Toner and two-component developer

Abstract

To provide toner and a two-component developer which have the less gloss variation within a printing surface in a case where printing is performed on one recording sheet and have the excellent image quality uniformity and image reproducibility.SOLUTION: There is provided toner in which an external additive adheres to a surface of a toner particle including a binder resin and an internal additive. The internal additive includes high melting point wax, middle melting point wax and a coloring agent. The melting temperature of the high melting point wax is equal to or higher than 133°C and the melting temperature of the middle melting point wax is lower by 30°C or greater than the melting temperature of the high melting point wax. The external additive comprises: a strontium titanate fine particle; a silica fine particle in which the average primary particle diameter is equal to or greater than 16 nm and which is subjected to oil processing; and a silica fine particle in which the average primary particle diameter is smaller than that of the silica fine particle subjected to the oil processing and which is subjected to hydrophobic treatment in a method other than the oil processing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a toner and a two-component developer. [Background technology]

[0002] Toner (toner for developing electrostatic images) used in electrophotographic image forming devices such as copiers, multifunction peripherals, printers, and facsimile machines usually has external additives attached to the surfaces of the toner particles. In the external addition step in the toner manufacturing method, the toner particles and the external additives are mixed in a powder mixer such as a Henschel mixer, thereby causing the external additives to adhere to the surfaces of the toner particles.

[0003] Conventionally, titanium oxide, a conductive oxide, has been used as an external additive to control the chargeability of toner. However, to realize safer toner, a conductive oxide that can replace titanium oxide is needed.

[0004] Strontium titanate is an example of a conductive oxide that can replace titanium oxide, but the crystals of strontium titanate have sharp edges, which can cause scratches on the photosensitive drum and over-discharge.

[0005] By adding silica microparticles to the surface of strontium titanate microparticles and modifying the surface of the strontium titanate with silica microparticles, these problems can be alleviated, and high-charge fogging in low-humidity environments and fogging in high-humidity environments can also be suppressed.

[0006] Regarding toner using such strontium titanate microparticles as an external additive, Patent Document 1 discloses that by using a fine powder of strontium titanate having Si-containing particles on the surface with a number-average equivalent circle diameter of 5 nm to 15 nm as an external additive, it is possible to prevent the occurrence of fogged images over time in low-temperature, low-humidity environments and suppress wear on the photoreceptor.

[0007] Furthermore, silica fine particles have been used as an external additive for some time, and Patent Document 2 discloses that a toner using titanium oxide as a conductive oxide as an external additive contains two types of silica fine particles with different BET specific surface areas as external additives, and both types of silica fine particles are treated with silane coupling and silicone oil, thereby improving transfer efficiency and making the image uniform when transferring a solid image of two or more colors in color, i.e., an image in which toners of two or more colors are superimposed, thereby obtaining a high-quality color image. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2020-190724 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-126240 Summary of the Invention [Problem to be solved by the invention]

[0009] However, toners using strontium titanate microparticles as an external additive have the problem that the image quality varies within the printed surface when printing on a single sheet of recording paper.

[0010] As shown in Figure 2, in the toner fixing process, when recording paper 21 passes between heating roller 11 and pressure roller 12, the recording paper 21 is heated and pressurized by each roller, and the toner image on the recording paper 21 is heated, melted, and fixed. However, in the case of toner T1 that uses strontium titanate microparticles as an external additive, a discharge charge is generated when recording paper 21 is peeled off from heating roller 11, and the charge is left on heating roller 11. After that, when heating roller 11 makes one rotation, as shown in Figure 3, at a position before normal heating and pressure are applied, the charge remaining on heating roller 11 reacts with toner T1 on recording paper 21, causing electrostatic offset, which creates a problem of disturbance in the fixed image.

[0011] In addition, there was a problem that the recording paper 21 was difficult to peel off from the heating roller 11 during fixing, and the peeling did not proceed properly even after the leading edge of the recording paper 21 contacted the peeling claw 13, leaving scratches on the fixed image area due to contact with the peeling claw 13.

[0012] The present invention has been made in light of the above circumstances, and its object is to provide a toner and a two-component developer that have little gloss variation within the printed surface when printed on a single sheet of recording paper, and that are excellent in image quality uniformity and image reproducibility. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention provides the following toner and two-component developer.

[0014] The toner of the present invention, which has been made to solve the above-mentioned problems, is a toner in which external additives are adhered to the surfaces of toner particles containing a binder resin and an internal additive, wherein the internal additives include a high-melting point wax, a mid-melting point wax, and a colorant, the high-melting point wax having a melting temperature of 133°C or higher, and the mid-melting point wax having a melting temperature that is 30°C or higher lower than the melting temperature of the high-melting point wax, and the external additives include strontium titanate microparticles, oil-treated silica microparticles having an average primary particle diameter of 16 nm or higher, and silica microparticles that have been hydrophobized by a method other than oil treatment and have an average primary particle diameter smaller than that of the oil-treated silica microparticles.

[0015] The toner of the present invention contains the high-melting point wax and mid-melting point wax as internal additives, thereby maintaining the storage stability of the toner while allowing the recording paper to begin peeling from the heating roller at a low temperature during the toner fixing process. Furthermore, by containing strontium titanate microparticles as an external additive, local charge transfer from the toner to the heating roller can be suppressed, thereby suppressing the occurrence of electrostatic offset. Furthermore, by containing the high-melting point wax and mid-melting point wax as internal additives and having the external additives on the surface of the toner particles, a stable gloss image can be obtained across the entire printed surface when printed on a single sheet of recording paper.

[0016] The two-component developer of the present invention, which has been made to solve the above problems, contains the toner of the present invention and a carrier. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a toner and a two-component developer that have little gloss variation within the printed surface when printed on a single sheet of recording paper, and that are excellent in image quality uniformity and image reproducibility. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view schematically illustrating a toner according to an embodiment of the present invention. [Figure 2]1 is a cross-sectional view of a fixing device, schematically illustrating how discharged charges are generated when the recording paper is separated from the heating roller in the toner fixing process. FIG. [Figure 3] 1 is a cross-sectional view of a fixing device, schematically illustrating how electrostatic offset occurs due to charges remaining on a heating roller during a toner fixing process. FIG. [Figure 4] 1 is a cross-sectional view of a fixing device, schematically illustrating how charge transfer occurs in a heating roller due to discharge from toner during a toner fixing process. FIG. [Figure 5] 10 is a cross-sectional view of a fixing device, schematically illustrating how the toner is more easily released from a heating roller and charge transfer is suppressed in the fixing step according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention includes a toner and a two-component developer, which will be described in detail below.

[0020] [toner] As shown in FIG. 1, the toner according to the present invention is a toner in which an external additive is attached to the surface of toner particles containing a binder resin and an internal additive.

[0021] The volume average particle diameter of the primary particles of the toner particles according to the present invention can be appropriately selected depending on the purpose, but is preferably 4 μm or more and 8 μm or less. By reducing the volume average particle diameter so that it falls within the above range, high-resolution images can be stably formed over a long period of time, high image density can be obtained even with a small amount of toner adhesion, and toner consumption can be reduced.

[0022] If the volume average particle diameter is less than the lower limit, the toner becomes highly charged and less fluid, making it impossible to stably supply the toner to the photoreceptor, which can result in background fogging and a decrease in image density.If the volume average particle diameter exceeds the upper limit, the layer thickness of the formed image becomes large, resulting in an image with significant granularity, making it impossible to obtain a high-resolution image.In addition, the specific surface area decreases, reducing the charge amount of the toner, which can prevent the toner from being stably supplied to the photoreceptor, causing contamination inside the machine due to toner scattering.

[0023] The particle size distribution of the toner particles according to the present invention is not particularly limited and can be appropriately selected depending on the purpose, but it is preferable that particles having a volume average particle size of 3 μm or less account for 40% or less by number. The method for measuring the particle size distribution will be described later.

