Toner

Abstract

To provide a toner which can be fixed at a low temperature by containing a crystalline polyester-based resin in toner particles, has sufficient hot offset resistance, and can suppress the occurrence of fogging and the deterioration of the uniformity of image density over a long period of time.SOLUTION: The toner has toner particles containing an amorphous polyester-based resin, a crystalline polyester-based resin and wax. The toner particles include metal-oxide particles having a number-average particle size of 60nm or less. The metal oxide particles are surface-treated with a hydrophobizing agent containing a linear alkyl group having 6 or more carbon atoms. The content of the metal oxide particles in the toner particles is from 0.02% by weight to 2% by weight.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to toner. [Background technology]

[0002] Toner (toner for developing electrostatic images) used in electrophotographic image forming devices such as copiers, multifunction machines, printers, and facsimile machines generally has an external additive attached to the surface of the toner particles (toner core).

[0003] In recent years, there has been a demand for further energy saving in image forming apparatuses, and toners are therefore required to have low-temperature fixability in order to achieve this. Toners containing crystalline polyester resins in toner particles are known to improve low-temperature fixability.

[0004] Furthermore, in order to continue forming images of stable quality, it is desirable for the toner to have stable chargeability throughout its life (product life). To stabilize the chargeability of a toner over a long period of time, it is considered effective to internally add a charge control agent to the toner particles or externally add metal oxide particles that have been surface-treated with a hydrophobic treatment agent to the surface of the toner particles. In this disclosure, "external addition" means adding an additive so that it adheres to the outer surface (surface) of the toner, and "internal addition" means adding an additive so that it is contained within the toner. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-34280 Summary of the Invention [Problem to be solved by the invention]

[0006] However, even though the macro-charge amount is stabilized by externally adding metal oxide particles that have been surface-treated with a hydrophobic treatment agent to the surface of toner particles, there is a problem in that the charge amount distribution becomes uneven (broad) as the toner life progresses due to the external additives being embedded in the toner particle surface and the external additives contaminating the carrier, resulting in worsening fogging.

[0007] Furthermore, by using toner particles containing a crystalline polyester resin, the melting temperature of the toner can be lowered, making it possible to fix the toner at a lower temperature, but this raises the problems of making hot offset more likely to occur, and of making the durability of the toner lower, making it more likely that external additives will be embedded in the surface of the toner particles, which in turn reduces the uniformity of the image density.

[0008] The contents of the present disclosure have been discovered in consideration of the above circumstances regarding toners that can be fixed at low temperatures because the toner particles contain a crystalline polyester resin, and a main object of the present disclosure is to provide a toner that has sufficient hot offset resistance and can suppress the occurrence of fogging and the decrease in uniformity of image density over a long period of time. [Means for solving the problem]

[0009] The toner disclosed herein, which has been made to solve the above-mentioned problems, is a toner having toner particles containing an amorphous polyester resin, a crystalline polyester resin, and a wax, wherein the toner particles contain metal oxide particles having a number average particle diameter of 60 nm or less, the metal oxide particles have been surface-treated with a hydrophobic treatment agent containing a linear alkyl group having 6 or more carbon atoms, and the content of the metal oxide particles in the toner particles is 0.02% by mass or more and 2% by mass or less.

[0010] In the above toner, the metal oxide particles are preferably titanium oxide particles.

[0011] In the toner, the metal oxide particles preferably have a needle-like shape.

[0012] In the toner, the linear alkyl group contained in the hydrophobic treatment agent preferably has 10 or less carbon atoms.

[0013] In the toner, the hydrophobicity of the metal oxide particles is preferably 40% or more and 80% or less.

[0014] In the toner, it is preferable that the SP value of the amorphous polyester resin is 10.85 or more and 11.3 or less, and the SP value of the crystalline polyester resin is 9.4 or more and 9.8 or less.

[0015] Furthermore, in the above toner, when the content of the metal oxide particles in the toner particles is A mass %, and the content of the crystalline polyester resin in the toner particles is B mass %, it is preferable that the mass ratio A / B is 0.003 or more and 0.4 or less.

[0016] In the above toner, the wax is preferably an ester wax.

[0017] Patent Document 1 discloses the use of a toner in which inorganic particles with an average particle size of 5 nm to 1000 nm are internally added to toner particles containing a crystalline polyester resin and an amorphous polyester resin in an image forming apparatus having a toner image fixing unit with a specific structure. However, Patent Document 1 does not disclose the use of metal oxide particles that have been surface-treated with a hydrophobic treatment agent containing a linear alkyl group as described above. The toner configuration disclosed in Patent Document 1 does not sufficiently increase the dispersibility of the crystalline polyester resin contained in the toner particles, and does not solve the problems related to the present disclosure described above. [Effects of the Invention]

[0018] According to the toner of the present disclosure, the toner particles contain a crystalline polyester-based resin, which provides excellent effects such as low-temperature fixability while also providing sufficient hot offset resistance, preventing fogging over a long period of time, and preventing a decrease in the uniformity of image density over a long period of time. [Brief explanation of the drawings]

[0019] [Figure 1] 2 is a cross-sectional view schematically illustrating a dispersion state of constituent components in a toner particle according to the exemplary embodiment. FIG. [Figure 2] FIG. 1 is a conceptual diagram of the interaction between metal oxide particles surface-treated with a hydrophobic treatment agent and the amorphous portion of a crystalline polyester resin. DETAILED DESCRIPTION OF THE INVENTION

[0020] The toner of the present disclosure will be described in detail below.

[0021] 1. Toner particles (toner cores) The toner particles according to the present embodiment contain at least an amorphous polyester resin as a binder resin, a crystalline polyester resin, and a wax, and may contain optional components as long as the effects of the present disclosure are not impaired. The volume 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] Furthermore, the toner particles according to this embodiment contain metal oxide particles, which have a number-average particle diameter of 60 nm or less and are surface-treated with a hydrophobic treatment agent containing a linear alkyl group having 6 or more carbon atoms.

[0023] Here, a description will be given of a presumed mechanism by which the toner according to this embodiment has sufficient hot offset resistance and can suppress the occurrence of image defects (the occurrence of fogging and the decrease in uniformity of image density) for a long period of time.

[0024] FIG. 1 is a cross-sectional view schematically illustrating the dispersion state of components in a toner particle according to this embodiment, and FIG. 2 is a conceptual diagram illustrating the interaction between metal oxide particles that have been surface-treated with a hydrophobic treatment agent and the amorphous portion of a crystalline polyester resin.

