.0 or less. In addition to hydrochloric acid, nitric acid, acetic acid, etc. can also be used for the acid treatment. The use of sulfuric acid is not preferable because it generates metal sulfates that have low solubility in water.

[0042] The strontium titanate microparticles of the present invention preferably have a coverage of 2% or more on the toner surface. When the coverage of the strontium titanate microparticles on the toner surface is 2% or more, the effect of environmental stability of charging is easily exhibited. More preferably, the coverage is 2% or more and 40% or less, from the viewpoint of suppressing image defects when the strontium titanate microparticles are detached from the toner.

[0043] The toner particles and the strontium titanate fine particles can be mixed using a known mixer such as a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.), a Mechano Hybrid (manufactured by Nippon Coke & Engineering Co., Ltd.), a Super Mixer (manufactured by Kawata Corporation), or a Nobilta (manufactured by Hosokawa Micron Corporation), and the device is not particularly limited. Examples of mixing conditions include the processing amount, the rotation speed of the stirring shaft, the stirring time, the shape of the stirring blades, and the temperature inside the tank.

[0044] <Binder resin> As the binder resin used in the toner used in electrophotography, a general resin can be used, and examples thereof include polyester resin, styrene-acrylic acid copolymer, polyolefin resin, vinyl resin, fluororesin, phenol resin, silicone resin, and epoxy resin. Among these, amorphous polyester resin is used from the viewpoint of improving low-temperature fixability, and it is known to use a low-molecular-weight polyester and a high-molecular-weight polyester in combination from the viewpoint of achieving both low-temperature fixability and hot offset resistance. Furthermore, from the viewpoint of further improving low-temperature fixability and blocking resistance during storage, crystalline polyester may also be used as a plasticizer.

[0045] <Magnetic iron oxide particles> The toner of the present invention may use magnetic iron oxide particles such as those exemplified below. Specific examples include magnetic iron oxide particles such as magnetite, maghemite, and ferrite, as well as magnetic iron oxide particles containing other metal oxides. Conventionally, iron oxides such as iron tetroxide (Fe3O4), iron sesquioxide (γ-Fe2O3), zinc iron oxide (ZnFe2O4), and yttrium iron oxide (Y3Fe5O 12), cadmium iron oxide (Cd3Fe2O4), gadolinium iron oxide (Gd3Fe5O 12 ), copper iron oxide (CuFe2O4), lead iron oxide (PbFe 12 O 19 ), nickel iron oxide (NiFe2O4), neodymium iron oxide (NdFe2O3), barium iron oxide (BaFe 12 O 19 Known magnetic iron oxide particles include iron oxide magnesium (MgFe2O4), iron oxide manganese (MnFe2O4), iron lanthanum (LaFeO3), and iron powder (Fe). Particularly suitable magnetic iron oxide particles are fine powders of iron tetroxide or gamma ferric oxide. The above-mentioned magnetic iron oxide particles can be used alone or in combination of two or more.

[0046] <Coloring agent> Examples of colorants that can be contained in the toner include the following.

[0047] Examples of the colorant include known organic pigments or oil-based dyes, carbon black, and magnetic materials.

[0048] Examples of cyan colorants include copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, and basic dye lake compounds.

[0049] Examples of magenta colorants include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds.

[0050] Examples of yellow colorants include condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds.

[0051] Examples of black colorants include carbon black, magnetic materials, and those toned to black using the above-mentioned yellow colorants, magenta colorants, and cyan colorants.

[0052] The colorants can be used alone or in combination of two or more.

[0053] <Release agent> If necessary, a release agent may be used to suppress the occurrence of hot offset during heat fixing of the toner. Typical examples of the release agent include low-molecular-weight polyolefins, silicone wax, fatty acid amides, ester waxes, carnauba wax, hydrocarbon waxes, and Fischer-Tropsch wax.

[0054] <Charge control agent> The toner particles according to the present invention may contain a charge control agent, if necessary. As the charge control agent, a metal compound of an aromatic carboxylic acid is preferred, from the viewpoints of being colorless, having a high charging speed of the toner, and being able to stably maintain a constant charge amount.

[0055] Examples of negative charge control agents include metal salicylate compounds, metal naphthoate compounds, metal dicarboxylic acid compounds, polymeric compounds having sulfonic acid or carboxylic acid on the side chain, polymeric compounds having sulfonate salts or sulfonic acid esters on the side chain, polymeric compounds having carboxylate salts or carboxylic acid esters on the side chain, boron compounds, urea compounds, silicon compounds, and calixarenes.

[0056] The charge control agent may be added internally or externally to the toner particles.

[0057] The content of the charge control agent in the toner particles is preferably 0.01 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin in the toner particles.

[0058] [Magnetic Carrier] The toner of the present invention may be mixed with a magnetic carrier and used as a toner for a two-component developer, from the viewpoint of obtaining stable images over a long period of time.

[0059] Examples of magnetic carriers include surface-oxidized iron powder, unoxidized iron powder, metal particles such as iron, lithium, calcium, magnesium, nickel, copper, zinc, cobalt, manganese, and rare earth elements, alloy particles of the above metals, oxide particles of the above metals, magnetic materials such as ferrite, and magnetic material-dispersed resin carriers (so-called resin carriers) containing a magnetic material and a binder resin that holds the magnetic material in a dispersed state.

[0060] [Toner Manufacturing Method] The toner of the present invention can be produced by known methods, but the procedure for producing it by the melt-kneading and pulverization method will be described below.

[0061] In the raw material mixing process, the materials that make up the toner particles, such as binder resin, colorant or pigment dispersion, wax, and, if necessary, charge control agent, are weighed out in predetermined amounts, blended, and mixed. Examples of mixing devices include a double cone mixer, V-type mixer, drum mixer, super mixer, Henschel mixer, Nauta mixer, and Mechano Hybrid (manufactured by Nippon Coke and Engineering Co., Ltd.).