[0024] The circularity of the toner particles according to the present invention is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.92 to 0.97. The method for measuring the circularity will be described later.

[0025] The toner particles according to the present invention preferably have a glass transition temperature (Tg) of not more than 60° C. The method for measuring the glass transition temperature will be described later.

[0026] <Binder resin> The binder resin in the toner according to the present invention may be a resin commonly used in the field of electrophotography, such as polyester resins, polystyrene resins such as styrene-acrylic resins, (meth)acrylic acid ester resins, polyolefin resins, polyurethane resins, and epoxy resins. One of these may be used alone, or two or more may be used in combination.

[0027] Among these, amorphous polyester resins are preferred, and it is more preferred to use a combination of an amorphous polyester resin consisting of a low molecular weight component and an amorphous polyester resin consisting of a medium to high molecular weight component. This can improve the productivity, quality, and performance of the toner of the present invention. In the present invention, the terms low molecular weight, medium molecular weight, and high molecular weight are used in relation to the molecular weight distribution of polyester resins, and will be described below.

[0028] In the present invention, crystalline resins and amorphous resins are distinguished by their crystallinity index, with resins having a crystallinity index in the range of 0.6 to 1.5 being crystalline resins, and resins having a crystallinity index of less than 0.6 or more than 1.5 being amorphous resins. Resins having a crystallinity index of more than 1.5 are amorphous, and resins having a crystallinity index of less than 0.6 have low crystallinity and a large amount of amorphous portions.

[0029] 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 point to the highest endothermic peak temperature (softening point / 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 temperature (melting point), and for amorphous polyester resins, the highest peak is the glass transition point.

[0030] The degree of crystallization can be controlled by adjusting the types and ratios of raw material monomers, as well as production conditions (for example, reaction temperature, reaction time, cooling rate), and the like.

[0031] (amorphous polyester resin) The amorphous polyester resin is a polyester resin having a crystallinity index of less than 0.6 or more than 1.5, with polyester resins having a crystallinity index of more than 1.5 being preferred.

[0032] The amorphous polyester resin is not particularly limited, but may be 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.

[0033] The reaction conditions are the same as those for producing 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 a temperature of 190 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].

[0034] The molar content of terephthalic acid or isophthalic acid in the dicarboxylic acid monomer is preferably 70 to 100%, more preferably 80 to 100%.

[0035] The dicarboxylic acid monomer may also include aromatic dicarboxylic acids such as fumaric acid, adipic acid, sebacic acid, succinic acid, and the like, and may also include ester-forming derivatives of terephthalic acid or isophthalic acid, ester-forming derivatives of aromatic dicarboxylic acids, ester-forming derivatives of aliphatic dicarboxylic acids, and acid anhydrides or alkyl esters of these carboxylic acids.

[0036] Furthermore, the dicarboxylic acid monomer may be used in combination with a polycarboxylic acid having three or more valences, such as trimellitic acid or pyromellitic acid, or an ester-forming derivative thereof.

[0037] The above dicarboxylic acid monomers and polycarboxylic acid monomers can be used alone or in combination of two or more.

[0038] The molar content of ethylene glycol in the polyhydric alcohol is preferably 70 to 100%, more preferably 80 to 100%. The polyhydric alcohol may contain other polyhydric alcohols such as 1,3-propylene glycol and 1,4-butanediol.

[0039] The above polyhydric alcohols can be used alone or in combination of two or more.

[0040] (crystalline polyester resin) The crystalline polyester resin is a polyester resin having a crystallinity index of 0.6 to 1.5, and preferably a polyester resin having a crystallinity index of 0.8 to 1.2.

[0041] The crystalline polyester resin is not particularly limited, but is preferably composed of a linear saturated aliphatic polyester unit obtained by a polycondensation reaction between 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.

[0042] The reaction conditions are the same as those for producing ordinary polyester resins, and for example, a crystalline 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 a temperature of 190 to 240° C. From the viewpoint of toner storage stability, the reaction ratio of the polyhydric alcohol to the carboxylic acid monomer is preferably an equivalent ratio of hydroxyl groups to carboxyl groups [OH]:[COOH] of 0.83:1 to 1.3:1.

[0043] The molar content of dicarboxylic acid in the carboxylic acid monomer is preferably 90 to 100%. If the molar content of dicarboxylic acid is low, the crystallization rate and speed may decrease, resulting in insufficient toner aggregation resistance.

[0044] Examples of the aliphatic dicarboxylic acid having 9 to 22 carbon atoms include azelaic acid, zebaic acid, 1,10-decanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, etc. The carboxylic acid monomer and polycarboxylic acid monomer may contain an ester-forming derivative of these aliphatic dicarboxylic acids.

[0045] Furthermore, the carboxylic acid monomer may be used in combination with a polycarboxylic acid having three or more valences, such as trimellitic acid or pyromellitic acid, or an ester-forming derivative thereof.

[0046] The above carboxylic acid monomers can be used alone or in combination of two or more.

[0047] The molar content of the aliphatic diol having 2 to 10 carbon atoms in the polyhydric alcohol is preferably 80 to 100%. Examples of the aliphatic diol having 2 to 10 carbon atoms include ethylene glycol, 1,4-butanediol, and 1,6-hexanediol.

[0048] Furthermore, examples of polyhydric alcohols that can be used in combination with the above aliphatic diols include trihydric or higher alcohols such as glycerin and trimethylolpropane.

[0049] The above polyhydric alcohols can be used alone or in combination of two or more.

[0050] (Polyester resin consisting of low to high molecular weight components) In the following description, the polyester resin made of low molecular weight components will be referred to as resin A, the polyester resin made of medium molecular weight components as resin B, and the polyester resin made of high molecular weight components as resin C.

[0051] (Resin A) Resin A has a molecular weight distribution of 1 x 10 3 ~1×10 4 75% or more are distributed in the range of 1 × 10 at 80 ° C when measured with a flow tester 5 It has a viscosity of less than Pa·s.

[0052] mass molecular weight 1×10 3 If the molecular weight distribution is less than 1×10, the resin becomes soft and the toner storage stability may deteriorate. 4 If the molecular weight distribution exceeds 1×10, the viscosity of the resin increases, which may result in a deterioration in the low-temperature fixability of the toner. 3 ~1×10 4 The molecular weight distribution in this range is preferably 80% or more.

[0053] Resin A is 1 x 10 at 80°C when measured with a flow tester. 5 When the viscosity is 1×10 or less, good low-temperature fixability suitable for low-temperature fixation such as pad fixation can be obtained. 5 If the viscosity exceeds Pa·s, the low-temperature fixing ability of the toner may deteriorate. The viscosity at 80°C measured with a flow tester is 2×10 4 Resin A preferably has a glass transition temperature Tg (°C) of 52 to 56°C, and a softening point Tm (°C) of 85 to 100°C.

[0054] (Resin B) Resin B has a molecular weight distribution of 1 x 10 4 ~1×10 5 and the molecular weight is 1×10 3 ~1×10 4 Resin B contributes to uniform melt-kneading of Resin A and Resin C, and if Resin B is not blended, not only the low-temperature fixability but also the high-temperature fixability of the toner may not be ensured.

[0055] Resin B is adjusted to have a viscosity between that of the low molecular weight component and the high molecular weight component, and has good mixability and kneadability with other resins, so various materials can be dispersed in Resin B in advance.

[0056] Resin B has a molecular weight distribution of 1 x 10 4 ~1×10 5and the molecular weight is 1×10 3 ~1×10 4 If the main peak does not lie within this range, it may be difficult to uniformly melt-knead Resin A and Resin C, making it difficult to ensure both low-temperature fixability and high-temperature fixability.