[0025] As shown in FIG. 2, metal oxide particles 14 have a structure in which a substrate 14a (metal oxide particle body) of the metal oxide particle is surface-treated with a hydrophobic treatment agent 14b containing a linear alkyl group having six or more carbon atoms. The crystalline polyester resin 12 has a structure having a crystalline portion 12a and an amorphous portion 12b. Hydrophobic interaction occurs between the linear alkyl group of the hydrophobic treatment agent 14b present on the surface of the metal oxide particle 14 and the amorphous portion 12b present at the end of the crystalline polyester resin 12, making it easier for the crystalline polyester resin 12 to be present around the metal oxide particle 14. This facilitates charge transfer between the amorphous portion 12b and the hydrophobic treatment agent 14b, making charge retention and charge transfer within the toner particles less susceptible to environmental influences and the embedding of external additives in the toner particle surface. This ultimately improves the charging performance of the toner throughout its life and suppresses the occurrence of fogging over a long period of time.

[0026] Furthermore, as shown in Figure 1, within the amorphous polyester resin 11 of the toner particle 1, the crystalline polyester resin 12 is distributed so as to surround the metal oxide particles 14, and hydrophobic interaction occurs between the crystalline polyester resin 12 and the hydrophobic treatment agent 14b on the surface of the metal oxide particles 14, which facilitates crystallization of the crystalline polyester resin 12. This improves the heat-resistant storage stability of the toner particle 1 and prevents the external additive from being embedded in the surface of the toner particle 1. This in turn prevents a decrease in the uniformity of image density over a long period of time.

[0027] If the metal oxide particles 14 are present in the toner particles 1, the crystalline polyester resin 12 becomes more finely dispersed in the toner particles 1, and the metal oxide particles 14 act as a filler, which may have the adverse effect of inhibiting low-temperature fixability. However, the presence of the crystalline polyester resin 12 on the surface of the metal oxide particles 14 counteracts this adverse effect, thereby expanding the fixable range of the toner. In other words, the toner is one that is fixable at low temperatures and yet has sufficient hot offset resistance.

[0028] Next, the components of the toner particles according to this embodiment will be described.

[0029] <Polyester resin> The toner particles according to this embodiment contain at least an amorphous polyester resin as a binder resin and a crystalline polyester resin. The addition of the crystalline polyester resin can lower the softening temperature and melt viscosity of the toner. In other words, the use of toner particles containing both an amorphous polyester resin and a crystalline polyester resin can result in a toner with improved low-temperature fixability.

[0030] The SP value (solubility parameter) of the amorphous polyester resin contained in the toner particles according to this embodiment is preferably 10.85 or more and 11.3 or less, and the SP value of the crystalline polyester resin is preferably 9.4 or more and 9.8 or less. By setting the SP values ​​of both resins within the above ranges, the compatibility between the two resins becomes optimal, and the durability of the toner can be improved while maintaining excellent low-temperature fixability. More preferably, the SP value of the amorphous polyester resin is 11 or more and 11.2 or less, and the SP value of the crystalline polyester resin is 9.5 or more and 9.65 or less. The unit of SP value in the present disclosure is (cal / cm 3 ) 1 / 2 is.

[0031] If the SP value of the amorphous polyester resin is less than the lower limit, its compatibility with the crystalline polyester resin increases, the durability of the toner decreases, and the uniformity of the image density may decrease. If the SP value of the amorphous polyester resin exceeds the upper limit, its compatibility with the crystalline polyester resin decreases, its dispersibility in the toner particles decreases, and the hot offset resistance may decrease. If the SP value of the crystalline polyester resin is less than the lower limit, its compatibility with the amorphous polyester resin decreases, its dispersibility in the toner particles decreases, and the hot offset resistance may decrease. If the SP value of the crystalline polyester resin exceeds the upper limit, its compatibility with the amorphous polyester resin increases, the durability of the toner decreases, and the uniformity of the image density may decrease.

[0032] In the present disclosure, amorphous resins and crystalline resins are distinguished by their crystallinity index, with resins with a crystallinity index of 0.6 or more and 1.5 or less being crystalline resins, and resins with a crystallinity index of less than 0.6 or more than 1.5 being amorphous resins. Resins with a crystallinity index of more than 1.5 are amorphous, while resins with a crystallinity index of less than 0.6 have low crystallinity and a large amount of amorphous portions.

[0033] The crystallinity index is a physical property that indicates the degree of crystallization of a resin and is defined as the ratio of the softening temperature to the highest endothermic peak temperature (softening temperature / highest endothermic peak temperature). Here, the highest endothermic peak temperature refers to the temperature of the highest endothermic peak observed. For crystalline polyester resins, the highest peak temperature is the melting point, and for amorphous polyester resins, the highest peak temperature is the glass transition temperature.

[0034] The degree of crystallization of the resin can be controlled by adjusting the types and ratios of the monomers used as raw materials, as well as the production conditions (for example, reaction temperature, reaction time, cooling rate), and the like.

[0035] -Amorphous polyester resin- The amorphous polyester resin contained in the toner particles according to this embodiment is obtained, for example, by a polycondensation reaction between a carboxylic acid monomer containing terephthalic acid or isophthalic acid as a main component and a polyhydric alcohol containing ethylene glycol as a main component.

[0036] The dicarboxylic acid monomer used in the synthesis of the amorphous polyester resin contains terephthalic acid or isophthalic acid as a main component, and the molar content of terephthalic acid or isophthalic acid in the dicarboxylic acid monomer is preferably 70% or more and 100% or less, and more preferably 80% or more and 100% or less.

[0037] The dicarboxylic acid monomer may also contain an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid other than terephthalic acid and isophthalic acid. Examples of aromatic dicarboxylic acids other than terephthalic acid and isophthalic acid include fumaric acid, and examples of aliphatic dicarboxylic acids include adipic acid, sebacic acid, and succinic acid. The dicarboxylic acid monomer may also contain an ester-forming derivative of terephthalic acid or isophthalic acid, an ester-forming derivative of an aromatic dicarboxylic acid other than terephthalic acid and isophthalic acid, or an ester-forming derivative of an aliphatic dicarboxylic acid. In the present disclosure, examples of the ester-forming derivative include an acid anhydride and an alkyl ester of a carboxylic acid. These dicarboxylic acid monomers may be used alone or in combination of two or more.

[0038] In synthesizing the amorphous polyester resin, a trivalent or higher polycarboxylic acid monomer may be used together with the dicarboxylic acid monomer. Examples of the trivalent or higher polycarboxylic acid monomer include trivalent or higher polycarboxylic acids such as trimellitic acid and pyromellitic acid, and ester-forming derivatives thereof. These trivalent or higher polycarboxylic acid monomers may be used alone or in combination of two or more.

