Toner and manufacturing method therefor

Abstract

To provide a toner with which it is possible to increase the addition amount of an inorganic particulate to a toner, and which, consequently, excels in charging characteristic and fixability, and with which occurrence of fogging can be prevented, and a method for manufacturing the toner.SOLUTION: Provided is a toner having the structure described below. An inorganic particulate of 10 to 60 nm in average particle diameter is included in the inside of the toner particle. The inorganic particulate is at least one element selected from the group consisting of strontium titanate, silica covered with alumina, and titania. When it is assumed that layers in depth of 0-10 nm, 10-100 nm, and 100 nm or greater from the surface of the toner particle are respectively toner layers A to C, then the abundance of the inorganic particulate is largest in the toner layer C. An interface α where the abundance of the inorganic particulate is small and an interface β where the abundance is large exist at an interface (toner layer B) in the electronic image of a toner particle cross section, and the interface length of both is 2 μm or greater. The abundance of the inorganic particulate at the interface α is 15% or less than the same at the interface β.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a toner and a method for producing the same. [Background technology]

[0002] In electrophotographic image forming devices such as copiers, multifunction machines, printers, and facsimile machines, a toner image is formed on a photoconductor by conveying a developer (toner in one-component development, or toner and carrier in two-component development) to the surface of the photoconductor on which an electrostatic latent image has been formed. Generally, the toner used is made by adhering an external additive to the surface of toner particles (toner cores) whose main component is a binder resin.

[0003] When the charge distribution of the toner in the developer varies locally, causing unevenness in the charge amount (hereinafter referred to as charge unevenness), there will be areas where the potential difference between the surface potential of the photosensitive member and the developing bias differs locally, making fogging more likely to occur.Fog refers to the phenomenon in which toner is developed in non-image areas where toner should not be developed.

[0004] One way to solve this problem is to add inorganic fine particles with a lower resistance than the toner particles as an external additive. Such inorganic fine particles function as a charge control agent in the toner, and can propagate the locally charged negative charge to surrounding toner particles or release it into the air.

[0005] As an example of a toner containing inorganic fine particles as an external additive, Patent Document 1 discloses a toner containing hydrophobized titania (titanium oxide) particles with an average particle diameter of 20 nm to 100 nm as an external additive, in which the titania particles account for 2% to 20% of the toner particle surface. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-3844 Summary of the Invention [Problem to be solved by the invention]

[0007] However, an increase in the amount of inorganic fine particles added as an external additive causes performance degradation such as a deterioration in the low-temperature fixability of the toner, an excessive increase in the fluidity of the toner, an excessive decrease in the charge amount of the toner, etc. Therefore, it is necessary to limit the amount of inorganic fine particles added, which causes a problem that it is difficult to fully exert the function of the inorganic fine particles as a charge adjusting agent.

[0008] The contents of the present disclosure have been discovered in view of the above circumstances, and a main object of the present disclosure is to provide a toner and a method for producing the same that can increase the amount of inorganic fine particles added to the toner, and ultimately have excellent charging properties and fixability, and can suppress the occurrence of fogging. [Means for solving the problem]

[0009] The toner of the present disclosure, which has been made to solve the above problems, A toner having toner particles including a binder resin, a colorant, and a release agent, the toner particles contain inorganic fine particles therein having an average particle diameter of 10 nm or more and 60 nm or less, the inorganic fine particles are at least one selected from the group consisting of strontium titanate fine particles, alumina-coated silica fine particles, titania fine particles, alumina fine particles, zinc oxide fine particles, cerium oxide fine particles, and calcium carbonate fine particles; When a layer having a depth from the surface of the toner particle of 0 nm or more and less than 10 nm is defined as toner layer A, a layer having a depth of 10 nm or more and less than 100 nm is defined as toner layer B, and a layer having a depth of 100 nm or more is defined as toner layer C, the toner layer B has a higher abundance ratio of the inorganic fine particles than the toner layer A and the toner layer C, In an electron image of the cross section of the toner particle obtained by a scanning electron microscope, when a region corresponding to the toner layer B is defined as an interface, there are an interface α where the inorganic fine particles are present in a small proportion and an interface β where the inorganic fine particles are present in a large proportion, The interface length of the interface α and the interface β is 2 μm or more, The abundance ratio of the inorganic fine particles in the interface α is 15% or less of the abundance ratio of the inorganic fine particles in the interface β.

[0010] In the toner, the inorganic fine particles are preferably at least one selected from the group consisting of strontium titanate fine particles, alumina-coated silica fine particles, and titania fine particles.

[0011] In the above toner, it is preferable that the proportion of the inorganic fine particles in the interface α is 10% or less in an electron image of the cross section of the toner particle obtained by a scanning electron microscope.

[0012] In the above toner, it is preferable that the proportion of the inorganic fine particles in the interface β is 90% or more in an electron image of the cross section of the toner particle obtained by a scanning electron microscope.

[0013] In the toner, it is preferable that the adhesive strength of the inorganic fine particles to the toner particles is 90% or more.

[0014] In the toner, the content of the inorganic fine particles in the toner particles is preferably 2% by mass or more and 10% by mass or less.

[0015] In the above toner, it is preferable that silica fine particles are attached to the surface of the toner particles as an external additive, and that the coverage of the toner particle surface with the silica fine particles is 70% or more and 110% or less.

[0016] In the toner, it is preferable that the adhesion strength of the silica fine particles to the toner particles is 50% or more and 80% or less.

[0017] The toner manufacturing method of the present disclosure, which has been made to solve the above problems, comprises: a melt-kneading step of melt-kneading a mixture of raw materials including a binder resin, a colorant, and a release agent; a coarse pulverization step of coarsely pulverizing the molten kneaded product obtained in the melt kneading step; an inorganic fine particle mixing step of mixing the coarsely pulverized product obtained in the coarse pulverization step with inorganic fine particles; a fine pulverization step of finely pulverizing the coarsely pulverized material containing the inorganic fine particles obtained in the inorganic fine particle mixing step; and a classification step of classifying the finely pulverized product obtained in the finely pulverizing step. [Effects of the Invention]

[0018] The toner and the method for producing the same according to the present disclosure exhibit excellent effects such as the ability to increase the amount of inorganic fine particles added to the toner, excellent charging properties and fixability, and ability to suppress the occurrence of fogging. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating a toner according to an exemplary embodiment. [Figure 2] FIG. 1 is a cross-sectional view schematically illustrating an example of a toner to which inorganic fine particles are added as an external additive. [Figure 3] 1 is an electron image of a cross section of a toner particle according to the exemplary embodiment, observed with a scanning electron microscope. [Figure 4] FIG. 4 is an enlarged view of the electronic image of FIG. 3, showing toner layers A to C. [Figure 5] FIG. 4 is an enlarged view of the electronic image of FIG. 3, showing toner layers A to C. [Figure 6] FIG. 4 is an enlarged view of the interface α and the interface β in the electron image of FIG. 3. [Figure 7] FIG. 2 is a front view schematically illustrating that, in the toner manufacturing method according to the present embodiment, after the coarsely pulverized material and inorganic fine particles are mixed, fine pulverization and classification are carried out. DETAILED DESCRIPTION OF THE INVENTION

[0020] The toner and its manufacturing method according to the present disclosure will be described in detail below. In this disclosure, "external addition" means adding an additive so that it adheres to the outer surface (surface) of an object to which the additive is added, and "internal addition" means adding an additive so that the additive is contained inside the object to which the additive is added.

