toner

Abstract

To provide a toner having excellent low-temperature fixability while maintaining sufficient heat-resistant storage property, and capable of suppressing occurrence of fogging.SOLUTION: The toner has an external additive adhering to the surface of a toner particle 2 containing a binder resin 3 and a crystalline polyester resin 4. The external additive includes silica particles 5 surface-treated with a silicone oil. When the SP value of the crystalline polyester resin 3 is SP1 and the SP value of the silica particles 5 surface-treated with silicone oil is SP2, SP1 - SP2 is 2.0 or more and 2.8 or less. In an electron image of the surface of the toner particle 2 obtained by a scanning electron microscope, an exposure rate of the crystalline polyester-based resin 4 calculated as an area ratio of the crystalline polyester-based resin 4 to the surface is 3% or more and 10% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Toners (toners for developing electrostatic images) used in electrophotographic image forming devices such as copiers, multifunction devices, printers, and facsimile machines usually have external additives attached to the surface of the toner particles. In recent years, there has been a demand for further energy savings in image forming devices, and toners are therefore required to have low-temperature fixability in order to achieve this. Low-temperature fixable toners with improved low-temperature fixability are known to contain crystalline polyester resins in the toner particles.

[0003] As an example of a toner in which toner particles contain a crystalline polyester resin, Patent Document 1 discloses a technology in which the toner particles further contain a styrene-acrylic resin, and the crystalline polyester resin is a polymer of monomers including an alcohol monomer, a carboxylic acid monomer, an acrylic acid monomer, and a styrene monomer, the temperature of the toner at a predetermined storage modulus is within a specific range, the dispersion diameter of the crystalline polyester resin in the toner particles is 100 nm or more and 500 nm or less, and the endothermic peak derived from the crystallized portion of the crystalline polyester resin measured by differential scanning calorimetry of the toner satisfies specific conditions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-20690 Summary of the Invention [Problem to be solved by the invention]

[0005] However, blending a crystalline polyester resin into toner particles increases the risk of fogging, a phenomenon in which toner adheres to areas on the surface of an image carrier (e.g., a photoreceptor) where a toner image should not be formed, resulting in overall staining of non-image areas on the recording paper.

[0006] Therefore, in order to suppress fogging, it is considered to use silica particles surface-treated with silicone oil (hereinafter also referred to as "silicone oil-treated silica") as an external additive. FIG. 3 is a cross-sectional view showing a schematic example of a toner using silicone oil-treated silica as an external additive as a reference example. The toner 100 in FIG. 3 has toner particles 200 containing binder resin 300, and silicone oil-treated silica 500 adheres to the surface of the toner particles 200. When the toner 100 is fixed to the recording paper 20, the toner 100 moves from the fixing roller (fixing device) 10 side to the recording paper 20 side.

[0007] However, silicone oil-treated silica has low affinity with paper, which causes a problem that the silicone oil-treated silica used as an external additive significantly impairs the low-temperature fixability of the toner.

[0008] The contents of the present disclosure have been discovered in consideration of the above circumstances regarding toners containing crystalline polyester resins and silicone oil-treated silica, and a main object of the present disclosure is to provide a toner that has excellent low-temperature fixing properties while maintaining sufficient heat-resistant storage stability and that 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 in which an external additive is attached to the surface of toner particles containing a binder resin and a crystalline polyester resin, the external additive contains silica particles surface-treated with silicone oil; When the SP value of the crystalline polyester resin is SP1 and the SP value of the silica particles surface-treated with silicone oil is SP2, SP1-SP2 is 2.0 or more and 2.8 or less; The exposure rate of the crystalline polyester resin, calculated as the area ratio of the crystalline polyester resin to the surface in an electron image of the toner particle surface obtained by a scanning electron microscope, is 3% or more and 10% or less.

[0010] In the above toner, it is preferable that the average dispersion diameter of the crystalline polyester resin in the toner particles is 50 nm or more and 200 nm or less.

[0011] In the above toner, the silica particles surface-treated with the silicone oil preferably have an average particle size of 50 nm or less.

[0012] In the above toner, it is preferable that the adhesion strength of the silica particles surface-treated with silicone oil to the surfaces of the toner particles is 60% or more and 80% or less.

[0013] In the toner, the content of the crystalline polyester resin in the toner particles is preferably 2% by mass or more and 10% by mass or less.

[0014] In the toner, the amount of the silica particles surface-treated with silicone oil added to 100 parts by mass of the toner particles is preferably 0.5 parts by mass or more and 2.0 parts by mass or less. [Effects of the Invention]

[0015] The toner of the present disclosure exhibits excellent effects such as excellent low-temperature fixability while maintaining sufficient heat-resistant storage stability and suppressing the occurrence of fogging. [Brief explanation of the drawings]

[0016] [Figure 1]3 is a cross-sectional view schematically illustrating how toner is fixed onto a recording sheet by a fixing roller in the present embodiment. FIG. [Figure 2] FIG. 2 is a cross-sectional view schematically showing silicone oil-treated silica added to the toner according to the present embodiment. [Figure 3] FIG. 1 is a cross-sectional view schematically illustrating, as a reference example, an example of a toner using silicone oil-treated silica as an external additive. DETAILED DESCRIPTION OF THE INVENTION

[0017] The toner of the present disclosure will be described 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.

[0018] 1. Overall composition of toner The toner according to this embodiment is a toner in which an external additive is adhered to the surface of toner particles containing a binder resin and a crystalline polyester resin, and satisfies the following requirements (A) to (C). The external additive (A) includes silicone oil-treated silica. (B) When the SP value of the crystalline polyester resin is SP1 and the SP value of the silicone oil-treated silica is SP2, SP1-SP2 is 2.0 or more and 2.8 or less. (C) The exposed rate of the crystalline polyester resin is 3% or more and 10% or less.

[0019] Here, the "exposure rate of crystalline polyester resin" in the present disclosure means the area ratio of the crystalline polyester resin to the surface in an electron image of the toner particle surface obtained by a scanning electron microscope, and can be measured specifically by the exposure rate method described in the examples below.Furthermore, the "SP value of silicone oil-treated silica" is essentially the SP value of silicone oil, which is a surface treatment agent for silicone oil-treated silica, and can be measured specifically by the SP value measurement method described in the examples below.

