JP2019158902A - Toner for electrostatic latent image development and image forming method - Google Patents

Abstract

To provide a toner for electrostatic latent image development that, when lubricant is applied to a photoreceptor via the toner, easily makes an amount of lubricant applied to an image part and a non-image part uniform and reduces a difference in density of an output image, and an image forming method using the toner for the electrostatic latent image development.SOLUTION: The present invention is a toner for electrostatic latent image development containing toner base particles each having an external additive on a surface, where the external additive contains inorganic particles and fatty acid metal salt particles; the inorganic particles have a number average particle diameter within a range of 10 to 50 nm; a surface shape of the inorganic particles has a plane portion; and the fatty acid metal salt particles have a number average particle diameter within a range of 0.4 to 2.0 μm.SELECTED DRAWING: None

Description

  The present invention relates to an electrostatic latent image developing toner and an image forming method. More specifically, in the present invention, when the lubricant is applied to the photoreceptor via the electrostatic latent image developing toner, the amount of the lubricant applied to the image portion and the non-image portion is likely to be uniform, and the output image has a density difference. The present invention relates to a toner for developing an electrostatic latent image that hardly occurs and an image forming method using the toner for developing an electrostatic latent image.

  In an electrophotographic image forming apparatus, a lubricant may be required from the viewpoint of the cleaning property of the photoreceptor. In particular, when used in a general office, from the viewpoint of cost, a lubricant coating mechanism is not provided as a process, but a lubricant is added to a toner for developing an electrostatic latent image (hereinafter also simply referred to as “toner”). There are many cases to do.

However, there is a problem that it is difficult to uniformly apply the lubricant to the surface of the photoreceptor when the lubricant is applied onto the photoreceptor via the toner containing the lubricant. Specifically, a lubricant such as a fatty acid metal salt particle is larger than other external additives even if the diameter is reduced, and thus is easily detached from the toner. In addition, since the lubricant tends to be positively charged, it is easily applied to the non-image portion for the negatively charged toner.
Further, if the lubricant is not uniformly applied on the surface of the photosensitive member, there is a problem that a difference in image density occurs between a portion where the lubricant concentration is high and a portion where the lubricant concentration is low. In particular, in the charging method using a charging roller, there is a problem that a difference in image density is remarkably generated because the lubricant on the surface of the photoreceptor is generally easily decomposed.

By the way, in the conventional toner, in addition to externally adding a lubricant (fatty acid metal oxide salt particles) for the purpose of improving cleaning properties to the toner base particles, an inorganic material for polishing the surface of the photoreceptor. It is known to add particles externally (see, for example, Patent Document 1).
However, since these inorganic particles are intended to polish the surface of the photoreceptor, the particle size of the inorganic particles to be added is large, and the effect of scraping the surface of the photoreceptor is great. Therefore, if there is a bias in the distribution of the inorganic particles, the difference in lubricant coating concentration tends to increase.

  In addition, with conventional toners, an attempt has been made to control the state of application of the lubricant onto the photoreceptor by combining a lubricant having a large particle size and a lubricant having a small particle size (see, for example, Patent Document 2). ). However, it did not fully satisfy the demand for reducing the image density difference from the market.

JP 2002-214823 A JP 2014-228773 A

  The present invention has been made in view of the above-described problems and situations, and the problem to be solved is that the amount of lubricant applied to the image portion and the non-image portion is likely to be uniform when the lubricant is applied to the photoreceptor via the toner. It is another object of the present invention to provide an electrostatic latent image developing toner that hardly causes a density difference in an output image and an image forming method using the electrostatic latent image developing toner.

As a result of studying the cause of the above-mentioned problem in order to solve the above-described problems, the present inventors have found that the toner has an external additive within a predetermined number-average particle diameter range, and the surface shape is a planar portion. Incorporating inorganic particles having a number average particle diameter within the range of a predetermined number average particle diameter, a lubricant is uniformly applied on the surface of the photoreceptor, and when an image is output, Thus, the present inventors have found that the difference in density is less likely to occur, resulting in the present invention.
That is, the subject concerning this invention is solved by the following means.

1. An electrostatic latent image developing toner containing toner base particles having an external additive on the surface,
The external additive contains inorganic particles and fatty acid metal salt particles,
The number average particle diameter of the inorganic particles is in the range of 10 to 50 nm,
The surface shape of the inorganic particles has a planar portion, and
The toner for developing an electrostatic latent image, wherein the number average particle diameter of the fatty acid metal salt particles is in a range of 0.4 to 2.0 μm.