[0021] 1. Toner particles (toner cores) The toner particles according to the present embodiment contain at least a binder resin, a colorant, and a release agent. Internal additives such as the colorant and the release agent are dispersed in the binder resin. Furthermore, the toner particles may contain optional components as long as the effects of the present disclosure are not impaired. The average particle diameter of the toner particles can be appropriately selected depending on the purpose, and may be, for example, 4 μm or more and 8 μm or less.

[0022] The toner particles according to the present embodiment contain inorganic fine particles having an average particle diameter of 10 nm to 60 nm. Preferably, the average particle diameter of the inorganic fine particles is 30 nm to 40 nm. Below, the inorganic fine particles will be described first, followed by a description of each component, such as the binder resin.

[0023] <Inorganic fine particles> Fig. 1 is a cross-sectional view that schematically shows a toner 1 according to this embodiment. As shown in Fig. 1, a large amount of inorganic fine particles 3 are embedded inside a toner particle 2. The toner particle 2 has a portion where many inorganic fine particles 3 are embedded (interface β, described later) and a portion where almost no inorganic fine particles 3 are present (interface α, described later). In other words, the inorganic fine particles 3 are unevenly distributed.

[0024] Here, the mechanism by which the toner according to this embodiment can increase the amount of inorganic fine particles added to the toner, and as a result, can have excellent charging properties and fixability and can suppress the occurrence of fogging will be described.

[0025] A developer containing toner is triboelectrically charged by stirring in a developer tank. FIG. 2 is a cross-sectional view of a toner 101, an example of a toner containing inorganic fine particles as external additives. External additives 103 and 104 (reference numeral 103 denotes inorganic fine particles that function as a charge control agent) are uniformly attached to the surface of toner particles 102. As mentioned above, when a charge control agent is added as an external additive, the amount of charge control agent added must be limited. In toner 101, even when toner particles 102 come into contact with each other when the developer is stirred in a developer tank, a conductive path is not formed as shown by the arrow in FIG. 2 because the amount of charge control agent 103 added is small. To form a conductive path in toner 101, the amount of charge control agent 103 added must be significantly increased. However, this would result in performance degradation, such as a deterioration in the toner's low-temperature fixability, an excessive increase in toner fluidity, and an excessive decrease in the toner's charge amount.

[0026] In contrast, the toner according to this embodiment has a large amount of inorganic fine particles embedded inside the toner particles (toner layer B, described later), serving as a charge control agent. The toner particles have a portion where many inorganic fine particles are embedded (interface β, described later) and a portion where almost no inorganic fine particles are present (interface α, described later). In this case, the apparent amount of inorganic fine particles added (coverage) when viewed from the surface of the toner particles is reduced, thereby suppressing deterioration of toner performance, such as a decrease in charge amount and an increase in fluidity. When the developer is stirred in the developer tank, the portions where many inorganic fine particles are embedded (interface β, described later) come into contact with each other, forming a conductive path as shown by the arrow in FIG. 1. This reduces the difference in toner charge amount within the developer.

[0027] Furthermore, in the toner according to this embodiment, inorganic fine particles are embedded inside the toner particles (toner layer B, which will be described later). Therefore, even if the amount of inorganic fine particles added as an external additive is increased to an amount that would be considered excessive, it is possible to suppress detachment of the inorganic fine particles from the toner particles, and it is possible to suppress changes in the charging characteristics throughout the product's life.

[0028] That is, in the toner according to the present embodiment, there are localized portions (interfaces β described later) where many inorganic fine particles are embedded, thereby making it possible to mitigate the environmental charge difference (charge amount in a low-humidity environment - charge amount in a high-humidity environment) while suppressing charge reduction, in other words, to realize a toner with excellent environmental charge characteristics. Furthermore, the toner according to the present embodiment exerts the effect of suppressing charge reduction while mitigating the environmental charge difference, thereby making it possible to suppress the occurrence of fogging, including after toner is replenished to the developer and after continuous image formation.

[0029] Next, the distribution of the inorganic fine particles in the toner particles according to this exemplary embodiment will be specifically described with reference to FIGS.

[0030] Fig. 3 is an electron image of a cross section of a toner particle according to this embodiment observed with a scanning electron microscope, and Figs. 4 and 5 are enlarged versions of the electron image of Fig. 3, showing toner layers A to C. Here, toner layer A is a layer having a depth from the surface of the toner particle of 0 nm or more but less than 10 nm, toner layer B is a layer having a depth of 10 nm or more but less than 100 nm, and toner layer C is a layer having a depth of 100 nm or more. As can be seen from Figs. 4 and 5, in the toner particles according to this embodiment, the concentration of the inorganic fine particles in toner layer B is higher than the concentrations of the inorganic fine particles in toner layer A and toner layer C. In other words, the abundance ratio of the inorganic fine particles in toner layer B is higher than the abundance ratio of the inorganic fine particles in toner layer A and toner layer C.

[0031] In the toner particles according to the present embodiment, when an electron image of a cross section of a toner particle obtained by a scanning electron microscope shows a region corresponding to toner layer B as an interface, there are an interface α where the inorganic fine particles are present in a small proportion and an interface β where the inorganic fine particles are present in a large proportion. The interface length between the interface α and the interface β is 2 μm or more.

[0032] 6 is an enlarged view of the interface α and the interface β in the electronic image of FIG. 3, and it can be seen that the toner particles according to this embodiment have interfaces α and β having lengths equal to or greater than a certain level. The reason why the toner particles according to this embodiment have interfaces α and β will be explained later in "3. Toner manufacturing method."

[0033] In the toner particles according to this embodiment, the abundance ratio of the inorganic fine particles at interface α is 15% or less of the abundance ratio of the inorganic fine particles at interface β. According to the manufacturing method according to this embodiment, which will be described later in "3. Toner Manufacturing Method," it is possible to manufacture a toner in which the inorganic fine particles are unevenly distributed in this manner, and by satisfying this abundance ratio, the effects according to the present disclosure can be achieved. The abundance ratio is preferably 10% or less, and more preferably 5% or less.

[0034] The volume resistivity of the inorganic fine particles is 2.0×10 9 Ω cm or more 2.0×10 14 It is preferably Ω·cm or less. By setting the volume resistivity within the above range, the charge distribution of the toner can be made sharper, and the toner can have better charge characteristics.

[0035] In the toner particles according to this embodiment, the inorganic fine particles are at least one selected from the group consisting of strontium titanate fine particles, alumina-coated silica fine particles, titania fine particles, alumina fine particles, zinc oxide fine particles, cerium oxide fine particles, and calcium carbonate fine particles. These inorganic fine particles have a lower resistance than the toner particles and function to transfer negative charges locally charged on the surface of the toner particles to surrounding toner particles or to release them into the air. When a large amount of inorganic fine particles is added to the toner, they form a conductive path as described above, reducing charging unevenness and effectively suppressing the occurrence of fogging, particularly in low-humidity environments.

[0036] Among these, the inorganic fine particles are preferably at least one selected from the group consisting of strontium titanate fine particles, alumina-coated silica fine particles, and titania fine particles from the viewpoints of volume resistivity and imparting fluidity to the toner.