[0020] FIG. 1 is a cross-sectional view illustrating the process of toner being fixed to recording paper by a fixing roller according to this embodiment. The toner 1 in FIG. 1 includes toner particles 2 containing a binder resin 3, with silicone oil-treated silica 5 adhering to the surface of the toner particles 2. When the toner 1 is fixed to recording paper 20, the toner 1 migrates from the fixing roller (fixing device) 10 side to the recording paper 20 side. In the toner 1 according to this embodiment, a crystalline polyester resin 4 is present on the surface of the toner particles 2 in a proportion specified by requirement (C) above. Additionally, the difference in SP value between the crystalline polyester resin 4 and the silicone oil-treated silica 5 is the value specified by requirement (B) above. Specifically, a crystalline polyester resin that is compatible with silicone oil, the surface treatment agent for the silicone oil-treated silica, is used. As a result, during fixing of the toner 1, as indicated by the arrows in FIG. 1, the crystalline polyester resin 4 exuded from the surface of the toner particles 2 and the silicone oil-treated silica 5 blend together, enhancing adhesion to the recording paper 20 and enabling fixing at low temperatures. This means that the toner according to this embodiment exhibits excellent low-temperature fixability.

[0021] Hereinafter, each component constituting the toner according to this embodiment will be described.

[0022] 2. Toner particles (toner cores) The toner particles according to the present embodiment contain an internal additive such as a colorant and a binder resin, and the internal additive is dispersed in the binder resin. An external additive is attached to the surface of the toner particles. If necessary, the toner particles may further contain optional components within a range that does not impair the effects of the present disclosure. The average primary particle diameter of the toner particles can be appropriately selected depending on the purpose, and may be, for example, 4.5 μm or more and 8 μm or less.

[0023] The method for producing toner particles is not particularly limited, and they can be produced, for example, by a pulverization method. The production of toner particles by the pulverization method can be carried out by, for example, performing a mixing step of dry-mixing raw materials including internal additives such as colorants and binder resins in a mixer, a melting and kneading step of melting and kneading the obtained mixture in a kneader, a pulverization step of cooling and solidifying the obtained molten and kneaded mixture, and pulverizing the solidified mixture in a pulverizer to obtain a finely pulverized product, and a classification step of adjusting the particle size of the obtained finely pulverized product using a classifier or the like, as necessary.

[0024] <Resin> The toner particles according to this embodiment contain at least a binder resin and a crystalline polyester resin, and the binder resin may be an amorphous polyester resin. The crystalline polyester resin can lower the softening temperature and melt viscosity of the toner, and when used in combination with the amorphous polyester resin, can improve the low-temperature fixability of the toner. Furthermore, when the amorphous polyester resin and the crystalline polyester resin used in combination are derived from different raw materials, specifically, when the main components of the dicarboxylic acid monomer and polyhydric alcohol are different, the compatibility of the two resins can be more reliably suppressed, and a greater improvement in low-temperature fixability can be expected. However, suppressing the compatibility of the two resins makes the crystalline polyester resin more likely to separate from the amorphous polyester resin and to be easily fixed to the developing roller together with the filler component.

[0025] In the present disclosure, a crystalline polyester resin refers to a polyester resin having a crystallinity index of 0.6 or more and 1.5 or less, preferably 0.8 or more and 1.2 or less, and an amorphous polyester resin refers to a polyester resin having a crystallinity index of more than 1.5 or less than 0.6, preferably more than 1.5.

[0026] Here, 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 endothermic maximum peak temperature (softening temperature / endothermic maximum peak temperature). 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. The degree of crystallinity can be adjusted by the type and ratio of raw material monomers, as well as production conditions (e.g., reaction temperature, reaction time, cooling rate). The endothermic maximum peak temperature refers to the temperature of the highest peak among the observed endothermic peaks. If the maximum peak temperature is within 20°C of the softening temperature, it is considered to be the melting point, and if the difference from the softening temperature is more than 20°C, it is considered to be a peak due to glass transition.

[0027] Crystalline polyester resins and amorphous polyester resins can be produced by known methods, such as those disclosed in JP-A-2006-113473, and are obtained by polycondensing an alcohol component and a carboxylic acid component as raw material monomers.

[0028] -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.

[0029] The reaction conditions are the same as those used in the production of ordinary polyester resins, and for example, an amorphous polyester resin can be obtained by reacting a dicarboxylic acid monomer with a polyhydric alcohol in a nitrogen gas atmosphere, optionally in the presence of an esterification catalyst, at 190°C to 240°C. The reaction ratio of the polyhydric alcohol to the carboxylic acid monomer is preferably 1.3:1 to 1:1.2 in terms of the equivalent ratio of hydroxyl groups to carboxyl groups [OH]:[COOH].

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] From the viewpoint of the fixability, storage stability, durability, etc. of the toner, the amorphous polyester resin preferably has a glass transition temperature Tg of 50°C or higher and 70°C or lower. If the glass transition temperature is outside this range, the balance among the fixability, storage stability, and durability of the toner may be lost.

[0036] Furthermore, from the viewpoint of achieving both low-temperature fixability and hot offset resistance of the toner, the amorphous polyester resin preferably has a softening temperature Tm of 100°C or higher and 150°C or lower. If the softening temperature is outside this range, the balance between the low-temperature fixability and hot offset resistance of the toner may be lost.

[0037] From the viewpoint of achieving both heat-resistant storage stability and low-temperature fixability of the toner, the amorphous polyester resin preferably has a peak top molecular weight Mp of 3,000 or more and 10,500 or less. If the peak top molecular weight is outside this range, the balance between the heat-resistant storage stability and low-temperature fixability of the toner may be lost.

[0038] Here, the peak top molecular weight Mp means the molecular weight showing the maximum peak height of the THF-soluble matter in gel permeation chromatography (GPC) using tetrahydrofuran (THF) as the mobile phase and polystyrene as the standard substance.

[0039] Furthermore, the amorphous polyester resin preferably has an acid value of 0 mgKOH to 60 mgKOH / g from the viewpoint of the toner's chargeability, and a hydroxyl value of 0 mgKOH / g to 50 mgKOH / g from the viewpoint of the toner's hot offset resistance. If the acid value exceeds 60 mgKOH / g, the toner's chargeability may deteriorate, and if the hydroxyl value exceeds 50 mgKOH / g, the toner's hot offset resistance may become insufficient.