[0039] The diol monomer used in the synthesis of the amorphous polyester resin contains ethylene glycol as a main component, and the molar content of ethylene glycol in the diol monomer is preferably 70% or more and 100% or less, and more preferably 80% or more and 100% or less.

[0040] The diol monomer may include 1,3-propylene glycol, 1,4-butanediol, etc. These diol monomers may be used alone or in combination of two or more.

[0041] The amorphous polyester resin used in the toner according to this embodiment can be produced in the same manner as in conventional polyester production methods. For example, the amorphous polyester resin can be synthesized by polycondensation of a dicarboxylic acid monomer, a polyhydric alcohol, and optionally a trivalent or higher polycarboxylic acid monomer in a nitrogen gas atmosphere at 190°C to 240°C. In the polycondensation reaction, the reaction ratio of the diol monomer to the carboxylic acid monomer (including the dicarboxylic acid monomer and optionally a trivalent or higher polycarboxylic acid monomer) is preferably 1.3:1 to 1:1.2 in terms of the equivalent ratio of hydroxyl groups to carboxy groups [OH]:[COOH]. In the polycondensation reaction, the molar content of the dicarboxylic acid monomer in the carboxylic acid monomer is preferably 80% to 100%. Furthermore, in the polycondensation reaction, an esterification catalyst such as dibutyltin oxide or titanium alkoxide (e.g., tetrabutoxytitanate) may be used as needed.

[0042] The content of the amorphous polyester resin in the toner particles according to this exemplary embodiment is preferably 60% by mass or more and 95% by mass or less, and more preferably 70% by mass or more and 90% by mass or less.

[0043] -Crystalline polyester resin- In the toner particles according to this embodiment, the crystalline polyester resin is dispersed in the amorphous polyester resin. The crystalline polyester resin is preferably composed of a linear saturated aliphatic polyester unit obtained by polycondensation of a carboxylic acid monomer containing, as a main component, an aliphatic dicarboxylic acid having 9 to 22 carbon atoms and a polyhydric alcohol containing, as a main component, an aliphatic diol having 2 to 10 carbon atoms. By being composed of the linear saturated aliphatic polyester unit, the crystalline polyester resin and the amorphous polyester resin are less likely to be compatible with each other.

[0044] The dicarboxylic acid monomer used in the synthesis of the crystalline polyester resin contains, as a main component, an aliphatic dicarboxylic acid having 9 to 22 carbon atoms. Here, the molar content of the aliphatic dicarboxylic acid having 9 to 22 carbon atoms in the dicarboxylic acid monomer is preferably 80% or more and 100% or less.

[0045] Examples of aliphatic dicarboxylic acids having 9 to 22 carbon atoms include azelaic acid, sebacic acid, dodecanedioic acid, and 1,18-octadecanedicarboxylic acid. The dicarboxylic acid monomer may also contain an ester-forming derivative of these aliphatic dicarboxylic acids. These dicarboxylic acid monomers may be used alone or in combination of two or more.

[0046] In the synthesis of the crystalline polyester resin, a trivalent or higher polycarboxylic acid monomer may be used together with the dicarboxylic acid monomer. Examples of the trivalent or higher polycarboxylic acid monomer include trivalent or higher polycarboxylic acids such as trimellitic acid and pyromellitic acid, and ester-forming derivatives thereof. These trivalent or higher polycarboxylic acid monomers may be used alone or in combination of two or more.

[0047] The diol monomer used in the synthesis of the crystalline polyester resin contains, as a main component, an aliphatic diol having 2 to 10 carbon atoms. Here, the molar content of the aliphatic diol having 2 to 10 carbon atoms in the diol monomer is preferably 80% or more and 100% or less.

[0048] Examples of the aliphatic diol having 2 to 10 carbon atoms include ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,9-nanonediol, 1,10-decanediol, etc. These diol monomers may be used alone or in combination of two or more.

[0049] In the synthesis of the crystalline polyester resin, a trivalent or higher polyol monomer may be used together with the diol monomer. Examples of the trivalent or higher polyol monomer that can be used include glycerin and trimethylolpropane. These trivalent or higher polyol monomers may be used alone or in combination of two or more.

[0050] The crystalline polyester resin used in the toner according to this embodiment can be produced in the same manner as in the ordinary polyester production method. For example, the crystalline polyester resin can be synthesized by carrying out a polycondensation reaction of a dicarboxylic acid monomer, a diol monomer, and optionally a trivalent or higher polycarboxylic acid monomer or a trivalent or higher polyol monomer in a nitrogen gas atmosphere at a temperature of 190°C to 240°C.

[0051] In the polycondensation reaction, the equivalent ratio (OH group / COOH group) of the hydroxyl group of the polyol monomer (including a diol monomer and, if necessary, a trivalent or higher polyol monomer) to the carboxyl group of the carboxylic acid monomer (including a dicarboxylic acid monomer and, if necessary, a trivalent or higher polycarboxylic acid monomer) is preferably 0.83 to 1.3 from the viewpoint of storage stability, etc.

[0052] In the polycondensation reaction, the molar content of the dicarboxylic acid monomer in the carboxylic acid monomer is preferably 90% to 100%. As the molar content of the dicarboxylic acid monomer decreases, the crystallization rate and speed decrease, and the toner aggregation resistance (resistance to toner aggregation) may become insufficient.

[0053] Furthermore, in the polycondensation reaction, the molar content of the diol monomer in the polyol monomer is preferably 80% to 100%. In the polycondensation reaction, an esterification catalyst such as dibutyltin oxide or titanium alkoxide (e.g., tetrabutoxytitanate) may be used as needed.

[0054] The content of the crystalline polyester resin in the toner particles according to this exemplary embodiment is preferably 2% by mass or more and 10% by mass or less, and more preferably 4% by mass or more and 8% by mass or less.

[0055] <Metal oxide particles> The metal oxide particles contained in the toner particles according to this embodiment have a number average particle diameter of 60 nm or less and are surface-treated with a hydrophobic treatment agent containing a linear alkyl group having 6 or more carbon atoms.

[0056] Titanium oxide, alumina, zinc oxide, tin oxide, cesium oxide, etc. can be used as the substrate of the metal oxide particles. These can exert the function of controlling the conductivity of the toner particles. Furthermore, these may be used alone or in combination of two or more. Among these, titanium oxide is preferably used.

[0057] The method for producing the substrate of metal oxide particles is not particularly limited, but for example, a method for producing rutile-type titanium oxide particles is described in JP 2001-26423 A, that is, a method for preparing a fine titania sol having rutile nuclei by hydrolyzing an aqueous titanium tetrachloride solution, which is then separated and heat-treated to obtain titanium oxide particles. A method for producing anatase-type titanium oxide particles is described in JP 2000-10335 A, that is, a method for producing titanium oxide particles by hydrolyzing and granulating a solution obtained by dissolving raw materials such as ilmenite ore in sulfuric acid, drying the solution, and then calcining it at a high temperature to obtain titanium oxide particles.