  2. 2. The electrostatic latent image developing toner according to item 1, wherein the inorganic particles are alumina particles.

  3. 3. The electrostatic latent image developing toner according to claim 1 or 2, wherein the fatty acid metal salt particles are at least one selected from zinc stearate particles, lithium stearate particles, and calcium stearate particles. .

  4). 3. The electrostatic latent image developing toner according to item 1 or 2, wherein the fatty acid metal salt particles are zinc stearate particles.

5). The inorganic particles are surface-modified with a silane coupling agent,
Item 5. The electrostatic latent image developing toner according to any one of Items 1 to 4, wherein the silane coupling agent has a structure represented by the following general formula (1).
General formula (1): X-Si (OR) ₃
[In said general formula (1), X represents a C4-C12 alkyl group. R represents a methyl group or an ethyl group. ]

  6). 2. An image forming method using the electrostatic latent image developing toner according to item 1, further comprising a step of charging the surface of the photosensitive member with a charging roller provided so as to be in contact with the photosensitive member. Method.

  According to the present invention, when the lubricant is applied to the photoreceptor via the toner, the amount of lubricant applied to the image portion and the non-image portion is likely to be uniform, and the electrostatic latent image developing toner is less likely to cause a density difference in the output image. And an image forming method using the electrostatic latent image developing toner.

The expression mechanism or action mechanism of the effect of the present invention is assumed to be as follows.
The electrostatic latent image developing toner of the present invention has, as an external additive, an inorganic particle having a number average particle diameter in the range of 10 to 50 nm and a surface shape having a planar portion, and a number average particle diameter. And fatty acid metal salt particles in the range of 0.4 to 2.0 μm.

  In such a toner, the fatty acid metal salt particles are likely to be pushed into the surface of the toner base particles by the inorganic particles having a planar portion in the surface shape, so that it is presumed that the fatty acid metal salt particles are unlikely to be detached from the toner base particles. . As a result, the fatty acid metal salt particles are uniformly dispersed in the state where they are embedded in the toner base particles, so that it is presumed that the density difference is less likely to occur in the output image.

  Further, from the viewpoint of manifesting the effects of the present invention, the number average particle size of the fatty acid metal salt particles contained in the toner is in the range of 0.4 to 2.0 μm. Since the fatty acid metal salt particles having a number average particle diameter in the range of 0.4 to 2.0 μm are easily pushed into the toner base particles and are not easily detached from the toner base particles, the effect of the present invention is effectively obtained. Inferred.

  From the viewpoint of manifesting the effects of the present invention, the number average particle diameter of the inorganic particles contained in the toner is in the range of 10 to 50 nm. The small-diameter inorganic particles having a number average particle diameter of 50 nm or less have a number average particle diameter of 8 times or more smaller than that of the fatty acid metal salt particles, so that one fatty acid metal salt particle is pressed with a plurality of inorganic particles. It is presumed that the fatty acid metal salt particles could be pushed into the toner base particles more efficiently. Moreover, it is guessed that the effect | action which the said inorganic particle pushes in a fatty-acid metal salt was fully acquired because the number average particle diameter of an inorganic particle shall be 10 nm or more.

Schematic showing an example of an image forming apparatus

  The toner for developing an electrostatic latent image of the present invention is a toner for developing an electrostatic latent image containing toner base particles having an external additive on the surface, wherein the external additive comprises inorganic particles and fatty acid metal salt particles. The number average particle size of the inorganic particles is in the range of 10 to 50 nm, the surface shape of the inorganic particles has a planar portion, and the number average particle size of the fatty acid metal salt particles is It is in the range of 0.4 to 2.0 μm. This feature is a technical feature common to or corresponding to the embodiments described below.

  As an embodiment of the present invention, the inorganic particles are preferably alumina particles from the viewpoint of more effectively obtaining the effects of the present invention. As the hardness difference between the toner base particles and the inorganic particles is larger, there is an advantage that the inorganic particles are easily embedded in the toner base particles and are easily fixed. Alumina particles are preferably used because they have high Mohs hardness and a large difference in hardness from toner base particles.

  As an embodiment of the present invention, the fatty acid metal salt particles are preferably at least one selected from zinc stearate particles, lithium stearate particles, and calcium stearate particles from the viewpoint of spreadability. High spreadability is preferable because the fatty acid metal salt particles can be stably and uniformly applied to the surface of the photoreceptor. Of these, zinc stearate particles are more preferable.