[0062] Next, the mixed materials are melt-kneaded to disperse the magnetic material, colorant, etc. into the binder resin. In the melt-kneading process, batch kneaders such as pressure kneaders and Banbury mixers, or continuous kneaders, can be used. Due to their advantage of continuous production, single-screw or twin-screw extruders are the mainstream. Examples include the KTK twin-screw extruder (manufactured by Kobe Steel, Ltd.), the TEM twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.), the PCM kneader (manufactured by Ikegai Corporation), the twin-screw extruder (manufactured by KCK Corporation), the Co-Kneader (manufactured by Buss Co., Ltd.), and the Kneedex (manufactured by Nippon Coke and Engineering Co., Ltd.).

[0063] The kneaded product obtained by melt-kneading may be rolled using a two-roll mill or cooled with water in a cooling step.

[0064] The cooled kneaded product is pulverized to a desired particle size in a pulverization process. In the pulverization process, the product is coarsely pulverized in a pulverizer, and then further pulverized in a fine pulverizer. Examples of pulverizers that perform coarse pulverization include crushers, hammer mills, and feather mills. Examples of fine pulverizers that perform fine pulverization include the Cryptron System (manufactured by Kawasaki Heavy Industries, Ltd.), Super Rotor (manufactured by Nisshin Engineering Inc.), Turbo Mill (manufactured by Turbo Kogyo Co., Ltd.), and fine pulverizers using an air jet system.

[0065] Thereafter, if necessary, the toner particles are classified using a classifier or sieving machine, such as an inertial classification machine such as Elbojet (manufactured by Nittetsu Mining Co., Ltd.), a centrifugal classification machine such as Turboplex (manufactured by Hosokawa Micron Corporation), TSP Separator (manufactured by Hosokawa Micron Corporation), or Faculty (manufactured by Hosokawa Micron Corporation).

[0066] Then, strontium titanate fine particles are added to the toner particles and mixed (externally added) with the toner particles to obtain a toner. If necessary, for example, to impart fluidity to the toner or to adjust the chargeability to an appropriate level, known external additives such as inorganic fine particles or resin particles may be added.

[0067] When large free aggregates of additives are present in the obtained toner, a sieving machine or the like may be used as necessary.

[0068] [Methods for measuring various physical properties] The methods for measuring various physical properties of the toner and raw materials are described below.

[0069] <Method for measuring weight average particle size (D4) of toner particles> The weight average particle diameter (D4) of the toner particles is calculated as follows. The measurement device used is a particle counting and analysis device "CDA-1000X" (manufactured by Sysmex Corporation) equipped with a 100 μm aperture tube and employing the pore electrical resistance method. The measurement conditions are set and the measurement data is analyzed using the accompanying dedicated software "CDA-1000X" (manufactured by Sysmex Corporation).

[0070] The aqueous electrolyte solution used for the measurement may be, for example, "Cell Pack" (manufactured by Sysmex Corporation).

[0071] Before carrying out the measurements and analysis, the dedicated software was set up as follows.

[0072] On the "measurement condition setting" screen of the dedicated software, set the total count number to 50,000, the number of repeated measurements to 1, and the measurement mode to total count (no limit).

[0073] The specific measurement method is as follows. (1) Pour approximately 150 ml of the electrolyte solution into a dedicated glass round-bottom beaker, set it on the sample stage, and stir with the stirring propeller at 500 rpm. Then, click "Blank Check Measurement" in the dedicated software to start the measurement and confirm that the count is less than 500. If the count is 500 or more, repeatedly clean the beaker and aperture. (2) Approximately 30 ml of the above-mentioned aqueous electrolyte solution is placed in a 100 ml flat-bottom glass beaker, and approximately 0.3 ml of a dilution of Contaminon N (a 10% aqueous solution of a pH 7 neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) diluted approximately three times by mass with ion-exchanged water is added as a dispersant. (3) Prepare an ultrasonic disperser "Ultrasonic Dispension System Tetra150" (manufactured by Nikkaki Bios Co., Ltd.) with an electrical output of 120 W and two built-in oscillators with an oscillation frequency of 50 kHz and a phase difference of 180 degrees. Place approximately 3.3 L of ion-exchanged water in the ultrasonic disperser's water tank and add approximately 2 mL of Contaminon N to this water tank. (4) Set the beaker (2) in the beaker fixing hole of the ultrasonic disperser, operate the ultrasonic disperser, and adjust the height of the beaker so that the resonance state of the liquid surface of the electrolytic solution in the beaker is maximized. (5) While ultrasonic waves are being applied to the electrolyte solution in the beaker from (4), approximately 10 mg of toner is added little by little and dispersed. The ultrasonic dispersion process is then continued for another 60 seconds. During the ultrasonic dispersion, the water temperature in the water tank is appropriately adjusted to be between 10°C and 40°C. (6) Using a pipette, add the electrolyte solution (5) containing the dispersed toner to the round-bottom beaker (1) placed in the sample stand, and adjust the measurement concentration to approximately 6%. Then, measure the particle count until it reaches 50,000 particles. (7) The measurement data is analyzed using the dedicated software provided with the device to calculate the weight average particle size (D4).

[0074] <Method for measuring the number-average particle size of strontium titanate microparticles> The number-average particle size of strontium titanate is calculated from images of inorganic particles separated from toner (or a mixture with pigment if the toner contains pigment) taken with a Hitachi ultra-high resolution field emission scanning electron microscope S-4800 (Hitachi High-Technologies Corporation). The image taking conditions for the S-4800 are as follows:

[0075] (1) Sample preparation A thin layer of conductive paste is applied to a sample stage (aluminum sample stage 15 mm x 6 mm), and the inorganic particles separated from the toner are sprayed onto it. An air blow is then used to remove excess inorganic particles from the sample stage, and the stage is allowed to dry thoroughly. The sample stage is then placed in the sample holder, and the sample stage height is adjusted to 36 mm using the sample height gauge.

