External additive for toner and toner

Abstract

The present invention relates to an external additive for toner and toner. An external additive for toner, which comprises silica particles surface-treated with polybasic acid metal salt particles, wherein the polybasic acid metal salt particles are particles of a salt of a polybasic acid and a titanium compound; and a toner, which comprises toner particles and an external additive for toner on the surface of the toner particles, wherein the external additive for toner is the aforementioned external additive for toner.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an external additive for toner used in an image forming method such as an electrophotographic method and a toner. BACKGROUND

[0002] In recent years, the field of using image forming apparatuses using an electrophotographic system has become widespread and more diversified from printers and copiers to commercial printers. In view of this, higher speed and higher quality are required in image forming apparatuses.

[0003] The charging characteristics, fluidity, and durability, etc. of toner used in image forming apparatuses are generally controlled by an external additive present on the surface of the toner, whereby characteristics optimized for the processes of the electrophotographic system are obtained. Inorganic fine particles typified by silica and titanium oxide are used as the external additive.

[0004] Generally, silica exhibits excellent fluidity, but tends to easily overcharge, has low environmental stability, and has low stability of charging properties. In contrast, titanium oxide has high electrical conductivity and is thus excellent in charging property stability; however, it is prone to charge leakage, and tends to produce a low amount of charged charges. Furthermore, due to the low fluidity of titanium oxide, the external additive tends to become embedded into the toner particles in long-term use, whereby deterioration of the toner easily occurs. Inorganic oxides such as silica used as external additives have hydroxyl groups on the surface, and are thus hydrophilic, and are characterized by being prone to moisture absorption. Therefore, this has a significant influence on the amount of charged charges and electrical conductivity as electrical properties, because the hydroxyl groups on the surface dissociate due to absorbed moisture.

[0005] Accordingly, an external additive having a sufficient amount of charged charges, exhibiting excellent stability of charging properties, and having high fluidity is required, and various surface treatment methods of external additives using silica or titanium oxide have been proposed. Japanese Patent Application Publication No. S59-52255 discloses titanium oxide hydrophobically treated with an alkyltrialkoxysilane having a C6 to C8 alkyl group, an external additive, with the aim of improving the fluidity of toner. Japanese Patent Application Publication No. 2017-134157 discloses an external additive in which titanium dioxide fine particles are attached to the surface of a silica core and the titanium dioxide fine particles are covered with a thermosetting nitrogen resin. Furthermore, Japanese Patent Application Publication No. 2018-163209 discloses an external additive that simultaneously uses a powder of silica particles having a C8 to C16 alkyl group and an amino group on the surface and titanium dioxide particles having an amino group on the surface. SUMMARY

[0006] The external additive disclosed in Japanese Patent Application Publication No. S59-52255 contains titanium oxide. The volume resistivity of the titanium oxide powder is generally 1.0 x 10 7 (Ω·m) to 1.0 x 10 9 (Ω·m). Titanium oxide has high electrical conductivity, and thus toner using an external additive containing titanium oxide exhibits a low amount of charge and a low charge decay characteristic, which makes it highly likely that transfer failure occurs.

[0007] In Japanese Patent Application Publication No. 2017-134157, composite particles of silica particles and titanium dioxide particles are used as an external additive, but the silica particles and the titanium dioxide particles are not chemically bonded to each other. Furthermore, it is extremely difficult to uniformly disperse the titanium dioxide particles on the surface of the silica particles having the same polarity sign as the titanium dioxide particles. Furthermore, titanium dioxide has high electrical conductivity, and thus the volume resistivity of the toner is low. Therefore, there is room for improvement in terms of ensuring both the amount of charge and stability.

[0008] When the external additive disclosed in Japanese Patent Application Publication No. 2018-163209 is used, since the volume resistivity of the toner becomes lower relative to the volume resistivity of the print intermediate transfer member or transfer roller in printing using the toner, the amount of charge of the toner decreases, and transfer resulting from Coulomb force is less likely to occur. Therefore, the external additive disclosed in Japanese Patent Application Publication No. 2018-163209 is susceptible to similar transfer failure as Japanese Patent Application Publication No. S59-52255, and has room for improvement.

[0009] The present disclosure relates to an external additive and a toner that have a sufficient amount of charge, exhibit excellent charge stability, and have high fluidity.

[0010] The present disclosure relates to an external additive for toner, which contains silica particles surface-treated with polybasic acid metal salt particles,

[0011] wherein the polybasic acid metal salt particles are particles of a salt of a polybasic acid and a titanium compound.

[0012] The present disclosure also relates to a toner containing toner particles and an external additive for toner on the surface of the toner particles,

[0013] wherein the external additive for toner is the above-described external additive for toner.

[0014] The present disclosure allows to provide an external additive having sufficient amount of electric charge, exhibiting excellent stability of charging property, and having high fluidity, and a toner. Further features of the present disclosure will become apparent from the following description of the exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 a graph showing the relationship between the relative dielectric constant and the conductivity index in the external additives 1 to 19;

[0016] Figure 2 a graph showing the relationship between the added amount of titanium lactate and the relative dielectric constant; and

[0017] Figure 3 a graph showing the relationship between the added amount of titanium lactate and the conductivity index. DETAILED DESCRIPTION

[0018] Hereinafter, the embodiments will be described in detail, but the present disclosure is not limited to the following description. Unless otherwise specified, the description of "from XX to YY" or "XX to YY" indicating a numerical range means the numerical range including the lower limit and the upper limit as the end points. When the numerical range is described in stages, the upper limit and the lower limit of each numerical range can be arbitrarily combined.

[0019] The present disclosure relates to an external additive for toner, which includes silica particles surface-treated with polybasic acid metal salt particles,

[0020] wherein the polybasic acid metal salt particles are particles of a salt of a polybasic acid and a titanium compound.

[0021] Further, the present disclosure relates to a toner including toner particles and the above-mentioned external additive for toner.

[0022] The present inventors found that, by using particles of a salt of a polybasic acid and a titanium compound as a surface modifier of silica particles, it became possible to provide an external additive for toner and a toner having sufficient amount of electric charge, being excellent in charging property, and capable of ensuring high fluidity. As to the deep reason thereof, the present inventors conjecture as follows.

[0023] Silica particles have high volume resistivity, but are hydrophilic due to hydroxyl groups (silanol groups) on the surface, and thus the silica particles exhibit a characteristic of being easily hygroscopic. When the silica particles are hygroscopic, the hydroxyl groups dissociate due to such moisture; as a result, this has a significant influence on the amount of electric charge and the conductivity as electric properties. The present inventors believe that the amount of electric charge and the charging stability can be ensured by chemically surface-treating the surface of silica particles using a titanium-based material which is excellent in charging stability.

[0024] Titanium oxide is generally exemplified as a titanium-based material for external additives for toner, but it is difficult to achieve chemical interaction with silica particles and titanium oxide. Further, conceivable methods can involve chemical bonding of titanium alkoxide to hydroxyl groups on the surface of silica particles using hydrolysis and polycondensation reactions. However, titanium alkoxide exhibits a high reaction speed in an aqueous system, and it is difficult to control the reaction, which makes titanium alkoxide problematic, for example, in terms of dispersibility. This is because water coordinates with titanium alkoxide, and then Ti-OH is formed, which reacts with titanium alkoxide of other molecules, resulting in formation of a metal oxoalkyl bond (Ti-O-Ti bond). A further conceivable reason is that the reaction continuously occurs to form a polytitanoxane structure.

[0025] Therefore, the present inventors found that, by using polyacid metal salt particles, which are particles of a salt of a polyacid and a titanium compound, as a surface treatment agent, interaction with silica particles can be stably and uniformly achieved while controlling the reaction speed.

[0026] A polyacid accepts an electron pair and easily becomes negatively charged. Further, titanium is a Group 4 element and is most stable when its oxidation number is +4. As a result, a titanium compound forms a crosslinked structure with a polyacid, thereby promoting movement of electrons through the crosslinked structure; this makes it possible to improve chargeability while suppressing excessive charging from occurring, and makes it possible to ensure excellent charge stability. Further, a reaction product of a polyacid and titanium, which is a Group 4 element, provides good environmental stability by blocking water molecules with the crosslinked structure. It is thought that polyacid metal salt particles, which are particles of a salt of a polyacid and a titanium compound, react with hydroxyl groups on the surface of silica particles, resulting in formation of a metal oxoalkyl bond (Si-O-Ti bond). As a result, it is possible to obtain an external additive particle that integrates the properties of silica and the properties of metal particles. Hydroxyl groups on the surface of silica particles react with polyacid metal salt particles to form a metal oxoalkyl bond, as a result, the number of hydroxyl groups dissociated on the surface of silica particles is reduced. Generally, in the case of excessively high electrical conductivity, that is, in the case of excessively low volume resistivity, the amount of charge decreases due to a leakage current. Further, in the case of excessively low electrical conductivity, that is, in the case of excessively high volume resistivity, excessive charging occurs. In contrast, when silica particles are surface-treated with polyacid metal salt particles, as described above, movement of electrons is controlled, thereby making it possible to obtain appropriate electrical conductivity (volume resistivity). As a result, it is possible to control a leakage current, it is possible to improve capacitance, and it is possible to achieve chargeability and suppression of occurrence of excessive charging, thereby improving charge performance stability.