[0057] Resin B preferably has a glass transition temperature Tg (°C) of 65 to 70°C, and a softening point Tm (°C) of 110 to 120°C.

[0058] (Resin C) Resin C has a molecular weight distribution of 1 x 10 5 Resin A contributes to lowering viscosity, while Resin C contributes to ensuring high-temperature fixability.

[0059] Resin C has a molecular weight distribution of 1 x 10 5 If the distribution of the resin C is not 5% or more in the above range, the elasticity of the toner is impaired, and high-temperature fixability may not be ensured. 5 If the difference is less than 5% of the above range, the low temperature region for pad fixing may not be ensured.

[0060] Resin C may contain a gel component. To improve the fixing quality on the high temperature side of the fixable region, it is preferable that the resin C has a gel content of 3 to 20% by mass. If the gel content of Resin C exceeds 20% by mass, the grindability may be deteriorated.

[0061] Resin C preferably has a glass transition temperature Tg (°C) of 55 to 65°C and a softening point Tm (°C) of 130 to 150°C.

[0062] <Wax> The toner particles according to the present invention contain a wax as a release agent. Waxes commonly used in the field of electrophotography can be used. Examples of such waxes include petroleum-based waxes such as paraffin wax, microcrystalline wax, and their derivatives; hydrocarbon-based synthetic waxes such as Fischer-Tropsch wax, polyolefin wax (polyethylene wax, polypropylene wax, etc.), low-molecular-weight polypropylene wax, polyolefin polymer wax (low-molecular-weight polyethylene wax, etc.), and their derivatives; vegetable waxes such as carnauba wax, rice wax, candelilla wax, and their derivatives, and Japan wax; animal waxes such as beeswax and spermaceti; oil-based synthetic waxes such as fatty acid amides and phenol fatty acid esters; long-chain carboxylic acids and their derivatives; long-chain alcohols and their derivatives; silicone polymers; and higher fatty acids.

[0063] The derivatives include oxides, block copolymers of vinyl monomers and wax, and graft modified products of vinyl monomers and wax.

[0064] In the present invention, one of the waxes described above may be used alone, or two or more of them may be used in combination.

[0065] The toner particles according to the present invention contain a high-melting point wax and a medium-melting point wax, the melting temperature of the high-melting point wax being 133°C or higher, and the melting temperature of the medium-melting point wax being 30°C or higher lower than the melting temperature of the high-melting point wax.

[0066] The inclusion of the two waxes provides a release effect at low temperatures, improving the releasability of the recording paper from the heating roller. Furthermore, the high-melting-point wax exudes at high temperatures, suppressing high-temperature offset. In particular, as shown by comparing Figures 2 and 5, the recording paper is stably released from the heating roller even at low temperatures when a large amount of toner adheres to the recording paper. This allows for stable gloss images across the entire printed surface when printing on a single sheet of recording paper, while also suppressing peel electrification.

[0067] If the difference in melting temperature between the high-melting wax and the mid-melting wax in the toner of the present invention is less than 30° C. due to the low melting temperature of the high-melting wax, the heat-resistant storage stability of the toner may deteriorate. Also, if the difference in melting temperature is less than 30° C. due to the high melting temperature of the mid-melting wax, poor peeling may occur on the low-temperature side of the fixable region.

[0068] Specifically, the melting temperature of the medium-melting wax in the toner of the present invention is preferably 70°C or higher and lower than 100°C, and the melting temperature of the high-melting wax is preferably 133°C or higher and lower than 160°C.

[0069] If the melting temperature of the mid-melting wax exceeds the upper limit, the releasability of the recording paper from the belt or heating roller on the low temperature side of the fixable region will be impaired, which may result in problems such as poor releasability and curling of the recording paper.

[0070] If the melting temperature of the high-melting wax is below the lower limit, the fixing quality may deteriorate on the high temperature side of the fixable region.

[0071] The mid-melting wax in the toner of the present invention preferably has a glass transition temperature change ΔTg of 2° C. or less, calculated by the following formula (1). ΔTg=(glass transition temperature of toner particles without mid-melting point wax)−(glass transition temperature of toner particles with mid-melting point wax) (1)

[0072] That is, ΔTg represents the amount of change in the glass transition temperature of the toner particles that occurs when a mid-melting point wax is blended as an internal additive. The glass transition temperature is measured by a differential scanning calorimeter using the method described below.

[0073] When ΔTg is within the above range, it is possible to ensure the storage stability of the toner in a high-temperature environment even if the glass transition temperature of the binder resin is not high.

[0074] The content of the mid-melting wax in the toner particles according to the present invention is preferably 0.2% by mass or more and 5.0% by mass or less, and more preferably 0.3% by mass or more and 1.5% by mass or less.

[0075] By keeping the content of the mid-melting point wax at or above the lower limit, the releasability of the recording paper from the heating roller during the toner fixing process is improved, and the effect of suppressing electrostatic offset due to peeling of the recording paper is enhanced. Also, by keeping the content of the mid-melting point wax at or below the upper limit, it is possible to suppress a decrease in the glass transition temperature (Tg) of the toner due to the incorporation of the mid-melting point wax as an internal additive.

[0076] The content of the high melting point wax in the toner particles according to the present invention is preferably 0.4% by mass or more and 5.5% by mass or less, and more preferably 0.7% by mass or more and 5.0% by mass or less.

[0077] When the content of the high-melting point wax is equal to or greater than the lower limit, the release effect at high temperatures is improved and the effect of suppressing high-temperature offset is enhanced. Also, when the content of the high-melting point wax is equal to or less than the upper limit, the low-temperature fixability of the toner is not affected.

[0078] The mid-melting wax in the toner of the present invention is preferably a Fischer-Tropsch wax.

[0079] By using a Fischer-Tropsch wax as the mid-melting wax and a polyester resin as the binder resin in the toner of the present invention, it is possible to realize a combination of a mid-melting wax and a binder resin having a small ΔTg.

[0080] <Coloring agent> The colorant contained in the toner particles according to the present invention may be any organic or inorganic pigment or dye commonly used in the field of electrophotography, and the type and color are not particularly limited. Examples include black, white, yellow, orange, red, purple, blue, and green colorants.

[0081] Examples of black colorants include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, non-magnetic ferrite, magnetic ferrite, and magnetite.

[0082] Examples of white colorants include zinc oxide, titanium oxide, antimony white, and zinc sulfide.

[0083] Examples of yellow colorants include yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, tartrazine lake, CI pigment yellow 12, CI pigment yellow 13, CI pigment yellow 14, CI pigment yellow 15, CI pigment yellow 17, CI pigment yellow 93, CI pigment yellow 94, and CI pigment yellow 138.

[0084] Examples of orange colorants include red lead yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, induthrene brilliant orange RK, benzidine orange G, induthrene brilliant orange GK, CI pigment orange 31, and CI pigment orange 43.

[0085] Examples of red colorants include red iron oxide, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, lithol red, pyrazolone red, watching red, calcium salt, lake red C, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B, CI pigment red 2, CI pigment red 3, CI pigment red 5, CI pigment red 6, CI pigment red 7, CI pigment red 8, CI pigment red 9, CI pigment red 10, CI pigment red 11, CI pigment red 12, CI pigment red 13, CI pigment red 14, CI pigment red 15, CI pigment red 16, CI pigment red 17, CI pigment red 18, CI pigment red 19, CI pigment red 20, CI pigment red 21, CI pigment red 22, CI pigment red 23, CI pigment red 24, CI pigment red 25, CI pigment red 26, CI pigment red 27, CI pigment red 28, CI pigment red 29 ... Examples of pigments that can be used include CI Pigment Red 7, CI Pigment Red 15, CI Pigment Red 16, 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.

[0086] Examples of purple colorants include manganese violet, fast violet B, and methyl violet lake.