[0076] (2) S-4800 observation condition setting The number average particle diameter is calculated using images obtained by backscattered electron image observation using the S-4800. Liquid nitrogen is poured into the anti-contamination trap attached to the S-4800 housing until it overflows, and then left for 30 minutes. Start the S-4800's "PC-SEM" and perform flushing (cleaning the FE chip, which is the electron source). Click the accelerating voltage display area on the control panel on the screen and press the [Flushing] button to open the flushing execution dialog. Confirm that the flushing intensity is 2 and execute it. Confirm that the emission current due to flushing is 20-40 μA. Insert the sample holder into the sample chamber of the S-4800 housing. Press [Origin] on the control panel to move the sample holder to the observation position.

[0077] Click the accelerating voltage display to open the HV setting dialog, and set the accelerating voltage to [1.1 kV] and the emission current to [20 μA]. In the [Basic] tab of the operation panel, set the signal selection to [SE], select [Upper (U)] and [+BSE] for the SE detector, and select [LA100] in the selection box to the right of [+BSE] to set the mode for observation using backscattered electron images. Also in the [Basic] tab of the operation panel, set the probe current in the electron optical system condition block to [Normal], the focus mode to [UHR], and the WD to [4.5 mm]. Press the [ON] button in the accelerating voltage display on the control panel to apply the accelerating voltage.

[0078] (3) Focus adjustment Rotate the focus knob [COARSE] on the control panel until the image is in focus to some extent, then adjust the aperture alignment. Click [Align] on the control panel to display the alignment dialog and select [Beam]. Rotate the STIGMA / ALIGNMENT knobs (X, Y) on the control panel to move the displayed beam to the center of the concentric circles. Next, select [Aperture] and rotate the STIGMA / ALIGNMENT knobs (X, Y) one by one to stop the image movement or minimize its movement. Close the aperture dialog and use autofocus to adjust the focus. Then, set the magnification to 80,000 (80k)x and adjust the focus using the focus knob and STIGMA / ALIGNMENT knob as described above, then use autofocus to adjust the focus again. Repeat this process to adjust the focus. Here, if the inclination angle of the observation surface is large, the measurement accuracy of the number average particle diameter tends to be low. Therefore, when adjusting the focus, select an object that can simultaneously bring the entire observation surface into focus, and select an object with as little surface inclination as possible for analysis.

[0079] (4) Save image Adjust the brightness in ABC mode, take a photo at a size of 640 x 480 pixels, and save it. This image file will be used for the following analysis. To measure the particle size of at least 500 inorganic microparticles and calculate the number-average particle size, take images at multiple locations so as to avoid photographing the same inorganic microparticles, and obtain the required number of particles.

[0080] (5) Image analysis The particle diameters of at least 500 inorganic fine particles are measured to determine the number-average particle diameter. In the present invention, the number-average particle diameter is calculated by binarizing the image obtained by the above-mentioned method using image analysis software Image-Pro Plus ver. 5.0.

[0081] If the inorganic fine particles separated from the toner contain pigments or other contaminants, they are first subjected to elemental analysis using an energy dispersive X-ray analyzer (EDS) and discrimination based on particle size and shape, and measurements are then carried out after excluding particles other than the inorganic fine particles to be measured.

[0082] <Method for measuring work function> A surface analyzer (AC-3 manufactured by Riken Keiki Co., Ltd.) was used to measure the work function. In the present invention, a D2 lamp was used as the ultraviolet light source, with the irradiation light intensity set to 500 nW and the spot size set to 2 × 5 mm. The energy scanning range was set to 4.00 to 7.00 eV at intervals of 0.05 eV, and the sample was irradiated with light at a measurement time of 10 sec / point, and photoelectrons emitted from the sample surface were detected. The work function was measured with a repeatability (standard deviation) of 0.02 eV. When measuring powder, a powder measurement cell was used.

[0083] Figure 1 is a schematic diagram of a powder measurement cell. (a) is a plan view of the cell 10, (b) is a partially cutaway side view, and (c) is a perspective view. This cell 10 is a stainless steel disk 30 mm in diameter and 5 mm in height, with a sample-holding recess 11 15 mm in diameter and 3 mm deep in the center. The sample is placed in the recess 11 using a weighing spoon without compacting it, and then the surface is smoothed and flattened using a knife edge. The measurement cell is then fixed in a specified position on the sample stage and measurement is performed.

[0084] As shown in Figure 2, the measurement cell is then fixed at a specified position on the sample stage so that the irradiated surface is smooth in the direction of irradiation with the measurement light L. This allows the emitted photoelectrons to be efficiently detected by a detector (photomultiplier tube). In this surface analysis, the excitation energy of the monochromatic light is scanned from low to high until photon emission begins at a certain energy value (eV), which is called the work function (eV). To ensure data reproducibility, the measurement sample was left for 24 hours under conditions of 23°C temperature and 60% RH.

[0085] [Configurations included in the embodiments of the present invention] The disclosure of this embodiment includes the following configuration. (Configuration 1) A toner comprising toner particles containing a binder resin and a colorant, and strontium titanate fine particles, wherein the work function of the strontium titanate fine particles is 5.65 eV or more and 7.00 eV or less. (Configuration 2) The toner according to configuration 1, wherein the strontium titanate fine particles are produced by a wet method. (Configuration 3) The toner according to configuration 1 or 2, wherein the strontium titanate fine particles are treated with a silane coupling agent and silicone oil. (Configuration 4) The toner according to Configuration 3, wherein the silane coupling agent is an alkyltrialkoxysilane having an alkyl group having 3 to 6 carbon atoms. (Configuration 5) The silicone oil has a viscosity of 1.0 × 10 -7 m 2 / s or more 0.1m 2 4. The toner according to claim 3, wherein the toner has a molecular weight of 1 / s or less. (Configuration 6) The toner according to any one of Configurations 1 to 5, wherein the strontium titanate fine particles have a number average particle diameter of 5 nm or more and 50 nm or less. (Configuration 7) The toner according to any one of Configurations 1 to 6, wherein the strontium titanate fine particles are contained in the toner in an amount of 0.1% by mass to 5.0% by mass. (Configuration 8) The toner according to any one of Configurations 1 to 7, wherein the toner particles contain the strontium titanate fine particles. [Example]

[0086] In the following examples, the parts are based on parts by weight.