[0027] Thus, by using the polybasic acid metal salt particles as the surface treatment agent, a toner external additive that allows both the charge amount and the charge stability to be ensured can be obtained while ensuring high flowability by using the silica particles as the core, at the same time. There has never been a toner external additive having the above-described constitution; therefore, the present inventors have succeeded for the first time in obtaining a toner external additive having the above-described constitution and a toner using the toner external additive.

[0028] The method for surface-treating the polybasic acid metal salt particles on the surface of the silica particles is not particularly limited, and can be one of the following methods. For example, the method can involve adding a polybasic acid and a titanium compound to a dispersion liquid of silica particles and mixing the whole, thereby causing the polybasic acid metal salt particles to react, and obtaining a reaction product, while stirring the dispersion liquid to cause attachment to and reaction with the surface of the silica particles, and further obtaining the surface-treated silica particles. Another method can involve adding the polybasic acid metal salt particles generated in advance to a dispersion liquid of silica particles and mixing the whole to cause attachment to and reaction with the surface of the silica particles, and obtaining the surface-treated silica particles.

[0029] As the polybasic acid, a conventionally known polybasic acid can be used without particular limitation. Specific examples of the polybasic acid include inorganic acids such as phosphoric acid (ternary), carbonic acid (binary), and sulfuric acid (binary); and organic acids such as dicarboxylic acids (binary) and tricarboxylic acids (ternary). Specific examples of the organic acid include dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, and terephthalic acid; and tricarboxylic acids such as citric acid, aconitic acid, and trimellitic anhydride.

[0030] The polybasic acid preferably contains an inorganic acid. The inorganic acid has a more rigid molecular skeleton than the organic acid, and thus exhibits a smaller change in shape upon long-term storage. Therefore, stable properties can be obtained even after long-term storage. The polybasic acid more preferably contains at least one selected from the group consisting of phosphoric acid, carbonic acid, and sulfuric acid, and still more preferably is phosphoric acid. In the case where the polybasic acid is phosphoric acid, when a metal oxane bond (Si-O-Ti bond) is formed due to a reaction between the salt of the phosphoric acid and the titanium compound and the hydroxyl group on the surface of the silica particles, a more strongly fixed and stable surface layer can be formed due to the fact that a pyrophosphate skeleton as a crosslinking body is formed between the polybasic acid and the titanium compound. Furthermore, the manner of addition to the water-based medium can involve adding the polybasic acid as it is, or adding a water-soluble polybasic acid metal salt particle to the water-based medium and dissociating in the water-based medium.

[0031] As the titanium compound, a known titanium compound can be used without particular limitation, as long as the titanium compound gives a polybasic acid metal salt by reaction with a polybasic acid ion. Specific examples of the titanium compound include at least one selected from the group consisting of titanium lactate, titanium tetraacetylacetonate, an ammonium salt of titanium lactate, and titanium triethanolamine, and the like. Among the foregoing, a titanium chelate is preferred because the reaction is easy to control, and the titanium chelate quantitatively reacts with a polybasic acid ion. From the viewpoint of solubility in an aqueous medium, a lactate chelate such as titanium lactate is more preferred.

[0032] Specific examples of the polybasic acid metal salt particles include particles of a salt of a polybasic acid such as phosphoric acid, sulfuric acid, carbonic acid, or oxalic acid, and a titanium compound. Examples include a titanium phosphate compound, a titanium sulfate compound, a titanium carbonate compound, and a titanium oxalate compound. The polybasic acid preferably contains at least one selected from the group consisting of sulfuric acid, carbonic acid, and phosphoric acid; more preferably, the polybasic acid is phosphoric acid. A phosphate ion provides high strength derived from intermetallic crosslinking, and is also excellent in terms of charge-up performance due to having an ionic bond within the molecule; thus, the polybasic acid metal salt particles more preferably contain particles of a salt of phosphoric acid and a titanium compound.

[0033] Preferably, in the surface-treated silica particles, Si-O-Ti bonds are formed from the polybasic acid metal salt particles. The silica particles surface-treated with the polybasic acid metal salt particles preferably form metallo-oxane bonds (Si-O-Ti bonds) between the hydroxyl groups (silanol groups) on the surface of the silica particles and the polybasic acid metal salt particles. As a result, the capacitance increases (i.e., the relative dielectric constant increases), and thus a sufficient amount of charge can be ensured. Furthermore, the amount of hydroxyl groups on the surface of the silica particles is reduced, and thus the electrical conductivity decreases (i.e., the volume resistivity increases), and it becomes possible to suppress a decrease in the amount of charge derived from a leakage current and to ensure a sufficient amount of charge. Preferably, a crosslinker between the polybasic acid and the titanium compound is formed in the polybasic acid metal salt particles. With the aid of this crosslinker, electron movement is facilitated and appropriate electrical conductivity is achieved, and thus the charge-up of the toner can be improved, the occurrence of excessive charge-up can be suppressed, and excellent charge stability can be ensured. Furthermore, the environmental stability is improved due to the fact that the polybasic acid metal salt particles can block water molecules with the aid of the crosslinker.

[0034] The number average particle diameter of the primary particles of the polybasic acid metal salt particles can be observed using a transmission electron microscope (TEM). The number average particle diameter of the primary particles of the polybasic acid metal salt particles is preferably 2.0 nm or more and 10.0 nm or less, and more preferably 2.0 nm or more and 5.0 nm or less, in order to improve the adhesion (van der Waals force) between the silica particles and the toner particles. The polybasic acid metal salt particles can exist in a partially aggregated state on the silica particles, and the height of the aggregate with respect to the normal direction of the silica particles is preferably 50 nm or less.

[0035] The primary particle diameter and aggregation state of the polybasic acid metal salt particles can be controlled by the shearing energy of the stirring device and the addition rate and concentration of the titanium compound.

[0036] The content of the polybasic acid metal salt particles in the silica particles is preferably 0.01 mass% or more and 1.00 mass% or less, and more preferably 0.05 mass% or more and 0.20 mass% or less. In the case where the content is 0.01 mass% or more and 1.00 mass% or less, a certain amount of hydroxyl groups on the surface of the silica particles reacts with the polybasic acid metal salt particles to form metal oxoalkyl bonds, so that the electrical conductivity decreases, the volume resistivity increases, and the relative dielectric constant increases, thereby suppressing the occurrence of excessive charging and obtaining a sufficient amount of charged electricity. The content of the polybasic acid metal salt particles in the silica particles can be controlled based on the addition amount of the silica particles, the polybasic acid, the titanium compound, or the polybasic acid metal salt particles, the specific surface area of the silica particles, and the kind of the polybasic acid metal salt particles.

[0037] The number average particle diameter of the silica particles is preferably 7 nm or more and 600 nm or less, and more preferably 10 nm or more and 500 nm or less. In the case where the number average particle diameter is less than 7 nm, the van der Waals force becomes dominant in the silica particles, and the non-electrostatic adhesion between the toner particles or between the toner and a developing roller or an intermediate transfer member increases. Due to this non-electrostatic adhesion, the flowability, the durability, and the transferability of the toner tend to decrease. In the case where the number average particle diameter of the silica particles exceeds 600 nm, during stirring of the toner, an external force easily acts on the silica particles externally added to the toner, and the silica particles easily embed or migrate. As a result, the toner surface becomes uneven, and fogging and reduced image density are likely to occur.

[0038] For the same reason, the number average particle diameter of the silica particles surface-treated with the polybasic acid metal salt particles is preferably 9 nm or more and 604 nm or less, and more preferably 14 nm or more and 504 nm or less.

[0039] The BET specific surface area of the silica particles is preferably 6 m 2 / g or more and 290 m 2 / g or less, and more preferably 7 m 2 / g or more and 210 m 2 / g or less. The larger the BET specific surface area of the silica particles, the smaller the number average particle diameter of the silica particles becomes, and the smaller the BET specific surface area of the silica particles, the larger the number average particle diameter of the silica particles becomes. In the case where the BET specific surface area exceeds 290 m 2In the case where the BET specific surface area of the silica particles is less than 6 m 2 In the case where the BET specific surface area of the silica particles is less than 6 m

[0040] The silica particles are not particularly limited, and can be silica particles obtained by a wet method, such as sol-gel silica particles, gel silica particles, aqueous colloidal silica particles, alcoholic silica particles; or fused silica particles; or silica particles obtained by a gas phase method, such as explosion method silica particles, and the like. Among the foregoing, sol-gel silica particles obtained by a sol-gel method are preferred. In the sol-gel method, an alkoxysilane is subjected to a hydrolysis and condensation reaction in an organic solvent in the presence of water to obtain a silica sol suspension, and then the solvent is removed therefrom, dried, to obtain silica fine particles. The sol-gel silica particles have many hydroxyl groups (silanol groups) on the surface, and thus uniform surface treatment is more easily achieved by reaction between the hydroxyl groups and the polybasic acid metal salt particles. In addition, the sol-gel silica particles have a high circularity and a sharp particle size distribution, and thus the characteristics of the sol-gel silica particles as an external additive are not easily fluctuated.