[0087] Examples of blue colorants include Prussian blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, fast sky blue, indanthrene blue BC, CI pigment blue 15, CI pigment blue 15:2, CI pigment blue 15:3, CI pigment blue 16, and CI pigment blue 60.

[0088] Examples of green colorants include chrome green, chromium oxide, pigment green B, micalite green lake, final yellow green G, and CI pigment green 7.

[0089] In the present invention, the above-mentioned colorants can be used alone or in combination of two or more, and the combination may be of different colors or the same color. Two or more colorants may also be used as composite particles. The composite particles can be produced, for example, by adding an appropriate amount of water, a lower alcohol, etc. to two or more colorants, granulating the mixture in a general granulator such as a high-speed mill, and drying the mixture.

[0090] Furthermore, in order to disperse the colorant uniformly in the binder resin, the colorant may be used in the form of a masterbatch. The composite particles and the masterbatch are mixed into the toner composition during dry mixing.

[0091] The amount of colorant to be added can be selected appropriately depending on the purpose, but is preferably 3 parts by mass or more and 15 parts by mass or less, and more preferably 5 parts by mass or more and 12 parts by mass or less, per 100 parts by mass of binder resin.

[0092] If the blending amount of the colorant is within the above range, it is possible to form an image having a high image density and very good image quality without impairing various physical properties of the toner.

[0093] <Other internal additives> Furthermore, the toner particles according to the present invention may contain, as internal additives, charge control agents, wax dispersants, grinding aids, and the like that are used in the field of electrophotography.

[0094] Charge control agents that can be used include those for positive charge control and negative charge control used in the field of electrophotography. Charge control agents for positive charge control include, for example, quaternary ammonium salts, pyrimidine compounds, triphenylmethane derivatives, guanidine salts, and amidine salts. 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, and the like), organic bentonite compounds, and boron compounds.

[0095] The amount of the charge control agent to be added can be appropriately selected depending on the purpose, but is preferably 0.5 parts by mass or more and 3 parts by mass or less per 100 parts by mass of the binder resin.

[0096] <External additives> In the present invention, the external additive comprises strontium titanate microparticles, oil-treated silica microparticles having an average primary particle diameter of 16 nm or more, and silica microparticles that have been hydrophobized by a method other than oil treatment and have an average primary particle diameter smaller than that of the oil-treated silica microparticles. The external additive may contain optional components depending on the purpose, as long as the effects of the present invention are not impaired.

[0097] The toner of the present invention contains the high-melting point wax and the mid-melting point wax as internal additives and strontium titanate microparticles as external additives, thereby suppressing local charge transfer from the toner to the heating roller and thereby suppressing the occurrence of electrostatic offset. Furthermore, by containing the high-melting point wax and the mid-melting point wax as internal additives and having the above external additives on the surface of the toner particles, an image with stable gloss can be obtained over the entire printed surface when printed on a single sheet of recording paper.

[0098] By using strontium titanate fine particles as an external additive, high charging in a low humidity environment is suppressed, thereby suppressing fogging and toner consumption.

[0099] By using oil-treated silica fine particles (medium to large particle size silica) with an average primary particle size of 16 nm or more as an external additive, fog can be suppressed, especially in high-temperature environments. Furthermore, since oil-treated silica fine particles with an average primary particle size of 16 nm or more are compatible with release agents (waxes) molten at low surface energy, using them together with the high-melting point wax and medium-melting point wax described above can produce images with minimal gloss variation. Furthermore, by using silica fine particles (small particle size silica) with an average primary particle size smaller than the oil-treated silica fine particles that have been hydrophobized by a method other than oil treatment, the low-temperature fixation is not hindered by the oil treatment.

[0100] The strontium titanate fine particles in the toner of the present invention are preferably strontium titanate fine particles modified with silica fine particles.

[0101] By modifying the strontium titanate fine particles with silica fine particles, static elimination from the strontium titanate fine particles is stabilized, high charge fogging in a low humidity environment is suppressed, and fogging in a high humidity environment is not aggravated.

[0102] Furthermore, as shown in Figure 4, in the toner fixing process, if charge transfer occurs to the heating roller due to discharge from the toner, it can cause electrostatic offset. However, by modifying the strontium titanate microparticles with silica microparticles, local charge transfer from the toner is suppressed, and electrostatic offset is also suppressed, thereby improving image reproducibility during continuous printing.

[0103] Strontium titanate microparticles modified with silica microparticles can be produced, for example, by the following procedures (1) to (5).

[0104] (1) Metatitanic acid obtained by the sulfuric acid method is deironized and bleached, then desulfurized by adding an aqueous solution of sodium hydroxide, and then neutralized with hydrochloric acid, filtered, and washed to obtain a washed cake. (2) Water is added to the washed cake to form a slurry, and then hydrochloric acid is added for deflocculation. This is called Solution 1, and is mixed with Solution 2, an aqueous solution of strontium chloride, and Solution 3, an aqueous solution of sodium silicate. The mixing ratio of Solutions 1, 2, and 3 is set so that the molar ratio of (Sr+Si) / Ti is 1.2. (3) The mixed solution is heated to 90°C under a nitrogen gas atmosphere, and the reaction is completed by stirring for 2 hours while adding an aqueous solution of sodium hydroxide. (4) After the reaction, the slurry is cooled to 50°C, hydrochloric acid is added, and the mixture is stirred for 2 hours. The resulting precipitate is washed, separated by filtration, and then dried. (5) The dried product is ground in a blender for 1 minute, and the resulting fine powder is removed using a 32 μm mesh sieve. The resulting fine powder is then surface-coated with a silane coupling agent. Examples of methods for surface coating with a silane coupling agent include surface treatments commonly used in the art using hexamethyldisilazane (HMDS), dimethyldichlorosilane (DDS), octylsilane (OTAS), polydimethylsiloxane (PDMS), etc.

[0105] The content of the strontium titanate fine particles relative to 100 parts by mass of the toner particles according to the present invention is preferably 0.02 parts by mass or more and 0.6 parts by mass or less, and more preferably 0.05 parts by mass or more and 0.5 parts by mass or less.

[0106] By ensuring that the content of the strontium titanate particles is equal to or greater than the lower limit, high charge fog in a low-humidity environment can be suppressed, and by ensuring that the content of the strontium titanate particles is equal to or less than the upper limit, a decrease in the charge of the toner in a high-humidity environment can be suppressed.

[0107] In the toner of the present invention, the average primary particle diameter of the strontium titanate fine particles is D ts , the average primary particle diameter of the oil-treated silica fine particles is D os The difference ΔD in average primary particle diameter calculated by the following formula (2) is preferably −24 nm or more and 70 nm or less, and more preferably 0 nm or more and 70 nm or less. ΔD=D os-D ts ···(2)

[0108] By ensuring that ΔD is within the above range, it is possible to suppress discharge occurring solely through the strontium titanate microparticles when the recording paper is peeled off from the heating roller during the toner fixing process, thereby suppressing excess charge from remaining on the heating roller after the peeling, thereby improving image reproducibility during continuous printing.

[0109] <Oil-treated silica particles> The toner of the present invention contains, as an external additive, oil-treated silica fine particles having an average primary particle diameter of 16 nm or more.

[0110] Oil-treated silica microparticles with an average primary particle diameter of 16 nm or more have low surface energy and are compatible with molten release agents (waxes). Therefore, by using them together with the high-melting point wax and medium-melting point wax described above, images with little gloss variation can be achieved.

[0111] The oil-treated silica particles are preferably hydrophobic silica particles treated with silicone oil. Examples of the hydrophobic silica particles treated with silicone oil include the hydrophobic silica particles described in JP-A-2012-236752. In the toner of the present invention, the free carbon content of the hydrophobic silica particles treated with silicone oil is preferably 1.0% by mass or more and 5.0% by mass or less. The method for measuring the free carbon content will be described later.