  As an embodiment of the present invention, from the viewpoint of more effectively obtaining the effects of the present invention, the inorganic particles are surface-modified with a silane coupling agent, and the silane coupling agent is represented by the general formula (1). It is preferable to have a structure. From the viewpoint of reactivity with the hydroxyl group on the surface of the inorganic particles, the inorganic particles are preferably surface-modified with a silane coupling agent. Here, the alkyl chain length of the silane coupling agent having the structure represented by the general formula (1) is 4 carbon atoms from the viewpoint of enhancing the adhesion to the toner base particles or the fatty acid metal oxide particles. From the viewpoint of increasing the surface coverage with the silane coupling agent, it is preferably 12 or less.

  The electrostatic latent image developing toner of the present invention can also be suitably applied to a charging roller type image forming method in which the surface of the photosensitive member is charged by a charging roller provided so as to be in contact with the photosensitive member. In image formation using a charging roller system, the lubricant on the surface of the photoreceptor is generally easily decomposed, and the difference in image density tends to increase. However, if the toner for developing an electrostatic latent image of the present invention is used, the difference in image density is suppressed. be able to.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" showing a numerical range is used by the meaning containing the numerical value described before and behind that as a lower limit and an upper limit.

[Toner for electrostatic latent image development (toner)]
In the present invention, “toner” refers to an aggregate of “toner particles”. The toner particles contain at least toner base particles, and the toner particles refer to toner base particles themselves or those obtained by adding at least an external additive to the toner base particles.

<Toner base particles>
The toner base particles according to the present invention preferably contain other components such as a colorant, a release agent (wax), and a charge control agent in the binder resin as necessary.
Further, an external additive is added to the surface of the toner base particles according to the present invention. As the external additive, at least inorganic particles and fatty acid metal salt particles are used.

(Particle size of toner base particles)
The toner base particles according to the present invention preferably have a volume average particle size in the range of 4.0 to 8 μm. From the viewpoint of improving the image quality, a smaller diameter is preferable. However, if the particle diameter is small, the adhesion of the toner base particles is increased and the cleaning property is deteriorated. When the volume average particle diameter of the toner base particles is within the above range, both the image quality of the output image and the cleaning property can be satisfied, and functions such as charging, development, and transfer can be compatible. The volume average particle diameter of the toner base particles is more preferably in the range of 5 to 6.7 μm from the above viewpoint, and the dot reproducibility is improved, so that a higher quality image can be obtained.
The volume average particle size of the toner base particles is, for example, a computer in which data processing software “Software V3.51” is installed in “Multisizer 3 (manufactured by Beckman Coulter)” as a volume-based median diameter (D ₅₀ ). Using a device connected to a system (manufactured by Beckman Coulter), measurement and calculation can be performed in the same manner as described above. As a measurement procedure, 0.02 g of toner particles are dispersed in 20 mL of a surfactant solution, and after mixing, ultrasonic dispersion is performed for 1 minute to prepare a toner particle dispersion. As the surfactant solution, for example, a neutral detergent containing a surfactant component diluted 10 times with pure water may be used. This toner particle dispersion is dropped into a beaker of ISOTON II (manufactured by Beckman Coulter) to a measured concentration of 5 to 10%, and measurement is performed with a measuring machine count set to 25,000. Here, the aperture diameter of the multisizer 3 is 100 μm. In the measurement, the frequency number obtained by dividing the range of 2 to 60 μm into 256 is calculated, and the particle diameter of 50% is obtained as the volume reference median diameter (D ₅₀ ) from the larger volume integrated fraction, and the toner base particles The volume average particle size is used.

(Circularity of toner base particles)
As for the circularity of the toner base particles used in the present invention, the average circularity represented by the following formula 1 is preferably 0.920 to 1.000. When the circularity of the toner base particles is within the above range, the contact point between the toner particles becomes small, and sufficient transfer efficiency can be obtained.
(Formula 1) Average circularity of toner base particles = (peripheral length of a circle having the same projected area as the toner base particle image) / (perimeter of toner base particle projected image)
A measurement example for obtaining the average circularity of the toner base particles includes measurement using an average circularity measuring device “FPIA-2100” (manufactured by Sysmex). Specifically, the toner base particles are moistened in an aqueous surfactant solution and dispersed by performing ultrasonic dispersion for 1 minute, and then using “FPIA-2100” in a measurement condition HPF (high magnification imaging) mode. Measurement is performed at an appropriate concentration of 3000 to 10,000 HPF detections.

(Core shell structure)
The toner base particles preferably have a core / shell structure. As an example of producing toner base particles having a core / shell structure, first, core resin is produced by aggregating, associating and fusing binder resin particles for core particles and colorant particles. Subsequently, the shell layer binder resin particles are added to the core particle dispersion, and the shell layer binder resin particles are agglomerated and fused on the core particle surface to form a shell layer covering the core particle surface. It can be obtained by forming.