[0037] Strontium titanate microparticles can be produced, for example, by a normal pressure heating reaction method. When producing them by the normal pressure heating reaction method, a mineral acid peptized product of a titanium compound hydrolyzate is used as the titanium oxide source, and a water-soluble acidic metal compound is used as the metal source other than titanium. For example, strontium nitrate or hydrochloride can be used as the strontium source. The nitrate salt can be strontium nitrate, and the hydrochloride salt can be strontium chloride. Strontium titanate microparticles can be produced by adding an aqueous alkaline solution to a mixture of these raw materials at 60°C or higher, reacting them, and then treating them with an acid. The strontium titanate microparticles obtained in this manner have a perovskite crystal structure, which is advantageous in that they have increased stability of charge to environmental changes.

[0038] The strontium titanate microparticles used as the inorganic microparticles may be silica-doped strontium titanate microparticles obtained by doping silica into strontium titanate microparticles. While ordinary strontium titanate microparticles have an angular shape when used alone, silica-doped strontium titanate microparticles have a rounded shape due to the doping with silica. Therefore, the silica-doped strontium titanate microparticles have better dispersibility.

[0039] The silica-doped strontium titanate fine particles can be produced, for example, by the following procedures (1) to (5). (1) After desulfurization and bleaching of metatitanic acid obtained by the sulfuric acid method, an aqueous solution of sodium hydroxide is added for desulfurization, and then the mixture is neutralized with hydrochloric acid, filtered, and washed to obtain a washed cake. (2) Water is added to the washed cake to form a slurry, and then hydrochloric acid is added to perform a peptization treatment. This is called Solution 1, and is mixed with Solution 2, an aqueous solution of strontium chloride, and Solution 3, an aqueous solution of sodium silicate. The mixing ratio of Solutions 1, 2, and 3 is set so that the molar ratio of (Sr+Si) / Ti is within the range of 1.18 to 2.10. (3) The mixed solution is heated to 90°C under a nitrogen gas atmosphere, stirred for 2 hours while adding an aqueous sodium hydroxide solution, and then stirred at 90°C for 1 hour to allow the reaction to proceed. (4) After the reaction, the slurry is cooled to 50°C, hydrochloric acid is added, and the mixture is stirred for 1 hour. The resulting precipitate is washed, separated by filtration, and then dried. (5) The dried product is ground in a blender for 1 minute, and the resulting fine powder is then sieved to remove coarse particles. The resulting fine powder is then surface-coated with a silane coupling agent. Examples of methods for surface coating with a silane coupling agent include surface treatments commonly used in the art, such as those using hexamethyldisilazane (HMDS), dimethyldichlorosilane (DDS), octylsilane (OTAS), and polydimethylsiloxane (PDMS).

[0040] The average particle size of the strontium titanate particles is preferably 20 nm or more and 50 nm or less. 9 Ω or more 5×10 10 It is preferably Ω or less.

[0041] The alumina-coated silica fine particles are silica fine particles whose surfaces are coated with aluminum hydroxide, and the surfaces thereof are preferably hydrophobized with a silane compound, such as by surface coating with a silane coupling agent.

[0042] The silica fine particles in the alumina-coated silica fine particles include silica fine particles commonly used in the technical field, such as dry-process silica such as fumed silica obtained by burning silicon tetrachloride and arc-process silica in which silica is microparticulated in the gas phase using high energy such as plasma; wet-process silica such as precipitation-process silica synthesized under alkaline conditions using an aqueous sodium silicate solution as a raw material and gel-process silica synthesized under acidic conditions; colloidal silica obtained by polymerizing acidic silicic acid in an alkaline state; and sol-gel-process silica obtained by hydrolysis of an organic silane compound.

[0043] The average particle diameter of the alumina-coated silica particles is preferably 10 nm or more and 40 nm or less. The resistance value is preferably 1.0×10 11 It is preferably Ω or less.

[0044] The titania microparticles may be anatase-type titania microparticles or rutile-type titania microparticles. Rutile-type titania microparticles can be produced, for example, by the method described in JP 2001-26423 A, i.e., by hydrolyzing an aqueous solution of titanium tetrachloride to prepare a fine titania sol having rutile nuclei, which is then separated and heat-treated to obtain titania microparticles. An anatase-type titania microparticle can be produced, for example, by the method described in JP 2000-10335 A, i.e., by hydrolyzing and granulating a solution obtained by dissolving raw materials such as ilmenite ore in sulfuric acid, followed by drying and high-temperature calcination to obtain titania microparticles.

[0045] In the toner according to the present embodiment, in an electron image of a toner particle cross section obtained with a scanning electron microscope, the proportion of the inorganic fine particles at interface α is preferably 10% or less, more preferably 5% or less. If the proportion of the inorganic fine particles at interface α exceeds the upper limit, a conductive path may be formed by the inorganic fine particles up to interface α, as with interface β. The presence of interface α with a sufficiently small proportion of the inorganic fine particles reduces the apparent amount of inorganic fine particles added (coverage) when the toner particles are viewed from the surface, making it possible to suppress deterioration of toner performance such as a decrease in charge amount and an increase in fluidity.

[0046] In the toner according to the present embodiment, in an electron image of the cross section of a toner particle obtained by a scanning electron microscope, the abundance ratio of the inorganic fine particles at interface β is preferably 90% or more, more preferably 95% or more. When the abundance ratio of the inorganic fine particles at interface β is within the above range, the inorganic fine particles present at interface β form conductive paths in the developer, thereby reducing charging unevenness and ultimately suppressing the occurrence of fogging. When the abundance ratio of the inorganic fine particles at interface β is below the above lower limit, conductive paths may not be formed, and the effect of reducing charging unevenness may be reduced.

[0047] The adhesion strength of the inorganic fine particles to the toner particles according to the present embodiment is preferably 90% or more, and more preferably 95% or more. In toners to which inorganic fine particles are added as external additives, the adhesion strength of the external additive to the toner particles is approximately 60% to 80%, and the external additive is detached due to the physical force applied when the developer is stirred, resulting in external additive contamination. In contrast, in the toner according to the present embodiment, the inorganic fine particles are added in an excessive amount when added as an external additive, but because the inorganic fine particles are embedded inside the toner particles, the adhesion strength can be kept within the above range, preventing the inorganic fine particles from detaching and preventing contamination due to the inorganic fine particles. Furthermore, the effect of the inorganic fine particles as a charge adjusting agent can be sustained.

[0048] The content of the inorganic fine particles in the toner particles according to the present embodiment is preferably 2% by mass to 10% by mass, more preferably 4% by mass to 8% by mass. In toners containing inorganic fine particles as an external additive, the amount of charge control agent added is approximately 0 to 1.5 parts by mass per 100 parts by mass of toner particles. Addition of a greater amount leads to a deterioration in toner performance, as described above. In contrast, in the toner according to the present embodiment, the presence of an interface α where the inorganic fine particles are present at a low concentration reduces the apparent amount of inorganic fine particles added (coverage) when viewed from the surface of the toner particles. Therefore, even when the inorganic fine particles are added to achieve a content within the above range, no significant deterioration in toner performance occurs. Furthermore, when the content of the inorganic fine particles is within the above range, a sufficient amount of the inorganic fine particles is present in the toner layer B of the toner particles, allowing conductive paths to be rapidly formed, thereby reducing uneven charging of the toner.

[0049] <Binder resin> The toner particles according to the present embodiment contain a binder resin. The binder resin is not particularly limited, and resins used in the field of electrophotography can be used, for example, polyester-based resins, polystyrene-based resins such as styrene-acrylic-based resins, (meth)acrylic acid ester-based resins, polyolefin-based resins, polyurethane-based resins, and epoxy-based resins. These resins may be used alone or in combination of two or more. Among these, polystyrene-based resins and polyester-based resins are preferred, and polyester-based resins are particularly preferred.