[0112] The average primary particle size of the oil-treated silica fine particles in the toner of the present invention is preferably 16 nm or more and 110 nm or less, and more preferably 40 nm or more and 110 nm or less.

[0113] By not using oil-treated silica fine particles having an average primary particle diameter of less than 16 nm, low-temperature fixability is improved, and more oil-treated silica fine particles having an average primary particle diameter of 16 nm or more can be added, thereby suppressing fogging in high-temperature environments.If oil-treated silica fine particles having an average primary particle diameter exceeding the above upper limit are used as an external additive, the amount added must be increased, and there is a risk of low-temperature fixability being deteriorated due to the spacer effect.

[0114] The content of the oil-treated silica fine particles in the toner of the present invention is preferably 0.1 to 1.8 parts by mass, more preferably 0.3 to 1.6 parts by mass, per 100 parts by mass of toner particles.

[0115] When the content of the oil-treated silica fine particles is equal to or greater than the lower limit, fogging in a high-humidity environment can be suppressed.When the content of the oil-treated silica fine particles is equal to or less than the upper limit, deterioration of low-temperature offset can be suppressed.

[0116] The content of the oil-treated silica fine particles in the toner of the present invention is preferably such that the coverage of the toner particle surface with the silica fine particles is 10% or more and 80% or less. The method for measuring the coverage will be described later.

[0117] In the toner of the present invention, the adhesion strength of the oil-treated silica fine particles to the toner particles is preferably 40% or more and 90% or less. The method for measuring the adhesion strength will be described later.

[0118] <Silica particles hydrophobized by methods other than oil treatment> The toner of the present invention contains, as an external additive, fine silica particles that have an average primary particle diameter smaller than that of the above-mentioned oil-treated fine silica particles and that have been hydrophobized by a method other than oil treatment.

[0119] By using small particle silica (fine silica particles having an average primary particle diameter smaller than that of the above-mentioned oil-treated silica particles) in the external additive that has been hydrophobized by a method other than oil treatment, low temperature fixation is not hindered by oil treatment.

[0120] Examples of silica particles that have been hydrophobized by methods other than oil treatment include silica particles that have been hydrophobized with dimethyldichlorosilane (DDS) (silica particles that have been surface-modified with dimethylsilyl groups), silica particles that have been hydrophobized with hexamethyldisilazane (HMDS) (silica particles that have been surface-modified with trimethylsilyl groups), silica particles that have been surface-modified with alkylsilyl groups, and silica particles that have been surface-modified with methacrylsilyl groups.In addition, if the functional group that surface-modifies the silica particles has an amino group, the particles will be more positively charged, so in the present invention, it is preferable that the functional group that surface-modifies the silica particles does not have an amino group.

[0121] In the toner of the present invention, the average primary particle size of the silica fine particles that have been hydrophobized by a method other than oil treatment is preferably 2 nm or more and less than 16 nm.

[0122] In the toner of the present invention, the content of the silica fine particles hydrophobized by a method other than oil treatment is preferably 0.1 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of toner particles.

[0123] <Other external additives> The external additive may contain an optional component that improves transportability, chargeability, cleanability, etc., depending on the purpose, within a range that does not impair the effects of the present invention. Examples of the optional component include inorganic fine particles such as fumed silica particles, titanium oxide particles, alumina particles, and magnetite.

[0124] [Two-component developer] The two-component developer according to the present invention contains the toner according to the present invention and a carrier. The two-component developer can be produced by mixing the toner and the carrier using a known mixer. The weight ratio of the toner to the carrier is not particularly limited, and may be, for example, 3:97 to 12:88.

[0125] The carrier is stirred and mixed with the toner in the developer tank, giving the toner the desired charge. The carrier also acts as an electrode between the developing device and the photosensitive drum, transporting the charged toner to the electrostatic latent image on the photosensitive drum and forming a toner image. The carrier is held on the developing roller of the developing device by magnetic force, and after using it for development, it returns to the developer tank, where it is stirred and mixed with new toner again and used repeatedly until it reaches its end of life.

[0126] The carrier has a carrier core material and a resin coating layer that coats the carrier core material. The carrier core material is not particularly limited as long as it is used in the electrophotography field. Specific examples of materials for the carrier core material include magnetic metals such as iron, copper, nickel, and cobalt, and magnetic metal oxides such as ferrite and magnetite. The volume average particle size of the carrier core material is not particularly limited, and may be, for example, 30 μm or more and 100 μm or less. The resin coating layer preferably contains a silicone resin or an acrylic resin. Silicone resins can delay the progression of contamination of the carrier coat layer and are suitable for long-life use. [Example]

[0127] The present invention will be described below based on examples and comparative examples, but the present invention is not limited to these examples. First, the measurement and evaluation methods used in the examples will be described.

[0128] <Method for measuring the volume average particle size of toner particles> 20 mg of sample and 1 mL of sodium alkyl ether sulfate were added to 50 mL of electrolyte (manufactured by Beckman Coulter, Inc., product name: ISOTON-II), and the mixture was dispersed for 3 minutes at a frequency of 20 kHz using an ultrasonic disperser (manufactured by AS ONE Corporation, model: tabletop dual-frequency ultrasonic cleaner VS-D100) to prepare the measurement sample.

[0129] The obtained measurement samples were measured using a particle size distribution analyzer (Beckman Coulter, Inc., Model: Multisizer 3) under conditions of aperture diameter: 100 μm, number of particles measured: 50,000 counts, and the volume average particle diameter (μm) was calculated from the volume particle size distribution of the sample particles.

[0130] <Method for measuring circularity of toner particles> Measurements were performed using a flow particle image analyzer "FPIA-3000" (manufactured by Malvern Instruments). Using Particle Sheath (manufactured by Malvern Instruments, product name: PSE-900A) as the sheath liquid and a 5 wt% aqueous dispersion of a commercially available household detergent as the dispersant, the sample was dispersed using the autosampler device of the analyzer. The resulting dispersion was introduced into the analyzer, and 10,000 toner particles were counted in total in HPF measurement mode. The binarization threshold for particle analysis was set to 85%, and the average circularity of the toner particles was determined over the entire particle size range.

[0131] In this device, the projected area S and perimeter L of the particle image are measured, and the circularity is calculated using the following formula. Circularity = 2 × (π × S) 1 / 2 / L

[0132] <Method for measuring the glass transition temperature of toner particles and resin> Using a differential scanning calorimeter (manufactured by PerkinElmer Japan Co., Ltd., model: Diamond DSC), approximately 10 mg of sample was heated at a heating rate of 10°C / min in accordance with Japanese Industrial Standards (JIS) K7121-1987 to measure a DSC (Differential Scanning Calorimetry) curve.

[0133] In the obtained DSC curve, the glass transition temperature (Tg) was determined as the temperature at the intersection of a straight line extending from the high-temperature side baseline of the endothermic peak corresponding to the glass transition toward the low-temperature side and a tangent drawn at the point where the gradient of the curve from the rising part of the peak to the apex is maximum.

[0134] <Method for measuring wax melting temperature> Using a differential scanning calorimeter (manufactured by PerkinElmer Japan Co., Ltd., model: Diamond DSC), approximately 20 mg of toner particles (or wax) was heated from a temperature of 20°C to 200°C at a heating rate of 10°C / min, and then rapidly cooled from 200°C to 30°C. This operation was repeated twice to measure the DSC curve, and the temperature of the endothermic peak corresponding to melting in the DSC curve measured in the second operation was taken as the melting temperature of the wax.

[0135] <Method for measuring the average primary particle size of external additives> The average primary particle diameter of the external additives was determined by photographing the toner particles using a scanning electron microscope (SEM) (manufactured by Hitachi High-Technologies Corporation, model: S-4800), measuring the particle diameters (major diameters) of 100 external additives on the toner surface from the obtained image, calculating the average value of the particle diameters of the 100 particles, and using this as the average primary particle diameter.