<Binder resin>
The toner base particles according to the present invention preferably contain an amorphous resin and a crystalline resin as a binder resin.

The crystalline resin in the present invention refers to a resin having a clear endothermic peak instead of a stepwise endothermic change in differential scanning calorimetry (DSC). The clear endothermic peak specifically refers to a peak having a half-value width of 15 ° C. or less in an endothermic curve when the temperature is increased at a rate of temperature increase of 10 ° C./min in differential scanning calorimetry.
On the other hand, the amorphous resin shows a baseline curve indicating that the glass transition has occurred in the endothermic curve obtained when the differential scanning calorimetry is performed as described above, but the above-mentioned clear endothermic A resin with no peak.
The differential scanning calorimetry can be performed using, for example, a DSC-7 differential scanning calorimeter (manufactured by PerkinElmer) or a TAC7 / DX thermal analyzer controller (manufactured by PerkinElmer). Specifically, 4.50 mg of a sample is sealed in an aluminum pan (KIT No. 0219-0041), which is set in a sample holder of “DSC-7”, and an empty aluminum pan is used for measuring the reference. Heat-Cool-Heat temperature control was performed at a measurement temperature of 0 to 200 ° C. under measurement conditions of a temperature increase rate of 10 ° C./min and a temperature decrease rate of 10 ° C./min. Get data in Heat. The melting point is the temperature at the peak top of the endothermic peak.

(Amorphous resin)
As the amorphous resin, it is preferable to use a vinyl resin formed using a vinyl monomer.
Specifically, as the vinyl resin, it is preferable to use a styrene-acrylic resin because charge control is easy. The styrene-acrylic resin here is formed by addition polymerization of a styrene monomer and a (meth) acrylic acid ester monomer. The styrene monomer includes those having a structure having a known side chain or functional group in the styrene structure in addition to styrene represented by the structural formula of CH ₂ ═CH—C ₆ H ₅ . In addition, the (meth) acrylic acid ester monomer referred to here is an acrylic acid ester derivative or methacrylic acid in addition to the acrylic acid ester compound or methacrylic acid ester compound represented by CH ₂ = CHCOOR (R is an alkyl group). It includes ester compounds having a known side chain or functional group in the structure of an ester derivative or the like.

Specific examples of the styrene monomer and (meth) acrylic acid ester monomer capable of forming a styrene-acrylic resin are shown below, but can be used for forming a styrene-acrylic resin unit used in the present invention. Things are not limited to those shown below.
Specific examples of the styrene monomer include, for example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene. , P-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, and the like. These styrene monomers can be used alone or in combination of two or more.

Specific examples of the (meth) acrylic acid ester monomer include, for example, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate. Acrylate monomers such as stearyl acrylate, lauryl acrylate, and phenyl acrylate; methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, Stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl meta Relate, methacrylic acid esters such as dimethyl aminoethyl methacrylate.
The content of the styrene-acrylic resin is preferably 60% by mass or more with respect to the total amount of the binder resin.

<Crystalline resin>
(Type of crystalline resin)
Examples of the crystalline resin include a crystalline polyester resin and a crystalline vinyl resin. Further, although not particularly limited, a crystalline polyester resin is preferable from the viewpoint of low-temperature fixability. As the crystalline polyester resin, a known polyester resin obtained by a polycondensation reaction between a divalent or higher carboxylic acid (polyvalent carboxylic acid) and a divalent or higher alcohol (polyhydric alcohol) can be used.

(Hybrid crystalline polyester resin)
Further, the crystalline polyester resin is more preferably a hybrid crystalline polyester resin containing an amorphous resin other than the crystalline polyester resin as a unit. The amorphous resin unit is preferably made of the same type of resin as the amorphous resin contained in the binder resin, that is, a resin other than the hybrid resin. By hybridizing in such a form, the affinity between the crystalline polyester resin and the binder resin is increased, and the hybrid resin is more easily taken into the amorphous resin. As a result, since a crystalline polyester unit that easily adsorbs moisture is present inside the toner base, the adhesion between the toner particles is prevented from increasing due to moisture absorption, and the cleaning property is further improved.
Here, “the same kind of resin” means that a characteristic chemical bond is commonly contained in the repeating unit. Here, “characteristic chemical bond” is described in the National Institute for Materials Science (NIMS) Substance / Material Database (http://polymer.nims.go.jp/PoLyInfo/guide/jp/term_polymer.html) According to “Polymer classification”. That is, polyacryl, polyamide, polyanhydride, polycarbonate, polydiene, polyester, polyhaloolefin, polyimide, polyimine, polyketone, polyolefin, polyether, polyphenylene, polyphosphazene, polysiloxane, polystyrene, polysulfide, polysulfone, polyurethane, polyurea Chemical bonds constituting polymers classified according to a total of 22 types of polyvinyl and other polymers are referred to as “characteristic chemical bonds”.