[0041] The relative dielectric constant of the external additive for toner at the frequency at which the dielectric loss tangent tan δ is the smallest is preferably 2.10 or greater and 2.20 or less. In the case where the relative dielectric constant is 2.10 or greater, a certain amount of the hydroxyl groups on the surface of the silica particles react with the polybasic acid metal salt particles to form metal oxane bonds, and a crosslinking body of the polybasic acid and the titanium compound is formed, and thus it is possible to impart an adequate amount of a charge to the external additive for toner. The relative dielectric constant can be controlled based on the added amounts of the silica particles, the polybasic acid, the titanium compound, or the polybasic acid metal salt particles. The measurement of the relative dielectric constant will be described later.

[0042] In the case where the volume resistivity is the inverse of the electrical conductivity κ at a measurement frequency of 0.021 Hz, the volume resistivity of the external additive for toner is preferably 1.54 x 10 12 (Ω·m) or greater, and more preferably 2.19 x 10 12 (Ω·m) or greater, and still more preferably 6.58 x 10 12(Ω-m) or more. The volume resistivity is preferably 1.32 x 10 14 (Ω-m) or more, and more preferably 1.10 x 10 14 (Ω-m) or more. In the case where the volume resistivity is 1.54 x 10 12 (Ω-m) or more, a certain amount of hydroxyl groups on the surface of the silica particles reacts with the polybasic acid metal salt particles to form metal-oxygen-alkyl bonds, and a crosslinking body of the polybasic acid and the titanium compound is formed, thereby suppressing occurrence of excessive charging in the external additive for toner and improving charging property stability, so that the toner produced using the external additive for toner exhibits good developing property and transferability. Further, the volume resistivity can be controlled based on the added amounts of the silica particles, the polybasic acid, the titanium compound, or the polybasic acid metal salt particles. Measurement of the volume resistivity will be described later.

[0043] In the case where the electric conductivity index K / ω is defined as a value obtained by dividing the electric conductivity K at a measurement frequency of 1 Hz by the angular frequency ω, the electric conductivity index K / ω of the external additive for toner is preferably 6.44 x 10 -12 (S / m) s or less, more preferably 4.51 x 10 -12 (S / m) s or less, and still more preferably 1.50 x 10 -12 (S / m) s or less. The electric conductivity index K / ω of the external additive for toner is preferably 7.56 x 10 -14 (S / m) s or more, and more preferably 9.02 x 10 -14 (S / m) s or more. In the case where the electric conductivity index K / ω is 6.44 x 10 -12 (S / m) s or less, a certain amount of hydroxyl groups on the surface of the silica particles reacts with the polybasic acid metal salt particles to form metal-oxygen-alkyl bonds, and a crosslinking body of the polybasic acid and the titanium compound is formed, thereby suppressing occurrence of excessive charging in the external additive for toner and improving charging property stability. The electric conductivity index K / ω can be controlled based on the added amounts of the silica particles, the polybasic acid, the titanium compound, or the polybasic acid metal salt particles. Measurement of the electric conductivity index K / ω will be described later.

[0044] With respect to the electric properties of the external additive for toner, preferably, the relative dielectric constant is 2.12 or more and 2.21 or less, and the electric conductivity index K / ω at a measurement frequency of 1 Hz ranges from 9.02 x 10 -14 (S / m) s or more and 4.51 x 10 -12 (S / m) s or less, or the volume resistivity at a measurement frequency of 0.021 Hz ranges from 2.19 x 10 12 (Ω-m) or more and 1.10 x 10 14 (Ω-m) or less.

[0045] According to necessity, the silica particles surface-treated with the polybasic acid metal salt particles can be further subjected to surface treatment such as hydrophobization treatment, provided that the properties of the toner external additive of the present disclosure are not impaired thereby. Examples of the hydrophobization treatment agent include unmodified silicone varnish, various modified silicone varnishes, unmodified silicone oil, various modified silicone oils, silane compounds, and silane coupling agents. These treatment agents can be used alone or in combination.

[0046] Next, a toner using the toner external additive of the present disclosure will be described.

[0047] The toner of the present disclosure contains toner particles and a toner external additive on the surface of the toner particles,

[0048] wherein the toner external additive is the toner external additive of the present disclosure.

[0049] The toner particles can contain known binder resins, colorants, and waxes, etc. The toner particles can contain a charge control agent in an amount not impairing the properties of the present disclosure, as necessary. An external additive other than the external additive of the present disclosure can be added to the toner particles.

[0050] The method for producing the toner particles is not particularly limited, and, for example, a production method such as a pulverization method, an emulsification aggregation method, a suspension polymerization method, or a dissolution suspension method, etc. can be employed herein. Furthermore, the toner external additive of the present disclosure can be externally added to the toner particles according to a known production method. The weight average particle diameter (D4) of the toner particles is preferably 4 to 12 μm, more preferably 5 to 8 μm.

[0051] Preferably, for the purpose of suppressing occurrence of excessive charging and in consideration of both good developing performance and good transferability, the volume resistivity at 0.021 Hz of the toner produced using the toner external additive of the present disclosure is 1.15 x 10 13 (Ω·m) or more and 1.00 x 10 14 (Ω·m) or less.

[0052] The binder resin is not particularly limited, provided that it can form toner particles. Illustrative examples include the following resin classes: styrene resins, acrylic resins, methacrylic resins, styrene-acrylic resins, styrene-methacrylic resins, polyvinyl resins, polyvinyl acetate resins, vinyl acetate resins, polybutadiene resins, phenol resins, polyurethane resins, polyoxymethylene resins, polyester resins, and hybrid resins in which the aforementioned resins are arbitrarily combined with each other.

[0053] Examples of the colorant include known organic pigments and dyes, carbon black, and magnetic bodies. The pigments can be used alone; alternatively, the dyes and pigments can be used in combination.

[0054] Examples of the colorant for magenta include C.I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48:1, 48:2, 48:3, 48:4, 48:5, 49, 50, 51, 52, 53, 54, 55, 57:1, 58, 60, 63, 64, 68, 81:1, 81:2, 81:3, 81:4, 81:5, 83, 87, 88, 89, 90, 112, 114, 122, 123, 146, 147, 150, 163, 184, 185, 202, 206, 207, 209, 238, 269, and 282; C.I. Pigment Violet 19; and C.I. Vat Red 1, 2, 10, 13, 15, 23, 29, and 35.

[0055] Examples of the colorant for cyan include copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, and basic dye lake compounds. Specific examples include C.I. Pigment Blue 1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, and 66.

[0056] Examples of the colorant for yellow include, for example, condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds. Specific examples include C.I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 62, 65, 73, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, and 185; and C.I. Vat Yellow 1, 3, and 20.

[0057] Examples of the colorant for black include carbon black, aniline black, acetylene black, and titanium black; iron oxide; and a colorant that is toned to black using a colorant for yellow, a toner for magenta, and a toner for cyan.

[0058] The content of the colorant in the toner particles is not particularly limited, as long as a desired coloring effect can be obtained. For example, the content of the colorant can be set to 3.0 parts by mass to 15.0 parts by mass with respect to 100 parts by mass of the binder resin or the polymerizable monomer.

[0059] Examples of the wax include petroleum-based waxes and derivatives thereof, such as paraffin wax, microcrystalline wax, and vaseline; montan wax and derivatives thereof; hydrocarbon waxes obtained according to the Fischer-Tropsch method and derivatives thereof; polyolefin waxes typified by polyethylene and derivatives thereof; and natural waxes and derivatives thereof, such as carnauba wax and candelilla wax. The derivatives also include oxides, block copolymers with vinyl monomers, and graft-modified products. Other examples include alcohols such as higher aliphatic alcohols, fatty acids such as stearic acid and palmitic acid, acid amides and esters of the aforementioned compounds, hardened castor oil and derivatives thereof, and plant waxes and animal waxes. The wax can be used alone or in a mixture of two or more kinds. The content of the wax in the toner particles is preferably 2.5 to 15.0 parts by mass with respect to 100 parts by mass of the binder resin or the polymerizable monomer.