[0058] The metal oxide particles used in the toner according to this embodiment are preferably acicular in shape. Here, acicular refers to a shape with an aspect ratio (major axis / minor axis) of 4.0 or greater. This aspect ratio is more preferably 6.0 or greater. When the metal oxide particles are acicular, the specific surface area of ​​the metal oxide particles is increased compared to when the metal oxide particles are spherical, and the contact interface with the crystalline polyester resin is increased. This makes it possible to uniformly distribute the charge amount of the toner and suppress the occurrence of fogging. Furthermore, during toner fixing, the filler effect of the metal oxide particles is less likely to cause fixing inhibition, improving hot offset resistance. While the upper limit of the aspect ratio is not particularly specified, from the viewpoint of facilitating the production of particles with a suitable particle size, it is preferably 20.0 or less, more preferably 15.0 or less.

[0059] An example of the acicular metal oxide particles is acicular titanium oxide particles. As shown in the examples below, acicular titanium oxide particles can be obtained by calcining a mixture of spherical rutile titanium oxide particles and sodium pyrophosphate decahydrate, heating the calcined product in pure water, and then washing the calcined product to remove soluble salts.

[0060] The number-average particle diameter of the metal oxide particles used in the toner according to this embodiment is 60 nm or less, more preferably 10 nm to 50 nm, and even more preferably 20 nm to 45 nm. If the number-average particle diameter of the metal oxide particles exceeds the upper limit, the conductive paths formed by the metal oxide particles in the toner particles become large, which may result in poor fogging. By keeping the number-average particle diameter of the metal oxide particles within the above range, conductive paths of a preferred size are formed in the toner particles.

[0061] The metal oxide particles used in the toner according to this embodiment are surface-treated with a hydrophobic treatment agent containing a linear alkyl group having 6 or more carbon atoms. The linear alkyl group contained in the hydrophobic treatment agent may have 6 or more and 12 or less carbon atoms, preferably 6 or more and 10 or less carbon atoms, and more preferably 8 carbon atoms.

[0062] If the carbon number of the linear alkyl group in the hydrophobic treatment agent is less than 6, the hydrophobic interaction with the amorphous part present in the molecule of the crystalline polyester resin is insufficient, the crystalline polyester resin is difficult to distribute around the metal oxide particles, and the dispersibility of the crystalline polyester resin deteriorates, which in turn may result in a deterioration in the hot offset resistance of the toner, a decrease in the durability of the toner, and a decrease in the uniformity of the image density.

[0063] If the number of carbon atoms in the linear alkyl group in the hydrophobic treatment agent exceeds the upper limit, the metal oxide particles tend to coalesce together via the hydrophobic treatment agent, reducing the specific surface area of ​​the metal oxide particles. If the specific surface area of ​​the metal oxide particles is reduced, the contact interface with the crystalline polyester resin decreases, resulting in non-uniform charge distribution of the toner, which may in turn lead to worsening of fogging and hot offset resistance.

[0064] If the alkyl group in the hydrophobic treatment agent is not linear, the effect of increasing the crystallinity of the crystalline polyester resin distributed around the metal oxide particles is weakened, which may result in a deterioration in hot offset resistance or a decrease in the durability of the toner, resulting in a decrease in the uniformity of image density.

[0065] The hydrophobic treatment agent used to surface treat the metal oxide particles used in the toner according to this embodiment can be one having a structure containing a linear alkyl group having 6 or more carbon atoms, such as a silane coupling agent. An example of a silane coupling agent containing a linear alkyl group having 6 or more carbon atoms is trimethoxysilane to which a linear alkyl group is bonded, and the preferred range of the carbon number of the linear alkyl group is as described above. The method for surface treating the metal oxide particles with the hydrophobic treatment agent is not particularly limited. For example, as in the examples below, metal oxide particles and a solvent containing the hydrophobic treatment agent are stirred and mixed, and the solvent is evaporated, followed by heating and crushing the resulting product, thereby obtaining metal oxide particles surface-treated with the hydrophobic treatment agent.

[0066] In the toner according to this embodiment, the hydrophobicity of the metal oxide particles surface-treated with a hydrophobic treatment agent is preferably 40% to 80%, more preferably 60% to 75%. If the hydrophobicity of the metal oxide particles is below the lower limit, the metal oxide particles may excessively form conductive paths, reducing the charge amount of the toner and causing fogging. If the hydrophobicity of the metal oxide particles exceeds the upper limit, the metal oxide particles may insufficiently form conductive paths, causing the charge amount distribution of the toner to become non-uniform and causing fogging.

[0067] The content of metal oxide particles in the toner particles according to this embodiment is 0.02% by mass or more and 2% by mass or less, more preferably 0.02% by mass or more and 0.5% by mass or less, and even more preferably 0.03% by mass or more and 0.1% by mass or less. If the content of metal oxide particles in the toner particles is less than the lower limit, the formation of conductive paths by the metal oxide particles is insufficient, and the effect of increasing the dispersibility of the crystalline polyester resin is insufficient. This can result in a non-uniform charge distribution of the toner, poor hot offset resistance, and reduced uniformity of image density. Furthermore, if the content of metal oxide particles in the toner particles exceeds the upper limit, the formation of conductive paths by the metal oxide particles is excessive, reducing the charge amount of the toner and causing increased fogging.

[0068] When the content of metal oxide particles in the toner particles according to this embodiment is A mass %, and the content of crystalline polyester resin is B mass %, the mass ratio A / B is preferably 0.003 or more and 0.4 or less, more preferably 0.003 or more and 0.1 or less, even more preferably 0.005 or more and 0.05 or less, and particularly preferably 0.007 or more and 0.02 or less.

[0069] If the mass ratio A / B is less than the lower limit, the volume of the metal oxide particles relative to the volume of the crystalline polyester resin in the toner particles becomes insufficient, resulting in fewer domains of the crystalline polyester resin in contact with the metal oxide particles, which weakens the effect of increasing the crystallinity of the crystalline polyester resin caused by contact between the metal oxide particles and the crystalline polyester resin, and may result in reduced toner durability.

[0070] If the mass ratio A / B exceeds the upper limit, the volume of the metal oxide particles relative to the volume of the crystalline polyester resin in the toner particles becomes excessive, resulting in fewer metal oxide particles in contact with the crystalline polyester resin. This can lead to unstable toner charging and worsening fogging. Furthermore, the filler effect of the metal oxide particles is more likely to be exhibited, which can worsen hot offset resistance.