(Content of crystalline resin)
The content of the crystalline resin contained in the toner base particles according to the present invention is preferably in the range of 1 to 30 mass. If the content of the crystalline resin in the toner base particles is 1% by mass or more, the effect can be suitably exhibited. Further, when the content of the crystalline resin in the toner base particles is 30% by mass or less, occurrence of thermal aggregation (blocking) of the toner can be avoided.

<Colorant>
As the colorant contained in the toner base particles of the present invention, known inorganic or organic colorants can be used. As the colorant, various organic and inorganic pigments and dyes can be used in addition to carbon black and magnetic powder. The amount of the colorant added is preferably in the range of 1 to 30% by mass, preferably 2 to 20% by mass, based on the toner particles.

<Release agent>
A release agent can be added to the toner base particles according to the present invention. As the release agent, wax is preferably used. Examples of the wax include low molecular weight polyethylene wax, low molecular weight polypropylene wax, Fischer-Tropsch wax, microcrystalline wax, hydrocarbon wax such as paraffin wax, carnauba wax, pentaerythritol behenate, behenyl behenate, And ester waxes such as behenyl acid. These can be used alone or in combination of two or more.
Further, the melting point of the wax is preferably 50 to 95 ° C. from the viewpoint of reliably obtaining low-temperature fixability and releasability of the toner. The content of the wax is preferably in the range of 2 to 20% by mass, more preferably in the range of 3 to 18% by mass, and still more preferably 4 to 15% by mass with respect to the total amount of the binder resin. Within range.

<Charge control agent>
A charge control agent can be added to the toner base particles according to the present invention as necessary. Various known materials can be used as the charge control agent. As the charge control agent, various known compounds that can be dispersed in an aqueous medium can be used. Specifically, nigrosine dyes, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, fourth compounds. Examples include quaternary ammonium salt compounds, azo metal complexes, salicylic acid metal salts or metal complexes thereof. The content ratio of the charge control agent is preferably in the range of 0.1 to 10% by mass, and more preferably in the range of 0.5 to 5% by mass with respect to the total amount of the binder resin.

<External additive>
The surface of the toner base particles according to the present invention contains inorganic particles and fatty acid metal salt particles as external additives. The fatty acid metal salt particles have a function as a lubricant that further improves the cleaning property and the transfer property.

<Inorganic particles>
The toner particles according to the present invention contain inorganic particles as an external additive having a number average particle diameter in the range of 10 to 50 nm and a surface shape having a planar portion.
In the present invention, the “inorganic particles whose surface shape has a planar portion” are inorganic particles in which the portion in contact with the toner base particles becomes a surface instead of a point. Further, the planar portion here is not limited to a strict plane, but may be a slightly curved surface. Specifically, the flatness defined by JIS B 0621-1984 (the difference between the maximum value and the minimum value measured when sandwiched between two straight lines parallel to the reference surface) is 0 nm or more, and the inorganic particles When a portion having a number average particle diameter of 1/10 nm or less is a planar portion, the planar portion is 1/6 or more of the number average surface area of the inorganic particles. It is defined as “inorganic particles having a shape portion”.

  In the toner of the present invention, the fatty acid metal salt particles are likely to be pushed into the surface of the toner base particles by the inorganic particles having a planar portion in the surface shape, so that it is presumed that the fatty acid metal salt particles are not easily detached from the toner base particles. . As a result, the fatty acid metal salt particles are uniformly dispersed in the state where they are embedded in the toner base particles, so that it is presumed that the density difference is less likely to occur in the output image.

(Inorganic particle size)
The number average particle diameter of the inorganic particles having a planar portion as described above is in the range of 10 to 50 nm, more preferably 15 to 25 nm, from the viewpoint that the surface can be fixed to the toner base particles with high adhesion. Within range. Small-sized inorganic particles having a number average particle size of 50 nm or less are much smaller than fatty acid metal salt particles, so one fatty acid metal salt particle is pressed with a plurality of inorganic particles, and the fatty acid metal salt particles are more efficiently applied. It is inferred that the toner could be pushed into the toner base particles. Moreover, it is guessed that the effect | action which the said inorganic particle pushes in a fatty-acid metal salt was fully acquired because the number average particle diameter of an inorganic particle shall be 10 nm or more.