[0040] -Crystalline polyester resin- In the toner particles according to this embodiment, the crystalline polyester resin is dispersed in the binder resin. Additionally, the exposure rate of the crystalline polyester resin, calculated as the area ratio of the crystalline polyester resin to the surface of a toner particle in an electron image of the surface obtained by a scanning electron microscope, is 3% or more and 10% or less. It is preferably 3.5% or more and 7% or less, and more preferably 4% or more and 6% or less. Having the exposure rate of the crystalline polyester resin within the above range can significantly improve low-temperature fixability. If the exposure rate of the crystalline polyester resin is below the lower limit, the amount of crystalline polyester resin present on the toner particle surface is small, and the effect of improving low-temperature fixability according to the present disclosure may be difficult to achieve. If the exposure rate of the crystalline polyester resin exceeds the upper limit, the amount of crystalline polyester resin present on the toner particle surface becomes excessive, which may significantly deteriorate the heat-resistant storage stability.

[0041] The crystalline polyester resin preferably contains, as an alcohol component, a monomer that promotes the crystallinity of the resin, such as an aliphatic diol having 2 to 8 carbon atoms.

[0042] Examples of the aliphatic diol having 2 to 8 carbon atoms include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, neopentyl glycol, and 1,4-butenediol, and α,ω-linear alkanediols are particularly preferred.

[0043] From the viewpoint of high crystallinity, the content of the aliphatic diol having 2 to 8 carbon atoms in the alcohol component is preferably 80 mol % or more, and more preferably, one kind of the aliphatic diol accounts for 70 mol % or more of the alcohol component.

[0044] Examples of carboxylic acid components include aliphatic dicarboxylic acids having 2 to 30 carbon atoms, preferably 2 to 8 carbon atoms, such as fumaric acid, adipic acid, oxalic acid, malonic acid, maleic acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, sebacic acid, azelaic acid, n-dodecylsuccinic acid, and n-dodecenylsuccinic acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; and polycarboxylic acids having a valence of 3 or more, such as trimellitic acid and pyromellitic acid. Among these, aliphatic dicarboxylic acids are preferred from the viewpoint of high crystallinity, and aliphatic dicarboxylic acids having 2 to 8 carbon atoms are preferred. Carboxylic acid components include carboxylic acids, their anhydrides, and their alkyl (C1 to C3) esters, with carboxylic acids being preferred. The content of the aliphatic dicarboxylic acid compound in the carboxylic acid component is preferably 70 mol% or more.

[0045] Regarding the molar ratio of the carboxylic acid component to the alcohol component (carboxylic acid component / alcohol component) in the crystalline polyester resin, when increasing the molecular weight of the crystalline polyester resin, it is preferable that the alcohol component is more than the carboxylic acid component. Furthermore, from the viewpoint of easily adjusting the molecular weight of the polyester by distilling off the alcohol component during the reduced pressure reaction, the molar ratio is preferably 0.9 or more and less than 1.

[0046] The condensation polymerization of an alcohol component and a carboxylic acid component when producing a crystalline polyester resin can be carried out, for example, in an inert gas atmosphere, using an esterification catalyst as needed, at a temperature of 120° C. to 230° C. The softening temperature of the crystalline polyester resin is preferably 70° C. to 140° C. from the viewpoint of low-temperature fixability.

[0047] From the viewpoint of satisfying the above requirement (B), the SP value (SP1) of the crystalline polyester resin is preferably 9.0 or more and 10.2 or less, and more preferably 9.5 or more and 10.0 or less.

[0048] In the toner according to this embodiment, the average dispersion diameter of the crystalline polyester resin in the toner particles is preferably 50 nm or more and 200 nm or less, more preferably 70 nm or more and 150 nm or less, and even more preferably 80 nm or more and 120 nm or less. When the average dispersion diameter of the crystalline polyester resin in the toner particles is within the above range, the toner can have excellent low-temperature fixability and heat-resistant storage stability. When the average dispersion diameter of the crystalline polyester resin in the toner particles is outside the above range, the low-temperature fixability and heat-resistant storage stability may be reduced.

[0049] The content of the crystalline polyester resin in the toner particles according to this embodiment is preferably 2% by mass or more and 10% by mass or less, more preferably 2% by mass or more and 7% by mass or less, and even more preferably 2.5% by mass or more and 5% by mass or less. When the content of the crystalline polyester resin in the toner particles is within the above range, the toner can have excellent low-temperature fixability and heat-resistant storage stability. When the content of the crystalline polyester resin in the toner particles is outside the above range, the low-temperature fixability and heat-resistant storage stability may be reduced.

[0050] -Styrene-based resin- The toner particles according to this embodiment may contain a resin other than the polyester resin, and an example of such a resin is a styrene resin. The styrene resin is dispersed in the binder resin and exists as dispersed particles. By adding (internal adding) the styrene resin to the toner particles, the crystalline polyester resin can be more uniformly dispersed in the amorphous polyester resin; in other words, the styrene resin functions as a dispersion aid.

[0051] Examples of styrene-based resins include homopolymers and copolymers of styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene, ethylstyrene, isopropylstyrene, and dimethylstyrene, as well as copolymers of styrene-based monomers and vinyl monomers copolymerizable with styrene-based monomers. Examples of vinyl monomers include monofunctional monomers such as alkyl (meth)acrylates (e.g., methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate), (meth)acrylonitrile, and bifunctional monomers (e.g., divinylbenzene and alkylene glycol dimethacrylate). Here, "(meth)acrylate" refers to acrylate or methacrylate. Among these styrene-based resins, copolymers of styrene or α-methylstyrene with (meth)acrylate (styrene-acrylic copolymers) are preferred.

[0052] The content of the styrene-based resin in the toner particles according to this exemplary embodiment is preferably 2.5% by mass or more and 6.5% by mass or less, and more preferably 4% by mass or more and 6% by mass or less.

[0053] <Internal additives> -Mold release agent- The toner particles according to this embodiment may contain a wax as a release agent. Examples of the wax include waxes commonly used in the field of electrophotography, 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. The wax content in the toner particles is not particularly limited, but may be 0.5% to 10% by mass, and preferably 1% to 5% by mass.

[0054] -Coloring agent- The toner particles according to this embodiment may contain a colorant. As the colorant, organic pigments, organic dyes, inorganic pigments, inorganic dyes, etc. used in the field of electrophotography can be used.

[0055] Examples of black colorants include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, non-magnetic ferrite, magnetic ferrite, and magnetite.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] The content of the colorant in the toner particles is not particularly limited, but may be 3% by mass to 15% by mass, and preferably 4% by mass or more and 10% 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.

[0060] -Charge adjuster- The toner particles according to this 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.

