Toner

Abstract

This invention relates to toners. A toner comprising toner particles and an external additive is provided, the external additive comprising strontium titanate particles, wherein the average sphericity of the toner is at least 0.935 and not greater than 0.995, the number-average particle size of the primary particles of the strontium titanate particles is at least 10 nm and not greater than 60 nm, and in a CuKα x-ray diffraction spectrum obtained in a 2θ range of at least 10° and not greater than 90°, the strontium titanate particles have peaks in the range of 39.700°±0.150° and in the range of 46.200°±0.150°, and the ratio of the area Sb of the peak at 46.200°±0.150° to the area Sa of the peak at 39.700°±0.150° is at least 1.80 and not greater than 2.30, where θ is the Bragg angle.

Description

[0001] This application is a divisional application of the application filed on February 27, 2018, with application number 201810162502.2 and invention title "Toner". Technical Field

[0002] This invention relates to toners for use in image forming methods such as electrophotography. Background Technology

[0003] Electrophotographic image forming apparatuses require higher speeds, longer lifespans, greater energy savings, and smaller sizes, and in response to these demands, toners also require further improvements in various properties. In particular, from the viewpoint of achieving longer lifespans, toners require further improvements in quality stability.

[0004] In particular, regarding the achievement of a longer lifespan, it is important that the quality does not undergo significant changes even during long-term repeated use, and various toners and external additives have been proposed here.

[0005] For example, to maintain excellent developing performance even during long-term repeated use, smooth, highly rounded toners are often used. The basis for this is that highly rounded toners readily undergo rolling, resulting in a uniformly charged surface. On the other hand, highly rounded toners are also prone to being overcharged, meaning they eventually become excessively charged. Therefore, in one method for controlling the charging properties of highly rounded toners, the charging properties are stabilized by using external additives as resistance modifiers.

[0006] Strontium titanate particles, which are materials with medium resistance, have been used as resistance modifiers that provide highly rounded toners with excellent charge regulation.

[0007] Strontium titanate particles used as external additives have a hexahedral shape and typically have smooth sides. When the strontium titanate particles have smooth sides, the contact area with the toner particles increases, which facilitates the movement of charge between the toner and strontium titanate particles. As a result, even when the toner particles are overcharged due to triboelectric charging, the charge can diffuse and the toner particles can be uniformly charged. Consequently, excellent developing performance can be exhibited from the initial stages of durability.

[0008] However, during repeated rubbing within the developing unit over long-term use, conventional strontium titanate particles sometimes migrate from the toner particles, leading to fluctuations in the toner's charge properties and a tendency for these properties to decrease in the final stages of long-term use. This migration indicates the phenomenon where external additives transfer from one toner particle to another or other components. Therefore, it signifies the phenomenon where external additives do not remain on the toner particles.

[0009] Japanese Patent Application Publication No. 2015-137208 proposes that by adding strontium titanate particles with a controlled SrO / TiO2 (molar ratio) to the outside of the toner particles, the environmental and charge characteristics of the toner can be improved.

[0010] Japanese Patent No. 4944980 proposes that by adding strontium titanate particles with controlled crystal structure and controlled shape to the outside of toner particles, the suppression of image smearing in high temperature and high humidity environments can be enhanced.

[0011] Japanese Patent Application Publication No. 2003-277054 proposes that the flowability and moisture resistance of a toner can be improved by adding strontium titanate particles with a controlled particle size distribution to the outside of the toner particles. Summary of the Invention

[0012] Using the techniques described in Japanese Patent Application Publication No. 2015-137208, Japanese Patent No. 4944980, and Japanese Patent Application Publication No. 2003-277054, some effects have been observed regarding the environmental characteristics of toners, the electrical properties of toners, and the suppression of image smudges. However, for the combination of this technique with high-roundness toners, further research is needed regarding long-term repeated use in various cases.

[0013] The present invention provides a colorant that solves the existing problem.

[0014] That is, the present invention provides a toner that has excellent developing performance even in the case of long-term repeated use of high roundness toner and can suppress the occurrence of fogging and component contamination.

[0015] This invention relates to a colorant containing colorant particles and an external additive, wherein the external additive contains strontium titanate particles.

[0016] The average roundness of the toner is at least 0.935 and not greater than 0.995.

[0017] The number-average particle size of the primary strontium titanate particles is at least 10 nm and not more than 60 nm.

[0018] In CuKα x-ray diffraction spectra obtained within a 2θ range of at least 10° and no greater than 90°, strontium titanate particles exhibit peaks in the range of 39.700° ± 0.150° and 46.200° ± 0.150°, where θ is the Bragg angle; and

[0019] When Sa is the area of ​​the peak at 39.700°±0.150° and Sb is the area of ​​the peak at 46.200°±0.150°, Sb / Sa is at least 1.80 and not greater than 2.30.

[0020] Therefore, the present invention can provide a toner that has excellent developing performance even in the case of long-term repeated use of high-roundness toners and can suppress the occurrence of fogging and component contamination.

[0021] Further features of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0022] Figure 1 This is a transmission electron microscope image of strontium titanate particle 1 (a photo that replaces the image). Detailed Implementation

[0023] For the purposes of this invention, unless otherwise specifically stated, phrases such as "at least XX and not greater than YY" or "XX to YY" that give a numerical range indicate a numerical range including a lower limit and an upper limit as endpoints.

[0024] As mentioned earlier, the use of strontium titanate particles is a means of controlling the charge properties of highly rounded toners.

[0025] Due to the increased contact area between the toner particles and the strontium titanate particles provided by the external addition of hexahedral strontium titanate particles, charge can diffuse and uniform charging can be achieved even when the toner particles are overcharged under triboelectric charging. As a result, excellent developing performance and fogging suppression are achieved from the initial stage of repeated use.

[0026] However, for conventional strontium titanate particles, during long-term repeated use, strontium titanate particles can migrate from toner particles in the developing unit under the effect of friction. This leads to fluctuations in the toner's charge properties and a deterioration trend in charge properties and fogging suppression in the final stage of long-term repeated use.

[0027] Therefore, in order to suppress the migration of strontium titanate particles from the toner particles, the inventors attempted to reduce the particle size of the strontium titanate particles.

[0028] It is believed that as the diameter decreases, migration is suppressed even during repeated rubbing within the developing unit. Furthermore, it is thought that a smaller diameter facilitates rolling on the surface of the toner particles, and therefore is also effective for the uniform charging of the toner.

[0029] Even during long-term repeated use in the developing unit during repeated rubbing, reducing the particle size of strontium titanate particles does indeed inhibit strontium titanate particle migration.

[0030] However, it was found that applying strontium titanate particles with reduced particle size to highly rounded, smooth toners facilitated scratching of the toner particle surface. It was also found that toner particle breakage occurred depending on the circumstances. The occurrence of toner particle breakage affected the charge distribution of the toner.

[0031] Specifically, it was found that when small-diameter strontium titanate particles were applied to highly rounded, smooth toners, particle breakage caused fluctuations in charge distribution and reduced the toner's developing performance; it was also found to increase fogging. Furthermore, it was found to promote component contamination caused by broken toner particles.

[0032] As a result of in-depth research, the inventors discovered that by using small-diameter strontium titanate particles with a specific profile in their X-ray diffraction spectra as an external additive, excellent development performance can be obtained even for long-term repeated use, and fogging and component contamination can also be suppressed. This invention is based on this discovery.

[0033] That is, the toner of the present invention is a toner containing toner particles and external additives, wherein the external additives contain strontium titanate particles, wherein

[0034] The average roundness of the toner is at least 0.935 and not greater than 0.995.

[0035] The number-average particle size of the primary strontium titanate particles is at least 10 nm and not more than 60 nm.

[0036] In CuKα x-ray diffraction spectra obtained within a 2θ range of at least 10° and no greater than 90°, strontium titanate particles exhibit peaks in the range of 39.700° ± 0.150° and 46.200° ± 0.150°, where θ is the Bragg angle; and

[0037] When Sa is the area of ​​the peak at 39.700°±0.150° and Sb is the area of ​​the peak at 46.200°±0.150°, Sb / Sa is at least 1.80 and not greater than 2.30.

[0038] In the CuKα x-ray diffraction spectra obtained within a 2θ range of at least 10° and no greater than 90°, strontium titanate particles have peaks in the range of 39.700°±0.150° and in the range of 46.200°±0.150°, where θ is the Bragg angle.

[0039] Strontium titanate with peaks at these locations adopts a perovskite structure in a cubic crystal system, and the peaks in the ranges of 39.700°±0.150° and 46.200°±0.150° are diffraction peaks originating from lattice planes with Miller indices of (111) and (200), respectively.

[0040] Particles belonging to the cubic crystal system usually tend to adopt a hexahedral shape for their external shape. Similarly, in the case of strontium titanate particles, the particles grow while maintaining the (100) and (200) faces corresponding to the face directions of the hexahedral shape during the production process.

[0041] However, as a result of the inventors' research, the inventors found that strontium titanate particles with (200) faces corresponding to the face directions of the hexahedron shape and (111) faces corresponding to the vertex directions exhibited superior properties.

[0042] Furthermore, as a result of detailed research, it was found that when Sa is the area of ​​the peak at 39.700°±0.150° and Sb is the area of ​​the peak at 46.200°±0.150°, a significant effect was achieved when Sb / Sa is at least 1.80 and not greater than 2.30. Preferably, Sb / Sa is at least 1.80 and not greater than 2.25.

[0043] The number average particle size of the primary particles of strontium titanate is at least 10 nm and not more than 60 nm. Preferably, the number average particle size of the primary particles is at least 10 nm and not more than 50 nm.

[0044] When the Sb / Sa ratio and the number-average particle size of the primary particles are within the above-mentioned ranges, the migration of Sb titanate particles and the breakage of toner particles from the toner particles can be suppressed even during long-term repeated use of high-roundness toners. As a result, the toner exhibits excellent developing performance and suppresses fogging and component contamination.

[0045] The number-average particle size and Sb / Sa ratio of strontium titanate particles can be controlled by adjusting the molar ratio of the raw materials and production conditions such as applying dry mechanical treatment.

[0046] The Sr / Ti (molar ratio) of the strontium titanate particles is preferably at least 0.70 and not more than 0.85, and more preferably at least 0.75 and not more than 0.83.

[0047] By keeping the Sr / Ti (molar ratio) within the above range, increasing the proportion of Ti to be close to negative in terms of charge, the result is beneficial for the presentation of a narrow charge distribution and improves the uniformity of halftone images.

[0048] The Sr / Ti molar ratio can be controlled by adjusting the molar ratio of the raw materials for strontium titanate particles and by adjusting the production conditions.

[0049] The average sphericity of the primary particles of strontium titanate is preferably at least 0.700 and not more than 0.920, and more preferably at least 0.790 and not more than 0.920.

[0050] By adopting an average roundness within the above range, it is beneficial to break up the strontium titanate particles on the toner particles and to increase the coverage of the strontium titanate particles.

[0051] As a result, the initial stage of reuse is favorable for the toner to gain charge, and the effects on developing performance and fogging suppression are easily obtained in the initial stage of reuse. The average sphericity of the primary strontium titanate particles can be controlled by adjusting the production conditions.

[0052] In the wettability test of strontium titanate particles with respect to a methanol / water mixed solvent, the methanol concentration is preferably at least 60% by volume and not more than 95% by volume when the transmittance of light at a wavelength of 780 nm is 50%, and more preferably at least 65% by volume and not more than 95% by volume.

[0053] Using the above-mentioned range for methanol concentration is beneficial for maintaining the developing performance after being placed in a high-temperature and high-humidity environment.

[0054] The wettability of strontium titanate particles relative to a methanol / water mixed solvent can be controlled by adjusting the surface treatment conditions of the particles.