(Measurement method of number average particle diameter)
The number average particle diameter of the inorganic particles according to the present invention can be measured by the following method.
Using a scanning electron microscope (SEM) “JSM-7401F” (manufactured by JEOL Ltd.), an SEM photograph magnified 50,000 times was taken, and the SEM photograph was taken as an image processing analyzer “LUZEX AP” (manufactured by Nireco). ) To calculate the horizontal ferret diameter for 100 inorganic particles, and the average value is taken as the number average particle diameter.

(Type of inorganic particles)
Examples of inorganic particles having a planar surface portion include inorganic particles known as external additives for toner, such as alumina particles having a double-sided shape, strontium titanate particles having a cubic shape, and calcium titanate particles having a rectangular column shape. The particles can be appropriately selected and used. Moreover, in order to obtain the effect of the present invention, inorganic particles having a planar portion on the surface shape may be used, but among the inorganic particles, alumina particles having high Mohs hardness are preferably used.
The Mohs hardness is Invented by Mohs, the following 10 types of minerals are selected, and if they are sequentially scratched and scratched, the hardness is assumed to be lower than that mineral. Minerals in order of decreasing hardness: 1: talc, 2: gypsum, 3: calcite, 4: fluorite, 6: apatite, 7: crystal, 8: yellow jade, 9: steel ball, 10: diamond It is.
The particles according to the present invention include cerium oxide (Mohs hardness: 7), aluminum oxide (Mohs hardness: 9), titanium oxide (Mohs hardness: 6), silicon oxide (Mohs hardness: 7), strontium titanate (Mohs hardness). : 5), zirconium oxide (Mohs hardness: 7) and surface-treated products thereof.

(Hydrophobic treatment)
It is preferable that the surface of the inorganic particle having the above-described surface shape having a planar portion is subjected to a hydrophobic treatment, and the degree of hydrophobicity is preferably 40 or more. Further, the liberation rate of the surface modifier when subjected to the hydrophobization treatment is preferably zero. This is because if there is a liberated surface modifier, it shifts to the carrier and the charge amount fluctuation increases.
For the surface modification, a known surface modification method can be used. For example, a dry method or a wet method can be used. Moreover, as a surface modifier, the well-known silane coupling agent mentioned later etc. can be used.

  In the dry method, it is preferable to agitate or mix the raw material particles and the hydrophobizing agent in the fluidized bed reactor. In the wet method, the following procedure is preferably performed. That is, the raw material particles are dispersed in a solvent to form a slurry of the raw material particles, and then a hydrophobizing agent is added to the slurry to denature (hydrophobize) the raw material particle surface. preferable. At this time, it is preferable to heat the raw material particles and the hydrophobizing agent in the range of 100 to 200 ° C. for 0.5 to 5 hours. By such heat treatment, the silanol groups on the surface of the particles used as raw materials can be effectively modified. The amount of the treatment agent (surface modifier) is not particularly limited, but is preferably 5 to 30 parts by mass, more preferably 8 to 20 parts by mass with respect to 100 parts by mass of the raw material particles.

  One or more hydrophobizing agents may be used, and known silane coupling agents, silicone oils, titanate coupling agents, aluminate coupling agents, fatty acids, fatty acid metal salts, esterified products thereof, and rosin acid. A silane coupling agent is preferable from the viewpoint of reactivity with the hydroxy group on the surface of the inorganic particles. Examples of the silane coupling agent include dimethyldimethoxysilane, hexamethyldisilazane (HMDS), methyltrimethoxysilane, isobutyltrimethoxysilane, and decyltrimethoxysilane.

In particular, the silane coupling agent preferably has a structure represented by the following general formula (1).
General formula (1): X-Si (OR) ₃
In the general formula (1), X represents an alkyl group having 4 to 12 carbon atoms. R represents a methyl group or an ethyl group.
The alkyl chain length of the silane coupling agent having the structure represented by the general formula (1) is 4 or more carbon atoms from the viewpoint of enhancing the adhesion to the toner base particles or the fatty acid metal oxide particles. It is preferable that the number of carbon atoms is 12 or less from the viewpoint of increasing the surface coverage with the silane coupling agent.