[0061] Examples of charge control agents for controlling positive charges include quaternary ammonium salts, pyrimidine compounds, triphenylmethane derivatives, guanidine salts, and amidine salts.

[0062] 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.

[0063] <External additives> -Silica particles surface-treated with silicone oil (silicone oil-treated silica)- The toner according to this embodiment contains at least silicone oil-treated silica as an external additive. The silicone oil-treated silica used in this embodiment is a particle containing a silica base material (silica particles before surface treatment) and silicone oil. Its specific surface area as measured by the BET method is not particularly limited, but is preferably 30 m 2 ~400m 2 / g.

[0064] Fig. 2 is a cross-sectional view showing a schematic diagram of the silicone oil-treated silica. As shown in Fig. 2, the silicone oil-treated silica 5 is obtained by coating the surface of a silica substrate 51 with silicone oil 52 as a surface treatment agent. Although Fig. 2 shows that the surface of the silica substrate 51 is completely coated with silicone oil 52, this is merely an example, and the toner according to this embodiment may contain silicone oil-treated silica in which part of the surface of the silica substrate is not coated with silicone oil.

[0065] In the toner according to this embodiment, where the SP value of the crystalline polyester resin is SP1 and the SP value of the silicone oil-treated silica is SP2, SP1-SP2 is 2.0 or more and 2.8 or less, preferably 2.3 or more and 2.7 or less. When SP1 and SP2 satisfy this relationship, the crystalline polyester resin exuded from the surface of the toner particles and the silicone oil-treated silica blend together during toner fixing, enhancing adhesion between the toner and recording paper and enabling fixing even at low temperatures. In other words, the toner according to this embodiment can exhibit excellent low-temperature fixability. If SP1-SP2 is less than the lower limit, the crystalline polyester resin and the silicone oil-treated silica may blend too well, resulting in poor heat-resistant storage stability of the toner.

[0066] From the viewpoint of satisfying the above requirement (B), the SP value (SP2) of the silicone oil-treated silica is preferably 7.0 or more and 8.0 or less, more preferably 7.0 or more and 7.5 or less. The SP value (SP2) of the silicone oil-treated silica is essentially the SP value of the silicone oil, which is the surface treatment agent of the silicone oil-treated silica, and can be measured by the SP value measurement method described in the Examples below.

[0067] The average dispersion diameter of the silicone oil-treated silica in the toner according to this embodiment is 60 nm or less, preferably 50 nm or less, more preferably 10 nm to 50 nm, and even more preferably 10 nm to 20 nm. When the average dispersion diameter of the silicone oil-treated silica is within the above range, the crystalline polyester resin exuded from the surface of the toner particles and the silicone oil-treated silica blend together, and the effect of increasing the adhesion between the toner and the recording paper can be fully exerted, and ultimately, excellent low-temperature fixability can be exhibited. When the average dispersion diameter of the silicone oil-treated silica exceeds the above upper limit, the large size of the silicone oil-treated silica makes it impossible to fully exert the effect, and low-temperature fixability may be deteriorated.

[0068] The adhesion strength of the silicone oil-treated silica to the toner particle surface according to this embodiment can be 50% to 90%, preferably 60% to 80%, and more preferably 60% to 70%. When the adhesion strength of the silicone oil-treated silica to the toner particle surface is within the above range, the crystalline polyester resin exuded from the surface of the toner particles and the silicone oil-treated silica blend together, thereby fully demonstrating the effect of increasing the adhesion between the toner and the recording paper, and ultimately demonstrating excellent low-temperature fixability. If the adhesion strength of the silicone oil-treated silica to the toner particle surface is below the lower limit, the effect cannot be fully demonstrated, and low-temperature fixability may deteriorate. If the adhesion strength of the silicone oil-treated silica to the toner particle surface exceeds the upper limit, the developability of the toner may deteriorate.

[0069] The amount of silicone oil-treated silica added per 100 parts by mass of toner particles according to this embodiment is, for example, 0.1 to 3.0 parts by mass, preferably 0.5 to 2.0 parts by mass, more preferably 0.5 to 1.5 parts by mass, and even more preferably 1.0 to 1.5 parts by mass. When the amount of silicone oil-treated silica added is within the above range, the crystalline polyester resin exuded from the surface of the toner particles and the silicone oil-treated silica blend together, thereby fully demonstrating the effect of increasing the adhesion between the toner and the recording paper, and ultimately, achieving excellent low-temperature fixability. If the amount of silicone oil-treated silica added is less than the above lower limit, the effect cannot be fully demonstrated, and low-temperature fixability may deteriorate. If the amount of silicone oil-treated silica added exceeds the above upper limit, the heat-resistant storage stability is improved, but low-temperature fixability and developability may deteriorate.

[0070] The silica substrate can be produced by known methods such as a dry method (gas phase method), a wet method, or a sol-gel method, and is preferably produced by a gas phase method because it does not use a solvent. The gas phase method is a method for producing a silica substrate by vapor-phase oxidation of a silicon halide compound. For example, a silica substrate called dry method (gas phase method) silica or fumed silica can be produced by the thermal decomposition oxidation reaction of silicon tetrachloride gas in an oxyhydrogen flame (basic reaction: SiCl4 + 2H2 + O2 → SiO2 + 4HCl).

[0071] The silica substrate may also be a composite of silica and another metal oxide, which is obtained by using a metal halide compound such as aluminum chloride or titanium chloride together with a silicon halide compound in the above-mentioned manufacturing process.

[0072] Silicone oil-treated silica can be produced, for example, by directly mixing a silica base material treated with an organosilicon compound with silicone oil using a mixer such as a Henschel mixer; by spraying silicone oil diluted with an appropriate solvent such as normal hexane onto a silica base material and then heat treating the mixture; or by dissolving or dispersing silicone oil in an appropriate solvent, adding the silica base material and mixing, and then removing the solvent.

[0073] The heat treatment after spraying is preferably carried out in an inert gas atmosphere such as helium, nitrogen, or argon for safety reasons, and is preferably carried out in a nitrogen gas atmosphere for cost reasons, etc. The temperature for this heat treatment is preferably 200°C or higher and 400°C or lower.