[0055] The coverage of strontium titanate particles on the surface of the toner, as measured by X-ray photoelectron spectroscopy (ESCA), is preferably at least 5.0 area % and not more than 20.0 area %, and more preferably at least 8.0 area % and not more than 20.0 area %.

[0056] When the above-mentioned range is used for coverage, it is beneficial for the toner to gain charge from the initial stage of reuse, and it is easier to obtain effects on developing performance and fogging suppression in the initial stage of reuse. Coverage can be controlled by adjusting the shape and amount of strontium titanate particles, production conditions, and the properties of the toner particles.

[0057] The average roundness of the toner is at least 0.935 and not greater than 0.995. Preferably, the average roundness of the toner is at least 0.940 and not greater than 0.990.

[0058] When this range is used for the average roundness of the toner, developing performance can be improved and fogging can be suppressed. The average roundness of the toner can be controlled by adjusting production conditions.

[0059] The glass transition temperature (Tg) of the toner is preferably at least 50°C and not more than 70°C, and more preferably at least 52°C and not more than 68°C.

[0060] When the glass transition temperature (Tg) is within the aforementioned range, it is beneficial for the dispersion of strontium titanate particles on the surface of the toner particles. Therefore, a dispersion state closer to that of primary particles can be formed, resulting in improved coverage by the strontium titanate particles. Consequently, for long-term repeated use, developing performance can be further improved, and a higher level of suppression of both fogging and component contamination can be achieved.

[0061] For example, the glass transition temperature (Tg) can be controlled by adjusting the composition of the binder resin that constitutes the toner.

[0062] Perovskite-type strontium titanate particles are preferably produced using an atmospheric pressure heating reaction method that carries out the reaction at normal pressure, rather than using hydrothermal treatment in a pressurized vessel.

[0063] The inorganic acid antiflocculation product of the hydrolysis product of titanium compounds is used as a titanium oxide source, and a water-soluble acidic compound is used as a strontium source. The method can be exemplified by reacting the mixture of the titanium oxide and strontium sources at at least 60°C with the addition of an alkaline aqueous solution, followed by acid treatment.

[0064] In addition, the shape of strontium titanate particles can be controlled by applying dry mechanical treatment, and the Sb / Sa value can also be controlled by this method.

[0065] The following describes the atmospheric pressure heating reaction method.

[0066] The inorganic acid antiflocculation products of the hydrolysis products of titanium compounds can be used as titanium oxide sources.

[0067] Preferably, an antiflocculation product is used, which is produced by means of the sulfuric acid process and has an SO3 content of not more than 1.0% by mass, and preferably not more than 0.5% by mass, provided by adjusting the pH to at least 0.8 and not more than 1.5 with hydrochloric acid. This allows for the production of fine strontium titanate particles with excellent particle size distribution.

[0068] On the other hand, strontium nitrate and strontium chloride can be used as strontium sources. Alkali metal hydroxides can be used as alkaline aqueous solutions, and in particular, aqueous solutions of sodium hydroxide are preferred.

[0069] Factors affecting the particle size of the obtained strontium titanate particles in this production method include, for example, the mixing ratio of the titanium oxide source and the strontium source, the concentration of the titanium oxide source in the initial stage of the reaction, and the temperature and addition rate when adding the alkaline aqueous solution. These factors can be appropriately adjusted to obtain strontium titanate particles with the target particle size and particle size distribution. To prevent the formation of strontium carbonate during the reaction process, it is preferable to conduct the reaction under a nitrogen atmosphere to prevent the introduction of carbon dioxide gas.

[0070] The mixing ratio between the strontium source and the titanium oxide source during the reaction, in terms of Sr / Ti (molar ratio), is preferably at least 0.90 and not more than 1.40, and more preferably at least 1.05 and not more than 1.20.

[0071] Compared to the high water solubility of strontium sources, titanium oxide sources have low water solubility. As a result, when the Sr / Ti (molar ratio) is less than 0.90, the reaction product will not be strontium titanate alone, and unreacted titanium oxide will tend to remain.

[0072] The concentration of the titanium dioxide source in the initial stage of the reaction, based on TiO2, is preferably at least 0.050 mol / L and not more than 1.300 mol / L, and more preferably at least 0.080 mol / L and not more than 1.200 mol / L.

[0073] By using a higher concentration of titanium dioxide source in the initial stage of the reaction, smaller number-average particle size of strontium titanate particles can be obtained.

[0074] Regarding the temperature during the addition of the alkaline aqueous solution, products exhibiting better crystallinity are obtained as the temperature increases. However, since pressure vessels such as autoclaves are required above 100°C, from a practical point of view, a range of at least 60°C and no more than 100°C is advantageous.

[0075] Regarding the addition rate of the alkaline aqueous solution, a lower addition rate yields strontium titanate particles with a larger particle size, while a higher addition rate yields strontium titanate particles with a smaller particle size. The addition rate of the alkaline aqueous solution relative to the added raw material is preferably at least 0.001 eq / h and not more than 1.2 eq / h, and more preferably at least 0.002 eq / h and not more than 1.1 eq / h. This can be adjusted appropriately according to the desired particle size.

[0076] The following describes acid treatment. When the mixing ratio of strontium source to titanium oxide source, in terms of Sr / Ti (molar ratio), exceeds 1.40, the unreacted strontium source remaining after the reaction will react with carbon dioxide gas in the air to produce impurities such as strontium carbonate, and the particle size distribution tends to broaden. Furthermore, when impurities such as strontium carbonate remain on the surface, the implementation of uniform coating by the surface treatment agent is impaired due to the influence of the impurities during surface treatment to impart hydrophobicity. Therefore, acid treatment is preferable to remove unreacted strontium source once an alkaline aqueous solution is added.

[0077] Preferably, hydrochloric acid is used in the acid treatment to adjust the pH to at least 2.5 and no more than 7.0, while adjusting the pH to at least 4.5 and no more than 6.0 is more preferred.

[0078] Acids other than hydrochloric acid, such as nitric acid and acetic acid, can be used in acid treatment. However, when sulfuric acid is used, strontium sulfate, which has low water solubility, is easily produced.

[0079] The control of shape will now be described. The implementation of dry mechanical processing is also an example of how the shape of the aforementioned strontium titanate particles can be obtained.

[0080] For example, the following can be used: Hybridizer (Nara Machinery Co., Ltd.), Nobilta (Hosokawa Micron Corporation), Mechanofusion (Hosokawa Micron Corporation), and High Flex Gral (Earthtechnica Co., Ltd.). By processing strontium titanate particles with these devices, the Sb / Sa ratio can be easily controlled to be at least 1.80 and no greater than 2.30.

[0081] When mechanical processing is used to control the shape of strontium titanate particles, fine powder can be generated from the particles. To remove this fine powder, acid treatment is preferably performed after mechanical processing. Hydrochloric acid is used in this acid treatment, and the pH is preferably adjusted to at least 0.1 and no greater than 5.0. Acids other than hydrochloric acid, such as nitric acid and acetic acid, can be used as acids in the acid treatment. The mechanical processing for controlling the shape of the strontium titanate particles is preferably performed before any surface treatment of the strontium titanate particles.

[0082] To improve charge regulation and environmental stability, strontium titanate particles can be surface-treated with inorganic oxides such as SiO2 and Al2O3, or with hydrophobic agents such as titanium coupling agents, silane coupling agents, silicone oils, and fatty acid metal salts.

[0083] Silane coupling agents with functional groups such as amino and fluorine can be used as silane coupling agents in this paper.

[0084] Examples of fatty acid metal salts include zinc stearate, sodium stearate, calcium stearate, zinc laurate, aluminum stearate, and magnesium stearate. The same effect is obtained using stearic acid, for example, as a fatty acid.

[0085] Surface treatment methods can be exemplified by a wet method in which a hydrophobic agent is dissolved or dispersed in a solvent; strontium titanate particles are added thereto; and the solvent is removed while stirring.

[0086] Alternatively, a dry method can be used, in which strontium titanate particles are directly mixed with the treatment agent and the treatment is carried out while stirring.

[0087] The content of strontium titanate particles, relative to 100 parts by weight of toner particles, is preferably at least 0.05 parts by weight and not more than 5.0 parts by weight, and more preferably at least 0.1 parts by weight and not more than 5.0 parts by weight.

[0088] The production method of toner particles should be one that can control the average sphericity of the toner to provide at least 0.935 and no greater than 0.995, but is not particularly limited thereto. Examples in this paper are methods for directly producing toner particles in an aqueous medium (hereinafter also referred to as polymerization methods), such as suspension polymerization, interfacial polymerization, and dispersion polymerization. A pulverization method can also be used, and toner particles produced by pulverization can be subjected to thermosphericization treatment to adjust their average sphericity to within the aforementioned range.

[0089] Suspension polymerization is preferred in the foregoing. Toner particles produced by suspension polymerization have high transferability because the individual particles are uniformly approximately spherical and also exhibit a relatively uniform distribution of charge.

[0090] In suspension polymerization, toner particles are produced by dispersing a polymeric monomer composition, including polymeric monomers that can form binder resins, colorants, and waxes, in an aqueous medium to form particles of the polymeric monomer composition, and then polymerizing the polymeric monomers in the particles.

[0091] Toner particles can be toner particles with a core and a shell present on the surface of the core. This structure makes it possible to suppress charged defects caused by the core seeping into the surface of the toner particle.

[0092] The shell preferably contains at least one selected from the group consisting of polyester resin, styrene-acrylic copolymer and styrene-methacrylic copolymer, wherein the introduction of polyester resin is more preferred.

[0093] The amount of resin forming the shell is preferably at least 0.01 parts by weight and not more than 20.0 parts by weight, and more preferably at least 0.5 parts by weight and not more than 10.0 parts by weight, relative to 100 parts by weight of the resin forming the nucleus.

[0094] Using polyester resin in the shell facilitates the disintegration of strontium titanate particles added externally to the surface of the toner particles and promotes their dispersion. As a result, development performance can be further improved during long-term repeated use, and fogging and component contamination can be better suppressed during long-term repeated use.

[0095] The weight-average molecular weight of the polyester resin is preferably at least 5,000 and not more than 50,000. A weight-average molecular weight within the above range is beneficial for further improving the dispersibility of strontium titanate particles on the surface of the toner particles.

[0096] Vinyl-based polymerizable monomers are examples of polymerizable monomers capable of forming adhesive resins. Specific examples are as follows:

[0097] Styrene; styrene derivatives such as α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, and 2,4-dimethylstyrene; acrylic polymerizable monomers such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, and 2-ethylhexyl acrylate; methacrylic polymerizable monomers such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and tert-butyl methacrylate; esters of methylene aliphatic monocarboxylic acids; and vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, and vinyl formate.

[0098] Toner particles may contain charge control agents. It is known that charge control agents control toner particles to be negatively charged and charge control agents control toner particles to be positively charged, and one or more of various charge control agents may be used depending on the type and purpose of the toner.

[0099] An example of a charge control agent that controls the toner particles to have a negative charge is as follows:

[0100] Organometallic complexes (monoazo metal complexes, acetylacetone metal complexes); metal complexes and metal salts of aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids; aromatic monocarboxylic and polycarboxylic acids, and their metal salts, anhydrides and esters; and phenolic derivatives such as bisphenols. One of these may be used alone, or two or more may be used in combination.

[0101] In the foregoing, metal complexes and metal salts of aromatic hydroxycarboxylic acids that provide stable charged properties are preferred.

[0102] On the other hand, an example of a charge control agent that controls the toner particles to be positively charged is as follows:

[0103] Aniline black and its modified derivatives by fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium 1-hydroxy-4-naphthalenesulfonic acid and tetrabutylammonium tetrafluoroborate, and their analogues; onium salts such as phosphonium salts, and their lake pigments; triphenylmethane dyes and their lake pigments (examples of lake agents are phosphotungstic acid, phosphomolybdic acid, phosphotungstic acid, tannic acid, lauric acid, gallic acid, ferricyanide, and ferrocyanide compounds); and metal salts of higher fatty acids. One of these may be used alone, or two or more may be used in combination.