[0050] The polystyrene resin is preferably a styrene-acrylic resin (styrene-acrylic copolymer resin), and examples of styrene monomers that can be used as resin raw materials include styrene derivatives such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, and 2,4-dimethylstyrene. Examples of acrylic monomers include acrylic acid derivatives and methacrylic acid derivatives such as acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate, and dimethylamino methacrylate.

[0051] Furthermore, vinyl monomers such as maleic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid monophenyl ester, maleic acid monoallyl ester, and divinylbenzene may be used as the resin raw material.

[0052] The polyester resin used in the binder resin is usually obtained by polycondensation reaction of one or more selected from dihydric alcohol components and trihydric or higher polyhydric alcohol components with one or more selected from dicarboxylic acids and trihydric or higher polycarboxylic acids via an esterification reaction or an ester exchange reaction by a known method.

[0053] The conditions for the polycondensation reaction may be appropriately set depending on the reactivity of the monomer components, and the reaction may be terminated when the polymer has reached the desired physical properties. For example, the reaction temperature is about 170°C to 250°C, and the reaction pressure is about 5 mmHg to atmospheric pressure.

[0054] Examples of the dihydric alcohol component include alkylene oxide adducts of bisphenol A such as polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(3.3)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(2.0)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(2.0)-polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane, and polyoxypropylene(6)-2,2-bis(4-hydroxyphenyl)propane; ethylene glycol Examples of suitable bisphenol A include diols such as glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; bisphenol A; propylene adducts of bisphenol A; ethylene adducts of bisphenol A; and hydrogenated bisphenol A.

[0055] Examples of trihydric or higher polyhydric alcohol components include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose (cane sugar), 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

[0056] In the toner particles according to this embodiment, one of the dihydric alcohol components and trihydric or higher polyhydric alcohol components may be used alone, or two or more of them may be used in combination.

[0057] Examples of divalent carboxylic acids include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n-dodecenylsuccinic acid, n-dodecylsuccinic acid, n-octylsuccinic acid, isooctenylsuccinic acid, isooctylsuccinic acid, and acid anhydrides and lower alkyl esters thereof.

[0058] Examples of trivalent or higher polyvalent carboxylic acids include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empol trimer acid, and acid anhydrides and lower alkyl esters thereof.

[0059] In the toner particles according to this exemplary embodiment, one of the dicarboxylic acids and tricarboxylic or higher polycarboxylic acids may be used alone, or two or more of them may be used in combination.

[0060] The weight-average molecular weight of the polyester resin is preferably 3,000 or more and 50,000 or less. If the weight-average molecular weight is less than the lower limit, the peelability may be poor on the high-temperature side of the fixable region (non-offset region). On the other hand, if the weight-average molecular weight exceeds the upper limit, the low-temperature fixability may be poor.

[0061] The polyester resin preferably has an acid value of 5 mgKOH / g or more and 30 mgKOH / g or less. If the acid value is less than the lower limit, the chargeability of the polyester resin decreases, and the charge control agent becomes difficult to disperse in the polyester resin, which may adversely affect the charge buildup and charge stability during continuous printing. On the other hand, if the acid value exceeds the upper limit, the hygroscopicity increases, which may cause the chargeability to become unstable.

[0062] <Coloring agent> The toner particles according to this embodiment contain a colorant, and examples of the colorant that can be used include organic pigments, organic dyes, inorganic pigments, and inorganic dyes that are used in the field of electrophotography.

[0063] Examples of black colorants include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, non-magnetic ferrite, magnetic ferrite, and magnetite.

[0064] Examples of yellow colorants include CI Pigment Yellow 12, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 15, CI Pigment Yellow 17, CI Pigment Yellow 74, CI Pigment Yellow 93, CI Pigment Yellow 94, CI Pigment Yellow 138, CI Pigment Yellow 180, and CI Pigment Yellow 185.

[0065] Examples of magenta colorants include CI Pigment Red 48:1, CI Pigment Red 53:1, CI Pigment Red 57:1, CI Pigment Red 122, CI Pigment Red 123, CI Pigment Red 139, CI Pigment Red 144, CI Pigment Red 149, CI Pigment Red 166, CI Pigment Red 177, CI Pigment Red 178, and CI Pigment Red 222.

[0066] Examples of cyan colorants include CI Pigment Blue 15, CI Pigment Blue 15:2, CI Pigment Blue 15:3, CI Pigment Blue 16, and CI Pigment Blue 60.

[0067] The content of the colorant in the toner particles is preferably 3 parts by mass or more and 10 parts by mass or less. The colorant may be used in the form of a masterbatch in order to disperse it uniformly in the binder resin.

[0068] <Release agent> The toner particles according to this embodiment contain a wax as a release agent. Examples of the wax include waxes used in the electrophotography field, such as paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polyethylene wax, polypropylene wax, carnauba wax, and synthetic ester wax. These waxes may be used singly or in combination of two or more.

[0069] The content of the release agent in the toner particles is preferably 0.5% by mass or more and 10% by mass or less.

[0070] <Charge control agent> The toner particles according to the present embodiment may contain a charge control agent. The charge control agent is added to impart a desired charge property to the toner. The charge control agent is not particularly limited, and charge control agents for positive charge control and negative charge control used in the field of electrophotography can be used.

[0071] Examples of charge control agents for controlling positive charges include quaternary ammonium salts, pyrimidine compounds, triphenylmethane derivatives, guanidine salts, and amidine salts.

[0072] Charge control agents for negative charge control include metal-containing azo compounds, azo complex dyes, metal complexes and metal salts of salicylic acid and its derivatives (metals include chromium, zinc, zirconium, etc.), organic bentonite compounds, and boron compounds.

[0073] These charge control agents may be used alone or in combination of two or more. The content of the charge control agent in the toner particles is preferably 0.5% by mass or more and 5% by mass or less.

[0074] 2.External additives The toner according to this embodiment may have an external additive attached to the surface of the toner particles, and silica fine particles are suitable as the external additive. By using silica fine particles as an external additive, it is possible to impart appropriate fluidity to the toner, thereby improving the stirring performance in the developer and facilitating the formation of conductive paths.

[0075] The silica microparticles used as external additives include silica microparticles commonly used in the art, such as fumed silica obtained by burning silicon tetrachloride, dry-process silica such as arc-process silica, which is obtained by microparticulating silica in the gas phase using high energy such as plasma; wet-process silica such as precipitation-process silica synthesized under alkaline conditions using sodium silicate aqueous solution as a raw material, and gel-process silica synthesized under acidic conditions; colloidal silica obtained by polymerizing acidic silicic acid in an alkaline state; and sol-gel-process silica obtained by hydrolysis of an organic silane compound.The silica microparticles may have their surfaces hydrophobized with a silane compound to improve the electrical properties of the photoreceptor.Examples of the hydrophobization treatment include surface coating with a silane coupling agent.

[0076] As the silica particles used as the external additive, commercially available hydrophobized silica particles may be used, or silica particles that have not been hydrophobized may be used after being subjected to a treatment.

[0077] In the toner according to the present embodiment, the coverage of the toner particle surface with silica fine particles as an external additive is preferably 70% to 110%, and more preferably 90% to 100%. By ensuring that the coverage with silica fine particles is within the above range, the heat resistance of the toner can be improved without deteriorating the fixability of the toner.