[0074] Examples of the silicone oil include straight silicone oils such as dimethyl silicone oil, methylphenyl silicone oil, and methylhydrogen silicone oil; epoxy-modified silicone oil, carboxyl-modified silicone oil, carbinol-modified silicone oil, methacrylic-modified silicone oil, mercapto-modified silicone oil, phenol-modified silicone oil, one-end reactive modified silicone oil, heterofunctional group-modified silicone oil, polyether-modified silicone oil, methylstyryl-modified silicone oil, alkyl-modified silicone oil, higher fatty acid ester-modified silicone oil, hydrophilic special modified silicone oil, higher alkoxy-modified silicone oil, higher fatty acid-containing modified silicone oil, and fluorine-modified silicone oil. These may be used alone or in combination of two or more.

[0075] Examples of the organosilicon compound include hexamethyldisilazane, trimethylsilane, trimethylethoxysilane, isobutyltrimethoxysilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, etc. These may be used alone or in combination of two or more.

[0076] Silicone oil-treated silica can be produced, for example, by the method described in Japanese Patent No. 6849352, and desired particles can be obtained by changing the average primary particle size of the silica base material and the amount of silicone oil used.

[0077] The toner according to this embodiment may be used in combination with external additives other than silicone oil-treated silica, as long as the effects of the present disclosure are not impaired. In other words, external additives other than silicone oil-treated silica may adhere to the surface of toner particles. Examples of such external additives include inorganic fine particles such as titanium oxide, alumina, and silica other than silicone oil-treated silica, having an average primary particle diameter of 5 nm or more and 200 nm or less. Inorganic fine particles having hydrophobicity imparted by a surface treatment agent such as a silane coupling agent or a titanium coupling agent on the surface thereof are more suitable because the decrease in electrical resistance and charge amount is less in a high-humidity environment.

Example

[0078] Hereinafter, the toner of the present disclosure will be specifically described based on Examples and Comparative Examples.

[0079] 1. Measurement methods for various physical properties <Calculation method of SP value> The SP value is measured as follows according to the method of Sue Clark (K.W. Suh, D.H. Clarke, "Cohesive Energy Densities of Polymers from Turbidimetric Titrations", Journal of Polymer Science, A-1, vol. 5, 1967, p. 1671-1681).

[0080] Weigh 0.5 g of the sample to be measured (crystalline polyester resin for the measurement of SP1, and silicone oil used for the surface treatment of silicone oil-treated silica for the measurement of SP2) into a beaker with a capacity of 100 mL, add 10 mL of a good solvent (a mixed solution of dioxane and acetone) using a whole pipette, and stir with a magnetic stirrer to dissolve the sample. Then, a hydrophobic solvent (a mixed solution of n-hexane and ion-exchanged water) is dropped using a burette with a capacity of 50 mL, and the dropping amount at which turbidity occurs is measured at a measurement temperature of 20°C. From this measurement value, the SP value δ of the sample is determined by the following formula. δ=(Vl / 2δl+Vh / 2δh) / (Vl / 2+Vh / 2)

[0081] In the above formula, Vl is the molar volume (mL / mol) of the solvent in the low SP solvent (hydrophobic solvent) mixed system, Vh is the molar volume (mL / mol) of the solvent in the high SP solvent (good solvent) mixed system, δl is the SP value of the solvent in the low SP solvent (hydrophobic solvent) mixed system, and δh is the SP value of the solvent in the high SP solvent (good solvent) mixed system.

[0082] <Method for measuring the exposure rate of crystalline polyester resin> The toner particles are dyed in an aqueous solution of ruthenium (VIII) tetroxide for 5 minutes. This stains the crystalline polyester resin contained in the toner particles most intensely. The stained toner particle surfaces are photographed using a scanning electron microscope (SEM, manufactured by Hitachi High-Technologies Corporation, model: S-4800). 20 to 30 toner particles are randomly selected from the image obtained and analyzed using image analysis software (manufactured by Asahi Kasei Engineering Co., Ltd., product name: A-zo-kun). The area ratio of the dyed crystalline polyester resin to the surface of the extracted toner particles is calculated, and this is taken as the exposure rate of the crystalline polyester resin.

[0083] <Method for measuring the average dispersed particle diameter of crystalline polyester resin> The toner was mixed with an epoxy resin (DEVCON, product name: DEV-TUBE S-31), poured into a mold, and left to harden for at least 24 hours to obtain a cured sample. Next, an ultrathin section (60 nm thick) was cut from the cured sample using a microtome (Leica, model: Ultramicrotome EM UC7). The cut ultrathin section was then sampled on a grid (Nissin EM Co., Ltd., product name: EM Fine Grid F-200). The sample on the grid was stained with a 0.5% aqueous solution of ruthenium (VIII) tetroxide for approximately one minute. The stained sample was then photographed using a scanning electron microscope (SEM, Hitachi High-Technologies Corporation, model: S-4800). Following the above procedure, the cross section of the toner particle was photographed.

[0084] Next, a considerable number (200 to 300) of dispersed particles of the crystalline polyester resin are randomly extracted from the cross-sectional image of the toner particles, and the images are analyzed using image analysis software (manufactured by Asahi Kasei Engineering Co., Ltd., product name: A-zo-kun). The average particle diameter of the crystalline polyester resin is determined by averaging the dispersion diameters of a considerable number of the dispersed particles.

[0085] <Method for measuring the average particle size of external additives> The average primary particle diameter of the external additive is measured by photographing the toner using a scanning electron microscope (SEM, manufactured by Hitachi High-Technologies Corporation, model: S-4800) and measuring the particle diameter (long diameter) of 100 external additive particles randomly selected from the image obtained. The average value of the particle diameters of these 100 particles is calculated and used as the average particle diameter of the external additive.

[0086] <Method for measuring adhesive strength of external additives> The toner sample obtained by carrying out the external additive removal treatments shown in the following (1) to (6) is referred to as "Sample 1," and the toner sample before carrying out the external additive removal treatment is referred to as "Sample 2."

[0087] -External additive 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 external additives. (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.

[0088] Next, the X-ray intensity of the specific element in the external additive 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 external additive to the toner particles is calculated using the following formula. Note that the specific element in the case of silicone oil-treated silica is "Si." Adhesion strength = (X-ray intensity in sample 2) / (X-ray intensity in sample 1) × 100

[0089] 2. Preparation and production of raw materials <Preparation of Silicone Oil-Treated Silica A> The fumed silica particles with an average primary particle diameter of 14 nm, which are produced by burning silicon tetrachloride in an oxyhydrogen flame (flame hydrolysis method), are placed in a reaction vessel.Under a nitrogen atmosphere, 100 parts by mass of the silica particles are sprayed with a solution of 20 parts by mass of dimethyl silicone oil diluted with 100 parts by mass of hexane.Then, under a nitrogen atmosphere, the mixture is stirred and dried at 250 ° C for 60 minutes, to obtain silicone oil-treated silica A.