[0104] In the foregoing, aniline black compounds and quaternary ammonium salts are preferred.

[0105] Since the aforementioned strontium titanate particles are positively charged, it is more preferable to use a charge control agent that controls the toner particles to be negatively charged, as this improves the electrostatic adhesion between the toner particles and the strontium titanate particles.

[0106] The content of the charge control agent, relative to 100 parts by weight of the binder resin or the polymerizable monomer that can form the binder resin, is preferably at least 0.1 parts by weight and not more than 10.0 parts by weight.

[0107] The use of charge control resin is also a preferred embodiment. When the toner particles contain charge control resin, the negative charge on the surface of the toner particles is enhanced. As a result, the electrostatic adhesion to the positively charged strontium titanate particles is improved, which in turn hinders the migration of strontium titanate particles from the toner particles, improves developing performance during long-term repeated use, and helps to suppress fogging and component contamination during long-term repeated use.

[0108] The charge control resin is preferably a polymer with sulfonic acid functional groups. This polymer with sulfonic acid functional groups is a polymer containing sulfonic acid groups, sulfonate groups, or sulfonate groups. Among these, polymers containing sulfonic acid groups are preferred.

[0109] Specific examples described herein include homopolymers of monomers such as styrene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, vinyl sulfonic acid, or methacrylamide sulfonic acid, as well as copolymers of such monomers with another monomer. Polymers provided by converting the sulfonic acid groups in such polymers to sulfonate groups or by esterification can also be used. The glass transition temperature (Tg) of this charge-controlled resin is preferably at least 40°C and not greater than 90°C.

[0110] The content of the charge-controlled resin, relative to 100 parts by weight of the binder resin or the polymerizable monomer capable of forming the binder resin, is preferably at least 0.1 parts by weight and not more than 10.0 parts by weight. Furthermore, by using it in conjunction with a water-soluble polymerization initiator, the charge-controlled resin can provide further improvement in the charged state of the toner particles.

[0111] A (atomic %) is specified as the amount of carbon atoms present on the surface of the toner particles as measured by X-ray photoelectron spectroscopy, and E (atomic %) is specified as the amount of sulfur atoms present on the surface of the toner particles as measured by X-ray photoelectron spectroscopy. E / A preferably satisfies the following formula (1) and more preferably satisfies the following formula (1)′.

[0112] For example, the E / A ratio can be adjusted by introducing the aforementioned charge control resin into the toner particles.

[0113] 3×10 –4 ≤E / A≤50×10 –4 (1)

[0114] 5×10 –4 ≤E / A≤30×10 –4 (1)′

[0115] By employing the aforementioned range, the electrostatic adhesion between toner particles and strontium titanate particles is further increased in E / A, and the migration of strontium titanate particles from the toner particles is hindered. Furthermore, because this also exhibits excellent resistance adjustment, development performance is further improved, and it helps to more thoroughly suppress fogging and component contamination.

[0116] Toner particles may contain wax. Examples of such wax include:

[0117] Petroleum-based waxes such as paraffin wax, microcrystalline wax, and petrolatum, and their derivatives; lignite wax and its derivatives; hydrocarbon waxes produced by the Fischer-Tropsch process, and their derivatives; polyolefin waxes such as polyethylene and polypropylene, and their derivatives; natural waxes such as carnauba wax and candelilla wax, and their derivatives; higher fatty alcohols; fatty acids such as stearic acid and palmitic acid; acid amide waxes; and ester waxes.

[0118] The derivatives described herein may be exemplified as oxides and block copolymers with vinyl monomers, as well as grafted modified compounds.

[0119] The wax content, relative to 100 parts by weight of adhesive resin or polymerizable monomers that can form adhesive resin, is preferably at least 2.0 parts by weight and not more than 15.0 parts by weight, and more preferably at least 2.0 parts by weight and not more than 10.0 parts by weight.

[0120] The toner particles may contain coloring agents.

[0121] The black colorant can be, for example, carbon black, a magnetic material, or a black colorant provided by matching the colors of the yellow, magenta, and cyan colorants described below to give black.

[0122] Examples of yellow colorants include condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds.

[0123] Specific examples are CI Pigment Yellow 12, 13, 14, 15, 17, 62, 73, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 128, 129, 138, 147, 150, 151, 154, 155, 168, 180, 185 and 214.

[0124] Examples of magenta colorants include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindole compounds, and perylene compounds.

[0125] Specific examples include CI Pigment Red 2, 3, 5, 6, 7, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 122, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221, 238, 254 and 269, and CI Pigment Violet 19.

[0126] Examples of cyan colorants include copper phthalocyanine compounds and their derivatives, anthraquinone compounds, and basic dye lake compounds.

[0127] Specific examples are CI Pigment Blue 1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62 and 66.

[0128] These colorants can be used individually or in mixtures, and they can also be used in a solid solution state.

[0129] Colorants can be selected by considering factors such as hue angle, chroma, brightness, lightfastness, OHP transparency, and dispersibility in toner particles.

[0130] The colorant content, relative to 100 parts by weight of binder resin or polymerizable monomers that can form binder resin, is preferably at least 1 part by weight and not more than 20 parts by weight.

[0131] Toner particles can also be made into magnetic toner particles by introducing magnetic materials as colorants. Examples of magnetic materials include iron oxides such as magnetite, hematite, and ferrite; metals such as iron, cobalt, and nickel; and alloys and mixtures of these metals with metals such as aluminum, copper, magnesium, tin, zinc, beryllium, calcium, manganese, selenium, titanium, tungsten, and vanadium.

[0132] The magnetic material is preferably a magnetic material that has undergone surface modification.

[0133] When preparing magnetic toners via polymerization, it is preferable to perform hydrophobic treatment on the magnetic material using a surface modifier that does not inhibit polymerization. Examples of such surface modifiers include silane coupling agents and titanium coupling agents.

[0134] The number-average particle size of the magnetic material is preferably not greater than 2.0 μm, and more preferably at least 0.1 μm and not greater than 0.5 μm.

[0135] The content of the magnetic material, relative to 100 parts by weight of the adhesive resin or the polymerizable monomer that can form the adhesive resin, is preferably at least 20 parts by weight and not more than 200 parts by weight, and more preferably at least 40 parts by weight and not more than 150 parts by weight.

[0136] On the other hand, the following describes an example of a production method for producing colorant granules by pulverization.

[0137] In the raw material mixing step, materials that constitute the colorant particles, such as binder resin, colorant and wax, are measured in a specified amount and blended.

[0138] Examples of mixing devices include twin-cone mixers, V-type mixers, drum mixers, super mixers, FM mixers, nut mixers, and Mechano Hybrid (Nippon Coke & Engineering Co., Ltd.).

[0139] The mixed materials are then melt-kneaded to disperse colorants and waxes in the binder resin. In the melt-kneading step, intermittent kneaders such as pressure kneaders or Banbury mixers, or continuous kneaders, can be used. Single-screw and twin-screw extruders are the mainstream choice in this paper because they offer the advantage of supporting continuous production. Examples include the KTK twin-screw extruder (Kobe Steel, Ltd.), the TEM twin-screw extruder (Toshiba Machine Co., Ltd.), the PCM kneader (Ikegai Corporation), the twin-screw extruder (KCK), Co-Kneader (Buss AG), and Kneadex (Nippon Coke & Engineering Co., Ltd.). The resin composition provided by melt-kneading can be calendered, for example, using a twin-roll mill, and cooled, for example, with water, in the cooling step.

[0140] Then, in the pulverizing step, the resulting cooled material is pulverized until the desired particle size is achieved.

[0141] In the pulverizing step, coarse pulverization is performed using a pulverizer, such as a crusher, hammer mill, or feather pulverizer. Fine pulverization can then be performed using a fine pulverizer such as the Kryptron System (Kawasaki Heavy Industries, Ltd.), Super Rotor (Nisshin Engineering Inc.), or Turbo Mill (Freund-Turbo Corporation), or using an air jet system.

[0142] The colorant particles are then obtained by grading using screening equipment or classifiers, such as inertial grading systems like Elbow Jet (Nittetsu Mining Co., Ltd.), centrifugal grading systems like Turboplex (Hosokawa Micron Corporation), and TSP Separator (Hosokawa Micron Corporation), or Faculty (Hosokawa Micron Corporation), as needed.

[0143] Toner particles can also be spheroidized. For example, after pulverization, toner particles can be spheroidized using a Hybridization System (Nara Machinery Co., Ltd.), a Mechanofusion System (Hosokawa Micron Corporation), a Faculty (Hosokawa Micron Corporation), or a Meteo Rainbow MRType (Nippon Pneumatic Mfg.Co., Ltd.).

[0144] Toners can be obtained by mixing strontium titanate particles and other external additives as needed with toner particles. Examples of mixers used for mixing external additives include FM mixers (Nippon Coke & Engineering Co., Ltd.), super mixers (Kawata Mfg. Co., Ltd.), Nobilta (Hosokawa Micron Corporation), and Hybridizers (Nara Machinery Co., Ltd.).

[0145] After the external additives are mixed, coarse particles can be screened out. Examples of screening equipment used for this purpose include:

[0146] Ultrasonic (Koei Sangyo Co., Ltd.), Rezona Sieve and Gyro-Sifter (Tokuju Corporation), Vibrasonic System (Dalton Corporation), Sonilean (Sintokogio, Ltd.), Turbo Screener (Freund-Turbo Corporation), and Microsifter (Makino Mfg.Co., Ltd.).

[0147] Toners may contain external additives other than strontium titanate particles. In particular, flow improvers may be added as external additives to improve the flowability and charge-carrying properties of the toner.

[0148] For example, the following can be used as such a flow improver:

[0149] Fluorine resin powders such as vinylidene fluoride fine powder and polytetrafluoroethylene fine powder; silica fine particles such as wet-processed silica and dry-processed silica; titanium oxide fine particles; aluminum oxide fine particles; hydrophobic fine particles provided by surface treatment of the above fine particles using hydrophobicating agents such as silane compounds, titanium coupling agents or silicone oils; oxides such as zinc oxide and tin oxide; composite oxides such as barium titanate, calcium titanate, strontium zirconate and calcium zirconate; and carbonate compounds such as calcium carbonate and magnesium carbonate.

[0150] In the foregoing, the preferred type is fine particles of dry-processed silica, also known as dry silica or fumed silica, which are fine particles produced by the fumed oxidation of silicon halide compounds.

[0151] This dry preparation method, for example, uses the thermal decomposition and oxidation reaction of silicon tetrachloride gas in an oxyhydrogen flame, wherein the basic reaction formula is as follows.

[0152] SiCl4 + 2H2 + O2 → SiO2 + 4HCl

[0153] In this production process, silicon halide compounds can also be combined with other metal halides such as aluminum chloride or titanium chloride to obtain composite fine particles of silicon dioxide and other metal oxides. The concept of silicon dioxide fine particles also includes these composite fine particles.

[0154] The flowability improver preferably has a number average particle size of at least 5 nm and no more than 30 nm for primary particles, as this enables high charge-carrying properties and high flowability.

[0155] More preferably, the silica fine particles are hydrophobic silica fine particles provided by performing surface treatment using the hydrophobic agent described above.

[0156] Flowability improvers preferably have a flowability of at least 30m 2 / g and not more than 300m 2 The specific surface area / g was measured by nitrogen adsorption using the BET method.

[0157] The content of the flowability improver, relative to 100 parts by weight of toner particles, as the total amount of the flowability improver, is preferably at least 0.01 parts by weight and not more than 3.0 parts by weight.

[0158] The following describes methods for measuring various properties related to toners and other materials.