(Measurement method of degree of hydrophobicity)
The degree of hydrophobicity can be determined by measuring as follows using a powder wettability tester (WET-101P; manufactured by Reska Co., Ltd.). Hereinafter, the example which measured the hydrophobization degree of the alumina particle is demonstrated.
Under a laboratory environment, a 20-mm long stirrer chip and 60 mL of 25 ° C. ion-exchanged water are placed in a 200-mL tall beaker and set in a powder wettability tester (WET-101P; manufactured by Reska Corporation). Float 50 mg of alumina particles on ion-exchanged water, immediately set a lid and a methanol supply nozzle, and start measurement simultaneously with the start of stirrer stirring. The supply rate of methanol (methanol special grade; manufactured by Kanto Chemical Co., Inc.) is 2.0 mL / min, and the measurement time is 70 minutes. The stirring speed of the stirrer is 380 to 420 rpm. The alumina particles are initially floating at the interface of the ion exchange water, but gradually get wet with the mixed solution of the ion exchange water and methanol and disperse in the liquid as the methanol concentration increases. Thereby, the light transmittance of the liquid gradually decreases. From the obtained data, the horizontal axis shows the methanol concentration (vol%) calculated from the methanol supply (mL), and the vertical axis shows the light transmittance (voltage ratio) (%). The light transmittance is the maximum value. The methanol concentration at the middle of the minimum value is defined as the “hydrophobicity”.

(Method for producing alumina particles)
Alumina refers to aluminum oxide represented by Al ₂ O ₃ and is known to be in the form of α-type, γ-type, σ-type, and mixtures thereof. Depending on the type, there is a range from cubic to spherical.
The alumina particles can be produced by a known method. As a method for producing alumina particles, the Bayer method is generally used. However, in order to obtain high-purity and nano-sized alumina particles, a hydrolysis method (manufactured by Sumitomo Chemical), a gas phase synthesis method (manufactured by C-I Kasei), Examples include flame hydrolysis (Nippon Aerosil), underwater spark discharge (Iwatani Chemical).

The shape of the alumina particles is based on the existing thermal spraying technology, and the raw material powder is put into a high-temperature flame formed with hydrogen, natural gas, acetylene gas, propane gas, butane or other fuel gas and melted into a sphere. Can be controlled by.
The supply method when the alumina raw material powder is put into the flame may be a dry method using oxygen, air, nitrogen, argon or the like as a carrier gas, and water, methanol, ethanol or the like is used as a dispersion medium. A wet method using a slurry may be used.

  An example of the manufacturing apparatus is based on a spheroidizing furnace and a collection device connected to the furnace. The spherical alumina powder produced in the spheronization furnace is pneumatically transported by a blower or the like and collected by a collection device. It is preferable that the spheroidizing furnace main body and the transportation piping are water cooled by a water cooling jacket method. As the collection device, a cyclone, gravity sedimentation, louver, bag filter, or the like is used. The collection temperature is determined by the amount of heat generated by the amount of combustible gas and the suction amount of the blower, and the adjustment is performed by the amount of cooling water, the intake amount of outside air provided in the line, and the like.

  The shape and particle size of the alumina particles can be changed depending on the reaction conditions such as flame temperature, hydrogen or oxygen content, quality of the alumina raw material powder, residence time in the flame, or length of the agglomeration zone.

<Fatty acid metal salt particles>
The surface of the toner base particles according to the present invention contains fatty acid metal salt particles as an external additive. The number average particle diameter of the fatty acid metal salt particles is in the range of 0.4 to 2.0 μm. Since the fatty acid metal salt particles having a number average particle diameter in the range of 0.4 to 2.0 μm are easily pushed into the toner base particles and are not easily detached from the toner base particles, the effect of the present invention is effectively obtained. Inferred.
Moreover, the measuring method of the number average particle diameter of fatty acid metal salt particles can be performed by the same method as the measuring method of the number average particle diameter of the inorganic particles described above.

As the fatty acid metal salt particles, known fatty acid metal salt particles can be used, but from the viewpoint of spreadability, it is preferable to use fatty acid metal salt particles having a Mohs hardness of 2 or less. The metal of the fatty acid metal salt particles is preferably a metal selected from zinc, calcium, magnesium, aluminum, and lithium.
Moreover, as the fatty acid metal salt particles according to the present invention, it is preferable to use at least one selected from zinc stearate particles, lithium stearate particles, and calcium stearate particles. Of these, zinc stearate particles are more preferable.
Moreover, as a fatty acid of fatty acid metal salt particles, a higher fatty acid having 12 to 22 carbon atoms is preferable. When fatty acids having 12 or more carbon atoms are used, the generation of free fatty acids can be suppressed, and if the fatty acid has 22 or less carbon atoms, the melting point of the fatty acid metal salt particles does not become too high and good fixability is obtained. be able to. As the fatty acid, stearic acid is particularly preferred, and as the fatty acid metal salt particles used in the present invention, zinc stearate particles, calcium stearate particles, lithium stearate particles and magnesium stearate particles are preferred, and among these, zinc stearate More preferably, it is a particle. Two or more of these fatty acid metal salt particles may be used in combination.