[0136] <Method for measuring the amount of free carbon in hydrophobic silica particles treated with silicone oil> Using a BUCHI Soxhlet extraction apparatus, 0.7 g of hydrophobic silica microparticles were placed in a 28 mm diameter cylindrical filter paper, and hexane was used as the extraction solvent. The extraction time was 60 minutes, followed by a 30 minute rinse time. The free silicone oil on the hydrophobic silica microparticles was extracted and the carbon content was measured. The percentage of the carbon content of the hydrophobic silica microparticles after extraction relative to the carbon content of the hydrophobic silica microparticles before extraction was calculated, and the amount of carbon lost during the extraction process was taken as the free carbon content. The carbon content of the hydrophobic silica microparticles was measured using an elemental analyzer (SUMIGRAPH NC-22F, manufactured by Sumitomo Chemical Analysis Center, Ltd.).

[0137] <Method for measuring coverage by external additives> The toner was photographed using a scanning electron microscope (SEM) (Hitachi High-Technologies Corporation, Model: S-4800). A model calculation was performed using the average primary particle size and specific gravity of the toner particles and the average primary particle size and specific gravity of each external additive to determine the coverage rate of each external additive using the following formula (3).

[0138]

number

[0139] In the above formula (3), D is the average primary particle diameter of the toner particles, ρ t is the specific gravity of the toner particles, d is the average primary particle diameter of the external additive, ρ i is the specific gravity of the external additive, and C is the number of parts by mass of the external additive added.

[0140] <Method for measuring adhesive strength of external additives> The adhesion strength of the external additive to the toner particles was measured by the following procedure. (1) 2.0 g of toner is added to 40 ml of a 0.2% by mass Triton (polyoxyethylene octylphenyl ether) aqueous solution, and the mixture is stirred for 1 minute. (2) The above aqueous solution is irradiated with ultrasonic waves using an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd., model: US-300T) (output: 40 μA, 4 minutes). (3) After the ultrasonic irradiation, the aqueous solution is left to stand for 3 hours, and the toner and the liberated external additives are separated. (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 filter is vacuum dried overnight. (7) Using a fluorescent X-ray analyzer (Rigaku Corporation, model: ZSX Primus II), the intensity of the element (Si) in the external additive of 1 g of toner before and after the series of processes (1) to (6) above is analyzed, and the adhesion strength of the external additive is calculated using the following formula. Adhesion strength (%) = {(Si strength after treatment) / (Si strength before treatment)} × 100

[0141] <Evaluation method for printed area (solid area)> A monochrome multifunction printer (Model MX-565, manufactured by Sharp Corporation) was used as the evaluation machine. The amount of toner adhesion was adjusted so that the print density was ID=1.4 approximately 6 cm from the leading edge of the recording paper in the paper feed direction, and the printed area formed by fixing the toner to the recording paper was evaluated for scratches caused by peeling fingernails, gloss variation, and fixing offset. Fixing offset was evaluated by setting the fixing temperature in 5°C increments from 150°C to 220°C and passing the paper, and comparing the temperature at which offset occurred with that of the reference toner (Example B-1) shown in Tables 1 and 8 below.

[0142] (Method for evaluating scratches caused by peeling nails) The damage caused by the peeling nail was evaluated according to the following criteria.

[0143] ◎ (Excellent): There are no scratches on the printed area caused by the peeling claws. Good: There are scratches caused by the peeling nails, but they are not noticeable. △ (Fair): There are noticeable scratches caused by peeling nails. × (Not acceptable): Residue has been generated due to scratches caused by the peeling claws.

[0144] (Gross fluctuation evaluation method) The gloss values ​​of the leading edge (1 cm from the leading edge), middle (3 cm from the leading edge), and trailing edge (5 cm from the leading edge) of the printed area in the paper feed direction were measured at three points on the FCR (front side, center side, rear side) using a gloss meter (manufactured by Nippon Denshoku Industries Co., Ltd., model: VG2000). The difference from the average value of the three measured values ​​was taken as gloss variation and evaluated according to the following criteria.

[0145] ◎ (Excellent): Gross variation is less than 10%. ○ (Good): Gloss variation is 10% or more and less than 30%. △ (Acceptable): Gross variation is 30% or more and less than 60%. × (unacceptable): noticeable gloss variation before and after the peeled portion.

[0146] (Method for evaluating high temperature offset) The high-temperature offset was evaluated according to the following criteria.

[0147] ◎ (Excellent): Compared to the standard toner, the offset temperature is the same or 5°C lower. ◯ (Good): The offset occurrence temperature is 10°C lower than that of the standard toner. △ (Fair): The offset occurrence temperature is 15°C lower than that of the standard toner. × (Fail): The offset occurrence temperature is 20°C or more lower than that of the reference toner.

[0148] (Evaluation method for low temperature offset) In evaluating low-temperature offset, a strength test was also conducted when the offset temperature was the same as that of the reference toner. In the strength test, a printed recording paper was folded and then unfolded, and the folded printed area was rubbed with the paper with a 1 kg weight placed on it. If the width of the scraped line did not increase compared to the reference toner, the strength was evaluated as unchanged, and if it did increase, the strength was evaluated as worse.

[0149] ◎ (Excellent): Compared to the standard toner, the offset temperature is the same and the intensity is also the same. ◯ (Good): Compared to the standard toner, the offset occurrence temperature is the same, but the strength is worse. △ (Fair): The offset occurrence temperature is 5°C higher than that of the standard toner. × (Not acceptable): The offset temperature is 10°C or more higher than the reference toner.

[0150] (Method for evaluating electrostatic offset) Ten sheets were printed in succession to check for the occurrence of electrostatic offset and evaluated according to the following criteria: After adjusting the adhesion amount in the solid area to ID=1.4 in the same way as the image for fixing evaluation above, a paper feed test was conducted using an image pattern in which ID=approximately 1.4 for the trailing 2 cm, ID=approximately 1.0 for the middle 2 cm, and ID=approximately 0.6 for the leading 2 cm, and electrostatic offset was evaluated.

[0151] ◎ (Excellent): No electrostatic offset occurs. Good: Electrostatic offset occurs (small) at the edge (area where density changes). △ (Fair): Large electrostatic offset occurs at the edge (density change area). × (Not possible): Electrostatic offset occurs in the white area.

[0152] <Evaluation method for low humidity fogging> The evaluation machine was operated in an environmental testing room at a temperature of 25°C and a humidity of 5% RH, and 5,000 images were printed on A4 paper, each of which had 5% of its printable area filled with monochrome toner. The whiteness of the unprinted areas was measured using a whiteness meter (manufactured by Nippon Denshoku Industries Co., Ltd., model: ZE6000). The difference in whiteness between the unprinted and unprinted areas was taken as fog and evaluated according to the following criteria.

[0153] ◎ (Excellent): The difference in whiteness is 1.0 or less. ◯ (Good): The difference in whiteness is more than 1.0 and 1.5 or less. △ (Acceptable): The difference in whiteness is more than 1.5 and 2.0 or less. × (unacceptable): The difference in whiteness is more than 2.0.

[0154] <Evaluation method for high humidity fogging> The same evaluation method for low-humidity fogging as above was used, except that the environment was changed to a temperature of 25°C and a humidity of 80% RH, and the evaluation was based on the following criteria. Furthermore, the samples that were left in the same environment and measured the next day (fogging after standing) were also evaluated based on the following criteria.

[0155] ◎ (Excellent): The difference in whiteness is 1.0 or less. ◯ (Good): The difference in whiteness is more than 1.0 and 1.5 or less. △ (Acceptable): The difference in whiteness is more than 1.5 and 2.0 or less. × (unacceptable): The difference in whiteness is more than 2.0.