[0159] The colorant was used as a sample to measure the properties of strontium titanate particles.

[0160] When measuring the properties of strontium titanate particles or toner particles by adding strontium titanate particles to the toner from external additives, the measurements are taken after separating the strontium titanate particles and other external additives from the toner.

[0161] The colorant is ultrasonically dispersed in methanol to separate strontium titanate particles and other external additives, and then allowed to stand for 24 hours. The settled colorant particles are separated from the strontium titanate particles and other external additives dispersed in the supernatant, recovered, and completely dried to separate the colorant particles. The supernatant can also be centrifuged to separate the strontium titanate particles.

[0162] Measurement of the number-average particle size of primary strontium titanate particles

[0163] The number-average particle size of strontium titanate particles was measured using a JEM-2800 transmission electron microscope (JEOL Ltd.).

[0164] The colorant containing externally added strontium titanate particles was observed, and the major diameter of 100 randomly selected strontium titanate particles was measured in a field of view with a maximum magnification of 200,000x, thereby determining the number-average particle size. The magnification can be adjusted appropriately according to the size of the strontium titanate particles.

[0165] Measurement of diffraction peaks of strontium titanate particles

[0166] The diffraction peaks of strontium titanate particles were measured using a SmartLab powder X-ray diffractometer (Rigaku Corporation, sample horizontal high-intensity X-ray diffractometer).

[0167] Calculate Sb / Sa from the obtained peaks using the "PDXL2 (version 2.2.2.0)" analysis software included with the instrument.

[0168] The toner or strontium titanate particles separated from the toner were used as measurement samples, and measurements were performed using the following procedure. The produced strontium titanate particles were also measured in the examples given below.

[0169] (Sample preparation)

[0170] Measurements were performed after the sample was uniformly introduced into a 0.5 mm diameter Boro-Silicate capillary (W. Muller USA Inc.).

[0171] (Measurement conditions)

[0172] · Tube: Cu

[0173] Optical system: CBO-E

[0174] • Sample stage: Capillary sample stage

[0175] • Detector: D / tex Ultra250 detector

[0176] Voltage: 45kV

[0177] Current: 200mA

[0178] • Starting angle: 10°

[0179] Final angle: 90°

[0180] • Sampling width: 0.02°

[0181] • Speed ​​measurement time setting: 10

[0182] • IS: 1mm

[0183] RS1: 20mm

[0184] RS2: 20mm

[0185] Attenuator: Open

[0186] • Capillary rotation speed setting: 100

[0187] For other conditions, use the initial settings on the instrument.

[0188] (analyze)

[0189] First, the obtained peaks are separated using the "PDXL2" software included with the instrument. Peak separation is determined by optimizing the peaks using the "segmented Voigt function" selectable with PDXL, and the obtained integrated intensity values ​​are used.

[0190] This determines the 2θ value of the diffraction peak and its area. Sb / Sa is calculated from the peak area at the specified 2θ value. When a large deviation occurs between the calculated peak separation results and the actual measured spectrum, this paper addresses this by manually setting a baseline and making adjustments to ensure consistency between the calculated results and the actual measured spectrum.

[0191] Measurement of Sr / Ti (molar ratio) of strontium titanate particles

[0192] The Sr and Ti contents in strontium titanate particles were measured using a wavelength dispersive X-ray fluorescence analyzer (Axios Advanced, PANalytical BV).

[0193] Weigh 1g of sample onto a special membrane, recommended by PANalytical BV, which is affixed to a special powder measuring cup, and measure the elements from Na to U in strontium titanate particles under helium atmosphere and atmospheric pressure using the FP method.

[0194] In this case, assuming that all detected elements exist as oxides, and using their total mass as 100%, the SrO content and TiO2 content (mass%) are determined using Spectra Evaluation (version 5.0L) software as values ​​in oxides relative to the total mass.

[0195] Subsequently, the Sr / Ti (mass ratio) was obtained by subtracting oxygen from the quantitative result, and then the Sr / Ti (molar ratio) was obtained from the atomic weight of each element.

[0196] The sample for use is obtained by separating strontium titanate particles from the toner. In the examples given below, the produced strontium titanate particles are also measured.

[0197] <Measurement of the average sphericity of primary strontium titanate particles>

[0198] The average sphericity of primary strontium titanate particles was measured using a JEM-2800 transmission electron microscope (JEOL Ltd.).

[0199] The colorant with added strontium titanate particles was observed and measured as follows.

[0200] Adjust the magnification of the observation appropriately according to the size of the strontium titanate particles.

[0201] Using Image-Pro Plus 5.1J (MediaCybernetics, Inc.) image processing software, the circumference of 100 randomly selected strontium titanate particles was measured within a field of view magnified up to 200,000x, and the average roundness was calculated. The circumference equivalent diameter is the diameter of a circle with an area equal to the projected area of ​​the particle.

[0202] Calculate the roundness using the following formula, and take the average roundness as its arithmetic mean.

[0203] (Formula) Circularity = Equivalent diameter of circle × 3.14 / circumference of particle

[0204] STEM-EDS measurements confirmed that the external additive was strontium titanate.

[0205] The measurement conditions are as follows.

[0206] JEM-2800 Transmission Electron Microscope: Accelerating Voltage = 200kV

[0207] EDS detector: JED-2300T (JEOL Ltd., element area = 100mm²) 2 )

[0208] EDS Analyzer: Noran System 7 (Thermo Fisher Scientific Inc.)

[0209] X-ray storage rate: 10,000 to 15,000 cps

[0210] Dead time: EDS analysis was performed using an adjustment to provide 20% to 30% of the electron beam dose (cumulative count = 100 or measurement time = 5 minutes).

[0211] <Measurement of hydrophobicity (volume %) of strontium titanate particles>

[0212] The hydrophobicity (volume %) of strontium titanate particles was measured using a WET-100P powder wettability tester (Rhesca Co., Ltd.).

[0213] A fluoropolymer-coated spindle-shaped stirring rod with a length of 25 mm and a maximum diameter of 8 mm is introduced into a cylindrical glass container with a diameter of 5 cm and a thickness of 1.75 mm.

[0214] A 70 ml methanol-water solution consisting of 50 vol% methanol and 50 vol% water was introduced into a cylindrical glass container. Then, 0.5 g of strontium titanate particles separated from the toner was added, and the container was placed in a powder wettability tester.

[0215] While stirring with a magnetic stirrer at 200 rpm, methanol was added to the liquid at a rate of 0.8 mL / min using a powder wettability tester.

[0216] The transmittance of light at a wavelength of 780 nm was measured, and the hydrophobicity was taken as the value given by the volume percentage of methanol (=(volume of methanol / volume of mixture)×100) when the transmittance reached 50%. The initial volume ratio between methanol and water can be appropriately adjusted according to the hydrophobicity of the sample. Additionally, the produced strontium titanate particles were also measured in the following examples.

[0217] <Measurement of the coverage of strontium titanate particles on the surface of the toner>

[0218] After measuring the toner under the following conditions, the coverage of the strontium titanate particles on the toner surface is calculated using the following formula (2) (simply given as "coverage" in Table 3).

[0219] • Measuring instrument: Quantum 2000 X-ray photoelectron spectrometer (Ulvac-Phi, Inc.)

[0220] • X-ray source: Monochromatic Al Kα

[0221] • X-ray settings:

[0222] • Photoelectron extraction angle: 45°

[0223] Neutralization conditions: Combined use of neutralization gun and ion gun

[0224] • Analysis area: 300×200μm

[0225] ·Pass energy: 58.70eV

[0226] • Step size: 0.125 eV

[0227] • Analysis software: MultiPak (Physical Electronics Inc.)

[0228] The quantitative values ​​of Ti atoms were calculated using the Ti 2p peak (BE 452 to 468 eV). The quantitative value of element Ti obtained in this way is designated as Z1.

[0229] Then, as described above, elemental analysis was performed on the strontium titanate particles themselves, and the quantitative value of element Ti obtained therefrom was designated as Z2. The coverage of the strontium titanate particles on the toner surface was calculated using the following formula (2).

[0230] Coverage rate = Z1 / Z2 × 100 (2)

[0231] <Measurement of the average roundness of toner>

[0232] The average roundness of the toner was measured using an FPIA-3000 (Sysmex Corporation) flow cytometer and the measurement and analysis conditions used during the calibration job.

[0233] The specific measurement method is as follows.

[0234] First, introduce approximately 20 mL of deionized water, pre-treated to remove solid impurities, into a glass container. Add approximately 0.2 mL of a diluent prepared by diluting "Contaminon N" (a 10% by mass aqueous solution of a neutral pH 7 cleaner for cleaning precision measuring instruments, comprising nonionic surfactants, anionic surfactants, and organic detergent builders, WakoPure Chemical Industries, Ltd.) with deionized water at approximately 3 times (by mass) as a dispersant.

[0235] Add approximately 0.02 g of the measurement sample and disperse it using an ultrasonic disperser for 2 minutes to provide a dispersion for measurement. During this process, cool appropriately to maintain the temperature of the dispersion between 10°C and 40°C.

[0236] A benchtop ultrasonic cleaner / dispersant with an oscillation frequency of 50 kHz and a power output of 150 W (e.g., “VS-150” (Velvo-Clear)) was used as the ultrasonic disperser, and a specified amount of deionized water was introduced into the tank, and about 2 mL of Contaminon N was added to the tank.

[0237] A flow cytometer equipped with a "LUCPLFLN" objective lens (20x, aperture number: 0.40) was used for measurement, and a "PSE-900A" (Sysmex Corporation) particle sheath was used as the sheath fluid. The dispersion prepared according to the above procedure was introduced into the flow cytometer, and 2,000 toners were measured in HPF measurement mode according to the total count mode.

[0238] The average roundness of the toner was determined by setting the binarization threshold to 85% and limiting the analytical particle size to a round equivalent diameter of at least 1.977 μm and less than 39.54 μm during particle analysis.

[0239] For this measurement, autofocus adjustment is performed before the measurement begins using standard latex particles (e.g., “RESEARCHAND TEST PARTICLES Latex Microsphere Suspensions 5100A”, Duke Scientific Corporation, diluted with deionized water). Thereafter, focus adjustment is preferably performed every two hours after the measurement begins.

[0240] In this embodiment, the flow cytometer used for particle imaging has been calibrated by Sysmex Corporation, and a calibration certificate has been issued by Sysmex Corporation. Measurements were performed under the same measurement and analysis conditions as when the calibration certificate was received, except that the analyzed particle size was limited to a circular equivalent diameter of at least 1.977 μm and less than 39.54 μm.

[0241] <Measurement of the glass transition temperature (Tg) of toners>

[0242] The glass transition temperature of toners was measured using a Q1000 (TA Instruments) differential scanning calorimeter based on ASTM D3418-82.

[0243] Temperature calibration in the instrument's detection section is performed using the melting points of indium and zinc, and heat calibration is performed using the heat of fusion of indium.

[0244] Specifically, approximately 5 mg of sample is accurately weighed and introduced into an aluminum pan. The measurement is performed using an empty aluminum pan as a reference at a heating rate of 10 °C / min within a measurement temperature range of at least 30 °C and no more than 200 °C.

[0245] The measurement was performed by first raising the temperature to 200°C, then cooling it to 30°C at a rate of 10°C / min, and then reheating it at a rate of 10°C / min.

[0246] Using the DSC curve obtained during the second heating process, the glass transition temperature (Tg) is taken as the intersection point between the DSC curve and the line connecting the midpoints of the baselines before and after the specific heat change.

[0247] <Measurement of E / A on the Surface of Toner Particles>

[0248] Based on the analysis results of the composition analysis of the toner particle surface using a "Type 1600S" X-ray photoelectron spectroscopy (ESCA) (Physical Electronics Industries, Inc.), the ratio (E / A) of the amount of sulfur atoms (E (atomic%)) to the amount of carbon atoms (A (atomic%)) present on the toner particle surface was determined.