[0071] The metal oxide particles used in the toner particles according to this embodiment are preferably subjected to a treatment to form a conductive layer on their surfaces before being surface-treated with the hydrophobic treatment agent. That is, the metal oxide particles contained in the toner particles according to this embodiment are preferably metal oxide particles having a conductive layer formed on their surfaces that have been surface-treated with the hydrophobic treatment agent. An example of the conductive layer is an aluminum oxide conductive layer, and an example of a method for forming the conductive layer is a method of dispersing metal oxide particles in an aqueous solution of sodium aluminate.

[0072] <Wax> The toner particles according to this embodiment contain a wax as a release agent. Examples of preferred waxes include ester wax, paraffin wax, Fischer-Tropsch wax, carnauba wax, and montan wax. These waxes may be used singly or in combination of two or more.

[0073] Among these, ester wax is more preferable. By using ester wax as the wax to be added to the toner particles, the dispersibility of the crystalline polyester resin and the amorphous polyester resin is improved, and the durability of the toner is improved. In addition, the polar group of the ester wax optimizes the charge distribution of the toner, and the occurrence of fogging is suppressed.

[0074] The ester wax to be used is not particularly limited, but is preferably an ester of a monohydric alcohol and a monocarboxylic acid, an ester of a tetrahydric to octahydric alcohol and an aliphatic monocarboxylic acid, or an ester of a tetrahydric to octahydric carboxylic acid and an aliphatic monoalcohol. Examples of the ester wax include the following. Esters of monohydric alcohols and monocarboxylic acids, such as behenyl behenate, stearyl stearate, and palmityl palmitate; Esters of dicarboxylic acids and monoalcohols, such as dibehenyl sebacate; Esters of dihydric alcohols and monocarboxylic acids, such as ethylene glycol distearate and hexanediol dibehenate; Esters of trihydric alcohols and monocarboxylic acids, such as glycerin tribehenate; Esters of tetrahydric alcohols and monocarboxylic acids, such as pentaerythritol tetrastearate and pentaerythritol tetrapalmitate; Esters of hexahydric alcohols and monocarboxylic acids, such as dipentaerythritol hexastearate, dipentaerythritol hexapalmitate, and dipentaerythritol hexabehenate; Esters of polyfunctional alcohols and monocarboxylic acids, such as polyglycerin behenate; Natural ester waxes such as carnauba wax and rice wax.

[0075] Among these, esters of hexahydric alcohols and monocarboxylic acids such as dipentaerythritol hexastearate, dipentaerythritol hexapalmitate, and dipentaerythritol hexabehenate are preferred.

[0076] The melting point of the ester wax is preferably 60° C. or higher and 90° C. or lower, more preferably 65° C. or higher and 85° C. or lower. The SP value of the ester wax is preferably 8.30 or higher and 9.10 or lower, more preferably 8.45 or higher and 8.95 or lower.

[0077] The wax content in the toner particles is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 5% by mass or less.

[0078] <Coloring agent> The toner particles according to this embodiment may contain a colorant, such as an organic pigment, an organic dye, an inorganic pigment, or an inorganic dye used in the field of electrophotography.

[0079] Examples of black colorants include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, non-magnetic ferrite, magnetic ferrite, and magnetite.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] <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.

[0085] Examples of charge control agents for controlling positive charges include quaternary ammonium salts, pyrimidine compounds, triphenylmethane derivatives, guanidine salts, and amidine salts.

[0086] 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.

[0087] 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.

[0088] <External additives> The toner according to the present embodiment may have an external additive attached to the surface of the toner particles. Examples of the functions of the external additive include improving the powder fluidity, triboelectric charging property, heat-resistant storage stability, and cleaning property of the toner, and controlling the abrasion property of the photoreceptor surface.

[0089] As the external additive, for example, inorganic particles such as silica and titanium oxide having an average particle size of 7 nm to 200 nm can be used. These inorganic particles are preferably made hydrophobic by surface treatment with a hydrophobic treatment agent such as a silane coupling agent, a titanium coupling agent, or silicone oil, because they reduce the decrease in electrical resistance and charge amount under high humidity conditions.

[0090] Examples of silica particles as external additives include silica particles commonly used in the technical field, such as fumed silica particles obtained by burning silicon tetrachloride and dry process silica particles such as arc process silica in which silica is atomized in the gas phase using high energy such as plasma; wet process silica particles 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 particles obtained by polymerizing acidic silicic acid in an alkaline state; and sol-gel process silica particles obtained by hydrolysis of an organic silane compound.

[0091] 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.

[0092] The titanium oxide particles used as an external additive may be either anatase-type titanium oxide particles or rutile-type titanium oxide particles. Rutile-type titanium oxide particles can be produced, for example, by the method described in JP 2001-26423 A, i.e., by hydrolyzing an aqueous titanium tetrachloride solution to prepare a fine titania sol having rutile nuclei, separating the sol, and then heat-treating it to obtain titanium oxide particles. An anatase-type titanium oxide particle 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 titanium oxide particles.

[0093] The content of the external additive is preferably 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of the toner particles. If the content of the external additive is less than the lower limit, it becomes difficult to impart the effect of improving fluidity. If the content of the external additive is more than the upper limit, fixability may decrease.

[0094] As a method for adding an external additive to toner particles, a method in which the toner particles and the external additive are mixed in an air flow mixer such as a Henschel mixer can be mentioned. [Example]

[0095] The toner of the present disclosure will be specifically described below based on examples and comparative examples.

[0096] 1.Measurement method <Method for measuring the volume average particle size of toner particles> 20 mg of toner particles and 1 ml of sodium alkyl ether sulfate were added to 50 ml of electrolyte (Beckman Coulter, Inc., product name: ISOTON-II), and the mixture was dispersed using an ultrasonic disperser (As One Corporation, tabletop dual-frequency ultrasonic cleaner, model: VS-D100) at a frequency of 20 kHz for 3 minutes to obtain a measurement sample. The resulting measurement sample was measured using a particle size distribution analyzer (Beckman Coulter, Inc., model: Multisizer 3) under conditions of an aperture diameter of 100 μm and a particle count of 50,000, and the volume average particle diameter was determined from the volume particle size distribution of the toner particles.

[0097] <Method for measuring resin melting temperature> Using a flow property evaluation device (Flow Tester, Shimadzu Corporation, Model: CFT-100C), 1 g of the resin sample was heated at a temperature increase rate of 6°C / min while applying a load of 20 kgf / cm 2 (9.8×10 5 A pressure of 1 Pa is applied to the resin, and the measurement sample is allowed to flow out of a die (nozzle diameter 1 mm, length 1 mm). The temperature at which half of the measurement sample has flowed out is taken as the melting temperature Tm [°C] of the resin.