[0060] As the charge control agent, a known charge control agent can be used. Examples of the charge control agent for controlling the toner particles so as to exhibit negative charging include high-molecular compounds having sulfonic acid groups, sulfonic acid base groups, or sulfonic acid ester groups; salicylic acid derivatives and metal complexes thereof; monoazo metal compounds; acetylacetone metal compounds; aromatic hydroxy carboxylic acids, aromatic monobasic acids, or polybasic acids, and metal salts, anhydrides, and esters thereof; phenol derivatives such as bisphenols; urea derivatives; boron compounds; and calixarenes. The charge control agent for controlling negative charging can be used alone or in a combination of two or more kinds. Examples of the charge control agent for controlling the toner particles so as to exhibit positive charging include aniline black and fatty acid metal salt-modified products thereof; guanidine compounds; imidazole compounds; onium salts such as quaternary ammonium salts such as tributylbenzyl-l-hydroxy-4-naphthalenesulfonic acid ammonium salt and tetrabutylammonium tetrafluoroborate and the like, and phosphonium salts as analogs of the aforementioned substances, and lake pigments of the aforementioned substances; triphenylmethane dyes and lake pigments thereof (examples of the fixing agent include phosphotungstic acid, phosphomolybdic acid, phosphotungstomolybdic acid, tannic acid, lauric acid, gallic acid, iron cyanide, and iron ferrocyanide); metal salts of higher fatty acids; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, and dicyclohexyltin oxide; and diorganotin borates such as dibutyltin borate, dioctyltin borate, and dicyclohexyltin borate. The charge control agent for controlling positive charging can be used alone or in a combination of two or more kinds. The content of the charge control agent in the toner particles is preferably 0.1 parts by mass or more and 10.0 parts by mass or less, more preferably 0.1 parts by mass or more and 5.0 parts by mass or less, with respect to 100 parts by mass of the binder resin or the polymerizable monomer.

[0061] Next, methods for measuring various properties of the external additive and the toner will be described.

[0062] Relative dielectric constant and volume resistivity of the external additive and the toner

[0063] Based on impedance measurement using a parallel-plate capacitor method, the electrical properties of external additives and toners were evaluated by measuring the capacitance and conductivity of air and powder.

[0064] The instrument used was a powder measurement jig consisting of a 4-terminal sample holder SH2-Z (manufactured by TOYO Corporation) and a torque wrench adapter SH-TRQ-AD (manufactured by TOYO Corporation, optional), and a material testing system ModuLab XM MTS (manufactured by Solartron Analytical) was also used. Furthermore, a noise cutting transformer NCT-I3 1.4kVA (manufactured by DENKENSEIKI Research Institute Co., Ltd.) for suppressing commercial power noise and a shield box for suppressing electromagnetic noise were used.

[0065] A configuration was adopted in which a 4-terminal sample holder and an optional torque wrench adapter SH-TRQ-AD were used as a powder measurement jig, and an upper electrode (Φ25 mm solid electrode) SH-H25AU and a liquid / powder lower electrode (central electrode Φ10 mm; guard electrode Φ26 mm) SH-2610AU were used as parallel plate electrodes, and the resistance was measured for an electric signal of at most 500 Vp-p, DC ~ AC 1 MHz, 0.1 Ω ~ 1 TΩ. In order to adjust the pressure on the powder sample, the torque wrench adapter SH-TRQ-AD was installed to a micrometer for film thickness measurement provided in the 4-terminal sample holder between the upper electrode and the lower electrode. The torque driver for controlling the pressure was configured so that the tightening torque for toner measurement could be controlled to 6.5 cN·m and the tightening torque for external additives could be controlled to 20.0 cN·m using a torque driver RTD15CN or RTD30CN (manufactured by Tohnichi Mfg. Co., Ltd.) and a square bit of 6.35 mm.

[0066] The electrical alternating current properties were measured by impedance measurement using a material testing system ModuLab XM MTS (manufactured by Solartron Analytical). The ModuLab XM MTS was composed of a control module XM MAT1 MHz, a high voltage module XMMHV100, a femto-current module XM MFA, and a frequency response analysis module XM MRA1 MHz; the control software used herein was XM-studio MTS version 3.4 made by the same company.

[0067] The measurement conditions for a powder material exhibiting insulating properties such as toner include a normal mode for measurement only, an alternating current level (AC level) of 7 Vrms, a direct current bias of 0 V, and a scan frequency of 1 MHz to 0.01 Hz (12 points / 10 decades or 6 points / 10 decades). In the case of a highly conductive powder material such as an external additive, the alternating current level is set in the range of 7 x 10 -3 Vrms to 7 Vrms so as to fall within the measurable current range of the measuring instrument.

[0068] The following settings are added for each scan frequency in consideration of noise suppression and shortening of measurement time.

[0069] Scan frequency: 1 MHz to 10 Hz Measurement integration time: 64 cycles

[0070] Scan frequency: 10 Hz to 1 Hz Measurement integration time: 24 cycles

[0071] Scan frequency: 1 Hz to 0.01 Hz Measurement integration time: 1 cycle

[0072] The impedance characteristics as electrical alternating current characteristics are measured under the above measurement conditions.

[0073] The impedance characteristics of air and a sample in the case of a measurement electrode S of Φ 10 mm and a film thickness d according to the pressurization torque can be obtained by measuring under the above conditions using a powder measurement jig based on the parallel plate capacitor method.

[0074] Data correction processing of the measurement system is performed based on the obtained impedance characteristics of air and a sample, and thus the capacitance C and the conductivity (electrical conductivity) G are obtained with high reliability. The relative dielectric constant and the electrical conductivity as electrical properties are calculated based on the obtained capacitance C and conductivity (electrical conductivity) G and the geometry (parallel plate electrode size S and sample film thickness) of the powder measurement jig.

[0075] When the 4-terminal sample holder SH2-Z is used for the first time, in view of individual differences of the 4-terminal sample holder SH2-Z for a jig for powder measurement, the following two verifications must be performed to find the optimum measurement conditions. The first verification is a film thickness dependency characteristic of the 4-terminal sample holder. The air thickness (distance between the upper electrode and the lower electrode) dependency is measured, and the error between the theoretical value and the measured value of the capacitance is confirmed to grasp the optimum range or optimum value of the film thickness at which the measurement error is the smallest. The second verification is a measurement of mechanical error. In powder sample measurement, a load is applied with torque control for the purpose of keeping the bulk density constant. In contrast, the measurement of air is performed in a no-load state. Here, a film thickness error occurs due to dimensional influences such as machining accuracy and the like. Therefore, the shift value of the tightening torque control value (6.5 cN-m in this jig) in the load state and in the no-load state is confirmed, and this result is used as a shift correction value.

[0076] The specific sample production and measurement procedure is as follows.

[0077] (1) The powder sample is placed on the center electrode portion of the lower electrode, and the sample is shaped into a trapezoidal shape with a height of 5 mm.

[0078] (2) The lower electrode on which the powder sample is placed is installed to the 4-terminal sample holder SH2-Z, and the upper electrode is lowered.

[0079] (3) While keeping vertical so as not to rotate inappropriately, the upper electrode is lowered to the upper end portion of the powder sample.

[0080] (4) Smoothing is performed so as to flatten the powder sample while rotating the upper electrode left and right.

[0081] (5) Using a micrometer, the rotation direction of the upper electrode is kept to a given direction while adjusting the film thickness to a predetermined value.

[0082] (6) In the case of toner, pressing is performed using a torque driver that controls the tightening torque to 6.5 cN-m. In the case of external additives, pressing is performed using a torque driver that controls the tightening torque to 20.0 cN-m.

[0083] (7) The film thickness of the powder sample is measured using a micrometer.

[0084] (8) Then, impedance measurement is performed under the above conditions.

[0085] (9) Once the measurement is completed, the upper electrode is raised and the lower electrode is taken out. Here, the lower electrode is taken out very carefully so as to prevent the powder sample from entering the lower electrode contact terminal of the 4-terminal sample holder, and then the taken-out lower electrode is protected with a shielding tape.

[0086] (10) The upper electrode and the lower electrode are cleaned.

[0087] (11) The masking tape is removed, and the lower electrode is installed.

[0088] (12) The sample film thickness d obtained in step (7) is adjusted to the air thickness t with the offset correction of the no-load state, and the rotation direction of the upper electrode is maintained in a given direction.

[0089] (13) The impedance of air is measured.

[0090] (14) In the case where the air measurement data (dielectric loss tangent; tan δ) measured in step (13) is greater than 0.001 in the frequency range of 100 Hz to 0.021 Hz, it is indicated that the cleaning here is insufficient, and therefore the operation is performed again from the cleaning step in step (10).

[0091] The measurement is performed at 25°C.

[0092] The specific data processing procedure is as follows.

[0093] (15) The error of the phase characteristic with respect to the theoretical value is calculated based on the measured impedance characteristic of air, to obtain the phase correction data of the material testing system ModuLab XM MTS (manufactured by Solartron).

[0094] (16) The phase correction data calculated in step (15) is applied to the impedance characteristic of air measured in step (13), to obtain the phase-corrected impedance characteristic of air.

[0095] (17) The capacitance Ca is calculated based on the admittance Ya = Ga + jωCa of the phase-corrected air impedance characteristic, and the error with respect to the theoretical value is calculated, to obtain the correction data a for the film thickness error.

[0096] (18) The phase correction process of step (15) is applied to the impedance characteristic of the powder sample as measured in step (8).