[0249] The measurement conditions were an X-ray source of MgKα (400W) and Spectral region.

[0250] The surface atomic concentration (atomic %) was calculated from the measured peak intensity of each atom using a relative sensitivity factor provided by Physical Electronics Industries, Inc., and then taken as the amount of each atom.

[0251] The measurement range for the peaks used to measure each atom is 283 to 293 eV for carbon atoms and 166 to 172 eV for sulfur atoms.

[0252] Example

[0253] The invention is described in more detail using the examples and comparative examples provided below; however, the invention is by no means limited thereto. Unless otherwise specifically stated, the number of parts in the examples and comparative examples is based on mass in all instances.

[0254] The following describes the production of strontium titanate particles. Table 1 shows the properties of strontium titanate particles 1 to 15.

[0255] <Strontium titanate particle production example 1>

[0256] The metatitanic acid produced via the sulfuric acid process was subjected to iron removal and bleaching; subsequently, desulfurization was carried out by adding an aqueous sodium hydroxide solution to adjust the pH to 9.0; then, it was neutralized to pH 5.8 with hydrochloric acid and subjected to filtration and washing. Once washing was complete, water was added to the filter cake to produce a slurry with a TiO2 concentration of 1.85 mol / L, and then anti-flocculation treatment was carried out by adjusting the pH to 1.0 with the addition of hydrochloric acid.

[0257] 1.88 mol of desulfurization and antiflocculation metatitanic acid (based on TiO2) was recovered and introduced into a 3L reactor. 2.16 mol of strontium chloride aqueous solution was added to the antiflocculation metatitanic acid slurry to make the Sr / Ti (molar ratio) 1.15, and then the TiO2 concentration was adjusted to 1.039 mol / L.

[0258] Then, while stirring and mixing, the mixture was heated to 90°C, and after 45 minutes, 440 mL of 10 mol / L sodium hydroxide aqueous solution was added. The mixture was then stirred at 95°C for 1 hour to complete the reaction.

[0259] The reaction slurry was cooled to 50°C; hydrochloric acid was added until the pH reached 5.0; and stirring was continued for 20 minutes. The resulting precipitate was washed by decantation, separated by filtration, and then dried in atmospheric air at 120°C for 8 hours.

[0260] Then, 300g of the dried product was introduced into a dry powder compounding apparatus (Nobilta NOB-130, Hosokawa Micron Corporation). It was processed for 10 minutes at a processing temperature of 30°C and a rotating blade speed of 90m / sec.

[0261] Hydrochloric acid was added to the dried product until the pH reached 0.1, and stirring was continued for 1 hour. The resulting precipitate was washed by decantation.

[0262] The slurry containing the precipitate was adjusted to 40°C; the pH was adjusted to 2.5 by adding hydrochloric acid; n-octyltriethoxysilane was added in an amount of 4.0% by mass relative to the solid content; and stirring was continued and maintained for 10 hours. The pH was adjusted to 6.5 by adding 5 mol / L sodium hydroxide solution, and stirring was continued for 1 hour. The filter cake obtained by filtration and washing was then dried at 120°C in atmospheric conditions for 8 hours to obtain strontium titanate particles 1. Figure 1 The image shows a transmission electron microscope image of strontium titanate particle 1.

[0263] <Production Example of Strontium Titanate Particles>

[0264] The metatitanic acid produced via the sulfuric acid process was subjected to iron removal and bleaching; subsequently, desulfurization was carried out by adding an aqueous sodium hydroxide solution to adjust the pH to 9.0; then, it was neutralized to pH 5.8 with hydrochloric acid and subjected to filtration and washing. Once washing was complete, water was added to the filter cake to produce a slurry with a TiO2 concentration of 1.85 mol / L, and then anti-flocculation treatment was carried out by adjusting the pH to 1.0 with the addition of hydrochloric acid.

[0265] 1.88 mol of desulfurization and antiflocculation metatitanic acid (based on TiO2) was recovered and introduced into a 3L reactor. 2.16 mol of strontium chloride aqueous solution was added to the antiflocculation metatitanic acid slurry to make the Sr / Ti (molar ratio) 1.15, and then the TiO2 concentration was adjusted to 1.083 mol / L.

[0266] Then, while stirring and mixing, the mixture was heated to 90°C, and after 45 minutes, 440 mL of 10 mol / L sodium hydroxide aqueous solution was added. The mixture was then stirred at 95°C for 1 hour to complete the reaction.

[0267] The reaction slurry was cooled to 50°C; hydrochloric acid was added until the pH reached 5.0; and stirring was continued for 20 minutes. The resulting precipitate was washed by decantation, separated by filtration, and then dried in atmospheric air at 120°C for 8 hours.

[0268] Then, 300g of the dried product was introduced into a dry powder compounding apparatus (Nobilta NOB-130, Hosokawa Micron Corporation). It was processed for 10 minutes at a processing temperature of 30°C and a rotating blade speed of 90m / sec.

[0269] Hydrochloric acid was added to the dried product until the pH reached 0.1, and stirring was continued for 1 hour. The resulting precipitate was washed by decantation.

[0270] The slurry containing the precipitate was adjusted to 40°C; the pH was adjusted to 2.5 by adding hydrochloric acid; n-octyltriethoxysilane was added in an amount of 4.0% by mass relative to the solid content; and stirring was continued and maintained for 10 hours. The pH was adjusted to 6.5 by adding 5 mol / L sodium hydroxide solution, and stirring was continued for 1 hour. The filter cake obtained by filtration and washing was then dried at 120°C in atmospheric conditions for 8 hours to obtain strontium titanate particles 2.

[0271] <Strontium titanate particle production example 3>

[0272] The metatitanic acid produced via the sulfuric acid process was subjected to iron removal and bleaching; subsequently, desulfurization was carried out by adding an aqueous sodium hydroxide solution to adjust the pH to 9.0; then, it was neutralized to pH 5.8 with hydrochloric acid and subjected to filtration and washing. Once washing was complete, water was added to the filter cake to produce a slurry with a TiO2 concentration of 1.85 mol / L, and then anti-flocculation treatment was carried out by adjusting the pH to 1.0 with the addition of hydrochloric acid.

[0273] 1.88 mol of desulfurization and antiflocculation metatitanic acid (based on TiO2) was recovered and introduced into a 3L reactor. 2.16 mol of strontium chloride aqueous solution was added to the antiflocculation metatitanic acid slurry to make the Sr / Ti (molar ratio) 1.15, and then the TiO2 concentration was adjusted to 1.015 mol / L.

[0274] Then, while stirring and mixing, the mixture was heated to 90°C, and after 45 minutes, 440 mL of 10 mol / L sodium hydroxide aqueous solution was added. The mixture was then stirred at 95°C for 1 hour to complete the reaction.

[0275] The reaction slurry was cooled to 50°C; hydrochloric acid was added until the pH reached 5.0; and stirring was continued for 20 minutes. The resulting precipitate was washed by decantation, separated by filtration, and then dried in atmospheric air at 120°C for 8 hours.

[0276] Then, 300g of the dried product was introduced into a dry powder compounding apparatus (Nobilta NOB-130, Hosokawa Micron Corporation). It was processed for 10 minutes at a processing temperature of 30°C and a rotating blade speed of 90m / sec.

[0277] Hydrochloric acid was added to the dried product until the pH reached 0.1, and stirring was continued for 1 hour. The resulting precipitate was washed by decantation.

[0278] The slurry containing the precipitate was adjusted to 40°C; the pH was adjusted to 2.5 by adding hydrochloric acid; n-octyltriethoxysilane was added in an amount of 4.0% by mass relative to the solid content; and stirring was continued and maintained for 10 hours. The pH was adjusted to 6.5 by adding 5 mol / L sodium hydroxide solution, and stirring was continued for 1 hour. The filter cake obtained by filtration and washing was then dried at 120°C in atmospheric conditions for 8 hours to obtain strontium titanate particles 3.

[0279] <4 Production Examples of Strontium Titanate Particles>

[0280] The metatitanic acid produced via the sulfuric acid process was subjected to iron removal and bleaching; subsequently, desulfurization was carried out by adding an aqueous sodium hydroxide solution to adjust the pH to 9.0; then, it was neutralized to pH 5.8 with hydrochloric acid and subjected to filtration and washing. Once washing was complete, water was added to the filter cake to produce a slurry with a TiO2 concentration of 1.85 mol / L, and then anti-flocculation treatment was carried out by adjusting the pH to 1.0 with the addition of hydrochloric acid.

[0281] 1.88 mol of desulfurization and antiflocculation metatitanic acid (based on TiO2) was recovered and introduced into a 3L reactor. 2.16 mol of strontium chloride aqueous solution was added to the antiflocculation metatitanic acid slurry to make the Sr / Ti (molar ratio) 1.15, and then the TiO2 concentration was adjusted to 0.988 mol / L.

[0282] Then, while stirring and mixing, the mixture was heated to 90°C, and after 45 minutes, 440 mL of 10 mol / L sodium hydroxide aqueous solution was added. The mixture was then stirred at 95°C for 1 hour to complete the reaction.

[0283] The reaction slurry was cooled to 50°C; hydrochloric acid was added until the pH reached 5.0; and stirring was continued for 20 minutes. The resulting precipitate was washed by decantation, separated by filtration, and then dried in atmospheric air at 120°C for 8 hours.

[0284] Then, 300g of the dried product was introduced into a dry powder compounding apparatus (Nobilta NOB-130, Hosokawa Micron Corporation). It was processed for 10 minutes at a processing temperature of 30°C and a rotating blade speed of 90m / sec.

[0285] Hydrochloric acid was added to the dried product until the pH reached 0.1, and stirring was continued for 1 hour. The resulting precipitate was washed by decantation.

[0286] The slurry containing the precipitate was adjusted to 40°C; the pH was adjusted to 2.5 by adding hydrochloric acid; n-octyltriethoxysilane was added in an amount of 4.0% by mass relative to the solid content; and stirring was continued and maintained for 10 hours. The pH was adjusted to 6.5 by adding 5 mol / L sodium hydroxide solution, and stirring was continued for 1 hour. The filter cake obtained by filtration and washing was then dried at 120°C in atmospheric conditions for 8 hours to obtain strontium titanate particles 4.

[0287] <5 Production Examples of Strontium Titanate Particles>

[0288] The metatitanic acid produced via the sulfuric acid process was subjected to iron removal and bleaching; subsequently, desulfurization was carried out by adding an aqueous sodium hydroxide solution to adjust the pH to 9.0; then, it was neutralized to pH 5.8 with hydrochloric acid and subjected to filtration and washing. Once washing was complete, water was added to the filter cake to produce a slurry with a TiO2 concentration of 1.85 mol / L, and then anti-flocculation treatment was carried out by adjusting the pH to 1.0 with the addition of hydrochloric acid.

[0289] 1.88 mol of desulfurization and antiflocculation metatitanic acid (based on TiO2) was recovered and introduced into a 3L reactor. 2.16 mol of strontium chloride aqueous solution was added to the antiflocculation metatitanic acid slurry to make the Sr / Ti (molar ratio) 1.15, and then the TiO2 concentration was adjusted to 1.039 mol / L.

[0290] Then, while stirring and mixing, the mixture was heated to 90°C, and after 45 minutes, 440 mL of 10 mol / L sodium hydroxide aqueous solution was added. The mixture was then stirred at 95°C for 1 hour to complete the reaction.

[0291] The reaction slurry was cooled to 50°C; hydrochloric acid was added until the pH reached 5.0; and stirring was continued for 20 minutes. The resulting precipitate was washed by decantation, separated by filtration, and then dried in atmospheric air at 120°C for 8 hours.