[0098] <Method for measuring the number average particle size of metal oxide particles> Using a scanning electron microscope (Hitachi, Ltd., model: S-4800), the circle-equivalent diameters (Heywood diameter: diameter of a circle having the same area as the projected area of ​​a primary particle) of 100 primary particles are determined, and the number-average value is calculated to obtain the number-average particle diameter.

[0099] <Method for measuring the hydrophobicity of metal oxide particles> The degree of hydrophobicity in the present disclosure represents a measure [%] of wettability with methanol and is calculated by the following formula: In the formula, V [ml] represents the amount of methanol required to wet all of the metal oxide particles (to cause all of the metal oxide particles to settle) when methanol is added dropwise to 50 ml of distilled water containing 0.2 g of metal oxide particles while stirring. Hydrophobicity [%] = {V / (50+V)} x 100

[0100] <Method for measuring the SP value of resin> The SP value (solubility parameter, unit: [(cal / cm 3 ) 1 / 2 ]) is calculated.

[0101] 2. Toner raw material manufacturing <Production of amorphous polyester resin L> 100 parts by mass of raw material monomers composed of the components in the molar parts shown in Table 1 below, 0.5 parts by mass of tin(II) 2-ethylhexanoate as an esterification catalyst, and 0.05 parts by mass of gallic acid (3,4,5-trihydroxybenzoic acid) as an esterification promoter were placed in a 10-liter four-neck flask equipped with a thermometer, a stainless steel stirring rod, a downflow condenser, and a nitrogen inlet tube, and the temperature was raised to 210°C in a nitrogen atmosphere in a mantle heater over 5 hours. Thereafter, the reaction was continued at a pressure of 8.0 kPa until the melting temperature Tm shown in Table 1 was reached, yielding amorphous polyester resins L1 to L7.

[0102] Table 1 below summarizes the types and blending ratios of raw material monomers and the physical properties of the resulting resins for amorphous polyester resins L1 to L7.

[0103] [Table 1]

[0104] <Production of amorphous polyester resin H> 100 parts by mass of raw material monomers composed of components in the molar parts shown in Table 2 below, excluding trimellitic anhydride, 0.5 parts by mass of tin (II) 2-ethylhexanoate as an esterification catalyst, and 0.05 parts by mass of gallic acid as an esterification promoter were placed in a 10-liter four-neck flask equipped with a thermometer, a stainless steel stirring rod, a downflow condenser, and a nitrogen inlet tube, and the temperature was raised to 235 ° C. in a mantle heater in a nitrogen atmosphere over 3 hours. After reaching the temperature of 235 ° C., the temperature was maintained for 7 hours. After that, the temperature was cooled to 210 ° C., and trimellitic anhydride was added. The temperature was maintained at 210 ° C. for 1 hour, and the reaction was carried out under reduced pressure at 8.0 kPa. The reaction was continued until the melting temperature Tm shown in Table 2 was reached, yielding amorphous polyester resins H1 to H7.

[0105] Table 2 below summarizes the types and blending ratios of raw material monomers and the physical properties of the resulting resins for amorphous polyester resins H1 to H7.

[0106] [Table 2]

[0107] <Production of Crystalline Polyester Resin C> 100 parts by mass of raw material monomers composed of the components in the molar parts shown in Table 3 below and 0.2 parts by mass of tin (II) 2-ethylhexanoate as an esterification catalyst were placed in a 10-liter four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple, and the temperature was raised from 130°C to 200°C over 10 hours under a nitrogen atmosphere, and the reaction was carried out at 200°C and a pressure of 8.0 kPa for 1 hour to obtain crystalline polyester resins C1 to C7.

[0108] Table 3 below summarizes the types and blending ratios of raw material monomers and the physical properties of the resulting resins for crystalline polyester resins C1 to C7.

[0109] [Table 3]

[0110] <Production of needle-shaped titanium oxide particles> Aqueous sodium hydroxide solution was added to metatitanic acid obtained by the sulfuric acid method and heated. After the heated product was thoroughly washed with pure water, hydrochloric acid was added to the product and heated at the boiling point of hydrochloric acid. The product was then cooled and neutralized by adding 1N aqueous sodium hydroxide solution until the pH reached 7. The resulting product was washed and dried to obtain rutile-type titanium oxide particles.

[0111] The resulting rutile-type titanium oxide particles were mixed with sodium pyrophosphate decahydrate (Na4P2O7·10H2O) using a vibrating ball mill to obtain a mixture. The resulting mixture was then fired at 600°C in an electric furnace. The fired material was then placed in pure water and heated. After heating, the fired material was washed with pure water to remove soluble salts, yielding acicular titanium oxide particles.

[0112] 100 parts by weight of the resulting acicular titanium oxide particles were dispersed in 500 parts by weight of pure water, and an aqueous solution containing 0.5 parts by weight of sodium aluminate was added to precipitate aluminum oxide (Al2O3) on the surface of the acicular titanium oxide particles. 100 parts by weight of the treated acicular titanium oxide particles were stirred and mixed with 500 parts by weight of toluene, and 18 parts by weight of n-octyltrimethoxysilane as a hydrophobic treatment agent was added and stirred for 2 hours. The toluene was then distilled off under reduced pressure, and the mixture was heated at 120°C for 3 hours. The resulting product was then crushed to obtain "Titanium Oxide 1," which is acicular titanium oxide particles surface-treated with n-octyltrimethoxysilane.

[0113] Furthermore, as shown in Table 4 below, "Titanium Oxides 2 to 10" and "Titanium Oxides 12 to 17" were obtained by the same procedure as above, except that the firing temperature was changed to obtain acicular titanium oxide particles with different number-average particle diameters, and the type and amount of hydrophobic treatment agent added was changed. Note that the particle diameter in Table 4 indicates the number-average particle diameter.

[0114] [Table 4]

[0115] <Production of spherical titanium oxide particles> Aqueous sodium hydroxide solution was added to metatitanic acid obtained by the sulfuric acid method and heated. After the heated product was thoroughly washed with pure water, hydrochloric acid was added to the product and heated at the boiling point of hydrochloric acid. The product was then cooled and neutralized by adding 1N aqueous sodium hydroxide solution until the pH reached 7. The resulting product was washed and dried to obtain rutile-type spherical titanium oxide particles.