[0078] The adhesion strength of the silica fine particles as an external additive to the toner particles according to this embodiment is preferably 50% to 80%, more preferably 50% to 70%. If the adhesion strength of the silica fine particles exceeds the upper limit, the silica fine particles are embedded in the surface of the toner particles, making it impossible to impart the desired fluidity. If the adhesion strength of the silica fine particles is less than the lower limit, the silica fine particles are likely to detach from the surface of the toner particles, making external additive contamination more likely to occur.

[0079] 3. Toner manufacturing method The toner manufacturing method according to this embodiment includes a melt-kneading step S1 in which a mixture of toner raw materials is melt-kneaded, a coarse pulverization step S2 in which the melt-kneaded mixture obtained in the melt-kneading step S1 is coarsely pulverized, an inorganic fine particle mixing step S3 in which the coarse pulverized mixture obtained in the pulverization step S2 is mixed with inorganic fine particles, a fine pulverization step S4 in which the coarse pulverized mixture containing inorganic fine particles obtained in the inorganic fine particle mixing step S3 is finely pulverized, and a classification step S5 in which the fine pulverized mixture obtained in the fine pulverization step S4 is classified.

[0080] In the melt-kneading step S1, toner raw materials such as a binder resin, a colorant, and a release agent are mixed in a mixer such as a Henschel mixer, and then kneaded using a kneader to obtain a melt-kneaded product.

[0081] Mixing is preferably dry, and any known mixer commonly used in the art can be used, such as a Henschel-type mixer such as Henschel Mixer (trade name, manufactured by Nippon Coke and Engineering Co., Ltd.), Super Mixer (trade name, manufactured by Kawata Corporation), or Mechano Mill (trade name, manufactured by Okada Seiko Co., Ltd.), as well as mixers such as Ang Mill (trade name, manufactured by Hosokawa Micron Corporation), Hybridization System (trade name, manufactured by Nara Machinery Works, Ltd.), or Cosmo System (trade name, manufactured by Kawasaki Heavy Industries, Ltd.).

[0082] The kneader may be a known device commonly used in the technical field, such as a twin-screw extruder, a three-roll mill, or a lab blast mill. Specific examples include single- or twin-screw extruders such as TEM-100B (trade name, manufactured by Toshiba Machine Co., Ltd.), PCM-65 / 87, or PCM-30 (all of which are trade names, manufactured by Ikegai Corporation), and open-roll type kneaders such as Kneadex (trade name, manufactured by Nippon Coke and Engineering Co., Ltd.). Among these, open-roll type kneaders are preferred because they exert a strong shear force during kneading and can highly disperse the toner materials.

[0083] In the coarse pulverization step S2, the molten and kneaded product obtained in the melt-kneading step S1 is cooled and solidified, and then coarsely pulverized using a pulverizer to obtain coarsely pulverized products (toner flakes) having an average particle size of 1 mm to 10 mm. As the pulverizer, a known device commonly used in the technical field can be used, and examples thereof include a speed mill, a hammer mill, and a cutting mill.

[0084] 7, in the toner manufacturing method according to this embodiment, after mixing the coarsely pulverized material 21 and the inorganic fine particles 3 in the inorganic fine particle mixing step S3, the finely pulverized material 21 and the inorganic fine particles 3 are subjected to a finely pulverized material 22. Since the surface (pulverized surface) formed by pulverizing the coarsely pulverized material 21 in the finely pulverized material 22 is almost free of inorganic fine particles 3, an interface α where the inorganic fine particles 3 are present in a small proportion and an interface β where the inorganic fine particles 3 are present in a large proportion are formed in the finely pulverized material 22. Furthermore, by performing the steps in this order, toner particles in which the inorganic fine particles 3 are embedded can be obtained.

[0085] In the inorganic fine particle mixing step S3, the coarsely pulverized material obtained in the coarse pulverization step S2 is mixed with inorganic fine particles. The amount of inorganic fine particles added per 100 parts by mass of the coarsely pulverized material (toner raw material) is preferably 2 parts by mass or more and 10 parts by mass or less, and more preferably 4 parts by mass or more and 8 parts by mass or less. The mixer used for this mixing can be a known device commonly used in the technical field.

[0086] In the fine pulverization step S4, the coarsely pulverized material (coarsely pulverized material containing inorganic fine particles) obtained in the inorganic fine particle mixing step S3 is finely pulverized. As the pulverizer, a known device commonly used in the technical field can be used, for example, a jet pulverizer that pulverizes using a supersonic jet airflow, or an impact pulverizer that pulverizes a solidified material by introducing it into the space formed between a rotor and a stator (liner) rotating at high speed.

[0087] In the classification step S5, the finely pulverized product obtained in the finely pulverized step S4 is classified using a classifier. A known device commonly used in the art can be used for classification. A classifier capable of removing excessively pulverized toner particles by centrifugal force and wind power, such as a rotary wind classifier, is preferred.

[0088] In the external addition step S6, the toner particles obtained in the classification step S5 are mixed with the external additives using a mixer, thereby adhering the external additives to the toner particles. The mixer may be a known device commonly used in the art. Examples include Henschel-type mixers such as Henschel Mixer (trade name, manufactured by Nippon Coke & Engineering Co., Ltd.), Super Mixer (trade name, manufactured by Kawata Corporation), and Mechano Mill (trade name, manufactured by Okada Seiko Co., Ltd.), as well as mixers such as Ang Mill (trade name, manufactured by Hosokawa Micron Corporation), Hybridization System (trade name, manufactured by Nara Machinery Works, Ltd.), and Cosmo System (trade name, manufactured by Kawasaki Heavy Industries, Ltd.). [Example]

[0089] The toner and its manufacturing method according to the present disclosure will be specifically described below based on examples and comparative examples.

[0090] 1.Measurement method <Method for measuring adhesive strength> The toner sample obtained by carrying out the deposit removal treatments shown in (1) to (6) below is referred to as "Sample 1," and the toner sample before carrying out the deposit removal treatment is referred to as "Sample 2."

[0091] - Deposit removal treatment - (1) 2.0 g of toner is added to 40 ml of a 0.2% by mass aqueous solution of polyoxyethylene octylphenyl ether (manufactured by The Dow Chemical Company, trade name: Triton), and the mixture is stirred for 1 minute. (2) Using an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd., model: US-300T), the aqueous solution obtained in (1) above is irradiated with ultrasonic waves at an output of 40 μA for 4 minutes. (3) After the ultrasonic irradiation, the aqueous solution is left to stand for 3 hours to separate the toner from the deposits. (4) After removing the supernatant, add approximately 50 ml of purified water to the precipitate and stir for 5 minutes. (5) The solution is subjected to suction filtration using a membrane filter (manufactured by Advantec) with a pore size of 1 μm. (6) The toner remaining on the membrane filter is vacuum dried overnight.

[0092] Next, the X-ray intensity of specific elements in the deposits for 1 g of each of "Sample 1" and "Sample 2" is analyzed using a fluorescent X-ray analyzer (Rigaku Corporation, Model: ZSX Primus II). Based on the analysis results, the adhesion strength of the deposits (inorganic fine particles or external additives present at the interface) to the toner particles is calculated using the following formula. The specific elements are "Si" for silica fine particles, "Sr" for strontium titanate fine particles, "Al" for alumina fine particles, and "Ti" for titania fine particles. Adhesion strength = (X-ray intensity in sample 2) / (X-ray intensity in sample 1) × 100

[0093] <Method for measuring the abundance of inorganic fine particles> Mix the toner with an epoxy resin (manufactured by DEVCON, product name: DEV-TUBE S-31), pour it into a mold, and let it stand for 24 hours or more to cure, obtaining a cured sample. Next, using a microtome (manufactured by Leica, model: ultramicrotome EM UC7), cut out an ultrathin section (thickness 60 nm) of the cured sample. Sample the cut ultrathin section onto a grid (manufactured by Nisshin EM Co., Ltd., product name: EM fine grid F-200). Vapor-phase stain the sample on this grid with a 0.5% aqueous solution of ruthenium (VIII) tetroxide for about 1 minute. Photograph the stained sample using a scanning electron microscope (SEM, manufactured by Hitachi High-Technologies Corporation, model: S-4800). By the above procedure, photograph the cross-section of the toner particles.