[0292] Then, 300g of the dried product was introduced into a dry powder compounding apparatus (Nobilta NOB-130, Hosokawa Micron Corporation). It was processed for 15 minutes at a processing temperature of 30°C and a rotating blade speed of 90m / sec.

[0293] Hydrochloric acid was added to the dried product until the pH reached 0.1, and stirring was continued for 1 hour. The resulting precipitate was washed by decantation.

[0294] The slurry containing the precipitate was adjusted to 40°C; the pH was adjusted to 2.5 by adding hydrochloric acid; n-octyltriethoxysilane was added in an amount of 4.0% by mass relative to the solid content; and stirring was continued and maintained for 10 hours. The pH was adjusted to 6.5 by adding 5 mol / L sodium hydroxide solution, and stirring was continued for 1 hour. The filter cake obtained by filtration and washing was then dried at atmospheric temperature at 120°C for 8 hours to obtain strontium titanate particles.

[0295] <Strontium titanate particle production example 6>

[0296] The metatitanic acid produced via the sulfuric acid process was subjected to iron removal and bleaching; subsequently, desulfurization was carried out by adding an aqueous sodium hydroxide solution to adjust the pH to 9.0; then, it was neutralized to pH 5.8 with hydrochloric acid and subjected to filtration and washing. Once washing was complete, water was added to the filter cake to produce a slurry with a TiO2 concentration of 1.85 mol / L, and then anti-flocculation treatment was carried out by adjusting the pH to 1.0 with the addition of hydrochloric acid.

[0297] 1.88 mol of desulfurization and antiflocculation metatitanic acid (based on TiO2) was recovered and introduced into a 3L reactor. 2.16 mol of strontium chloride aqueous solution was added to the antiflocculation metatitanic acid slurry to make the Sr / Ti (molar ratio) 1.15, and then the TiO2 concentration was adjusted to 1.039 mol / L.

[0298] Then, while stirring and mixing, the mixture was heated to 90°C, and after 45 minutes, 440 mL of 10 mol / L sodium hydroxide aqueous solution was added. The mixture was then stirred at 95°C for 1 hour to complete the reaction.

[0299] The reaction slurry was cooled to 50°C; hydrochloric acid was added until the pH reached 5.0; and stirring was continued for 20 minutes. The resulting precipitate was washed by decantation, separated by filtration, and then dried in atmospheric air at 120°C for 8 hours.

[0300] Then, 300g of the dried product was introduced into a dry powder compounding apparatus (Nobilta NOB-130, Hosokawa Micron Corporation). It was processed for 5 minutes at a processing temperature of 30°C and a rotating blade speed of 90m / sec.

[0301] Hydrochloric acid was added to the dried product until the pH reached 0.1, and stirring was continued for 1 hour. The resulting precipitate was washed by decantation.

[0302] The slurry containing the precipitate was adjusted to 40°C; the pH was adjusted to 2.5 by adding hydrochloric acid; n-octyltriethoxysilane was added in an amount of 4.0% by mass relative to the solid content; and stirring was continued and maintained for 10 hours. The pH was adjusted to 6.5 by adding 5 mol / L sodium hydroxide solution, and stirring was continued for 1 hour. The filter cake obtained by filtration and washing was then dried at 120°C in atmospheric conditions for 8 hours to obtain strontium titanate particles 6.

[0303] <Strontium titanate particle production example 7>

[0304] The metatitanic acid produced via the sulfuric acid process was subjected to iron removal and bleaching; subsequently, desulfurization was carried out by adding an aqueous sodium hydroxide solution to adjust the pH to 9.0; then, it was neutralized to pH 5.8 with hydrochloric acid and subjected to filtration and washing. Once washing was complete, water was added to the filter cake to produce a slurry with a TiO2 concentration of 1.85 mol / L, and then anti-flocculation treatment was carried out by adjusting the pH to 1.0 with the addition of hydrochloric acid.

[0305] 1.88 mol of desulfurization and antiflocculation metatitanic acid (based on TiO2) was recovered and introduced into a 3L reactor. 2.01 mol of strontium chloride aqueous solution was added to the antiflocculation metatitanic acid slurry to make the Sr / Ti (molar ratio) 1.07, and then the TiO2 concentration was adjusted to 1.039 mol / L.

[0306] Then, while stirring and mixing, the mixture was heated to 90°C, and after 45 minutes, 440 mL of 10 mol / L sodium hydroxide aqueous solution was added. The mixture was then stirred at 95°C for 1 hour to complete the reaction.

[0307] The reaction slurry was cooled to 50°C; hydrochloric acid was added until the pH reached 5.0; and stirring was continued for 20 minutes. The resulting precipitate was washed by decantation, separated by filtration, and then dried in atmospheric air at 120°C for 8 hours.

[0308] Then, 300g of the dried product was introduced into a dry powder compounding apparatus (Nobilta NOB-130, Hosokawa Micron Corporation). It was processed for 10 minutes at a processing temperature of 30°C and a rotating blade speed of 90m / sec.

[0309] Hydrochloric acid was added to the dried product until the pH reached 0.1, and stirring was continued for 1 hour. The resulting precipitate was washed by decantation.

[0310] The slurry containing the precipitate was adjusted to 40°C; the pH was adjusted to 2.5 by adding hydrochloric acid; n-octyltriethoxysilane was added in an amount of 4.0% by mass relative to the solid content; and stirring was continued and maintained for 10 hours. The pH was adjusted to 6.5 by adding 5 mol / L sodium hydroxide solution, and stirring was continued for 1 hour. The filter cake obtained by filtration and washing was then dried at 120°C in atmospheric conditions for 8 hours to obtain strontium titanate particles 7.

[0311] <8 Production Examples of Strontium Titanate Particles>

[0312] The metatitanic acid produced via the sulfuric acid process was subjected to iron removal and bleaching; subsequently, desulfurization was carried out by adding an aqueous sodium hydroxide solution to adjust the pH to 9.0; then, it was neutralized to pH 5.8 with hydrochloric acid and subjected to filtration and washing. Once washing was complete, water was added to the filter cake to produce a slurry with a TiO2 concentration of 1.85 mol / L, and then anti-flocculation treatment was carried out by adjusting the pH to 1.0 with the addition of hydrochloric acid.

[0313] 1.88 mol of desulfurization and antiflocculation metatitanic acid (based on TiO2) was recovered and introduced into a 3L reactor. 2.54 mol of strontium chloride aqueous solution was added to the antiflocculation metatitanic acid slurry to make the Sr / Ti (molar ratio) 1.35, and then the TiO2 concentration was adjusted to 1.039 mol / L.

[0314] Then, while stirring and mixing, the mixture was heated to 90°C, and after 45 minutes, 440 mL of 10 mol / L sodium hydroxide aqueous solution was added. The mixture was then stirred at 95°C for 1 hour to complete the reaction.

[0315] The reaction slurry was cooled to 50°C; hydrochloric acid was added until the pH reached 5.0; and stirring was continued for 20 minutes. The resulting precipitate was washed by decantation, separated by filtration, and then dried in atmospheric air at 120°C for 8 hours.

[0316] Then, 300g of the dried product was introduced into a dry powder compounding apparatus (Nobilta NOB-130, Hosokawa Micron Corporation). It was processed for 10 minutes at a processing temperature of 30°C and a rotating blade speed of 90m / sec.

[0317] Hydrochloric acid was added to the dried product until the pH reached 0.1, and stirring was continued for 1 hour. The resulting precipitate was washed by decantation.

[0318] The slurry containing the precipitate was adjusted to 40°C; the pH was adjusted to 2.5 by adding hydrochloric acid; n-octyltriethoxysilane was added in an amount of 4.0% by mass relative to the solid content; and stirring was continued and maintained for 10 hours. The pH was adjusted to 6.5 by adding 5 mol / L sodium hydroxide solution, and stirring was continued for 1 hour. The filter cake obtained by filtration and washing was then dried at atmospheric temperature at 120°C for 8 hours to obtain strontium titanate particles 8.

[0319] <Strontium titanate particle production example 9>

[0320] The metatitanic acid produced via the sulfuric acid process was subjected to iron removal and bleaching; subsequently, desulfurization was carried out by adding an aqueous sodium hydroxide solution to adjust the pH to 9.0; then, it was neutralized to pH 5.8 with hydrochloric acid and subjected to filtration and washing. Once washing was complete, water was added to the filter cake to produce a slurry with a TiO2 concentration of 1.85 mol / L, and then anti-flocculation treatment was carried out by adjusting the pH to 1.0 with the addition of hydrochloric acid.

[0321] 1.88 mol of desulfurization and antiflocculation metatitanic acid (based on TiO2) was recovered and introduced into a 3L reactor. 2.54 mol of strontium chloride aqueous solution was added to the antiflocculation metatitanic acid slurry to make the Sr / Ti (molar ratio) 1.35, and then the TiO2 concentration was adjusted to 1.039 mol / L.

[0322] Then, while stirring and mixing, the mixture was heated to 90°C, and after 45 minutes, 440 mL of 10 mol / L sodium hydroxide aqueous solution was added. The mixture was then stirred at 95°C for 1 hour to complete the reaction.

[0323] The reaction slurry was cooled to 50°C; hydrochloric acid was added until the pH reached 5.0; and stirring was continued for 20 minutes. The resulting precipitate was washed by decantation, separated by filtration, and then dried in atmospheric air at 120°C for 8 hours.

[0324] Then, 300g of the dried product was introduced into a dry powder compounding apparatus (Nobilta NOB-130, Hosokawa Micron Corporation). It was processed for 10 minutes at a processing temperature of 30°C and a rotating blade speed of 90m / sec.

[0325] Hydrochloric acid was added to the dried product until the pH reached 0.1, and stirring was continued for 1 hour. The resulting precipitate was washed by decantation.

[0326] The slurry containing the precipitate was adjusted to 70°C; sodium stearate was added in an amount of 4.0% by mass relative to the solid content; and stirring was continued and maintained for 1 hour. The pH was adjusted to 6.5 by adding 5 mol / L sodium hydroxide solution, and stirring was continued for 1 hour. The filter cake obtained by filtration and washing was then dried at 120°C in atmospheric conditions for 8 hours to obtain strontium titanate particles.

[0327] <10 Production Examples of Strontium Titanate Particles>

[0328] The metatitanic acid produced via the sulfuric acid process was subjected to iron removal and bleaching; subsequently, desulfurization was carried out by adding an aqueous sodium hydroxide solution to adjust the pH to 9.0; then, it was neutralized to pH 5.8 with hydrochloric acid and subjected to filtration and washing. Once washing was complete, water was added to the filter cake to produce a slurry with a TiO2 concentration of 1.85 mol / L, and then anti-flocculation treatment was carried out by adjusting the pH to 1.0 with the addition of hydrochloric acid.

[0329] 1.88 mol of desulfurization and antiflocculation metatitanic acid (based on TiO2) was recovered and introduced into a 3L reactor. 2.54 mol of strontium chloride aqueous solution was added to the antiflocculation metatitanic acid slurry to make the Sr / Ti (molar ratio) 1.35, and then the TiO2 concentration was adjusted to 1.039 mol / L.

[0330] Then, while stirring and mixing, the mixture was heated to 90°C, and after 45 minutes, 440 mL of 10 mol / L sodium hydroxide aqueous solution was added. The mixture was then stirred at 95°C for 1 hour to complete the reaction.

[0331] The reaction slurry was cooled to 50°C; hydrochloric acid was added until the pH reached 5.0; and stirring was continued for 20 minutes. The resulting precipitate was washed by decantation, separated by filtration, and then dried in atmospheric air at 120°C for 8 hours.

[0332] Use a Hybridizer (Nara Machinery Co., Ltd.), and then process the dried product three times for 3 minutes at 6000 rpm.