[0090] <Preparation of Silicone Oil-Treated Silica B> Silicone oil-treated silica B was obtained in the same manner as in the above "Preparation of silicone oil-treated silica A", except that fumed silica particles having an average primary particle diameter of 50 nm were used instead of fumed silica particles having an average primary particle diameter of 14 nm.

[0091] <Preparation of Silicone Oil-Treated Silica C> Silicone oil-treated silica B was obtained in the same manner as in the above "Preparation of silicone oil-treated silica A", except that fumed silica particles having an average primary particle diameter of 50 nm were used instead of fumed silica particles having an average primary particle diameter of 14 nm.

[0092] <Preparation of amorphous polyester resin A> A reactor was charged with 440 g (2.7 mol) of terephthalic acid, 235 g (1.4 mol) of isophthalic acid, 7 g (0.05 mol) of adipic acid, 554 g (8.9 mol) of ethylene glycol, and 0.5 g of tetrabutoxy titanate as a polymerization catalyst. The mixture was reacted at 210 °C for 5 hours under a nitrogen stream while distilling off the resulting water and ethylene glycol. The reaction was then continued for 1 hour under a reduced pressure of 666.7 Pa (5 mmHg) to 2666.4 Pa (20 mmHg). Next, 103 g (0.54 mol) of trimellitic anhydride was added, and the mixture was reacted for 1 hour under normal pressure. The reaction was then continued under a reduced pressure of 2666.4 Pa (20 mmHg) to 5332.9 Pa (40 mmHg). The resin was extracted at the specified softening point. 219 g (3.5 mol) of ethylene glycol was recovered. The resulting resin was cooled to room temperature and then pulverized into particles. This was designated as amorphous polyester resin A. The SP value of amorphous polyester resin A was 11.6.

[0093] <Production Example of Styrene-Based Resin A> 20 parts by mass of a xylene solution in which 1.5 parts by mass of di-t-butyl peroxide was uniformly dissolved in a solution consisting of 76 parts by mass of styrene, 24 parts by mass of n-butyl acrylate, and 80 parts by mass of xylene solvent was added to a flask at an internal temperature of 190°C and an internal pressure of 6 kg / cm. 2 The resulting mixture was continuously supplied at 750 mL / hour to a 5 L reactor maintained at 90°C and polymerized to obtain a styrene-acrylic copolymer solution. The mixture was flushed into a vessel at 90°C and 10 mmHg to distill off the solvent, and then coarsely pulverized using a coarse pulverizer to obtain 1 mm chips of the styrene-acrylic copolymer, which were designated as styrene-based resin A.

[0094] The physical properties of the silica particles and resins prepared as raw materials are summarized in Tables 1 and 2. Note that "Silica D" shown in Table 1 is silica particles surface-treated with dimethyldichlorosilane, i.e., not silica particles surface-treated with silicone oil.

[0095] [Table 1]

[0096] [Table 2]

[0097] 3. Manufacture of toner and two-component developer <Toner manufacturing process> [Example 1] -Material mixing, melt-kneading, crushing, and classification processes- The toner raw materials used are as follows: Binder resin Amorphous polyester resin A 82.5% by mass Dispersing agent Styrene-based resin A 5.0% by mass Crystalline resin Crystalline polyester resin A 3.0% by mass Coloring agents Carbon black (manufactured by Cabot Corporation, product name: Regal 330) 6.0% by mass ·Mold release agent Paraffin wax (manufactured by Nippon Seiro Co., Ltd., product name: HNP10) 2.5% by mass Charge control agent Salicylic acid compound (Orient Chemical Industry Co., Ltd., product name: Bontro E84) 1.0% by mass

[0098] The 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 (melt-kneading process). In this melt-kneading process, the cylinder temperature was set to 110°C, the barrel rotation speed was 300 rpm, and the raw material supply rate was 20 kg / hour.

[0099] The resulting molten and kneaded material was cooled on a cooling belt, then coarsely pulverized using a cutting mill (coarse pulverization step), then finely pulverized using a jet pulverizer (fine pulverization step), and further classified using an air classifier (classification step) to obtain toner particles with an average particle size of 6.7 μm.

[0100] -External addition process- To 100 parts by mass of the obtained toner particles, 1.2 parts by mass of silicone oil-treated silica A and 0.5 parts by mass of titanium oxide (manufactured by Teika Corporation, product name: JMT-150, average primary particle diameter 15 nm) were added, and the mixture was stirred 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 to obtain a toner.

[0101] [Example 2] A toner was obtained in the same manner as in Example 1, except that the crystalline resin used as the toner raw material was changed to crystalline polyester resin B.

[0102] [Example 3] A toner was obtained in the same manner as in Example 1, except that the crystalline resin used as the toner raw material was changed to crystalline polyester resin C.

[0103] [Example 4] A toner was obtained in the same manner as in Example 1, except that the cylinder temperature in the melt-kneading step was changed to 120°C.

[0104] [Example 5] A toner was obtained in the same manner as in Example 1, except that the cylinder temperature in the melt-kneading step was changed to 100°C.

[0105] [Example 6] A toner was obtained in the same manner as in Example 1, except that the proportion of the styrene resin in the toner raw materials was changed to 6.0% by mass and the proportion of the amorphous polyester resin was changed to 80.8% by mass.

[0106] [Example 7] A toner was obtained in the same manner as in Example 1, except that the proportion of the styrene resin in the toner raw materials was changed to 3.0% by mass and the proportion of the amorphous polyester resin was changed to 83.8% by mass.

[0107] [Example 8] A toner was obtained in the same manner as in Example 1, except that the proportion of the styrene resin in the toner raw materials was changed to 7.0% by mass and the proportion of the amorphous polyester resin was changed to 79.8% by mass.

[0108] [Example 9] A toner was obtained in the same manner as in Example 1, except that the proportion of the styrene resin in the toner raw materials was changed to 2.0% by mass and the proportion of the amorphous polyester resin was changed to 84.8% by mass.

[0109] [Example 10] A toner was obtained in the same manner as in Example 1, except that silicone oil-treated silica B was added instead of silicone oil-treated silica A in the external addition step.

[0110] [Example 11] A toner was obtained in the same manner as in Example 1, except that silicone oil-treated silica C was added instead of silicone oil-treated silica A in the external addition step.