[0094] Next, from the cross-sectional image of the photographed toner particles, cut out an image of the region (the region corresponding to toner layers A to C or the region corresponding to interface α or interface β) for which the abundance ratio of inorganic fine particles is to be measured, and calculate the "abundance ratio of inorganic fine particles" by the following formula based on the occupancy ratio of inorganic fine particles within the range of the cut-out image. Note that the cut-out of this image is performed such that the number n of inorganic fine particles within the range of the cut-out image satisfies 50 < n. In the following formula, d is the average particle diameter of the inorganic fine particles, n is the number of inorganic fine particles within the range of the cut-out image, and A is the total area of the range of the cut-out image.

Equation

[0095] <Method for measuring the average particle diameter of external additives> Photograph the toner with a scanning electron microscope (SEM, manufactured by Hitachi High-Technologies Corporation, model: S-4800), measure the particle diameters (major diameters) of 100 arbitrary external additives on the surface of the toner particles from the obtained image, and take the average value as the average particle diameter of the external additives.

[0096] <Method for measuring the average particle diameter of inorganic fine particles> From the image taken by the above "Method for measuring the abundance ratio of inorganic fine particles," the particle diameters (major diameters) of 100 arbitrary inorganic fine particles present in the toner layer B are measured, and the average value is taken as the average particle diameter of the inorganic fine particles.

[0097] <Method for measuring the coverage of toner particle surfaces with external additives> The toner is photographed using a scanning electron microscope (SEM, manufactured by Hitachi High-Technologies Corporation, model: S-4800). The coverage rate F of the external additive is calculated using the following formula derived from a model calculation of the projected area. In the formula, D is the average particle diameter of the toner particles, ρ t is the specific gravity of the toner particles, d is the average particle diameter of the external additive, ρ i is the specific gravity of the external additive, and C is the number of parts by mass of the external additive added.

number

[0098] 2. Manufacture of toner and two-component developer [Example 1] <Melting and kneading process> The toner raw materials used in the melt-kneading step are as follows: Binder resin: amorphous polyester resin 83% by mass Colorant: CI Pigment Red 269 6% by mass Release agent: WE-22 (trade name, manufactured by NOF Corporation) 4% by mass Charge control agent: salicylic acid compound 1% by mass Crystalline polyester resin 6% by mass

[0099] The above toner raw materials were premixed for 5 minutes using a Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd., model: FM20C), and then melt-kneaded using an open-roll continuous kneader (manufactured by Nippon Coke and Engineering Co., Ltd., model: MOS320-1800) to obtain a molten mixture. The open-roll settings were: a heating roll temperature of 150°C on the supply side, a discharge side of 125°C, and a cooling roll temperature of 20°C on the supply side, a discharge side of 20°C. The heating roll and cooling roll both had a diameter of 320 mm and an effective length of 1550 mm, with a roll gap of 0.3 mm on both the supply and discharge sides. The heating roll rotation speed was 75 rpm, the cooling roll rotation speed was 65 rpm, and the toner raw materials were supplied at a rate of 6.5 kg / h.

[0100] <Coarse grinding process> The resulting melt-kneaded product was cooled on a cooling belt and then coarsely pulverized using a speed mill equipped with a φ2 mm screen to obtain a coarsely pulverized product.

[0101] <Inorganic fine particle mixing process> To 100 parts by mass of the obtained coarsely pulverized material, 6.0 parts by mass of strontium titanate microparticles (manufactured by Titan Kogyo Co., Ltd., product name: SWS-450CF, average particle diameter 34 nm) as inorganic microparticles were added, and the mixture was stirred for 1 minute using a Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd., model: FM20C) with the tip speed of the stirring blade set to 20 m / s, to obtain a coarsely pulverized material with inorganic microparticles added.

[0102] <Fine grinding process> The obtained coarsely pulverized product containing the inorganic fine particles was pulverized using a jet pulverizer (manufactured by Nippon Pneumatic Mfg. Co., Ltd., model: IDS-2) to obtain a finely pulverized product.

[0103] <Classification process> The resulting finely pulverized material was classified using an elbow jet classifier (manufactured by Nittetsu Mining Co., Ltd., model: EJ-LABO) to obtain toner particles, which had an average particle size of 6.2 μm.

[0104] <External addition process> A toner was obtained by mixing 100 parts by mass of the obtained toner particles and 1.2 parts by mass of silica microparticles (manufactured by Nippon Aerosil Co., Ltd., product name: RX200, average particle diameter 7 nm) for 2 minutes using a Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd., model: FM20C) with the tip speed of the stirring blade set to 40 m / s.

[0105] <Manufacturing process of two-component developer> The obtained toner and a resin-coated carrier were mixed so that the concentration of the toner relative to the total amount of the two-component developer was 7%, to obtain a two-component developer with a toner concentration of 7%.

[0106] [Examples 2 to 6, 9 to 12, 17, and 18, and Comparative Examples 1 to 3] As shown in Table 1 below, toner particles, toner, and two-component developers were obtained in the same manner as in Example 1, except that the type and amount of inorganic fine particles added and the coverage rate with external additives were changed. The inorganic fine particles used in Example 17 were alumina-coated silica fine particles (manufactured by Teika Corporation, product name: MSW-02, average particle diameter 15 nm), and the inorganic fine particles used in Example 18 were titania fine particles (manufactured by Titan Kogyo Co., Ltd., product name: ST-550R, average particle diameter 40 nm). The inorganic fine particles used in Comparative Example 1 were silica fine particles (manufactured by Nippon Aerosil Co., Ltd., product name: RX200, average particle diameter 12 nm), the inorganic fine particles used in Comparative Example 2 were silica fine particles (manufactured by Nippon Aerosil Co., Ltd., product name: R976S, average particle diameter 7 nm), and the inorganic fine particles used in Comparative Example 3 were strontium titanate fine particles (manufactured by Titan Kogyo Co., Ltd., product name: SW-100, average particle diameter 390 nm).

[0107] [Examples 7 and 8] In the pulverization step and classification step, the average particle size of the obtained toner particles was kept at 6.2 μm, and the air volume and rotation speed were adjusted to adjust the adhesion strength of the inorganic fine particles to the values ​​shown in Table 1 below. In the same manner as in Example 1, toner particles, a toner, and a two-component developer were obtained.

[0108] [Example 13] Toner particles, a toner, and a two-component developer were obtained in the same manner as in Example 1, except that the stirring time in the external addition step was changed to 3 minutes.

[0109] [Example 14] Toner particles, a toner, and a two-component developer were obtained in the same manner as in Example 1, except that the stirring time in the external addition step was changed to 1 minute 30 seconds.