[0097] (19) For the complex admittance Ym = Gm + jωCm of the characteristic that has undergone the phase correction process in step (18), the capacitance Ca of air calculated in step (17) and the correction data a are used for calculation, and as a result, the relative dielectric constant and the electrical conductivity of the powder sample with high reliability are obtained.

[0098] The quantitative method of the relative dielectric constant and the volume resistivity as electrical properties will be described below.

[0099] Quantitative method of relative dielectric constant

[0100] The relative dielectric constant is a factor related to the charging characteristics of the particles, and thus it is observed that an increase in the relative dielectric constant confirms that the silica particles have been surface-treated with the polybasic acid metal salt particles. In the external additive of the present disclosure, it is considered that the capacitance increases and the relative dielectric constant becomes larger due to the chemical adsorption of the polybasic acid metal salt particles to the hydroxyl groups present on the surface of the silica particles. Specifically, as shown in Figure 2 the relative dielectric constant increases as the addition amount of titanium lactate as the surface treatment agent increases, and a saturated characteristic is obtained (external additives 1, 2, and 3 in the following examples) compared to the untreated silica particles (external additive 16 in the following examples). Herein, the value of the relative dielectric constant at the frequency at which the dielectric loss tangent tan δ is the smallest in the measured high frequency range is used as the relative dielectric constant representing the orientation polarization component of the powder sample.

[0101] Quantitative method of conductivity index κ / ω

[0102] In general, the conductivity κ of a dielectric (insulator) exhibits a characteristic that is proportional to the angular frequency; thus, it is useful to use the conductivity index κ / ω obtained by dividing the conductivity κ by the angular frequency ω as a conductivity parameter value. The conductivity index κ / ω represents a frequency characteristic similar to the dielectric loss tangent tan δ, and thus in a case where the electrode interface component and the powder bulk component exhibit different dielectric relaxation values, a characteristic having a maximum value can be obtained. It is found that the maximum value of the conductivity index κ / ω represents the conductivity of the powder bulk including the inside of the particles, the surface of the particles, and the (particle-particle) interface. Thus, the above-mentioned maximum value is defined as the conductivity parameter of the powder component.

[0103] It is considered that the conductivity is generated due to the dissociation of the hydroxyl groups present on the surface of the silica particles. Thus, it is considered that due to the chemical adsorption of the surface treatment agent to the hydroxyl groups, the number of dissociated hydroxyl groups as a factor of conductivity decreases, and the conductivity also decreases. Specifically, as shown in Figure 3 the conductivity index κ / ω is obtained to decrease as the addition amount of titanium lactate as one component of the surface treatment agent increases, so that the particles (external additives 1, 2, and 3) exhibit a characteristic similar to the usual hydrophobization treatment compared to the untreated silica particles (external additive 16). Furthermore, herein, the frequency characteristic at the time of obtaining the maximum value of the conductivity index κ / ω of the external additives 1, 2, and 3 is 1 Hz, and thus the value at 1 Hz is used as the conductivity index κ / ω of the external additives.

[0104] Quantitative method of conductivity and volume resistivity

[0105] The powder sample having both capacitance and conductivity can be considered as an RC parallel circuit model, and thus the conductivity κ in a low frequency range appears as a constant value. The volume resistivity is defined as the inverse of the conductivity κ.

[0106] The powder sample of the dielectric (insulator) exceeds the measurable range of the measuring device, and thus it is difficult to obtain the true volume resistivity. As a result, the volume resistivity (f = 0.021 Hz) is defined as the inverse of the conductivity κ at a measurement frequency of 0.021 Hz, which allows the accuracy of the measuring device to be ensured.

[0107] Method for detecting polyacid metal salt particles

[0108] The polyacid metal salt particles present on the surface of the silica particles were detected by time-of-flight secondary ion mass spectrometry (TOF-SIMS) in the following manner.

[0109] The external additive sample was analyzed by TOF-SIMS (TRIFT IV: manufactured by Ulvac-Phi, Inc.) under the following conditions.

[0110] - Primary ion species: gold ions (Au + )

[0111] - Primary ion current value: 2 pA

[0112] - Analysis area: 300 x 300 μm 2

[0113] - Number of pixels: 256 pixels x 256 pixels

[0114] - Analysis time: 3 min

[0115] - Repetition frequency: 8.2 kHz

[0116] - Charge neutralization: ON

[0117] - Secondary ion polarity: positive

[0118] - Secondary ion mass range: m / z 0.5 to 1850

[0119] - Sample substrate: indium

[0120] The polybasic acid metal salt particles present on the surface of the silica particles are identified based on the peaks obtained in the above analysis. In the case where peaks derived from secondary ions including metal ions and polybasic acid ions (for example, TiPO3 (m / z 127) and TiP2O5 (m / z 207) and the like in the case of a salt of phosphoric acid and a titanium compound) are detected, the polybasic acid metal salt particles are present on the surface of the silica particles.

[0121] Method for measuring the content of polybasic acid metal salt particles with respect to silica particles

[0122] The content of the polybasic acid metal salt particles with respect to the silica particles is calculated based on the fluorescent X-ray measurement. The fluorescent X-ray measurement of each element conforms to JIS K 0119-1969, and is specifically as follows. The measurement device used herein is a wavelength dispersion type fluorescent X-ray analyzer "Axios" (manufactured by PANalytical B.V.) with an attached special software "SuperQ version 4.0F" (manufactured by PANalytical B.V.) for setting measurement conditions and analyzing measurement data. Rhodium (Rh) is used as the anode of the X-ray tube bulb, the measurement atmosphere is vacuum, the measurement diameter (collimator mask diameter) is set to 27 mm, and the measurement time is set to 10 seconds. Detection is performed using a proportional counter (PC) to measure light elements, and a scintillation counter (SC) is used to measure heavy elements.

[0123] Herein, 4.0 g of the toner is placed in a special aluminum ring for compression, and the toner is flattened; then, a measurement sample is obtained in the form of a pellet having a thickness of 2 mm and a diameter of 39 mm by compression at 20 MPa for 60 seconds using a tablet forming compressor "BRE-32" (manufactured by Maekawa Testing Machine Mfg. Co. Ltd.). Measurement is performed under the above conditions, followed by identification of the elements based on the obtained X-ray peak positions; the concentration is calculated from the count rate (unit: cps) which is the number of X-ray photons per unit time.

[0124] Method for measuring the number average particle diameter of silica particles and external additive particles

[0125] The particle size distribution of the silica particles and the external additive particles is measured using a dynamic light scattering type particle size distribution meter Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.) according to the operation manual of the device. Specifically, the measurement sample is adjusted in the sample introduction portion of the measurement device so that the transmittance falls within the measurable range (70% to 95%), followed by measurement of the particle diameter corresponding to the cumulative value of 50% based on the number distribution (median particle diameter).

[0126] Method for measuring BET specific surface area of core particles

[0127] The BET specific surface area of core particles such as silica particles can be calculated by a low-temperature gas adsorption method using a dynamic constant pressure method in accordance with the BET method (preferably, the BET multipoint method). For example, using a specific surface area measuring device (Gemini 2375 version 5.0, manufactured by Shimadzu Corporation), nitrogen gas is adsorbed to the surface of a sample, and then measurement is performed in accordance with the BET multipoint method to thereby calculate the BET specific surface area (m 2 / g). Specifically, measurement is performed in accordance with the following procedure.

[0128] The mass of an empty sample cell is measured, after which the sample cell is filled with a sample to about 80% of the cell volume. The sample cell filled with the sample is set in a degassing device, and the sample is degassed for 7 hours at room temperature. After degassing, the mass of the entire sample cell is measured, and the accurate mass of the sample is calculated based on the difference with respect to the empty sample cell. The empty sample cell is then set in the equilibrium port and the analysis port of the BET measuring device. Then, a Dewar bottle containing liquid nitrogen is set at a predetermined position, and the saturation vapor pressure (P0) is measured by a P0 measurement command. Once the P0 measurement is completed, the degassed sample cell is set in the analysis port, the sample mass and P0 are input, and then measurement is started by a BET measurement command. Thereafter, the BET specific surface area is automatically calculated.

[0129] Method for measuring weight average particle diameter (D4) of toner particles

[0130] The weight average particle diameter (D4) of toner (or toner particles) is measured with an effective measurement channel number of 25,000 by using a precision particle size distribution measuring device "Coulter Counter Multisizer 3" (registered trademark, manufactured by Beckman-Coulter Inc.) based on the pore resistance method and equipped with a 100-μm orifice tube, and a dedicated software "Beckman Coulter Multisizer 3 version 3.51" (produced by Beckman-Coulter Inc.) for setting measurement conditions and analyzing measurement data, the measurement data is analyzed and calculated. An aqueous electrolyte solution to be used for measurement can be prepared by dissolving special-grade sodium chloride in ion-exchange water so as to have a concentration of about 1 mass%. For example, "ISOTON II" (manufactured by Beckman-Coulter Inc.) can be used.