[0087] <Production example of binder resin L> Polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane: 72.0 parts (0.20 moles; 100.0 mole% based on the total number of moles of polyhydric alcohol) Terephthalic acid: 28.0 parts (0.17 moles; 100.0 mole % based on the total number of moles of polycarboxylic acids) 0.5 parts tin 2-ethylhexanoate (esterification catalyst) The above materials were weighed and placed in a reaction vessel equipped with a condenser, a stirrer, a nitrogen inlet tube, and a thermocouple. The atmosphere in the reaction vessel was then replaced with nitrogen gas, and the temperature was gradually raised with stirring. The mixture was allowed to react at 200°C for 4 hours with stirring.

[0088] The pressure inside the reactor was then reduced to 8.3 kPa and maintained at this temperature for 1 hour, after which the reactor was cooled to 180°C and returned to atmospheric pressure.

[0089] Trimellitic anhydride: 3 parts (0.01 mole; 4.0 mole% based on the total number of moles of polycarboxylic acids) tert-butylcatechol (polymerization inhibitor): 0.1 parts Thereafter, the above materials were added, the pressure in the reaction vessel was reduced to 8.3 kPa, and the reaction was carried out for 1 hour while maintaining the temperature at 180°C. After confirming that the softening point measured in accordance with ASTM D36-86 reached 90°C, the temperature was reduced to stop the reaction, and binder resin L was obtained.

[0090] <Production example of binder resin H> Polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane: 72.3 parts (0.20 moles; 100.0 mole% based on the total number of moles of polyhydric alcohol) Terephthalic acid: 18.3 parts (0.11 mole; 65.0 mol% based on the total number of moles of polycarboxylic acids) Fumaric acid: 2.9 parts (0.03 moles; 15.0 mole% based on the total number of moles of polycarboxylic acids) 0.5 parts tin 2-ethylhexanoate (esterification catalyst) The above materials were weighed and placed in a reaction vessel equipped with a condenser, a stirrer, a nitrogen inlet tube, and a thermocouple. After the atmosphere in the reaction vessel was replaced with nitrogen gas, the temperature was gradually raised with stirring, and the reaction was carried out at 200°C for 2 hours with stirring.

[0091] The pressure inside the reactor was then reduced to 8.3 kPa and maintained for 1 hour, after which the reactor was cooled to 180 and returned to atmospheric pressure.

[0092] Trimellitic anhydride: 6.5 parts (0.03 moles; 20.0 mole% based on the total number of moles of polycarboxylic acids) tert-butylcatechol (polymerization inhibitor): 0.1 parts Thereafter, the above materials were added, the pressure in the reaction vessel was reduced to 8.3 kPa, and the reaction was carried out for 15 hours while maintaining the temperature at 160°C. After it was confirmed that the softening point measured in accordance with ASTM D36-86 had reached 137°C, the temperature was reduced to stop the reaction, and binder resin H was obtained.

[0093] <Production Example of Inorganic Fine Particles 1> Metatitanic acid produced by the sulfuric acid method was deironized and bleached, then desulfurized by adding a 3N aqueous solution of sodium hydroxide to adjust the pH to 9.0, and then neutralized to pH 5.6 with 5N hydrochloric acid, filtered, and washed with water. Water was added to the washed cake to make a slurry of 1.90 mol / L in terms of TiO2, and hydrochloric acid was added to adjust the pH to 1.4, which was then subjected to peptization.

[0094] After desulfurization and peptization, 1.90 moles of metatitanic acid (TiO2) was collected and placed in a 3-L reaction vessel. To the peptized metatitanic acid slurry, 2.185 moles of strontium chloride aqueous solution was added to achieve a SrO / TiO2 molar ratio of 1.15, and the TiO2 concentration was adjusted to 1.039 moles / L. The mixture was then heated to 90°C with stirring, and 440 mL of 10N sodium hydroxide aqueous solution was added over 40 minutes. Stirring was continued at 95°C for 30 minutes, after which the mixture was poured into ice water and rapidly cooled to terminate the reaction.

[0095] The reaction slurry was heated to 70°C, 12N hydrochloric acid was added until the pH reached 5.0, and stirring was continued for 1 hour. The resulting precipitate was decanted. The slurry containing the resulting precipitate was adjusted to 40°C, and hydrochloric acid was added to adjust the pH to 2.5. 4.0 mass% isobutyltrimethoxysilane based on the solid content was then added, and the mixture was stirred for 10 hours. The viscosity was then 1.0 x 10 -3 m 2Dimethyl silicone oil (100%) was added at 4.0 mass% based on the solid content, and the mixture was stirred for 10 hours. A 5N aqueous solution of sodium hydroxide was added to adjust the pH to 6.5, and stirring was continued for 1 hour. The mixture was then filtered and washed, and the resulting cake was dried in air at 120°C for 8 hours to obtain inorganic microparticle 1, strontium titanate microparticles. The work function of the resulting strontium titanate microparticles was 5.78 eV. Their physical properties are shown in Table 1.

[0096] <Production Examples of Inorganic Fine Particles 2 to 12> Strontium titanate microparticles of inorganic microparticles 2 to 12 were obtained by the same production procedure as in Production Example of Inorganic Microparticles 1, except that the particle size, silane coupling agent, and silicone oil were changed as shown in Table 1. The physical properties are shown in Table 1.

[0097] <Production Example of Inorganic Fine Particles 13> 600 g of strontium carbonate and 350 g of titanium oxide were wet mixed in a ball mill for 8 hours, then filtered and dried. The mixture was then subjected to a pressure of 10 kg / cm 2 The powder was compacted under a pressure of 1000 kJ / cm2 and sintered at 1200°C for 7 hours. This was then mechanically pulverized to obtain strontium titanate microparticles (Inorganic Microparticles 13) with an average primary particle size of 60 nm after the sintering process. The work function was 5.66 eV. The physical properties are shown in Table 1.