[0110] [Example 15] In the external addition step, 100 parts by mass of the obtained toner particles and 1.2 parts by mass of silica fine particles (manufactured by Nippon Aerosil Co., Ltd., product name: RX200, average particle diameter 7 nm) were first stirred for 2 minutes (first stirring) using a Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd., model: FM20C) with the tip speed of the stirring blade set to 40 m / s. Next, the mixture obtained in the first stirring was stirred for an additional 2 minutes (second stirring) under the same conditions as the first stirring to obtain a toner. Except for this change in the external addition step, the toner particles, toner, and two-component developer were obtained in the same manner as in Example 1.

[0111] [Example 16] Toner particles, a toner, and a two-component developer were obtained in the same manner as in Example 1, except that the stirring time in the external addition step was changed to 1 minute.

[0112] Comparative Example 4 The process up to the coarse pulverization step was carried out in the same manner as in Example 1, and the coarsely pulverized material was finely pulverized and classified without carrying out the inorganic fine particle mixing step (the coarsely pulverized material to which inorganic fine particles had not been added was finely pulverized and classified), thereby obtaining toner particles with an average particle size of 6.2 μm in the same manner as in Example 1. The external addition step was modified from Example 1 so that strontium titanate fine particles were also added in addition to silica fine particles, and a toner was obtained. A two-component developer was produced in the same manner as in Example 1.

[0113] [Table 1]

[0114] Table 1 is a table summarizing the types of inorganic fine particles used in the inorganic fine particle mixing step, the average particle diameter and the number of parts added, the coverage by the external additive, and various measurement results.

[0115] 4. Evaluation <Evaluation item 1: Evaluation of charging characteristics (environmental charging characteristics)> 0.3 g of toner and 3.7 g of carrier were weighed into a screw tube and placed in one of three environmental chambers (25°C, 5% humidity (NL), 25°C, 50% humidity (NN), or 35°C, 80% humidity (HH)) with the screw tube cap removed for 24 hours. The screw tube cap was then closed and the developer was shaken at 25.3 Hz for 1 minute in a mixer mill (Verder Scientific, Model MM200). The charge (μC / g) of the two-component developer in each environment was measured using a suction-type charge analyzer (Trek, Model 210HS). The environmental charge characteristics were evaluated based on the difference in charge between the environments using the following criteria:

[0116] ◎ (Excellent): The difference in charge amount in each environment is 5 μC / g or less. ◯ (Good): The difference in charge amount in each environment is more than 5 μC / g and 10 μC / g or less. △ (Acceptable): The difference in charge amount in each environment is more than 10 μC / g and 15 μC / g or less. × (bad): The difference in charge amount between the environments exceeds 15 μC / g.

[0117] <Evaluation item 2: Evaluation based on fog value> Using a commercially available copier (Model MX-5100FN, manufactured by Sharp Corporation) modified as an evaluation machine, an image was printed on recording paper (PPC paper, Model SF-4AM3, manufactured by Sharp Corporation) in which 10% of the printable area was filled with toner, and the brightness of a specific unfilled area was measured using a colorimeter (Model ZE6000, manufactured by Nippon Denshoku Industries Co., Ltd.). The difference between this brightness and the brightness measured before printing was taken as the fog value. Evaluation was performed based on the measured fog value according to the following criteria. The specified fog value refers to the specified value determined depending on the evaluation machine and evaluation content.

[0118] ◎ (Excellent): The measured value is 80% or less of the specified fogging value. ◯ (Good): The measured value is more than 80% and 90% or less of the specified fog value. △ (Acceptable): The measured value is more than 90% and 100% or less of the specified fog value. × (bad): The measured value is more than 100% of the specified fog value.

[0119] <Evaluation Item 3: Evaluation of Fixability (Low Temperature Fixability)> A fixed image was formed using a two-component developer using a commercially available copying machine (manufactured by Sharp Corporation, model: MX-5100FN) modified as an evaluation machine. First, a sample image including a solid image (a rectangle measuring 20 mm in height and 50 mm in width) was formed as an unfixed image on recording paper (manufactured by Sharp Corporation, PPC paper, model: SF-4AM3). At this time, the amount of toner adhering to the recording paper in the solid image was 0.5 mg / cm. 2 It was adjusted to be.

[0120] Next, a fixed image was formed using a hard roller fixing device. The fixing process speed was set to 283 mm / sec, and the temperature of the fixing roller was increased in 5°C increments from 110°C to determine the lowest temperature at which low-temperature offset did not occur. Here, "low-temperature offset" refers to the toner not being fixed to the recording paper during fixing, but remaining attached to the fixing belt and adhering to the recording paper after the fixing belt has made one revolution. From the results obtained, "low-temperature fixability" was evaluated according to the following criteria.

[0121] ◎ (Excellent): The minimum temperature is less than 110°C. ○ (Good): The minimum temperature is between 110℃ and 120℃. △ (Acceptable): The minimum temperature is 120°C or higher and less than 130°C. × (bad): The minimum temperature is 130°C or higher.

[0122] <Overall Judgment> Based on the results of the above evaluation items 1 to 3, an overall evaluation was made according to the following criteria. ◎ (Excellent): All evaluation items are ◎. Usable. ○ (Good): The lowest rating among all evaluation items is ○. Usable. △ (Acceptable): The lowest evaluation of all evaluation items is △. Usable. × (bad): The lowest rating among all evaluation items is ×. Unusable.

[0123] [Table 2]

[0124] Table 2 shows the evaluation results of Examples and Comparative Examples. Note that, in the toner of Comparative Example 4, inorganic fine particles (strontium titanate fine particles) were added in the external addition process, so the inorganic fine particles were evenly distributed on the toner particle surface, and there was no concept of interfaces α and β where the abundance ratio of the inorganic fine particles differed. However, in Table 2, R α and R β For convenience, the percentage of the toner particles present on the toner particle surface (toner layer A) is shown in the column .

[0125] As is clear from Tables 1 and 2, the toners of Examples 1 to 18, which have toner particles containing a binder resin, a colorant, and a release agent and satisfy the following requirements (A) to (E), were excellent in charging properties and fixing properties, and were able to suppress the occurrence of fogging. (A) The toner particles contain inorganic fine particles with an average particle diameter of 10 nm or more and 60 nm or less. (B) The inorganic fine particles are at least one selected from the group consisting of strontium titanate fine particles, alumina-coated silica fine particles, titania fine particles, alumina fine particles, zinc oxide fine particles, cerium oxide fine particles, and calcium carbonate fine particles. (C) The toner layer B has a higher content of inorganic fine particles than the toner layer A and the toner layer C. (D) In ​​an electron image of a cross section of a toner particle obtained by a scanning electron microscope, if the region corresponding to toner layer B is considered to be the interface, there exists an interface α where the inorganic fine particle content is low and an interface β where the inorganic fine particle content is high, and the interface length of interfaces α and β is 2 μm or more. (E) The proportion of inorganic particles in the interface α is 15% or less of the proportion of inorganic particles in the interface β.

[0126] In contrast, Comparative Examples 1 to 4, which did not satisfy these requirements, were inferior to the Examples in the evaluation results of at least one of the three evaluation items. Comparative Example 1 is an example that does not satisfy the above requirement (B), Comparative Example 2 is an example that does not satisfy the above requirements (A) and (B), and Comparative Example 3 is an example that does not satisfy the above requirement (A). Furthermore, Comparative Example 4 is an example that does not satisfy all of the above requirements because strontium titanate microparticles are added as an external additive.