[0116] 100 parts by mass of the obtained spherical titanium oxide particles were dispersed in 500 parts by mass of pure water, and an aqueous solution containing 0.5 parts by mass of sodium aluminate was added to precipitate aluminum oxide (Al2O3) on the surface of the spherical titanium oxide particles. 100 parts by mass of the treated spherical titanium oxide particles were stirred and mixed with 500 parts by mass of toluene, and 18 parts by mass of n-octyltrimethoxysilane as a hydrophobic treatment agent was added and stirred for 2 hours. The toluene was then distilled off under reduced pressure, and the mixture was heated at 120°C for 3 hours. The resulting product was then crushed to obtain "titanium oxide 11," which is spherical titanium oxide particles surface-treated with n-octyltrimethoxysilane.

[0117] <Production of alumina particles> Aluminum oxide was refined using bauxite as a raw material using the Bayer process. Sodium hydroxide was added to the bauxite and heated to 250°C for dissolution. Insoluble matter was removed by filtration, and the mixture was cooled to recover aluminum hydroxide as a solid. This aluminum hydroxide was then dehydrated by heating at 1050°C to obtain alumina. The resulting alumina was then dispersed in toluene and crushed using a bead mill (NVM-2 model, manufactured by Imex Co., Ltd.) with beads of 0.5 mm diameter to obtain alumina particles.

[0118] 100 parts by mass of the obtained alumina particles were mixed with 500 parts by mass of toluene and stirred, and 18 parts by mass of n-octyltrimethoxysilane as a hydrophobic treatment agent was added thereto and stirred for 2 hours. The toluene was then distilled off under reduced pressure, and the mixture was heated at 120°C for 3 hours. The resulting product was then crushed to obtain "Alumina 1," alumina particles surface-treated with n-octyltrimethoxysilane.

[0119] The metal oxide particles used in the examples and comparative examples are listed in the following Table 5. The particle size in Table 5 represents the number average particle size.

[0120] [Table 5]

[0121] 3. Manufacture of toner and two-component developer [Example 1] <Material mixing, kneading, pulverization, and classification processes> Binder resin Amorphous polyester resin L1: 39.2% by mass Amorphous polyester resin H1: 39.2% by mass Crystalline resin Crystalline polyester resin C1: 5.0% by mass Coloring agents Carbon black (manufactured by Cabot Corporation, product name: Regal 330): 6% by mass ·Mold release agent Ester wax (NOF Corporation, product name: WEP-3): 3% by mass ·Release agent dispersant Styrene-acrylic copolymer (manufactured by Mitsui Chemicals, Inc., product name: SA800): 5% by mass Charge control agent Salicylic acid compound (Orient Chemical Industry Co., Ltd., product name: Bontro E84): 2% by mass ·Metal oxide particles Titanium oxide 1: 0.6% by mass

[0122] The above toner raw materials were premixed for 5 minutes using a Henschel mixer (manufactured by Nippon Coke & Engineering Co., Ltd., model: FM20C), and then melt-kneaded using a twin-screw extruder to obtain a melt-kneaded product. The melt-kneading conditions using the twin-screw extruder were a cylinder setting temperature of 110°C, a barrel rotation speed of 300 rpm, and a raw material supply rate of 20 kg / hour.

[0123] The resulting molten and kneaded product was cooled on a cooling belt, then coarsely pulverized using a cutting mill, then finely pulverized using a jet pulverizer, and further classified using an air classifier to obtain toner particles having a volume average particle diameter of 6.5 μm.

[0124] <External addition process> Next, 1.0 part by mass of a first external additive (manufactured by Cabot Corporation, product name: TG-C190, silica particles with a primary average particle diameter of 115 nm) and 1.5 parts by mass of a second external additive (manufactured by Nippon Aerosil Co., Ltd., product name: R974, silica particles with a primary average particle diameter of 12 nm) were added to 100 parts by mass of the obtained toner particles, and the mixture was stirred in a Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd., model: FM20C) to obtain a toner with a volume average particle diameter of 6.5 μm.

[0125] <Manufacturing of two-component developers> The obtained toner and a ferrite core carrier having a volume average particle diameter of 40 μm were mixed so that the toner concentration relative to the total amount of the two-component developer was 7%, to obtain a two-component developer having a toner concentration of 7%.

[0126] [Examples 2 to 39, Comparative Examples 1 to 5] Toners and two-component developers were obtained in the same manner as in Example 1, except that the types and amounts of the constituent components of the toner raw materials were changed as shown in Tables 6 and 7 below. In Examples 2 to 39 and Comparative Examples 1 to 5, the blending ratio of amorphous polyester resin L to amorphous polyester resin H was 1:1, the same as in Example 1. The paraffin wax in Example 39 in Table 6 was "HNP-10PD," a product name manufactured by Nippon Seiro Co., Ltd.

[0127] [Table 6]

[0128] [Table 7]

[0129] 4. Evaluation <Evaluation item 1: Evaluation of hot offset resistance> A fixed image was formed using a two-component developer using a color multifunction printer (manufactured by Sharp Corporation, model: BP-70C55) modified for evaluation. 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 A4-size recording paper (manufactured by Sharp Corporation, model: PP117WA4). 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.

[0130] Next, a fixed image was created using a belt fixing device. The fixing process speed was set to 140 mm / sec, and the temperature of the fixing belt was increased in 5°C increments from 150°C to determine the maximum temperature at which hot offset did not occur. Note that "hot 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, "hot offset resistance" was evaluated according to the following criteria.

[0131] ◎ (Excellent): The maximum temperature is 195°C or higher. ○ (Good): The maximum temperature is 190℃ or higher and less than 195℃. △ (Acceptable): The maximum temperature is 185°C or higher and less than 190°C. × (Not acceptable): The maximum temperature is less than 185°C.

[0132] <Evaluation item 2: Evaluation of image density uniformity> The prepared developer and toner were loaded into the developing device and toner cartridge of a color multifunction printer (Sharp Corporation, Model: BP-70C55), respectively. Next, a continuous print test was conducted on 50,000 sheets of A4-size recording paper (Sharp Corporation, Model: PP117WA4) at a temperature of 25°C and humidity of 5%, so that a 10 mm square solid image (ID = 1.45-1.50) was formed at three positions: the center and both ends in the axial direction of the developing roller. Image density was measured at 10 random locations on the 50,000th print sample, and the standard deviation was calculated from each image density. A larger standard deviation indicates lower uniformity. Evaluation was based on the calculated standard deviation according to the following criteria.

[0133] ◎ (Excellent): Standard deviation is less than 0.1. ○ (Good): Standard deviation is 0.1 or more and less than 0.2. △ (Acceptable): The standard deviation is 0.2 or more and less than 0.4. × (unacceptable): The standard deviation is 0.4 or more.