[0098] <Production Example of Inorganic Fine Particles 14> 600 g of strontium carbonate and 350 g of titanium oxide were wet mixed in a ball mill for 8 hours, then filtered and dried. The mixture was then subjected to a pressure of 10 kg / cm 2The mixture was compacted under a pressure of 1000 kJ / cm2 and sintered at 1200°C for 7 hours. This was then mechanically pulverized to obtain strontium titanate microparticles with an average primary particle size of 60 nm. 50 g of the resulting dispersion was dispersed in 500 mL of ion-exchanged water. The pH of the resulting dispersion was adjusted to between 3 and 4 by adding 5N hydrochloric acid. 4.0% by mass of methyltriethoxysilane (based on the solid content) was added to the pH-adjusted dispersion and stirred for 10 hours. The resulting solution was transferred to a 1 L separable flask. The contents of the flask were then reacted at 70°C for 30 minutes. The pH was adjusted to 6.5 by adding 5N aqueous sodium hydroxide solution and stirring continued for 1 hour. After filtration and washing, the resulting cake was dried in air at 120°C for 8 hours to obtain inorganic microparticle 14, strontium titanate microparticles. The work function was 5.60 eV. The physical properties are shown in Table 1.

[0099] <Production example of inorganic fine particles 15> 50 g of fumed silica (silica particle raw material) with a number-average particle diameter of 60 nm was dispersed in 500 mL of ion-exchanged water. 5N hydrochloric acid was added to the resulting silica particle dispersion to adjust the pH of the silica particle dispersion to 3 or more and 4 or less. 4.0 mass % of methyltriethoxysilane based on the solid content was added to the pH-adjusted silica particle dispersion, and the mixture was stirred for 10 hours. After that, the viscosity of the dispersion was 0.2 m. 2 Dimethyl silicone oil (4.0 mass % based on the solid content) was added and stirred for 10 hours. A 5N aqueous solution of sodium hydroxide was added to adjust the pH to 6.5, and stirring was continued for 1 hour. After that, the mixture was filtered and washed, and the resulting cake was dried in the air at 120°C for 8 hours to obtain silica microparticles of inorganic microparticle 15. The work function was 5.50 eV. The physical properties are shown in Table 1.

[0100] <Production example of inorganic fine particles 16> 50 g of titanium oxide particles (titanium oxide microparticles raw material) with a number-average particle size of 60 nm were dispersed in 500 mL of ion-exchanged water. 5N hydrochloric acid was added to the resulting titanium oxide particle dispersion to adjust the pH of the titanium oxide particle dispersion to 3 or more and 4 or less. 4.0 mass % of methyltriethoxysilane based on the solid content was added to the pH-adjusted titanium oxide dispersion, and the mixture was stirred for 10 hours. After that, the viscosity of the dispersion was adjusted to 0.2 m. 2 Dimethyl silicone oil (4.0 mass % based on the solid content) was added and stirred for 10 hours. A 5N aqueous solution of sodium hydroxide was added to adjust the pH to 6.5, and stirring was continued for 1 hour. After that, the mixture was filtered and washed, and the resulting cake was dried in the air at 120°C for 8 hours to obtain titanium oxide particles (Inorganic Particle 16). The work function was 5.45 eV. The physical properties are shown in Table 1.

[0101] [Table 1]

[0102] <Toner 1 manufacturing example> 70 parts of binder resin L Binding resin H 30 parts Fischer-Tropsch wax (hydrocarbon wax, maximum endothermic peak temperature 90°C) 5 parts CI Pigment Blue 15:3 5 parts ·Inorganic fine particles 1 3 parts First, the above materials were premixed in a Henschel mixer, and then melt-kneaded using a twin-screw kneading extruder. The residence time was adjusted so that the temperature of the kneaded resin reached 140°C. The resulting kneaded product was cooled, coarsely pulverized using a hammer mill, and then pulverized using a turbo mill. The resulting fine particles were classified using a multi-division classifier utilizing the Coanda effect (product name: Elbow Jet Classifier, manufactured by Nittetsu Mining Co., Ltd.), yielding toner particles with a weight-average particle size (D4) of 6.5 μm.

[0103] For 100 parts of the toner particles, Hydrophobic silica (BET: 200m 2 / g):0.5 copies ·Inorganic fine particles 1:0.5 part The mixture was mixed in a Henschel mixer (FM-75 type, manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 30 s -1 The mixture was mixed at a rotation time of 10 minutes and externally added to the toner particles. The mixture was then sieved through a mesh with 150 μm openings to obtain Toner 1. The composition of the toner is shown in Table 2.

[0104] <Production example of toners 2 to 20> Except for changing the composition and number of inorganic fine particles shown in Table 1, production was carried out in the same manner as for Toner 1. The compositions of Toners 2 to 20 are shown in Table 2.

[0105] [Table 2]

[0106] <Production example of magnetic core particle 1> Process 1 (weighing and mixing process): Fe2O362.7 parts MnCO329.5 parts Mg(OH)26.8 parts SrCO31.0 parts The ferrite raw materials were weighed so as to achieve the above composition ratio, and then pulverized and mixed for 5 hours in a dry vibration mill using stainless steel beads with a diameter of 1 / 8 inch.

[0107] Step 2 (pre-baking): The resulting pulverized material was made into pellets of approximately 1 mm square using a roller compactor. The pellets were passed through a vibrating sieve with 3 mm openings to remove coarse particles, and then through a vibrating sieve with 0.5 mm openings to remove fine particles. The pellets were then fired in a burner-type firing furnace at 1000°C for 4 hours in a nitrogen atmosphere (oxygen concentration 0.01% by volume) to produce calcined ferrite. The composition of the resulting calcined ferrite was as follows: (MnO)a(MgO)b(SrO)c(Fe2O3)d In the above formula, a=0.257, b=0.117, c=0.007, d=0.393

[0108] Step 3 (Crushing): After crushing the material to about 0.3 mm using a crusher, 30 parts of water were added to 100 parts of the calcined ferrite and crushed in a wet ball mill using zirconia beads with a diameter of 1 / 8 inch for 1 hour. The resulting slurry was crushed in a wet ball mill using alumina beads with a diameter of 1 / 16 inch for 4 hours to obtain a ferrite slurry (finely crushed calcined ferrite).