[0111] [Example 12] A toner was 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.

[0112] [Example 13] A toner was obtained in the same manner as in Example 1, except that the stirring time in the external addition step was changed to 2 minutes 45 seconds.

[0113] [Example 14] A toner was obtained in the same manner as in Example 1, except that the stirring time in the external addition step was changed to 1 minute 15 seconds.

[0114] [Example 15] A toner was obtained in the same manner as in Example 1, except that the stirring time in the external addition step was changed to 3 minutes.

[0115] [Example 16] A toner was obtained in the same manner as in Example 1, except that the proportion of crystalline polyester resin A in the toner raw materials was changed to 2.0% by mass and the proportion of amorphous polyester resin was changed to 82.8% by mass.

[0116] [Example 17] A toner was obtained in the same manner as in Example 1, except that the proportion of crystalline polyester resin A in the toner raw materials was changed to 10.0% by mass and the proportion of amorphous polyester resin was changed to 74.8% by mass.

[0117] [Example 18] A toner was obtained in the same manner as in Example 1, except that the proportion of crystalline polyester resin A in the toner raw materials was changed to 1.0% by mass and the proportion of amorphous polyester resin was changed to 83.8% by mass.

[0118] [Example 19] A toner was obtained in the same manner as in Example 1, except that the proportion of crystalline polyester resin A in the toner raw materials was changed to 15.0% by mass and the proportion of amorphous polyester resin was changed to 69.8% by mass.

[0119] [Example 20] A toner was obtained in the same manner as in Example 1, except that the amount of silicone oil-treated silica A added in the external addition step was changed to 0.5 parts by mass.

[0120] [Example 21] A toner was obtained in the same manner as in Example 1, except that the amount of silicone oil-treated silica A added in the external addition step was changed to 1.5 parts by mass.

[0121] [Example 22] A toner was obtained in the same manner as in Example 1, except that the amount of silicone oil-treated silica A added in the external addition step was changed to 0.1 parts by mass.

[0122] [Example 23] A toner was obtained in the same manner as in Example 1, except that the amount of silicone oil-treated silica A added in the external addition step was changed to 3.0 parts by mass.

[0123] [Comparative Example 1] A toner was obtained in the same manner as in Example 1, except that in the external addition step, silica D (silica particles surface-treated with dimethyldichlorosilane) was used instead of silicone oil-treated silica A.

[0124] Comparative Example 2 A toner was obtained in the same manner as in Example 1, except that the crystalline resin used as the toner raw material was changed to crystalline polyester resin D.

[0125] Comparative Example 3 A toner was obtained in the same manner as in Example 1, except that the crystalline resin used as the toner raw material was changed to crystalline polyester resin E.

[0126] Comparative Example 4 A toner was obtained in the same manner as in Example 1, except that the cylinder temperature in the melt-kneading step was changed to 130°C.

[0127] Comparative Example 5 A toner was obtained in the same manner as in Example 1, except that the cylinder temperature in the melt-kneading step was changed to 90°C.

[0128] <Carrier manufacturing process> A coating resin solution was prepared by dissolving 0.375 parts by weight of silicone resin 1 (Shin-Etsu Chemical Co., Ltd., product name: KR240) and 0.375 parts by weight of silicone resin 2 (Shin-Etsu Chemical Co., Ltd., product name: KR251) in 12 parts by weight of toluene, and then dispersing 0.0375 parts by weight of conductive particles (Cabot Corporation, product name: VULCAN XC-72) and 0.0225 parts by weight of a coupling agent (Dow Corning Toray Co., Ltd., product name: AY43-059). 12.8 parts by weight of the coating resin solution was used per 100 parts by weight of the carrier core material. The surface of the carrier core material was coated with the coating resin solution by immersion. After a curing process at 200°C for 1 hour, the carrier was prepared by sieving through a 150 μm mesh sieve.

[0129] <Production process of two-component developer> The toners of Examples 1 to 23 and Comparative Examples 1 to 5 were combined with the prepared carrier to prepare the two-component developers of Examples 1 to 23 and Comparative Examples 1 to 5. These two-component developers were prepared by mixing for 20 minutes in a V-type mixer (manufactured by Tokuju Kogyosho Co., Ltd., product name: V-5) so that the toner concentration became 7% by mass.

[0130] Table 3 below summarizes the types and amounts of raw materials used in producing the toners of the examples and comparative examples, as well as the physical properties of the toners.

[0131] [Table 3]

[0132] 4. Evaluation <Evaluation 1: Evaluation method for low-temperature fixability> A fixed image was formed using a two-component developer using a commercially available copier (model MX-5100FN, manufactured by Sharp Corporation) 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 recording paper (model SF-4AM3, manufactured by Sharp Corporation, PPC paper). At this time, the amount of toner adhering to the recording paper in the solid image was 1.0 mg / cm. 2 It was adjusted to be.

[0133] Next, a fixed image was produced using a belt fixing device. The fixing process speed was set to 283 mm / sec, and the temperature of the fixing belt 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.

[0134] ◎ (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. × (Not possible): The minimum temperature is 130°C or higher.

[0135] <Evaluation 2: Evaluation method for heat resistance storage stability> Heat-resistant storage stability was evaluated based on the presence or absence of agglomerates after high-temperature storage. 20 g of toner was sealed in a plastic container and left at 50°C for 72 hours, after which the toner was removed and sieved through a 230-mesh sieve. The weight of the toner remaining on the sieve was measured, and the remaining amount, which was the ratio of this weight to the total weight of toner (20 g), was calculated and evaluated according to the following criteria. A lower remaining amount indicates less agglomeration (blocking) of the toner.

[0136] ◎ (Excellent): No aggregation. Residual amount is less than 0.5%. Good (Good): Minor amount of aggregation. Residual amount is 0.5% or more and less than 7%. △ (Fair): A large amount of aggregation. The remaining amount is 7% or more but less than 12%. × (Fail): Large amount of aggregation. Remaining amount is 12% or more.

[0137] <Evaluation 3: Fog evaluation method> The prepared developer and toner were loaded into the developing device and toner cartridge of a color multifunction printer (manufactured by Sharp Corporation, model: BP-20C25), respectively. An image was printed on recording paper (manufactured by Sharp Corporation, PPC paper, model: SF-4AM3) in which 10% of the printable area was filled with toner, and the brightness of a specific unfilled area of ​​the image was measured using a colorimetric color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., model: ZE6000). The difference between this brightness and the brightness measured before printing was taken as the fogging value.