[0156] <Method for evaluating toner storage stability> A container containing 20 g of toner was left standing in a thermostatic chamber at 50°C for 48 hours, after which 2 g of the toner was placed on a mesh with 150 μm openings. The toner on the mesh was vibrated for 10 seconds using a powder tester (Hosokawa Micron Corporation, model: PT-X), and the storage stability was evaluated according to the following criteria.

[0157] ◎ (Excellent): Not agglomerated and in powder form before vibration is applied. Good (Good): Softly aggregated, breaks down with vibration and passes through the mesh. △ (Acceptable): Toner that does not crumble due to vibration can be expelled from the mesh by crushing it with a spatula or similar. × (Not acceptable): The toner clumps together so much that it cannot be removed from the container.

[0158] <Evaluation method based on glass transition temperature change ΔTg> The change in glass transition temperature ΔTg due to the mid-melting point wax was measured and evaluated according to the following criteria: ΔTg was calculated using the following formula (1). ΔTg=(glass transition temperature of toner particles without mid-melting point wax)−(glass transition temperature of toner particles with mid-melting point wax) (1) For example, in the examples and comparative examples described later, comparative example A-0 and comparative examples B-2 to B-5 correspond to cases in which no mid-melting point wax is contained, and serve as the reference values ​​for calculating ΔTg as shown in the table below. Note that the object for measuring the glass transition temperature is the "toner particles," in other words, the object for measuring the glass transition temperature is the toner core before the external additive is attached.

[0159] ◎ (Excellent): ΔTg is 0.5℃ or less. ◯ (Good): ΔTg is greater than 0.5°C and equal to or less than 1.0°C. △ (Acceptable): ΔTg is greater than 1.0°C and equal to or less than 2.0°C. × (unacceptable): ΔTg is greater than 2.0°C.

[0160] <Toner overall evaluation method> Based on the above evaluation results, an overall evaluation was made according to the following criteria.

[0161] ◎ (Excellent): All evaluation items are ◎. ○ (Good): The lowest rating among all evaluation items is ○. △ (Acceptable): The lowest rating among all evaluation items is △. × (Fail): The lowest rating among all evaluation items is ×.

[0162] Next, the process for producing the toner and two-component developer in the examples and comparative examples will be described.

[0163] <Preparation of toner particles> The following raw materials for the toner particles were premixed for 5 minutes at 1500 rpm using a Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd., model: FM20C) to obtain a mixture [premixing step]. The blending ratios were 8% by mass of colorant, 2% by mass of charge control agent, and the mass % of release agent shown in the table below. The ratio of H-isomer to L-isomer in the binder resin was 5:5. Binder resin: Amorphous polyester resin (H body: high molecular weight component, Tg around 60°C) Amorphous polyester resin (L-body: low molecular weight component, Tg around 55°C) Colorant: Carbon black (Mitsubishi Chemical Corporation, product name: MA-77) Release agent: Medium melting point wax (listed in the table below) High melting point wax (listed in the table below) Charge control agent: Potassium bis[benzilate(2-)-κ(2)O,O]borate(1-) (Nippon Carlit Co., Ltd., product name: LR-147)

[0164] The mixture obtained in the pre-mixing process was melt-kneaded using a twin-screw extruder (manufactured by Ikegai Corporation, model: PCM-30) under the conditions of a cylinder setting temperature of 100°C, a barrel rotation speed of 250 rpm, and a raw material supply rate of 10 kg / hour to obtain a molten kneaded product [melt-kneading process].

[0165] The molten mixture obtained in the melt-kneading process was cooled and solidified on a cooling belt, and then the solidified mixture was finely pulverized using a fluidized bed opposed jet mill (manufactured by Hosokawa Micron Corporation, model: Counter Jet Mill AFG) and classified (particle size adjustment) using a rotary (centrifugal airflow) classifier (manufactured by Hosokawa Micron Corporation, model: TSP Separator) to obtain toner particles. [Cooling and pulverization, classification process]

[0166] Next, the resulting finely pulverized material was classified using an elbow jet classifier (manufactured by Nittetsu Mining Co., Ltd., model: EJ-LABO) to obtain toner particles [classification step].

[0167] <External Addition Process (Addition of External Additives to Toner Particles)> The toner particles and the following external additives were mixed in the ratios shown in the table below using a Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd., model: FM20C) at a rotation speed of 3000 rpm for 3 minutes to obtain a toner. Small particle silica: Fumed silica fine particles (hydrophobic treatment: dimethyldichlorosilane (DDS), manufactured by Nippon Aerosil Co., Ltd., product name: R976s) Medium to large particle size silica: Hydrophobic silica particles treated with silicone oil (hydrophobic treatment: polydimethylsiloxane (PDMS)) Metal oxide: Strontium titanate microparticles (average primary particle diameter 40 nm)

[0168] The procedure for producing the strontium titanate microparticles is as follows. Metatitanic acid obtained by the sulfuric acid method was deironized and bleached, then desulfurized with the addition of aqueous sodium hydroxide. It was then neutralized with hydrochloric acid, filtered, and washed to obtain a washed cake. Water was added to the washed cake to form a slurry, after which hydrochloric acid was added and the cake was deflocculated. This was designated Solution 1, and it was mixed with Solution 2, an aqueous strontium chloride solution, and Solution 3, an aqueous sodium silicate solution. The mixture ratio of Solutions 1, 2, and 3 was adjusted so that the (Sr + Si) / Ti molar ratio was 1.2. The mixed solution was heated to 90°C under a nitrogen gas atmosphere, and the reaction was completed by stirring for 2 hours while adding aqueous sodium hydroxide. The reaction-completed slurry was cooled to 50°C, and hydrochloric acid was added and stirred for 2 hours. The precipitate obtained after stirring was washed, separated by filtration, and dried. The dried product was ground in a blender for 1 minute, and then passed through a 32 μm mesh sieve to remove coarse particles. The resulting fine powder substrate was then surface-coated with a silane coupling agent.

[0169] <Creating the carrier> A resin liquid was prepared by adding 10 parts by mass of PTFE (manufactured by Daikin Industries, Ltd., product name: LDE-410) as fluororesin microparticles to 100 parts by mass of silicone resin, and a carrier core material was immersed in this resin liquid to obtain carrier "SC-1."

[0170] <Preparation of two-component developer> The obtained externally added toner and carrier "SC-1" were mixed for 20 minutes in a V-type mixer (manufactured by Tokuju Kogyosho Co., Ltd., product name: V-5) so that the toner concentration was 7% by mass, to prepare a two-component developer.

[0171] The types and blending ratios of raw materials in the toners of Examples and Comparative Examples are shown in Tables 1 to 7 below. The evaluation results of the toners and two-component developers of Examples and Comparative Examples are shown in Tables 8 to 14 below. The names of the mid-melting point wax and high-melting point wax in the tables specifically mean the following: WE-12: Ester wax (NOF Corporation, melting temperature 76°C, product name: WE-12) FNP0090: Fischer-Tropsch wax (manufactured by Nippon Seiro Co., Ltd., melting temperature 97°C, product name: FNP0090) 550P: Polypropylene wax (manufactured by Sanyo Chemical Industries, Ltd., melting temperature 144°C, product name: 550P) PE130: Polyethylene wax (Clariant Chemicals, melting temperature 133°C, product name: LICOWAX PE 130) L103: Polyethylene wax (Clariant Chemicals, melting temperature 106°C, product name: L103)

[0172] In addition, RY300, RY200S, NY90L, and RY50 listed as types of oil-treated silica in the table are product names manufactured by Nippon Aerosil Co., Ltd., and their average primary particle sizes are as follows: The oil-treated silicas listed in the table as "changed base" were produced in the same way as these oil-treated silicas, but with a different base size. RY300:7nm RY200S:16nm NY90L:20nm RY50:40nm