[0109] ·Process 4 (granulation process): To the ferrite slurry, 1.0 part of ammonium polycarboxylate as a dispersant and 2.0 parts of polyvinyl alcohol as a binder were added per 100 parts of calcined ferrite, and the mixture was granulated into spherical particles using a spray dryer (manufacturer: Okawahara Kakoki Co., Ltd.). After adjusting the particle size of the resulting particles, they were heated in a rotary kiln at 650°C for 2 hours to remove the organic components of the dispersant and binder.

[0110] Step 5 (firing): To control the firing atmosphere, the material was heated from room temperature to 1300°C in a nitrogen atmosphere (oxygen concentration 1.00% by volume) in an electric furnace over two hours, and then fired at 1150°C for four hours. The material was then cooled to 60°C over four hours, returned from the nitrogen atmosphere to the air, and removed at a temperature of 40°C or below.

[0111] Step 6 (sorting): After crushing the agglomerated particles, low magnetic particles were removed by magnetic separation, and coarse particles were removed by sieving through a sieve with a mesh size of 250 μm to obtain magnetic core particles 1 with a volume distribution-based 50% particle size (D50) of 37.0 μm.

[0112] <Preparation of Coating Resin 1> Cyclohexyl methacrylate monomer 26.8% by mass Methyl methacrylate monomer 0.2% by mass Methyl methacrylate macromonomer 8.4% by mass (a macromonomer with a weight-average molecular weight of 5000 and a methacryloyl group at one end) Toluene 31.3% by mass Methyl ethyl ketone 31.3% by mass Azobisisobutyronitrile 2.0% by mass Of the above materials, cyclohexyl methacrylate monomer, methyl methacrylate monomer, methyl methacrylate macromonomer, toluene, and methyl ethyl ketone were placed in a four-neck separable flask equipped with a reflux condenser, thermometer, nitrogen inlet tube, and stirrer, and nitrogen gas was introduced to replace the atmosphere inside the system. The mixture was then heated to 80°C, azobisisobutyronitrile was added, and the mixture was refluxed for 5 hours to polymerize. Hexane was added to the resulting reaction mixture to precipitate a copolymer. The precipitate was filtered and then vacuum-dried to obtain Coating Resin 1. 30 parts of the resulting Coating Resin 1 were dissolved in 40 parts of toluene and 30 parts of methyl ethyl ketone to obtain Polymer Solution 1 (solids content 30% by mass).

[0113] <Preparation of Coating Resin Solution 1> Polymer solution 1 (resin solids concentration 30%) 33.3% by mass Toluene 66.4% by mass Carbon black (Regal 330; manufactured by Cabot Corporation) 0.3% by mass (Primary particle size 25 nm, nitrogen adsorption specific surface area 94 m 2 / g, DBP oil absorption 75ml / 100g) The resulting dispersion was dispersed for 1 hour using zirconia beads with a diameter of 0.5 mm in a paint shaker. The resulting dispersion was filtered through a 5.0 μm membrane filter to obtain coating resin solution 1.

[0114] <Magnetic Carrier 1 Manufacturing Example> (Resin coating process): Coating resin solution 1 was added to a vacuum degassing kneader maintained at room temperature so that the resin component was 2.5 parts per 100 parts of magnetic core particles 1. After addition, the mixture was stirred at a rotation speed of 30 rpm for 15 minutes, and after a certain amount of solvent (80% by mass) had evaporated, the mixture was heated to 80°C while mixing under reduced pressure, and the toluene was distilled off over 2 hours, after which it was cooled. The obtained magnetic carrier was separated into low-magnetic particles by magnetic separation, passed through a sieve with 70 μm openings, and then classified with an air classifier to obtain magnetic carrier 1 having a 50% particle size (D50) based on volume distribution of 38.2 μm.

[0115] <Production example of two-component developer 1> To 92.0 parts of magnetic carrier 1, 8.0 parts of toner 1 were added and mixed in a V-type mixer (V-20, manufactured by Seishin Enterprises) to obtain two-component developer 1.

[0116] <Production examples of two-component developers 2 to 20> In the production example of two-component developer 1, the same procedure was carried out except that the combination of toners was changed as shown in Table 3, to obtain two-component developers 2 to 20.

[0117] [Table 3]

[0118] Example 1 The above two-component developer 1 was used for evaluation.

[0119] The image forming apparatus used was a Canon full-color POD machine, imagePRESS V1350, modified to a process speed of 650 mm / sec. Two-component developer 1 was loaded into the cyan station's developer, and the DC voltage VDC of the developer carrier, the charging voltage VD of the electrostatic latent image carrier, and the laser power were adjusted so that the desired amount of toner was applied to the electrostatic latent image carrier or paper, and the evaluation described below was carried out. The modification involved changing the process speed so that it could be freely set. The evaluation paper was copy paper GF-C081 (A4, basis weight 81.0 g / m 2 ) sold by Canon Marketing Japan Inc.) was used.

[0120] The evaluation was carried out based on the following evaluation methods, and the results are shown in Table 4.