[0138] A continuous printing test of the above image was carried out on 5,000 sheets of recording paper in an environment of 25°C temperature and 50% humidity. The first sheet of the continuous printing test was designated as the first print sample, and the 5,000th sheet was designated as the second print sample. Based on the higher of the fog values ​​of the first and second print samples, "fog" was evaluated according to the following criteria.

[0139] ◎ (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.

[0140] <Evaluation 4: Evaluation method for developability> The prepared developer was filled into the developing device of a color multifunction printer (manufactured by Sharp Corporation, model: BP-20C25) in an environment with a temperature of 25°C and humidity of 50%, and the amount of toner adhered to the photoconductor was 0.45 mg / cm 2 An image was formed on recording paper (PPC paper, model SF-4AM3, manufactured by Sharp Corporation) by adjusting the color density so that the image was formed. The image density of the image was measured using a spectrophotometric densitometer (model X-Rite 938, manufactured by X-Rite Corporation).

[0141] Based on the measured image density, the developability was evaluated according to the following criteria. ◎ (Excellent): Image density is 1.5 or higher. ◯ (Good): Image density is 1.4 or more and less than 1.5. △ (Acceptable): Image density is 1.3 or more and less than 1.4. × (unacceptable): Image density is less than 1.3.

[0142] [Table 4]

[0143] Table 4 shows the evaluation results of Examples and Comparative Examples. As is clear from the evaluation results in Table 4, the toners of Examples 1 to 23, which are toners containing a binder resin and a crystalline polyester resin and toner particles having external additives attached to their surfaces and which satisfy the following requirements (A) to (C), were excellent in low-temperature fixability and were able to suppress the occurrence of fogging. In addition, they had sufficient heat-resistant storage stability and developability. The external additive (A) includes silicone oil-treated silica. (B) When the SP value of the crystalline polyester resin is SP1 and the SP value of the silicone oil-treated silica is SP2, SP1-SP2 is 2.0 or more and 2.8 or less. (C) The exposed rate of the crystalline polyester resin is 3% or more and 10% or less.

[0144] In contrast, Comparative Examples 1 to 5, which did not satisfy these requirements, were inferior to the Examples in at least one of the evaluation items of low-temperature fixability, heat-resistant storage stability, and fogging.

[0145] It can be seen that Examples 1 and 6, in which the average dispersion diameter of the crystalline polyester resin in the toner particles is 50 nm or more, are particularly superior in the evaluations of low-temperature fixability and fogging compared to Example 8, in which the average dispersion diameter is less than 50 nm. It can also be seen that Examples 1 and 7, in which the average dispersion diameter of the crystalline polyester resin is 200 nm or less, are particularly superior in the evaluations of heat-resistant storage stability, fogging, and developability compared to Example 9, in which the average dispersion diameter exceeds 200 nm.

[0146] It can be seen that Examples 1 and 10, in which the average particle size of the silicone oil-treated silica is 50 nm or less, are particularly superior in the evaluation of low-temperature fixability and heat-resistant storage stability to Example 11, in which the average particle size exceeds 50 nm.

[0147] It can be seen that Examples 1 and 12, in which the adhesion strength of the silicone oil-treated silica to the toner particle surface is 60% or more, are particularly superior in the evaluations of low-temperature fixability and heat-resistant storage stability compared to Example 14, in which the adhesion strength is less than 60%. It can also be seen that Examples 1 and 13, in which the adhesion strength of the silicone oil-treated silica to the toner particle surface is 80% or less, are particularly superior in the evaluations of fogging and developability compared to Example 15, in which the adhesion strength exceeds 80%.

[0148] It can be seen that Examples 1 and 16, in which the content of the crystalline polyester resin in the toner particles is 2% by mass or more, are particularly superior in the evaluation of low-temperature fixability compared to Example 18, in which the content is less than 2% by mass. It can also be seen that Examples 1 and 17, in which the content of the crystalline polyester resin in the toner particles is 10% by mass or less, are particularly superior in the evaluation of heat-resistant storage stability and developability compared to Example 19, in which the content exceeds 10% by mass.

[0149] It can be seen that Examples 1 and 20, in which the amount of silicone oil-treated silica added relative to 100 parts by mass of toner particles is 0.5 parts by mass or more, are superior in the evaluation results of low-temperature fixability, heat-resistant storage stability, and developability compared to Example 22, in which the amount added is less than 0.5 parts by mass. It can also be seen that Examples 1 and 21, in which the amount of silicone oil-treated silica added relative to 100 parts by mass of toner particles is 2.0 parts by mass or less, are particularly superior in the evaluation results of low-temperature fixability, fogging, and developability compared to Example 23, in which the amount added exceeds 2.0 parts by mass.

[0150] 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]

[0151] 1 toner 2 Toner particles 3. Binder resin 4. Crystalline polyester resin 5 Silica particles surface-treated with silicone oil 51 Silica substrate (SiO2) 52 Silicone oil (surface treatment agent)

Claims

1. A toner in which an external additive is attached to the surface of toner particles containing a binder resin and a crystalline polyester resin, the external additive contains silica particles surface-treated with silicone oil; When the SP value of the crystalline polyester resin is SP1 and the SP value of the silica particles surface-treated with silicone oil is SP2, SP1-SP2 is 2.0 or more and 2.8 or less; A toner characterized in that the exposure rate of the crystalline polyester resin, calculated as the area ratio of the crystalline polyester resin to the surface in an electron image of the toner particle surface obtained with a scanning electron microscope, is 3% or more and 10% or less.

2. 2. The toner according to claim 1, The toner is characterized in that the average dispersion diameter of the crystalline polyester resin in the toner particles is 50 nm or more and 200 nm or less.

3. 3. The toner according to claim 1 or claim 2, The toner is characterized in that the average particle diameter of the silica particles surface-treated with the silicone oil is 50 nm or less.

4. 3. The toner according to claim 1 or claim 2, The toner is characterized in that the adhesion strength of the silica particles surface-treated with the silicone oil to the surfaces of the toner particles is 60% or more and 80% or less.

5. 3. The toner according to claim 1 or claim 2, The toner, wherein the content of the crystalline polyester resin in the toner particles is 2% by mass or more and 10% by mass or less.

6. 3. The toner according to claim 1 or claim 2, The toner, wherein the amount of the silica particles surface-treated with silicone oil added is 0.5 parts by mass or more and 2.0 parts by mass or less relative to 100 parts by mass of the toner particles.

Images