[0131] Before measurement and analysis, the dedicated software was set as follows. On the "change standard measurement method (SOM) interface" of the dedicated software, the total count in the control mode was set to 50000 particles, the number of measurement cycles was set to 1, and the Kd value was set to the value obtained using "standard particles 10.0 pm" (manufactured by Beckman-Coulter Inc.). The threshold and noise levels were automatically set by pressing the threshold / noise level measurement button. In addition, the current was set to 1600 pA, the gain was set to 2, and the electrolyte solution was set to ISOTON II, and the post-measurement mouth tube flushing was checked. On the "pulse-to-particle size conversion setting interface" of the dedicated software, the element interval was set to the logarithmic particle size, the particle size elements were set to 256 particle size elements, and the particle size range was 2 pm or more and 60 pm or less.

[0132] The specific measurement method was as follows.

[0133] (1) About 200 ml of the electrolyte aqueous solution was placed in a glass 250 ml round-bottom beaker dedicated to the Multisizer 3, the beaker was placed on the sample stage, and stirring was performed with a stir bar and at 24 revolutions / second in a counterclockwise direction. Then, the dirt and air bubbles in the mouth tube were removed by the "flushing of the mouth tube" function of the dedicated software.

[0134] (2) About 30 ml of the electrolyte aqueous solution was placed in a glass 100 ml flat-bottom beaker, and about 0.3 ml of a diluent prepared by 3 mass-fold dilution of "Contaminone N" (a neutral cleaner for precision measuring instruments composed of a nonionic surfactant, an anionic surfactant, and an organic builder and having a pH of 7, manufactured by Wako Pure Chemical Industries, Ltd.) with ion exchange water as a dispersant was added thereto.

[0135] (3) A predetermined amount of ion exchange water was placed in a water tank of an ultrasonic disperser "Ultrasonic Dispersion System Tetora 150" (manufactured by Nikkaki Bios Co., Ltd.) having two oscillators with an oscillation frequency of 50 kHz and a power output of 120 W built therein in a state of phase shift of 180 degrees, and about 2 ml of Contaminone N was added to the water tank.

[0136] (4) The beaker in (2) was set in the fixing hole of the ultrasonic disperser, and the ultrasonic disperser was started. The height position of the beaker was adjusted to maximize the resonance state of the liquid level of the electrolyte solution in the beaker.

[0137] (5) While the state of the electrolyte aqueous solution in the beaker in (4) is irradiated with ultrasonic waves, about 10 mg of the toner (or toner particles) is gradually added to the electrolyte aqueous solution and dispersed. Then, the ultrasonic dispersion treatment is continued for 60 seconds. While the ultrasonic dispersion is performed, the temperature of the water in the water tank is appropriately adjusted to 10°C or higher and 40°C or lower.

[0138] (6) The electrolyte aqueous solution in which the toner is dispersed in (5) is dropped by using a pipette into the round bottomed beaker in (1) provided in a sample stage, and the measurement concentration is adjusted to about 5%. Then, the measurement is performed until the number of measured particles reaches 50,000.

[0139] (7) The measurement data is analyzed by using a dedicated software attached to the apparatus, and the weight average particle diameter (D4) is calculated. When the dedicated software is set to a graph / volume%, the "average diameter" on the analysis / volume statistical value (arithmetic mean) interface is the weight average particle diameter (D4).

[0140] Method for confirming polyacid metal salt particles on the surface of silica particles

[0141] Herein, the scanning electron microscope (SEM, TEM) can confirm that the silica particle of the external additive is surface-treated with the particulate polyacid metal salt. The observation by the TEM is performed in accordance with the following procedure.

[0142] The cross section of the silica particle is observed by using a transmission electron microscope (TEM) in accordance with the following method.

[0143] First, the silica particles are sufficiently dispersed in a room temperature curing type epoxy resin, after which the silica particles are cured in an atmosphere of 40°C for 2 days. A microtome (EMUC: manufactured by Leica Camera AG) equipped with a diamond blade is used to cut a thin sheet-shaped sample having a thickness of 50 nm from the obtained cured product. The sample is magnified 500,000 times under conditions including an acceleration voltage of 200 V and an electron probe size of 1 mm by using a TEM (JEM2800 type: manufactured by JEOL Ltd.), and the cross section of the silica particle is observed. Herein, the cross section of the silica particle having a number average particle diameter that is 0.9 to 1.1 times the number average particle diameter when measured in accordance with the method for measuring the number average particle diameter of the silica particle is selected. Then, it can be confirmed that the polyacid metal salt particles exist on the surface of the silica particle. Further, the cross-sectional area of the confirmed polyacid metal salt particle (primary particle) is measured and the circle equivalent diameter is calculated. The same treatment is performed on 100 or more particles, and the number average diameter of the primary particles is calculated.

[0144] Next, the constituent elements of the obtained cross section were analyzed by energy dispersive X-ray spectroscopy (EDX) to create an EDX mapping image (256 pixels x 256 pixels; 2.2 nm / pixel; 200 scans). In the created EDX mapping image, signals such as silicon inside the silica particles and phosphorus and titanium derived from the elements of the metal salt of the polyacid on the surface of the silica particles can be observed. The presence of the reaction product of the polyacid and the compound containing the Group 4 element can be confirmed by analysis with the above-mentioned time-of-flight secondary ion mass spectrometry (TOF-SIMS analysis).

[0145] Separation of external additives from toner

[0146] Separation of external additives from toner is done in the following manner.

[0147] Here, 1 g of toner was weighed and dispersed in 100 ml of water to which 1 mg of "Contaminon N" (a 10 mass% aqueous solution of a pH 7 precision measuring instrument cleaning neutral cleaner composed of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries) was added. The resulting dispersion was irradiated with ultrasonic waves, treated in a centrifuge at a predetermined strength, and the obtained supernatant was dried to thereby separate only the external additives.

[0148] Example

[0149] Next, the present disclosure will be described in more detail with reference to Production Examples and Examples, but these Examples are not intended to limit the present disclosure in any way. As used in the Examples, the language "parts" refers to mass parts in all instances.

[0150] Production Example of silica particles 1

[0151] Here, 500 parts of methanol and 70 parts of 10 mass% ammonia water were added to a 1.5 L glass reaction vessel equipped with a stirrer, a dropping nozzle, and a thermometer, and all the materials were mixed to obtain an alkaline catalyst solution. The alkaline catalyst solution was adjusted to 30°C, after which 100 parts of tetramethoxysilane (TMOS) and 20 parts of 8.0 mass% ammonia water were simultaneously added dropwise over 60 minutes while stirring to obtain a hydrophilic spherical silica particle dispersion liquid. The obtained spherical silica particle dispersion liquid was filtered, washed, and dried to obtain silica particles 1 as sol-gel silica particles. The number average particle diameter of the obtained silica particles 1 was 100 nm.

[0152] Production Examples of silica particles 2 to 9

[0153] Silica particles 2 to 9 were produced as sol-gel silica particles in the same manner as in the production example of silica particles 1 except that the adjustment temperature and the addition amount of the basic catalyst solution and the dropping time of tetramethoxysilane were appropriately changed. The physical properties of the obtained silica particles 2 to 9 are given in Table 1.

[0154] Silica particles 10 and 11

[0155] A dry silica particle having a particle diameter of 7 nm (AEROSIL (registered trademark) 300, manufactured by Nippon Aerosil Co., Ltd.) was prepared as silica particle 10, and a dry silica particle having a particle diameter of 600 nm (SO-E2 manufactured by Admatechs Co., Ltd.) was prepared as silica particle 11. Table 1 shows the physical properties of silica particles 10 and 11.

[0156] [Table 1]

[0157] Table 1

[0158]

[0159] Production example of external additive 1

[0160] - ion exchange water 100.0 parts

[0161] - sodium phosphate (dodecahydrate) (manufactured by RASA Industries, Ltd.) 8.5 parts

[0162] The above components were mixed to produce an aqueous phosphoric acid solution. Next, 63.0 parts of the aqueous phosphoric acid solution and 7.0 parts of silica particle 1 were added to a reaction vessel, and the whole was stirred at 55°C using a T.K. homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) at 12,000 rpm, and further 13.8 parts of a 44% aqueous titanium lactate solution (TC-310: manufactured by Matsumoto Fine Chemical Co., Ltd.) was added. Thereafter, while mixing using a propeller stirring blade, the pH was adjusted to 9.5 using a 1.0 mol / L aqueous NaOH solution, and the temperature was maintained at 55°C for 3 hours while stirring.

[0163] The temperature was lowered to 25°C, after which the solid component was taken out by centrifugation. Thereafter, the process of redispersion in ion-exchanged water and taking out the solid component by centrifugation was repeated three times to remove ions such as sodium. The solid component was again dispersed in ion-exchanged water and dried by spray drying to obtain silica particles on which particles of a salt of phosphoric acid and a titanium compound were covered. This silica particles were used as the external additive 1. The results of time-of-flight secondary ion mass spectrometry (TOF-SIMS) performed on the external additive 1 showed peaks originating from the salt of phosphoric acid and a titanium compound. The content of the particles of the salt of phosphoric acid and a titanium compound was calculated by fluorescence X-rays. Table 2 shows other physical properties. Here, the frequency at which the maximum value of the conductivity index K / ω of the external additive 1 was obtained was 1 Hz.