[0333] Hydrochloric acid was added to the dried product until the pH reached 0.1, and stirring was continued for 1 hour. The resulting precipitate was washed by decantation, and the filter cake obtained by filtration and washing was dried at 120°C in atmospheric conditions for 8 hours to obtain strontium titanate particles 10.

[0334] <Production Example of Strontium Titanate Particles>

[0335] The metatitanic acid produced via the sulfuric acid process was subjected to iron removal and bleaching; subsequently, desulfurization was carried out by adding an aqueous sodium hydroxide solution to adjust the pH to 9.0; then, it was neutralized to pH 5.8 with hydrochloric acid and subjected to filtration and washing. Once washing was complete, water was added to the filter cake to produce a slurry with a TiO2 concentration of 1.85 mol / L, and then anti-flocculation treatment was carried out by adjusting the pH to 1.0 with the addition of hydrochloric acid.

[0336] 1.88 mol of desulfurization and antiflocculation metatitanic acid (based on TiO2) was recovered and introduced into a 3L reactor. 2.16 mol of strontium chloride aqueous solution was added to the antiflocculation metatitanic acid slurry to make the Sr / Ti (molar ratio) 1.15, and then the TiO2 concentration was adjusted to 1.039 mol / L.

[0337] Then, while stirring and mixing, the mixture was heated to 90°C, and after 45 minutes, 440 mL of 10 mol / L sodium hydroxide aqueous solution was added. The mixture was then stirred at 95°C for 1 hour to complete the reaction.

[0338] The reaction slurry was cooled to 50°C; hydrochloric acid was added until the pH reached 5.0; and stirring was continued for 1 hour. The resulting precipitate was washed by decantation.

[0339] The slurry containing the precipitate was adjusted to 40°C; the pH was adjusted to 2.5 by adding hydrochloric acid; n-octyltriethoxysilane was added in an amount of 4.0% by mass relative to the solid content; and stirring was continued and maintained for 10 hours. The pH was adjusted to 6.5 by adding 5 mol / L sodium hydroxide solution, and stirring was continued for 1 hour. The filter cake obtained by filtration and washing was then dried at 120°C in atmospheric conditions for 8 hours to obtain strontium titanate particles 11.

[0340] <Production Example of Strontium Titanate Particles (12)>

[0341] The metatitanic acid slurry obtained by hydrolysis of titanium oxysulfate aqueous solution is washed with alkaline aqueous solution.

[0342] Hydrochloric acid was then added to the metatitanic acid slurry to adjust the pH to 0.65, thereby obtaining a titanium dioxide sol dispersion.

[0343] The pH of the titanium dioxide sol dispersion was adjusted to 4.5 by adding NaOH, and the mixture was repeatedly washed until the conductivity of the supernatant reached 70 μS / cm.

[0344] Strontium hydroxide octahydrate was added to the metatitanic acid slurry at a molar ratio of 0.97, and then introduced into a stainless steel reactor and purged with nitrogen.

[0345] Distilled water was added to bring the concentration of TiO2 to 0.5 mol / L. The slurry was heated to 83°C at 6.5°C / h under a nitrogen atmosphere, and the reaction was carried out for 6 hours after reaching 83°C. The resulting precipitate was washed by decantation, then filtered and separated, and then dried in atmospheric air at 120°C for 8 hours to obtain strontium titanate particles 12.

[0346] <13 Production Examples of Strontium Titanate Particles>

[0347] The metatitanic acid produced via the sulfuric acid process was subjected to iron removal and bleaching; subsequently, desulfurization was carried out by adding an aqueous sodium hydroxide solution to adjust the pH to 9.0; then, it was neutralized to pH 5.8 with hydrochloric acid and subjected to filtration and washing. Once washing was complete, water was added to the filter cake to produce a slurry with a TiO2 concentration of 1.85 mol / L, and then anti-flocculation treatment was carried out by adjusting the pH to 1.0 with the addition of hydrochloric acid.

[0348] 1.88 mol of desulfurization and antiflocculation metatitanic acid (based on TiO2) was recovered and introduced into a 3L reactor. 2.16 mol of strontium chloride aqueous solution was added to the antiflocculation metatitanic acid slurry to make the Sr / Ti (molar ratio) 1.15, and then the TiO2 concentration was adjusted to 0.960 mol / L.

[0349] Then, while stirring and mixing, the mixture was heated to 90°C, and after 45 minutes, 440 mL of 10 mol / L sodium hydroxide aqueous solution was added. The mixture was then stirred at 95°C for 1 hour to complete the reaction.

[0350] The reaction slurry was cooled to 50°C; hydrochloric acid was added until the pH reached 5.0; and stirring was continued for 20 minutes. The resulting precipitate was washed by decantation, separated by filtration, and then dried in atmospheric air at 120°C for 8 hours.

[0351] Then, 300g of the dried product was introduced into a dry powder compounding apparatus (Nobilta NOB-130, Hosokawa Micron Corporation). It was processed for 10 minutes at a processing temperature of 30°C and a rotating blade speed of 90m / sec.

[0352] Hydrochloric acid was added to the dried product until the pH reached 0.1, and stirring was continued for 1 hour. The resulting precipitate was washed by decantation.

[0353] The slurry containing the precipitate was adjusted to 40°C; the pH was adjusted to 2.5 by adding hydrochloric acid; n-octyltriethoxysilane was added in an amount of 4.0% by mass relative to the solid content; and stirring was continued and maintained for 10 hours. The pH was adjusted to 6.5 by adding 5 mol / L sodium hydroxide solution, and stirring was continued for 1 hour. The filter cake obtained by filtration and washing was then dried at 120°C in atmospheric conditions for 8 hours to obtain strontium titanate particles 13.

[0354] <14 Production Examples of Strontium Titanate Particles>

[0355] Hydrolyzed titanium oxide is obtained by hydrolysis with the addition of ammonia to an aqueous solution of titanium tetrachloride; the hydrolyzed titanium oxide is washed with pure water; and sulfuric acid is added to the slurry of hydrolyzed titanium oxide in an amount of 0.25% relative to the hydrolyzed titanium oxide as SO3.

[0356] Hydrochloric acid was then added to the aqueous titanium dioxide slurry to adjust the pH to 0.65, thereby obtaining a titanium dioxide sol dispersion. The pH of the dispersion was adjusted to 4.7 by adding NaOH, and the mixture was repeatedly washed until the conductivity of the supernatant reached 50 μS / cm.

[0357] Strontium hydroxide octahydrate was added to the hydrous titanium oxide at a molar ratio of 0.95, and then introduced into a stainless steel reactor and purged with nitrogen. Distilled water was added to bring the concentration to 0.6 mol / L based on SrTiO3.

[0358] The slurry was heated to 65°C at a rate of 10°C / h in a nitrogen atmosphere, and the reaction was carried out for 8 hours after reaching 65°C. After the reaction, it was cooled to room temperature; the supernatant was removed; and then washing with pure water was repeated.

[0359] The operation is carried out under a nitrogen atmosphere, in which a slurry is introduced into an aqueous solution prepared by dissolving sodium stearate in an amount of 2% by mass relative to the solid content in the slurry. While stirring, an aqueous solution of magnesium sulfate is added dropwise to precipitate magnesium stearate on the surface of the perovskite crystals.

[0360] The slurry was repeatedly washed with pure water, then filtered through a vacuum filter (Nutsche filter), and the resulting filter cake was dried to obtain magnesium stearate-treated strontium titanate particles 14.

[0361] <15 Production Examples of Strontium Titanate Particles>

[0362] The aqueous titanium dioxide slurry obtained by hydrolysis of titanium oxysulfate aqueous solution was washed with alkaline aqueous solution. Hydrochloric acid was then added to the aqueous titanium dioxide slurry to adjust the pH to 4.0, thereby obtaining a titanium dioxide sol dispersion. The pH of the dispersion was adjusted to 8.0 by adding NaOH, and washing was repeated until the conductivity of the supernatant reached 100 μS / cm.

[0363] Strontium hydroxide octahydrate was added to the aqueous titanium oxide in an amount based on 1.02 molars, and then introduced into a stainless steel reactor and purged with nitrogen.

[0364] Distilled water was added to bring the concentration of SrTiO3 to 0.3 mol / L. The slurry was heated to 90°C at 30°C / h under a nitrogen atmosphere and reacted for 5 hours after reaching 90°C. After the reaction, the mixture was cooled to room temperature, the supernatant was removed, and the mixture was repeatedly washed with pure water and then filtered using a vacuum suction filter. The resulting filter cake was dried to obtain SrTiO3 particles 15.

[0365] [Table 1]

[0366]

[0367] <Example of charge control resin production>

[0368] 250 parts of methanol, 150 parts of 2-butanone and 100 parts of 2-propanol as solvents, and 83 parts of styrene, 12 parts of butyl acrylate and 5 parts of 2-acrylamido-2-methylpropanesulfonic acid as monomers were added to a pressurized reactor equipped with a reflux condenser, stirrer, thermometer, nitrogen inlet pipe, dropping device and pressure reducing device, and heated to reflux temperature while stirring.

[0369] A solution of 0.45 parts of tert-butyl peroxide, diluted with 20 parts of 2-butanone, was added dropwise over 30 minutes, and stirring was continued for 5 hours. Then, a solution of 0.28 parts of tert-butyl peroxide, diluted with 20 parts of 2-butanone, was added dropwise over 30 minutes, and stirring was continued for another 5 hours to complete the polymerization.

[0370] The polymerization solvent was removed by distillation under reduced pressure, and the resulting polymer was coarsely pulverized to below 100 μm using a shredder equipped with a 150-mesh sieve to obtain charge control resin 1. The glass transition temperature (Tg) of the obtained polymer was approximately 70 °C.

[0371] The toner granules are produced as described below. The properties of the resulting toner granules 1 to 9 are given in Table 2.

[0372] <Production Example of Toner Granules>

[0373] 710 parts of deionized water and 850 parts of 0.1 mol / L Na3PO4 aqueous solution were added to a four-necked container and stirred at 12,000 rpm using a TKHomomixer high-speed stirrer (Tokushu Kika Kogyo Co., Ltd.) while maintaining the temperature at 60°C. 68 parts of 1.0 mol / L CaCl2 aqueous solution were gradually added to prepare an aqueous medium containing a dispersant stabilizer.

[0374] · 124 portions of styrene

[0375] · 36 parts of n-butyl acrylate

[0376] • Copper phthalocyanine pigment (pigment blue 15:3) 13 parts

[0377] · Polyester resin 1 10 parts

[0378] (Terephthalic acid-propylene oxide modified bisphenol A (2 mol adduct) copolymer, acid value: 10 mg KOH / g, glass transition temperature (Tg): 70℃, weight average molecular weight (Mw): 10,500)

[0379] • Charge control resin 1-2 parts

[0380] ·Fischer wax (melting point: 78℃) 15 parts

[0381] These materials were stirred for 3 hours using a grinder (Nippon Coke & Engineering Co., Ltd.) to disperse the components in the polymerizable monomers to prepare a monomer mixture.

[0382] 20.0 parts (50% toluene solution) of polymerization initiator 1,1,3,3-tetramethylbutylperoxide-2-ethylhexanoate was added to the monomer mixture to prepare a polymerizable monomer composition.

[0383] The polymerizable monomer composition was introduced into an aqueous medium and granulated for 5 minutes while maintaining the stirrer speed at 10,000 rpm. The high-speed stirrer was then switched to a propeller stirrer; the internal temperature was raised to 70°C; and the reaction was carried out for 6 hours with slow stirring.

[0384] The container was then heated to 80°C and held for 4 hours; subsequently cooled to obtain a slurry. Dilute hydrochloric acid was added to the container containing the slurry to remove the dispersing stabilizer. The mixture was then filtered, washed, and dried to obtain toner particles 1.