[0134] <Evaluation item 3: Evaluation method for fogging> The prepared developer and toner were loaded into the developing device and toner cartridge of a color multifunction printer (Sharp Corporation, Model: BP-70C55), respectively. A continuous print test of 50,000 sheets of A4-size recording paper (Sharp Corporation, Model: PP117WA4) was conducted under an environment of 25°C and 5% humidity, so that an image was formed in which 10% of the printable area of ​​the recording paper was filled with toner. For the 50,000th print sample, the brightness of a specific unfilled area of ​​the image was measured using a colorimeter (Nippon Denshoku Industries Co., Ltd., Model: ZE6000). The difference between this brightness and the brightness measured before printing was taken as the fogging value. Evaluation was based on the measured fogging value according to the following criteria.

[0135] ◎ (Excellent): The fogging value is less than 1.4. ◯ (Good): The fog value is 1.4 or more and less than 1.7. △ (Acceptable): The fogging value is 1.7 or more and less than 2.0. × (unacceptable): The fogging value is 2.0 or more.

[0136] [Table 8]

[0137] Table 8 shows the evaluation results of Examples and Comparative Examples. As is clear from Table 8, the toners of Examples 1 to 39, which have toner particles containing an amorphous polyester resin, a crystalline polyester resin, and a wax, the toner particles containing metal oxide particles having a number average particle size of 60 nm or less, the metal oxide particles being surface-treated with a hydrophobic treatment agent containing a linear alkyl group having 6 or more carbon atoms, and the content of the metal oxide particles in the toner particles being 0.02% by mass or more and 2% by mass or less, had sufficient hot offset resistance and were able to suppress the occurrence of fogging and a decrease in uniformity of image density over a long period of time.

[0138] In contrast, Comparative Examples 1 to 5, which did not satisfy these requirements, were inferior to the Examples in the evaluation results of at least one of the three evaluation items. Note that Comparative Example 1 is an example in which the number average particle size of the metal oxide particles does not satisfy the above requirement, Comparative Example 2 is an example in which the number of carbon atoms in the linear alkyl group contained in the hydrophobic treatment agent does not satisfy the above requirement, Comparative Example 3 is an example in which the alkyl group contained in the hydrophobic treatment agent is not linear, and Comparative Examples 4 and 5 are examples in which the content of metal oxide particles in the toner particles does not satisfy the above requirement.

[0139] It can be seen that Example 1, which used titanium oxide particles as metal oxide particles, was superior to Example 28, which used alumina particles, in the evaluations of hot offset resistance and fogging, and was particularly superior in the evaluation of fogging.

[0140] It can be seen that Example 1, in which the titanium oxide particles used as the metal oxide particles are acicular, is superior in the evaluations of hot offset resistance and fogging, and is particularly superior in the evaluation of fogging, to Example 29, in which the titanium oxide particles are spherical.

[0141] It can be seen that Examples 1 and 11, in which the linear alkyl group contained in the hydrophobizing agent has 10 or less carbon atoms, are particularly superior in the evaluation of hot offset resistance and fogging compared to Example 30, in which the carbon number exceeds the upper limit.

[0142] It can be seen that Examples 1 and 14, in which the hydrophobicity of the metal oxide particles is 40% or more, are particularly superior in the evaluation of fogging compared to Example 31, in which the hydrophobicity of the metal oxide particles is below the lower limit. It can also be seen that Examples 1 and 15, in which the hydrophobicity of the metal oxide particles is 80% or less, are particularly superior in the evaluation of fogging compared to Example 32, in which the hydrophobicity of the metal oxide particles exceeds the upper limit.

[0143] It can be seen that Examples 1 and 18, in which the SP value of the amorphous polyester resin is 10.85 or more, are particularly superior in the evaluation of uniformity of image density compared to Example 33, in which the SP value of the amorphous polyester resin is below the lower limit. It can also be seen that Examples 1 and 19, in which the SP value of the amorphous polyester resin is 11.3 or less, are particularly superior in the evaluation of hot offset resistance compared to Example 34, in which the SP value of the amorphous polyester resin exceeds the upper limit.

[0144] When the content of metal oxide particles in the toner particles is A% by mass and the content of crystalline polyester resin in the toner particles is B% by mass, it can be seen that Examples 1 and 26, in which the mass ratio A / B is 0.003 or more, are particularly superior in the evaluations of hot offset resistance and image density uniformity compared to Example 37, in which the mass ratio A / B is below the lower limit. It can also be seen that Examples 1 and 27, in which the mass ratio A / B is 0.4 or more, are superior in the evaluations of all three evaluation items compared to Example 38, in which the mass ratio A / B exceeds the upper limit.

[0145] It can be seen that Example 1, which used ester wax as the wax, was superior to Example 39, which used paraffin wax, in the evaluation of uniformity of image density and fogging, and was particularly superior in the evaluation of fogging.

[0146] 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]

[0147] 1 Toner particles 11 Amorphous polyester resin 12 Crystalline polyester resin 12a Crystal part 12b Amorphous part 13. Wax 14 Metal oxide particles surface-treated with hydrophobic treatment agents 14a Substrate (metal oxide particle body) 14b Hydrophobic treatment agent

Claims

1. A toner having toner particles containing an amorphous polyester resin, a crystalline polyester resin, and a wax, the toner particles contain metal oxide particles having a number average particle diameter of 60 nm or less, the metal oxide particles are surface-treated with a hydrophobic treatment agent containing a linear alkyl group having 6 or more carbon atoms; The toner, wherein the content of the metal oxide particles in the toner particles is 0.02% by mass or more and 2% by mass or less.

2. 2. The toner according to claim 1, The toner is characterized in that the metal oxide particles are titanium oxide particles.

3. 3. The toner according to claim 1 or claim 2, The toner is characterized in that the metal oxide particles have a needle shape.

4. 3. The toner according to claim 1 or claim 2, The toner is characterized in that the linear alkyl group contained in the hydrophobic treatment agent has 10 or less carbon atoms.

5. 3. The toner according to claim 1 or claim 2, The toner is characterized in that the hydrophobicity of the metal oxide particles is 40% or more and 80% or less.

6. 3. The toner according to claim 1 or claim 2, the SP value of the amorphous polyester resin is 10.85 or more and 11.3 or less; The toner is characterized in that the SP value of the crystalline polyester resin is 9.4 or more and 9.8 or less.

7. 3. The toner according to claim 1 or claim 2, The toner is characterized in that, when the content of the metal oxide particles in the toner particles is A mass %, and the content of the crystalline polyester resin in the toner particles is B mass %, the mass ratio A / B is 0.003 or more and 0.4 or less.

8. 3. The toner according to claim 1 or claim 2, The toner, wherein the wax is an ester wax.

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