[0121] <Evaluation 1: NN initial evaluation, overcast> Under an N / N (23°C, 50%) environment, the development contrast of the printer was adjusted, and the reflection density of a solid image printed was measured using an optical densitometer. The setting was adjusted to a reflection density of 1.50. Under these settings, an image pattern with a 40% cyan monochromatic image ratio relative to the paper surface was continuously printed 10,000 times. Three full-white A3 size sheets were then printed, and the third image was used for evaluation. The average reflectance Dr (%) of six points on the unprinted paper and the average reflectance Ds (%) of six points on the printed paper were measured using a reflectometer (Tokyo Denshoku Co., Ltd.'s "REFLECTOMETER MODEL TC-6DS") to determine the fogging rate (%). Higher electrostatic charge reduces unintended scattering and improves fogging suppression. Fog rate (%) = Dr (%) - Ds (%) (Evaluation criteria) A: Fog rate is less than 0.3% (very good) B: Fog rate is 0.3% or more and less than 0.6% (excellent) C: Fog rate is 0.6% or more and less than 0.9% (good) D: Fog rate is 0.9% or more and less than 1.2% (a level that is acceptable for the present invention) E: Fog rate is 1.2% or more (unacceptable in the present invention)

[0122] <Evaluation 2: NN initial evaluation, concentration> The reflection density of a solid image printed under an N / N (23°C, 50%) environment was measured using an optical densitometer, and the reflection density was set. After continuously printing 10,000 sheets of an image pattern with a cyan monochromatic image ratio of 5% to the paper surface, three solid images were printed on the entire surface of A4 paper, and the third image was used for evaluation. The image density was measured at five locations and the average value was calculated. The image density was measured using a spectrodensitometer 500 series (X-Rite) and judged according to the following criteria. (Evaluation criteria) A: Density is 1.40 or higher (very good) B: Density is 1.35 or more and less than 1.40 (excellent) C: Concentration is 1.30 or more and less than 1.35 (good) D: Density is 1.25 or more and less than 1.30 (a level that is acceptable for the present invention) E: Density less than 1.25 (unacceptable according to the present invention)

[0123] <Evaluation 3: NN initial evaluation, fine line reproducibility (transfer voids)> Under an N / N (23°C, 50%) environment, the development contrast of the printer was adjusted, and the reflection density of a solid image printed was measured using an optical densitometer. The setting was adjusted to achieve a reflection density of 1.50. Under these settings, an image pattern with a 1% cyan monochromatic image ratio relative to the paper surface was printed 10,000 times in succession, followed by a single 500 μm horizontal line pattern. The fine lines were magnified using a digital microscope to obtain an image, which was then binarized to calculate the amount of voids within the line width as the void rate based on the area ratio. For example, a void rate of 50% means that 50% of the background white area is visible within the line width. The void rate obtained was evaluated based on the following criteria. (Evaluation criteria) A: The defect rate is less than 1% (very good). B: Hollow rate is 1% or more and less than 5% (excellent) C: The hollowing rate is 5% or more and less than 10% (good) D: The hollowing rate is 10% or more and less than 20% (a level that is acceptable for the present invention). E: Hollow rate is 20% or more (unacceptable in the present invention)

[0124] <Evaluation 4: NN initial evaluation, image uniformity (material contamination)> The development contrast of the printer was adjusted under an N / N (23°C, 50%) environment, and the reflection density of a solid image printed was measured using an optical densitometer. The setting was adjusted to a reflection density of 1.50. With this setting, an image pattern with a 40% cyan monochrome image ratio to the paper surface was printed continuously on 10,000 sheets, and then three halftone images were printed on the entire surface of A3 paper. The third image was used for evaluation. Image uniformity was evaluated by measuring the image density at five points and calculating the difference between the maximum and minimum values. Image density was measured using a 500 Series spectrodensitometer (X-Rite) and evaluated according to the following criteria: Contamination of components such as the charging roller worsens, resulting in poorer in-plane uniformity. (Evaluation criteria) A: Density difference is less than 0.03 (very good) B: Density difference is 0.03 or more and less than 0.06 (excellent) C: Density difference is 0.06 or more and less than 0.09 (good) D: The density difference is 0.09 or more and less than 0.12 (a level that is acceptable for the present invention) E: Density difference is 0.12 or more (unacceptable in the present invention)

[0125] <Rating 5: NN durability rating, fogging> Under an N / N (23°C, 50%) environment, the development contrast of the printer was adjusted, and the reflection density of a solid image printed was measured using an optical densitometer, with the setting set to a reflection density of 1.50. With these settings, an image pattern with a cyan monochrome image ratio of 40% to the paper surface was printed 100,000 times in succession, and then three full-white A3 size sheets were printed, with the third image being used for evaluation. The average reflectance Dr (%) of six points on the unprinted paper and the average reflectance Ds (%) of six points on the printed paper were measured using a reflectometer (Tokyo Denshoku Co., Ltd.'s "REFLECTOMETER MODEL TC-6DS"), and the fog rate (%) was calculated in the same manner as in Evaluation 1. (Evaluation criteria) A: Fog rate is less than 0.3% (very good) B: Fog rate is 0.3% or more and less than 0.6% (excellent) C: Fog rate is 0.6% or more and less than 0.9% (good) D: Fog rate is 0.9% or more and less than 1.2% (a level that is acceptable for the present invention) E: Fog rate is 1.2% or more (unacceptable in the present invention)

[0126] <Rating 6: NN durability rating, density> The reflection density of a solid image printed under an N / N (23°C, 50%) environment was measured using an optical densitometer, and the reflection density was set. After continuously printing 100,000 sheets of an image pattern with a cyan monochrome image ratio of 5% to the paper surface, three solid images were printed on the entire surface of A4 paper, and the third image was used for evaluation. The image density was measured at five locations and the average value was calculated. The image density was measured using a spectrodensitometer 500 series (X-Rite) and judged according to the following criteria. (Evaluation criteria) A: Density is 1.40 or higher (very good) B: Density is 1.35 or more and less than 1.40 (excellent) C: Concentration is 1.30 or more and less than 1.35 (good) D: Density is 1.25 or more and less than 1.30 (a level that is acceptable for the present invention) E: Density less than 1.25 (unacceptable according to the present invention)