[0385] <Production Example of Colorant Granules 2>

[0386] Except for the following changes: polyester resin 1 is changed to polyester resin 2 (terephthalic acid-propylene oxide modified bisphenol A (2 mol adduct) copolymer, acid value: 13 mg KOH / g, glass transition temperature (Tg): 67 °C, weight average molecular weight (Mw): 9,800), and while maintaining the stirrer speed at 7,500 rpm, the granulation conditions after introducing the polymerizable monomer composition into the aqueous dispersion medium are changed to granulation for 8 minutes, and to obtain toner particles 2 in the same manner as in the toner particle 1 production example.

[0387] <Production Example of Toner Granules 3>

[0388] Except for the following changes: polyester resin 1 is changed to polyester resin 3 (terephthalic acid-propylene oxide modified bisphenol A (2 mol adduct) copolymer, acid value: 5 mg KOH / g, glass transition temperature (Tg): 71 °C, weight average molecular weight (Mw): 11,800), and while maintaining the stirrer speed at 12,000 rpm, the granulation conditions after introducing the polymerizable monomer composition into the aqueous dispersion medium are changed to granulation for 5 minutes, and toner particles 3 are obtained in the same manner as in the toner particle 1 production example.

[0389] <Production Example of Colorant Granules 4>

[0390] Except for changing the amount of styrene added from 124 parts to 130 parts and the amount of n-butyl acrylate added from 36 parts to 30 parts, the toner particles 4 were obtained in the same manner as in the toner particle 1 production example.

[0391] <Production Example of Colorant Granules (5)>

[0392] Except for changing the amount of styrene added from 124 parts to 115 parts and the amount of n-butyl acrylate added from 36 parts to 45 parts, the toner particles 5 were obtained in the same manner as in the toner particle 1 production example.

[0393] <Production Example of Colorant Granules 6>

[0394] Except for changing the amount of styrene added from 124 parts to 135 parts and the amount of n-butyl acrylate added from 36 parts to 25 parts, the toner particles 6 were obtained in the same manner as in the toner particle 1 production example.

[0395] <Production Example of Colorant Granules 7>

[0396] Except for changing the amount of styrene added from 124 parts to 110 parts and the amount of n-butyl acrylate added from 36 parts to 50 parts, the toner particles 7 were obtained in the same manner as in the toner particle 1 production example.

[0397] <Production Example of Colorant Granules 8>

[0398] Except that polyester resin 1 is not added, toner particles 8 are obtained in the same manner as in the toner particle 7 production example.

[0399] <Production Example of Colorant Granules 9>

[0400] Except for not adding charge control resin 1, toner particles 9 are obtained in the same manner as in the toner particle 7 production example.

[0401] [Table 2]

[0402]

[0403] <Production Example of Toner 1>

[0404] Using FM10C (Nippon Coke & Engineering Co., Ltd.), 1.5 parts of strontium titanate particles and 1.5 parts of fumed silica fine particles (BET: 200 μm) were mixed. 2 (g) is added externally to 100 parts of the resulting toner granules 1 and mixed.

[0405] The external addition conditions are as follows: amount of toner granules added: 1.8 kg, rotation speed: 3600 rpm, external addition time: 5 minutes.

[0406] The toner was then sieved through a sieve with a 200 μm opening to obtain toner 1.

[0407] The properties of toner 1 are given in Table 3. The average roundness, Tg, and E / A of the toner are the same as those in Table 2. In addition, the properties of the strontium titanate particles 1 externally added to the toner are also the same as those in Table 1.

[0408] <Example 1>

[0409] The obtained toner 1 was used for the following evaluation. The evaluation results are given in Tables 4-1 and 4-2.

[0410] <Machine used for evaluation>

[0411] The evaluation was conducted using an HP Color LaserJet Enterprise M651n laser printer from Hewlett-Packard Company, modified to operate with a single-color processing cartridge installed. Evaluation paper was CS-680, sold by Canon Marketing Japan Inc. Toner was filled into the specified processing cartridge.

[0412] <Developing performance>

[0413] The developing performance was evaluated under low temperature and low humidity conditions (temperature = 10°C, relative humidity = 14%), where the effects of charge properties are easily observed. These low temperature and low humidity conditions also constitute harsh conditions for toner breakage, as the toner is not easily heated during long-term repeated use, and plasticization is less likely to occur.

[0414] Assuming a long-term, repetitive testing scenario, in a mode where the machine is set to temporarily stop between jobs and then begin the next job, a total of 20,000 images will be output using a horizontal line pattern with a print rate of 1% and in 2-page / 1-job tests. Image density will be measured on the first and 20,000th images.

[0415] Image density was measured by outputting a solid image in the form of a 5mm circle and by using a MacBeth density meter (GretagMacbeth GmbH) as a reflectance density meter and measuring the reflectance density using an SPI filter.

[0416] In this article, a larger numerical value indicates better development performance.

[0417] Fog

[0418] The fogging phenomenon was evaluated under low temperature and low humidity conditions, where the effects of electrical properties are easily apparent. Low temperature and low humidity conditions also constitute harsh conditions for toner breakage, because toners are not easily heated and plasticization is not likely to occur during long-term repeated use.

[0419] In the evaluation of developing performance, after outputting the first and 20,000th images, a solid white image is output, and Dr-Ds is taken as the fogging value, where Ds is the worst value of the reflectance concentration in the white background area and Dr is the average reflectance concentration of the evaluation paper before image formation.

[0420] The Reflectometer Model TC-6DS (Tokyo Denshoku Co., Ltd.) is used to measure the reflectance concentration of a white background area, and an amber filter is used for the filter.

[0421] In this article, smaller values ​​indicate better fog levels.

[0422] <Developing performance after placement>

[0423] Operating in a high temperature and high humidity environment (temperature = 30℃, relative humidity = 80%), in a mode where the machine is set to temporarily stop between jobs and then start the next job, a total of 5,000 images were output using horizontal line patterns with a print rate of 1% and using 2 sheets / 1 job.

[0424] Image density was measured on the 5,000th image. Evaluation was conducted under high temperature and high humidity conditions, as this represents a more stringent evaluation under conditions concerning the maintenance of charge-carrying properties.

[0425] After the 5,000th image is output, a solid image in 5mm circle format is output. After being placed in a high temperature and high humidity environment (temperature = 30℃, relative humidity = 80%) for 3 days, a solid image in 5mm circle format is also output.

[0426] Image density is measured by measuring the reflection density using an SPI filter on a MacBeth density meter (GretagMacbeth GmbH) that functions as a reflection density meter.

[0427] Compared to the reflectance of the solid image after the 5000th print, a smaller reduction in reflectance of the solid image after 3 days of storage indicates better post-storage development performance.

[0428] <Component contamination>

[0429] Image defects can occur when the developer blade is contaminated. Developer blade contamination was evaluated by outputting images under harsh low-temperature and low-humidity conditions to prevent toner breakage, followed by transferring the cartridge to a high-temperature and high-humidity environment.

[0430] The reason for transferring it to a high-temperature and high-humidity environment is that this is conducive to the occurrence of developer plate contamination caused by toner breakage.

[0431] The 20,000 boxes output from the low-temperature, low-humidity environment assessment will be transferred to the high-temperature, high-humidity environment.

[0432] In a mode where the machine is set to pause temporarily between jobs and then begin the next job, an experiment was conducted to output 3,000 images using a horizontal line pattern with a print rate of 1% and using 1 sheet per job.

[0433] Then, to facilitate the differentiation of image defects caused by developer blade contamination, a halftone image displaying an image density of 0.6 provided by the aforementioned MacBeth reflectance meter relative to the transport direction of the evaluation paper is output. This image is visually inspected, and the presence / absence of longitudinal stripes occurring along the transport direction due to developer blade contamination is evaluated based on the following criteria.

[0434] A: I don't see any white striped vertical lines in the image at all.

[0435] B: One or two thin white vertical lines can be seen in the image.

[0436] C: One or two distinct white stripe-like vertical lines can be seen in the image.

[0437] D: More than three distinct white stripe-like vertical lines are visible in the image.

[0438] <Halftone density uniformity>

[0439] The uniformity of halftone concentration was evaluated in a low-temperature, low-humidity environment (temperature = 10°C, relative humidity = 14%) where the effects of charge properties are easily apparent.

[0440] To rigorously observe the effect of charge distribution on the toner, the first halftone image is evaluated. A halftone image with a reflectance density of 0.60 is output; the reflectance density of the image is measured at multiple points; and the halftone density uniformity is evaluated by calculating the density difference between multiple points. The evaluation criteria are given below.

[0441] A: The concentration difference due to reflection is less than 0.05

[0442] B: The reflection concentration difference is at least 0.05 and less than 0.10.

[0443] C: The reflection concentration difference is at least 0.10 and less than 0.15.

[0444] D: The reflection concentration difference is at least 0.15.

[0445] <Production Examples of Toners 2 to 20 and Comparative Toners 1 to 5>

[0446] Except for changing the type and amount of toner particles and strontium titanate particles used in the toner 1 production example, as shown in Table 3, toners 2 to 20 and comparative toners 1 to 5 were obtained in the same manner as in the toner 1 production example. The properties of toners 2 to 20 and comparative toners 1 to 5 are given in Table 3. The average roundness, Tg, and E / A of the toners 2 to 20 and comparative toners 1 to 5 are the same as these values ​​for the toner particles in Table 2. The properties of the strontium titanate particles externally added to the toners are also the same as those in Table 1.

[0447] <Examples 2 to 20 and Comparative Examples 1 to 5>

[0448] The same evaluation was performed as in Example 1. The evaluation results are given in Tables 4-1 and 4-2.

[0449] [Table 3]

[0450]

[0451] [Table 4-1]

[0452]

[0453] [Table 4-2]

[0454]

[0455] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims is to be interpreted in the broadest sense to cover all such modifications and equivalent structures and functions.

Claims

1. A toner comprising: Toner granules; and An external additive containing strontium titanate particles, characterized in that: The toner has an average roundness of at least 0.935 and no greater than 0.

995. The number-average particle size of the primary strontium titanate particles is at least 10 nm and not more than 60 nm. In the CuKα x-ray diffraction spectrum obtained within a 2θ range of at least 10° and no greater than 90°, the strontium titanate particles have peaks in the range of 39.700°±0.150° and in the range of 46.200°±0.150°, where θ is the Bragg angle; When Sa is the area of ​​the peak at 39.700°±0.150° and Sb is the area of ​​the peak at 46.200°±0.150°, Sb / Sa is at least 1.80 and not greater than 2.

30. The strontium titanate particles have a molar Sr / Ti ratio of at least 0.70 and not greater than 0.85, and The average sphericity of the primary particles of the strontium titanate particles is at least 0.700 and not greater than 0.

920.

2. The toner according to claim 1, wherein the toner has a glass transition temperature of at least 50°C and not higher than 70°C.

3. The toner according to claim 1 or 2, wherein the coverage of the strontium titanate particles on the surface of the toner, as measured by X-ray photoelectron spectroscopy, is at least 5.0 area% and not more than 20.0 area%.

4. The toner according to claim 1 or 2, wherein the content of the strontium titanate particles is at least 0.05 parts by weight and not more than 5.0 parts by weight relative to 100 parts by weight of the toner particles.

5. The toner according to claim 1 or 2, wherein the toner particles have a core and a shell present on the surface of the core.

6. The toner according to claim 5, wherein the shell layer comprises at least one selected from the group consisting of polyester resin, styrene-acrylic copolymer and styrene-methacrylic copolymer.

7. The toner according to claim 1 or 2, wherein E / A satisfies the following formula (1), wherein A is the amount of carbon atoms present on the surface of the toner particles as measured by X-ray photoelectron spectroscopy, and E is the amount of sulfur atoms present on the surface of the toner particles as measured by X-ray photoelectron spectroscopy, wherein A and E are expressed in atomic percent: 3×10 –4 ≤E / A≤50×10 –4 (1)。

Images