[0173] [Table 1]

[0174] [Table 2]

[0175] [Table 3]

[0176] [Table 4]

[0177] [Table 5]

[0178] Table 6

[0179] Table 7

[0180] Table 8

[0181] Table 9

[0182] Table 10

[0183] Table 11

[0184] Table 12

[0185] Table 13

[0186] Table 14

[0187] As is clear from Tables 1 to 14, the toners and two-component developers of Examples A-1 to H-4, which are toners having external additives attached to the surfaces of toner particles containing a binder resin and an internal additive, wherein the internal additives include a high-melting point wax, a mid-melting point wax, and a colorant, wherein the melting temperature of the high-melting point wax is 133°C or higher and the melting temperature of the mid-melting point wax is 30°C or higher lower than the melting temperature of the high-melting point wax, and the external additives include strontium titanate microparticles, oil-treated silica microparticles having an average primary particle diameter of 16 nm or higher, and silica microparticles hydrophobized by a method other than oil treatment and having an average primary particle diameter smaller than that of the oil-treated silica microparticles, were excellent in all of the evaluations of scratches caused by peeling nails, evaluation of gloss variation, evaluation of fixing offset, evaluation of low-humidity and high-humidity fog, and evaluation of toner quality.

[0188] In contrast, Comparative Examples A-0 to F-5, which did not meet these requirements, were inferior to the Examples in at least one of the following evaluations: damage caused by the peeling claw, gloss variation, fixing offset, low-humidity and high-humidity fogging, and toner quality.

[0189] From Tables 1 and 8, it can be seen that Examples A-2 to A-6, in which the content of mid-melting point wax in the toner particles is 0.2% by mass or more and 5.0% by mass or less, are superior in various evaluations, particularly in the evaluation of toner quality, to Comparative Example A-1, in which the content exceeds this range. It can also be seen that Examples A-2 to A-6 are superior in various evaluations, particularly in the evaluation of electrostatic offset, to Comparative Example A-0, which does not contain a mid-melting point wax.

[0190] It can be seen that Examples A-2 to A-9, in which the content of high-melting point wax in the toner particles is 0.4% by mass or more and 5.5% by mass or less, are superior in various evaluations to Comparative Example A-1, which does not contain high-melting point wax, and are particularly superior in the evaluation of toner quality.

[0191] Examples A-2 to A-9 differ from Examples B-1 to B-2 in the type of wax, and it can be seen that Examples B-1 to B-2, in which the mid-melting point wax is Fischer-Tropsch wax, are superior in various evaluations.

[0192] From Tables 2 and 9, it can be seen that Examples C-1 to C-4, in which the content of strontium titanate microparticles modified with silica microparticles per 100 parts by mass of toner particles is 0.02 parts by mass or more and 0.6 parts by mass or less, have superior low-humidity fogging evaluations to Comparison Example C-5, which does not contain strontium titanate microparticles.

[0193] From Tables 3 and 10, it can be seen that Examples D-1 to D-4, which contain strontium titanate microparticles that are not modified with silica microparticles, also have superior low-humidity fogging evaluations than Comparison Example C-5, which does not contain strontium titanate microparticles, while Examples C-1 to C-4, which contain strontium titanate microparticles modified with silica microparticles, have superior electrostatic offset evaluations and high-humidity fogging evaluations after storage than Examples D-1 to D-4.

[0194] Tables 4 and 11 show that Examples E-2 to E-6, in which the average primary particle diameter of the oil-treated silica microparticles is 16 nm or more and 110 nm or less, are superior to Comparative Example E-1, in which the average primary particle diameter is outside the range, particularly in the evaluation of gloss variation and low-temperature offset. Also, Tables 5 and 12 show that Comparative Examples F1 to F5, in which the average primary particle diameter of the oil-treated silica microparticles is outside the range, are inferior to the Examples in various evaluations even when the content of the silica microparticles is changed.

[0195] From Tables 6, 7, 13, and 14, it can be seen that Examples G-1 to G-4 and Examples H-1 to H-4, in which the content of oil-treated silica fine particles per 100 parts by mass of toner particles is 0.1 parts by mass or more and 1.8 parts by mass or less, are superior in various evaluations to Comparative Example F-5, which does not contain oil-treated silica fine particles, and are particularly superior in the evaluation of high-humidity fogging. Furthermore, when Examples G-1 to G-4 are compared with Examples H-1 to H-4, it can be seen that Examples G-1 to G-4, in which the average primary particle diameter of the oil-treated silica fine particles is 40 nm, are superior in the overall evaluation.

[0196] <Other embodiments> It should be noted that the embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present invention should not be interpreted solely by the above-described embodiments, but should be defined by the claims. The technical scope of the present invention also includes all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0197] T Toner T1 Conventional toner using strontium titanate particles as an external additive T2 Toner using strontium titanate particles as an external additive that are not modified with silica particles P Toner particles (toner base particles) 1. Strontium titanate nanoparticles modified with silica nanoparticles 2. Oil-treated silica particles 3. Silica particles that have been hydrophobized by methods other than oil treatment 4. Medium melting point wax 5. High-melting wax 11 Heating roller 12 Pressure roller 13 Peeling Claw 21 Recording Sheet

Claims

1. A toner in which an external additive is attached to the surface of toner particles containing a binder resin and an internal additive, the internal additives include a high-melting point wax, a medium-melting point wax, and a colorant; The melting temperature of the high-melting point wax is 133°C or higher, The melting temperature of the medium-melting point wax is lower than the melting temperature of the high-melting point wax by 30°C or more, The toner is characterized in that the external additive comprises strontium titanate microparticles, oil-treated silica microparticles having an average primary particle diameter of 16 nm or more, and silica microparticles that have been hydrophobized by a method other than oil treatment and have an average primary particle diameter smaller than that of the oil-treated silica microparticles.

2. 2. The toner according to claim 1, The toner is characterized in that the change in glass transition temperature ΔTg due to the mid-melting point wax, calculated by the following formula (1), is 2° C. or less. ΔTg=(glass transition temperature of the toner particles when the mid-melting point wax is not contained)−(glass transition temperature of the toner particles) (1)

3. The toner according to claim 1 or claim 2, The toner, wherein the content of the mid-melting point wax in the toner particles is 0.2% by mass or more and 5.0% by mass or less.

4. The toner according to any one of claims 1 to 3, The toner, wherein the content of the high melting point wax in the toner particles is 0.4% by mass or more and 5.5% by mass or less.

5. The toner according to any one of claims 1 to 4, the mid-melting point wax is a Fischer-Tropsch wax; The toner is characterized in that the binder resin is a polyester resin.

6. The toner according to any one of claims 1 to 5, The toner is characterized in that the strontium titanate fine particles are fine particles in which the surface of a fine powder base containing strontium titanate and silicon element is coated with a silane coupling agent.

7. 7. The toner according to claim 1, The toner, wherein the content of the strontium titanate fine particles relative to 100 parts by mass of the toner particles is 0.02 parts by mass or more and 0.6 parts by mass or less.

8. The toner according to any one of claims 1 to 7, The average primary particle diameter of the strontium titanate fine particles is D ｔｓ The average primary particle diameter of the oil-treated silica fine particles is D ｏｓ and the difference ΔD in average primary particle diameter calculated by the following formula (2) is -24 nm or more and 70 nm or less. ΔD=D ｏｓ -D ｔｓ ・・・(2)

9. 9. The toner according to claim 1, The toner is characterized in that the average primary particle diameter of the oil-treated silica fine particles is 16 nm or more and 110 nm or less.

10. 10. The toner according to claim 1, The toner, wherein the content of the oil-treated silica fine particles relative to 100 parts by mass of the toner particles is 0.1 parts by mass or more and 1.8 parts by mass or less.

11. A two-component developer comprising the toner according to claim 1 and a carrier.

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