[0127] <Rating 7: NL durability rating, fogging> The development contrast of the printer was adjusted in a N / L (23°C, 5%) environment, and the reflection density of a solid image printed was measured using an optical densitometer, with the setting set to a reflection density of 1.50. With these settings, an image pattern with a 1% cyan monochrome image ratio to the paper surface was continuously printed 100,000 times, and then three full-white A3 size sheets were printed, with the third image being used for evaluation. The average reflectance Dr (%) of six points on the unprinted paper and the average reflectance Ds (%) of six points on the printed paper were measured using a reflectometer (Tokyo Denshoku Co., Ltd.'s "REFLECTOMETER MODEL TC-6DS"), and the fog rate (%) was calculated in the same way as in Evaluation 1. (Evaluation criteria) A: Fog rate is less than 0.3% (very good) B: Fog rate is 0.3% or more and less than 0.6% (excellent) C: Fog rate is 0.6% or more and less than 0.9% (good) D: Fog rate is 0.9% or more and less than 1.2% (a level that is acceptable for the present invention) E: Fog rate is 1.2% or more (unacceptable in the present invention)

[0128] <Rating 8: NL durability rating, density> The reflection density of a solid image printed under a N / L (23°C, 5%) environment was measured using an optical densitometer, and the reflection density was set. After continuously printing 100,000 sheets of an image pattern with a cyan monochromatic image ratio of 1% to the paper surface, three solid images were printed across the entire surface of an A4 sheet of paper, and the third image was used for evaluation. The image density was measured at five locations and the average value was calculated. The image density was measured using a spectrodensitometer 500 series (X-Rite) and judged according to the following criteria. (Evaluation criteria) A: Density is 1.40 or higher (very good) B: Density is 1.35 or more and less than 1.40 (excellent) C: Concentration is 1.30 or more and less than 1.35 (good) D: Density is 1.25 or more and less than 1.30 (a level that is acceptable for the present invention) E: Density less than 1.25 (unacceptable according to the present invention)

[0129] <Evaluation 9: HH initial evaluation, fine line reproducibility (transfer voids)> The development contrast of the printer was adjusted in a H / H (30°C, 80%) environment, and the reflection density of a solid image printed was measured using an optical densitometer. The setting was adjusted to a reflection density of 1.50. Under these settings, an image pattern with a 40% cyan monochromatic image ratio relative to the paper surface was printed 10,000 times in succession. Then, one 500 μm horizontal line pattern was printed. The fine lines were enlarged using a digital microscope to obtain an image. The image was then binarized to calculate the amount of voids within the line width as the void rate, calculated as an area ratio. For example, a void rate of 50% means that 50% of the white background is visible within the line width. The void rate obtained was evaluated based on the following criteria. (Evaluation criteria) A: Missing rate less than 1% (very good) B: Hollow rate 1% or more and less than 5% (excellent) C: Hollow rate 5% or more and less than 10% (good) D: Hollow rate of 10% or more and less than 20% (a level that is acceptable for the present invention) E: Hollow rate of 20% or more (unacceptable in the present invention)

[0130] <Evaluation 10: NL initial evaluation, image uniformity (material contamination)> The development contrast of the printer was adjusted in a N / L (23°C, 5%) environment, and the reflection density of a solid image printed was measured using an optical densitometer. The setting was adjusted to a reflection density of 1.50. With this setting, an image pattern with a 1% cyan monochromatic image ratio to the paper surface was printed 10,000 times in succession. Three halftone images were printed across the entire surface of an A3 sheet of paper, and the third image was used for evaluation. Image uniformity was evaluated by measuring the image density at five points and calculating the difference between the maximum and minimum values. Image density was measured using a 500 Series spectrodensitometer (X-Rite) and evaluated according to the following criteria: Contamination of components such as the charging roller worsens, resulting in poorer in-plane uniformity. (Evaluation criteria) A: Density difference is less than 0.03 (very good) B: Density difference is 0.03 or more and less than 0.06 (excellent) C: Density difference is 0.06 or more and less than 0.09 (good) D: The density difference is 0.09 or more and less than 0.12 (a level that is acceptable for the present invention) E: Density difference is 0.12 or more (unacceptable in the present invention)

[0131] [Examples 2 to 17 and Comparative Examples 1 to 3] Except for changing the developer, evaluation was carried out in the same manner as in Example 1. The evaluation results are shown in Table 4.

[0132] [Table 4]

[0133] In Comparative Example 1, the fine particles were strontium titanate, but were only surface-treated with methyltriethoxysilane, resulting in a work function of 5.60 eV, which failed to achieve the objective of the present invention.

[0134] Comparative Example 2 uses silica instead of strontium titanate. Even after silane coupling treatment and silicone oil treatment, the work function did not increase to 5.50 eV. As a result, the evaluation did not meet the target.

[0135] Comparative Example 3 uses titanium oxide instead of strontium titanate. Even after silane coupling treatment and silicone oil treatment, the work function did not increase to 5.45 eV. As a result, the evaluation did not meet the target. [Explanation of symbols]

[0136] 10: Powder measurement cell, 11: Recess for accommodating sample

Claims

1. A toner comprising toner particles containing a binder resin and a colorant, and strontium titanate fine particles, wherein the strontium titanate fine particles have a work function of 5.65 eV or more and 7.00 eV or less.

2. 2. The toner according to claim 1, wherein the strontium titanate fine particles are produced by a wet method.

3. 3. The toner according to claim 1, wherein the strontium titanate fine particles are treated with a silane coupling agent and silicone oil.

4. 4. The toner according to claim 3, wherein the silane coupling agent is an alkyltrialkoxysilane having an alkyl group having 3 to 6 carbon atoms.

5. The silicone oil has a viscosity of 1.0×10 -7 m 2 / s or more 0.1m 2 4. The toner according to claim 3, wherein the toner has a viscosity of 1 / s or less.

6. 3. The toner according to claim 1, wherein the strontium titanate fine particles have a number average particle diameter of 5 nm or more and 50 nm or less.

7. 3. The toner according to claim 1, wherein the strontium titanate fine particles are contained in the toner in an amount of 0.1% by mass to 5.0% by mass.

8. 3. The toner according to claim 1, wherein the toner particles contain the strontium titanate fine particles.

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