[0127] In Comparative Examples 1 and 2, in which silica fine particles were used in the inorganic fine particle mixing step, it is thought that the silica fine particles had a high resistance value and did not function as a charge control agent, and the evaluation of the charge characteristics was inferior to that of the Examples in Table 2. Furthermore, when inorganic fine particles were added in the inorganic fine particle mixing step in amounts similar to those of Examples 1, 3, and 4, the fluidity-imparting effect of the silica fine particles was so high that the fluidity increased excessively, causing toner scattering, and the evaluation based on fogging was inferior to that of the Examples.

[0128] In Comparative Example 3, in which strontium titanate microparticles with a large average particle size were used in the inorganic microparticle mixing process, the microparticles were embedded in the toner particle surface, but the embedding was shallower, resulting in greater exposure to the toner particle surface compared to inorganic microparticles with a small particle size. As a result, the adhesion strength of the microparticles to the toner particles was also reduced. In Comparative Example 3, the microparticles were more exposed to the toner particle surface, making it easier to form conductive paths and expected to have the effect of improving environmental charging characteristics. However, it is thought that this caused a decrease in fog suppression performance and fixation inhibition due to factors such as deterioration in fluidity and separation of external additives, and as a result, the evaluation based on the fog value in Table 2 was inferior to that of the Examples.

[0129] Comparative Example 4 was inferior to the Examples in the evaluation based on the fog value and the evaluation of fixability. In Comparative Example 4, strontium titanate microparticles are externally added to the toner particles, so the toner particles are evenly coated with the microparticles, and the concepts of interfaces α and β, where the abundance ratio of inorganic microparticles is different, do not exist (in particular, interface α, where the abundance ratio of inorganic microparticles is low, does not exist). The following two points are thought to be the reasons why such a toner has poor fixability. (1) The presence of an excessive amount of inorganic fine particles causes the inorganic fine particles to absorb fixing heat, inhibiting the toner particles from melting, resulting in poor fixing. (2) Because the toner particles are exposed to very little light, the function of the release agent is inhibited during fixing, the cohesive force between toner particles is reduced, and the anchoring effect between the toner and paper is reduced, resulting in poor fixing.

[0130] Next, when comparing the Examples, it is found that Example 3, in which the abundance rate of inorganic fine particles in the interface α is 10% or less, is particularly superior in the evaluation of charging characteristics and the evaluation based on fog value compared to Example 5, in which the abundance rate exceeds the above upper limit.

[0131] It can be seen that Example 4, in which the proportion of inorganic fine particles in the interface β is 90% or more, is particularly superior in the evaluation of charging characteristics to Example 6, in which the proportion is less than the lower limit.

[0132] It can be seen that Example 7, in which the adhesion strength of the inorganic fine particles to the toner particles is 90% or more, is particularly superior in the evaluation based on the fog value and the evaluation of fixability to Example 8, in which the adhesion strength is below the lower limit.

[0133] It can be seen that Example 4, in which the content of inorganic fine particles in the toner particles is 2% by mass or more, is particularly superior in the evaluation of charging characteristics to Example 6, in which the content is below the above lower limit. Also, it can be seen that Example 3, in which the content of inorganic fine particles in the toner particles is 10% by mass or less, is particularly superior in the evaluation based on fog value to Example 5, in which the content exceeds the above upper limit.

[0134] It can be seen that Example 10, in which the coverage of the toner particle surface with silica fine particles as an external additive is 70% or more, is particularly superior in the evaluation of charging properties compared to Example 12, in which the coverage is below the lower limit. Also, it can be seen that Example 9, in which the coverage of the toner particle surface with silica fine particles as an external additive is 110% or less, is superior in the evaluation of all evaluation items compared to Example 11, in which the coverage exceeds the upper limit, and is particularly superior in the evaluation of charging properties.

[0135] It can be seen that Example 14, in which the adhesion strength of the silica fine particles to the toner particles is 50% or more, is particularly superior in the evaluation based on the fog value than Example 16, in which the adhesion strength is below the lower limit. Also, it can be seen that Example 13, in which the adhesion strength of the silica fine particles to the toner particles is 80% or less, is particularly superior in the evaluation of the charging characteristics than Example 15, in which the adhesion strength exceeds the upper limit.

[0136] The embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be defined based on the claims. Furthermore, all modifications within the scope and meaning equivalent to the claims are included. [Explanation of symbols]

[0137] 1 toner 2 Toner particles 3 Inorganic fine particles 4 External additives 21 Coarsely crushed material 22 Finely ground materials A Toner layer A B Toner layer B C Toner layer C

Claims

1. A toner having toner particles including a binder resin, a colorant, and a release agent, the toner particles contain inorganic fine particles therein having an average particle diameter of 10 nm or more and 60 nm or less, the inorganic fine particles are at least one selected from the group consisting of strontium titanate fine particles, alumina-coated silica fine particles, titania fine particles, alumina fine particles, zinc oxide fine particles, cerium oxide fine particles, and calcium carbonate fine particles; When a layer having a depth from the surface of the toner particle of 0 nm or more and less than 10 nm is defined as a toner layer A, a layer having the depth of 10 nm or more and less than 100 nm is defined as a toner layer B, and a layer having the depth of 100 nm or more is defined as a toner layer C, the toner layer B has a higher abundance ratio of the inorganic fine particles than the toner layer A and the toner layer C, In an electron image of the cross section of the toner particle obtained by a scanning electron microscope, when a region corresponding to the toner layer B is defined as an interface, there are an interface α where the inorganic fine particles are present in a small amount and an interface β where the inorganic fine particles are present in a large amount, The interface length of the interface α and the interface β is 2 μm or more, The toner is characterized in that the abundance ratio of the inorganic fine particles in the interface α is 15% or less of the abundance ratio of the inorganic fine particles in the interface β.

2. 2. The toner according to claim 1, The toner is characterized in that the inorganic fine particles are at least one selected from the group consisting of strontium titanate fine particles, alumina-coated silica fine particles, and titania fine particles.

3. 3. The toner according to claim 1 or claim 2, The toner, wherein in an electron image of the cross section of the toner particle obtained by a scanning electron microscope, the proportion of the inorganic fine particles in the interface α is 10% or less.

4. 3. The toner according to claim 1 or claim 2, The toner, wherein in an electron image of a cross section of the toner particle obtained by a scanning electron microscope, the proportion of the inorganic fine particles in the interface β is 90% or more.

5. 3. The toner according to claim 1 or claim 2, The toner is characterized in that the adhesive strength of the inorganic fine particles to the toner particles is 90% or more.

6. 3. The toner according to claim 1 or claim 2, The toner, wherein the content of the inorganic fine particles in the toner particles is 2% by mass or more and 10% by mass or less.

7. 3. The toner according to claim 1 or claim 2, silica fine particles as an external additive are attached to the surfaces of the toner particles, The toner is characterized in that the coverage of the toner particle surfaces with the silica fine particles is 70% or more and 110% or less.

8. 8. The toner according to claim 7, The toner is characterized in that the adhesion strength of the silica fine particles to the toner particles is 50% or more and 80% or less.

9. 3. The method for producing the toner according to claim 1 or 2, a melt-kneading step of melt-kneading a mixture of raw materials including a binder resin, a colorant, and a release agent; a coarse pulverization step of coarsely pulverizing the molten kneaded product obtained in the melt kneading step; an inorganic fine particle mixing step of mixing the coarsely pulverized product obtained in the coarse pulverization step with inorganic fine particles; a fine pulverization step of finely pulverizing the coarsely pulverized material containing the inorganic fine particles obtained in the inorganic fine particle mixing step; a classification step of classifying the finely pulverized product obtained in the finely pulverized product; A method for producing a toner, comprising:

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