[0164] Production example of external additives 2 to 11

[0165] The external additives 2 to 11 were obtained in the same manner as in the production example of the external additive 1 except that the kind of the silica particles and the added amount of titanium lactate in the production example of the external additive 1 were changed as shown in Table 2. In all of the obtained external additives 2 to 11, peaks originating from the salt of phosphoric acid and a titanium compound were observed. Table 2 shows other physical properties.

[0166] Here, the frequency at which the maximum value of the conductivity index K / ω of the external additives 2 and 3 was obtained was 1 Hz.

[0167] Production example of external additive 12

[0168] The external additive 12 was obtained in the same manner as in the production example of the external additive 1 except that the silica particles 11 were used and the added amount of titanium lactate was changed to the amount shown in Table 2. In the obtained external additive 12, peaks originating from the salt of phosphoric acid and a titanium compound were observed. Table 2 shows other physical properties.

[0169] Production example of external additive 13

[0170] The external additive 13 was obtained in the same manner as in the production example of the external additive 1 except that the silica particles 10 were used and the added amount of titanium lactate was changed to the amount shown in Table 2. In the obtained external additive 13, peaks originating from the salt of phosphoric acid and a titanium compound were observed. Table 2 shows other physical properties.

[0171] Production example of external additive 14

[0172] The external additive 14 was obtained in the same manner as in the production example of the external additive 1 except that the sodium phosphate in the production example of the external additive 1 was changed to sodium carbonate. In the obtained external additive 14, peaks originating from a titanium carbonate compound were observed. Table 2 shows other physical properties.

[0173] Production example of external additive 15

[0174] The external additive 15 was obtained in the same manner as in the production example of the external additive 1 except that sodium phosphate in the production example of the external additive 1 was changed to sodium sulfate. In the obtained external additive 15, a peak derived from a titanium sulfate compound was observed. Table 2 shows other physical properties.

[0175] External additive 16

[0176] Silica particles 1 were used as the external additive 16.

[0177] Production example of external additive 17

[0178] An ilmenite containing 50 mass% of Ti02was used as a starting material. The starting material was dried at 150°C for 2 hours, and then dissolved by adding sulfuric acid, resulting in an aqueous solution of TiOS04. The aqueous solution of TiOS04was concentrated, and then 4.5 mass parts of a titanium dioxide sol having rutile crystals was added as a seed crystal, after which hydrolysis was performed at 110°C to obtain a slurry of impurity-containing TiO(OH)2. The slurry was repeatedly washed with water having a pH of 5 to 6 to sufficiently remove sulfuric acid, FeS04, and impurities. Thereby, a slurry of high-purity metatitanic acid [TiO(OH)2] was obtained. The slurry was filtered and calcined at 180°C for 2 hours, and then subjected to a repeated crushing treatment using a jet mill until no aggregate of fine particles remained. The titanium oxide was dispersed in ethanol, and then, while stirring sufficiently, 4.6 mass% of isobutyltrimethoxysilane and 4.6 mass% of trifluoropropyltrimethoxysilane were added dropwise with respect to 100 mass parts of titanium oxide solid and mixed to initiate a reaction, thereby preventing coalescence of the particles. While stirring sufficiently, the pH of the slurry was adjusted to 6.5. The slurry was then filtered and dried, followed by heat treatment at 170°C for 2 hours, and then subjected to a repeated crushing treatment using a jet mill until no aggregate of titanium oxide remained. This was used as the external additive 17. Table 2 shows the physical properties of the obtained external additive 17.

[0179] Production example of external additive 18

[0180] Ilmenite containing 50 mass% of Ti02was used as a starting material. The starting material was dried at 150°C for 2 hours, and then dissolved by adding sulfuric acid, resulting in an aqueous solution of TiOS04. The aqueous solution of TiOS04was concentrated, and then 4.5 mass parts of titanium dioxide sol having rutile crystals was added as a seed crystal, after which hydrolysis was performed at 110°C to obtain a slurry of impurity-containing TiO(OH)2. The slurry was repeatedly washed with water having a pH of 5 to 6 to sufficiently remove sulfuric acid, FeS04, and impurities. A slurry of high-purity metatitanic acid [TiO(OH)2] was thus obtained. The slurry was filtered and calcined at 180°C for 2 hours, and then subjected to a repeated crushing process using a jet mill until no aggregate of fine particles remained, resulting in titanium oxide core particles. Measurement of the BET specific surface area of the titanium oxide core particles showed a result of 75.3 m 2 / g.

[0181] The following components were mixed to produce an aqueous phosphoric acid solution.

[0182] - ion-exchanged water 100.0 parts

[0183] - sodium phosphate (dodecahydrate) (manufactured by RASA Industries, Ltd.) 8.5 parts

[0184] Next, 63.0 parts of the aqueous phosphoric acid solution and 7.0 parts of the titanium oxide core particles were added to a reaction vessel, and the whole was stirred at 55°C using a T.K. homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) at 12,000 rpm, and further 3.27 parts of a 44% aqueous titanium lactate solution (TC-310: manufactured by Matsumoto Fine Chemical Co., Ltd.) was added. Thereafter, while mixing using a propeller stirring blade, the pH was adjusted to 9.5 using a 1.0 mol / L aqueous NaOH solution, and then the temperature was maintained at 55°C for 3 hours while stirring. The temperature was lowered to 25°C, after which the solid component was taken out by centrifugation. Thereafter, the process of redispersing in ion-exchanged water and taking out the solid component by centrifugation was repeated three times to remove ions such as sodium. The product was again dispersed in ion-exchanged water, and dried by spray drying to obtain titanium oxide particles in which the particles of the salt of phosphoric acid and a titanium compound were covered. These coated titanium oxide particles were used as the external additive 18. The results of time-of-flight secondary ion mass spectrometry (TOF-SIMS) performed on the external additive 18 showed peaks derived from the salt of phosphoric acid and a titanium compound. Table 2 shows other physical properties.

[0185] Production example of external additive 19

[0186] Herein, 100 parts by mass of a dry silica powder having a volume median particle diameter (D50) of 80 nm obtained by a gas phase synthesis method and 25 parts by mass of a titanium dioxide powder (AEROXIDE (registered trademark) NKT90, manufactured by Nippon Aerosil Co., Ltd.) having a volume median particle diameter (D50) of 15 nm were mixed for 30 seconds using a pin mill ("Sample Mill SAM-0 type" manufactured by Nara Machinery Co., Ltd.) under the condition that the rotation speed was 600 rpm. As a result, a silica-titanium dioxide composite particle in which a plurality of titanium dioxide particles (externally added titanium dioxide particles) were attached to the surface of each silica particle contained in the silica powder was obtained. These silica-titanium dioxide composite particles were used as the external additive 19. Table 2 shows the physical properties of the external additive 19.

[0187] [Table 2]

[0188] Table 2

[0189]

[0190] In the table, the number average particle diameter (nm) indicates the number average particle diameter of primary particles of the polybasic acid metal salt particles.

[0191] It is considered that, in the external additive of the present disclosure, the polybasic acid metal salt particles as the surface treatment agent become chemisorbed to the surface of the untreated silica particles, and at least a reaction occurs between and a bond is formed between the polybasic acid metal salt particles and the surface of the untreated silica particles in part. This is indicated by the changes in the relative dielectric constant and the electrical conductivity as the electrical properties. The results are shown in Table 2. Figure 1

[0192] Figure 2 The dependency of the relative dielectric constant on the added amount of the surface treatment agent (titanium lactate) in the external additives 1 to 3 and 16 is shown; the dependency will be described below.

[0193] Figure 2 It is indicated that, due to the fact that the polybasic acid metal salt particles become chemisorbed to the hydroxyl groups present on the surface of the external additive 16 (untreated silica particles), the capacitance of the charging property is improved, and the relative dielectric constant increases. It was found that the relative dielectric constant increases with the added amount of titanium lactate until saturation.

[0194] Figure 3 The dependency of the electrical conductivity on the added amount of the surface treatment agent (titanium lactate) in the external additives 1 to 3 and 16 is shown; the dependency will be described below.

[0195] ​The fact that the polybasic acid metal salt particles become chemisorbed to the hydroxyl groups present on the surface of the externally added agent 16 (untreated silica particles) reduces the number of dissociated hydroxyl groups, which are factors of electrical conductivity, and also reduces the electrical conductivity.

[0196] The electrical conductivity K of the titanium phosphate and titanium trioxide produced by Mitsuwa Chemicals Co., Ltd. was 1.27 x 10 -4 ((S / m) s) and 9.80 x 10 -6 ((S / m) s). Thus, the polybasic acid metal salt particles generally exhibit high electrical conductivity. In view of the electrical conductivity of the toner external additive of the present disclosure, it is considered that the polybasic acid metal salt particles do not simply adhere to the silica particles, but at least a portion of the polybasic acid metal salt particles reacts with the surface of the silica particles.

[0197] Production Example of Toner Particles 1

[0198] Production Example of Polymerizable Monomer Composition

[0199] The following components were mixed and then dispersed in a ball mill for 3 hours.

[0200]

[0201]

[0202] [Polycondensate of propylene oxide-modified bisphenol A and isophthalic acid (glass transition temperature: 65°C, weight average molecular weight (Mw): 10,000, number average molecular weight (Mn): 6,000)]

[0203] The obtained dispersion liquid was heated at 60°C while being stirred at 300 rpm, and then 12.0 parts of ester wax (peak temperature of the largest endothermic peak obtained by differential scanning calorimetry: 70°C, and number average molecular weight (Mn): 704) and 3.0 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) were added and dissolved to obtain a polymerizable monomer composition.

[0204] Production Example of Water-Based Dispersion Medium

[0205] Here, 710 parts of ion-exchanged water and 450 parts of a 0.1 mol / L sodium phosphate aqueous solution were added to a 2L four-necked flask equipped with a high-speed stirring device, T.K. homomixer (manufactured by Primix Corporation), and the whole was heated at 60°C while being stirred at 12,000 rpm. Then, 68.0 parts of a 1.0 mol / L calcium chloride aqueous solution was gradually added thereto to prepare a water-based dispersion medium containing calcium phosphate as a minute water-insoluble dispersion stabilizer.

[0206] Granulation / polymerization step

[0207] The polymerizable monomer composition was put into an aqueous dispersion medium, and granulation was performed for 15 minutes while maintaining a rotation speed of 12000 rpm. Thereafter, the high-speed stirrer was replaced with a propeller stirring blade, and polymerization was continued for 5 hours at an internal temperature of 60°C. The internal temperature was then raised to 80°C, and polymerization was continued for another 3 hours. Once the polymerization reaction was completed, the residual monomers were distilled off under reduced pressure at 80°C, followed by cooling to 30°C, to obtain a polymer fine particle dispersion liquid.

[0208] Washing / drying step

[0209] The obtained polymer fine particle dispersion liquid was transferred to a washing vessel, and the pH was adjusted to 1.5 by adding dilute hydrochloric acid while stirring. The dispersion liquid was stirred for 2 hours, and then solid-liquid separation was performed using a filter to obtain polymer fine particles. The obtained polymer fine particles were put into 1.0 L of ion exchange water and stirred to again generate a dispersion liquid, and then solid-liquid separation was performed using a filter. This operation was performed three times, after which the polymer fine particles obtained from the final solid-liquid separation were sufficiently dried in a drier at 30°C to obtain toner particles 1 having a weight average particle diameter (D4) of 6.8 μm.

[0210] Production example of toner 1

[0211] Here, 2.0 parts of external additive 1 was mixed with 100 parts of toner particles 1 using an FM mixer (manufactured by Nippon Coke & Engineering Co., Ltd.). The external addition conditions included a toner particle input amount of 1.8 kg, a rotation speed of 3600 rpm, and an external addition time of 30 minutes. Thereafter, toner 1 was obtained by sieving using a screen having a mesh size of 200 μm.

[0212] Production examples of toners 2 to 19

[0213] Toner 2 to 19 were obtained in the same manner except that the external additive used in the production example of toner 1 was changed as shown in Table 3.

[0214] Production example of toner 20

[0215] Herein, 2.0 parts of external additive 16 and 1.0 part of external additive 17 were mixed with 100 parts of toner particles 1 using an FM mixer (manufactured by Nippon Coke & Engineering Co., Ltd.). The external addition conditions included a toner particle input amount of 1.8 kg, a rotation speed of 3600 rpm, and an external addition time of 30 minutes. Thereafter, toner 20 was obtained by sieving using a sieve having a mesh size of 200 μm.

[0216] Examples 1, 4 to 15 and Comparative Examples 1 to 5

[0217] The following describes the methods of various evaluations performed on toner 1 and toners 4 to 20. The evaluation results are shown in Table 3. In the evaluations, a laser beam printer LBP652C manufactured by Canon Inc. was used. The toners were taken out of the cyan cartridge, and then toners 1 and 4 to 20 were respectively filled, and the following evaluations were performed.

[0218] Evaluation of fogging

[0219] The charging amount control performance of the external additives was evaluated based on the fogging evaluation. In an environment of 15°C and a humidity of 10.0% RH, which is a severe environment in terms of excessive charging, 3000 images were output, and then an image having a white background portion was output, and then the fogging density (%) was calculated based on the difference between the whiteness of the white background portion as measured using a "REFLECTOMETER MODEL TC-6DS: manufactured by Tokyo Denshoku Co., Ltd." and the whiteness of the evaluation paper; and then the fogging was evaluated in accordance with the following criteria. An amber color filter was used as the filter. A grade of A or more was judged to be good.

[0220] A: 0.5% or less

[0221] B: 0.6% or more and 1.5% or less

[0222] C: 1.6% or more and 2.5% or less

[0223] D: 2.6% or more

[0224] Evaluation of transferability

[0225] The performance of leakage along with the external additives was evaluated by the evaluation of transferability. The transferability was evaluated in a high temperature high humidity environment (temperature of 30.0°C, relative humidity of 85%) which is considered to be relatively severe in terms of transferability. The evaluation paper used was FOX RIVER BOND paper (110 g / m 2), which is a rough paper. The untransferred toner on the photosensitive member after transfer of the solid black image was affixed and peeled off using a polyester adhesive tape (No. 31B, width 15 mm) (manufactured by Nitto Denko Corporation). Herein, C is the value of Macbeth reflective density on the tape affixed to the paper, D is the value of Macbeth density in the case where the tape is affixed to the paper having toner before fixation after transfer, and E is the value of Macbeth density of the tape affixed to unused paper. As a close approximation, the transferability was approximately calculated according to the following expression. The larger the resulting value, the better the transferability indicated thereby. A level of C or more was judged to be good.

[0226] Transferability (%) = {(D - C) / (D - E)} x 100

[0227] A: Transferability is 95% or more

[0228] B: Transferability is 90% or more and less than 95%

[0229] C: Transferability is 85% or more and less than 90%

[0230] D: Transferability is less than 85%.

[0231] Evaluation of Image Density

[0232] The durability performance depending on the external additive was evaluated based on the change in image density. The image density was evaluated in a high-temperature high-humidity environment (temperature: 30.0°C, relative humidity: 80%). As a long-term durability test, an output test of a total of 12,000 sheets was performed in a mode in which a horizontal line pattern having an image coverage of 1% was set to 1 sheet / 1 job according to a setting in which the instrument is stopped between jobs and then starts the next job. The difference in image density between the 1st sheet and the 12,000th sheet was measured. Herein, A4 color laser copier paper (manufactured by Canon Inc., 80 g / m 2 ) was used. The image density was measured by outputting a solid black patch image of 5 mm x 5 mm and by measuring the reflective density using an SPI filter in a Macbeth densitometer (manufactured by Macbeth Corporation) as a reflective densitometer. The smaller the difference in image density between the 1st sheet and the 12,000th sheet, the better the durability indicated thereby, and a level of C or more was judged to be good.

[0233] A: Difference in image density is less than 0.10.

[0234] B: Difference in image density is 0.10 or more and less than 0.20.

[0235] C: The image density difference is 0.20 or more and less than 0.25.

[0236] D: The image density difference is 0.25 or more.

[0237] The evaluation results are shown in Table 3.

[0238] [Table 3]

[0239] Table 3

[0240]

[0241] While the present disclosure has been described with reference to example embodiments, it is to be understood that the disclosure is not limited to the disclosed example embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An external additive for toner, comprising silica particles surface-treated with polybasic acid metal salt particles, characterized in that the polybasic acid metal salt particles are particles of a titanium phosphate compound or a titanium carbonate compound, the relative dielectric constant of the external additive at a frequency at which the dielectric loss tangent tan d is the smallest is 2.10 or more and 2.20 or less, the content of the polybasic acid metal salt particles in the silica particles is 0.01 mass% or more and 1.00 mass% or less, the number average particle diameter of primary particles of the polybasic acid metal salt particles is 2.0 nm or more and 10.0 nm or less, The BET specific surface area of the silica particles is 6 m 2 / g or more and 290 m 2 / g or less, and The volume resistivity of the toner external additive is 1.54 x 10 12 Ω·m or more and 1.32 x 10 14 Ω·m or less.

2. The external additive for toner according to claim 1, wherein the polybasic acid metal salt particles are particles of a titanium phosphate compound.

3. The external additive for toner according to claim 1, wherein the number average particle diameter of the silica particles is 10 nm or more and 500 nm or less.

4. The external additive for toner according to claim 1, wherein the silica particles are sol-gel silica particles.

5. A toner comprising toner particles and an external additive for toner on the surface of the toner particles, characterized in that the external additive for toner is the external additive for toner according to any one of claims 1 to 4.

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