<Other external additives>
As external additives for the toner according to the present invention, in addition to inorganic particles and fatty acid metal salt particles whose surface shape has a planar portion as described above, other external additives include known inorganic particles and organic particles. Particles can be used.
One or more external additives may be used, and it is particularly preferable to use two or more external additives having different particle diameters. When the particle size is different, the role as an external additive is different. Generally, the larger the diameter, the more the spacer effect is exerted and the adhesion between the toners is reduced. The smaller the particle size, the easier it is to coat the surface of the toner base particles. The fluidity can be raised. Regarding the shape, not only a spherical external additive, but also an acicular shape typified by rutile type titanium oxide, an indefinite shape, a spindle shape, and a confetti shape can be used without limitation.

Examples of the inorganic particles used for other external additives include silica particles, titanium oxide particles, alumina particles, zirconia particles, zinc oxide particles, chromium oxide particles, cerium oxide particles, antimony oxide particles, tungsten oxide particles, tin oxide. Examples include particles, tellurium oxide particles, manganese oxide particles, and boron oxide particles. Among these, particles such as silica, titanium oxide, alumina, and strontium titanate are preferable. The surface of the inorganic particles is preferably subjected to a hydrophobic treatment, and a known surface modifier is used for the hydrophobic treatment. The surface modifier may be one kind or more, and the collar has a silane coupling agent, silicone oil, titanate coupling agent, aluminate coupling agent, fatty acid, fatty acid metal salt, esterified product thereof, and the like. And rosin acid.
Examples of the silane coupling agent include dimethyldimethoxysilane, hexamethyldisilazane (HMDS), methyltrimethoxysilane, isobutyltrimethoxysilane, and decyltrimethoxysilane. Examples of the silicone oil include cyclic compounds, linear or branched organosiloxanes, and more specifically, organosiloxane oligomers, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, tetramethyl. And cyclotetrasiloxane and tetravinyltetramethylcyclotetrasiloxane.

  Examples of the organic particles used for other external additives include spherical organic particles having a number average primary particle diameter of about 10 to 2000 nm. Specifically, homopolymers such as styrene and methyl methacrylate, and organic particles of these copolymers can be used.

(Titanium oxide particles)
The toner according to the present invention contains, as an external additive, 0.10 to 0.80 mass% of titanium oxide particles having an average aspect ratio of 2 to 15, more preferably 5 to 13, determined from the number average particle diameter. It is preferable. By using titanium oxide having a high aspect ratio as described above as an external additive, the toner coverage can be increased, and since the contact area with the toner base is large, it is difficult to detach from the toner and the printing conditions are reduced. Therefore, the surface condition of the toner can be kept good.
The average aspect ratio of the titanium oxide particles can be determined using the number average major axis and minor axis (major axis / minor axis). The number average major axis and minor axis are measured by measuring the particle diameter of titanium oxide particles in an electron micrograph obtained using a scanning electron microscope (SEM) “JSM-7401F” (manufactured by JEOL Ltd.), and n = It can be determined as an average value of 20. The crystal structure of titanium oxide is preferably a rutile type. Rutile titanium oxide has a higher firing temperature and fewer surface hydroxy groups than anatase. From this, it is possible to prevent an increase in adhesion between toner particles due to moisture adsorption.

(Silica particles)
The toner according to the present invention preferably contains silica particles as an external additive.
Examples of the method for producing silica particles include a known production method, that is, a dry method such as a combustion method, an arc method, and a melting method, and a wet method such as a sedimentation method, a gel method, and a sol-gel method. Moreover, when using a silica compound, although there is no restriction | limiting in particular, it is preferable to mix and use about 3-4 types of silica compounds of a different average particle diameter. This is because the silica compound having a smaller particle size contributes to the fluidity of the toner, and the silica compound having a larger particle size plays a role of protecting the silica compound having a smaller particle size from external force. For example, a silica compound having a particle size of 5 to 18 nm, 20 to 40 nm, 70 to 90 nm, or 100 to 140 nm can be mixed and used. The mixing ratio is not particularly limited and may be appropriately adjusted and used. For example, silica compounds having different particle diameters may be used in an amount of 0.05 to 1.0% by mass with respect to the toner base particles.

<Two-component developer>
The two-component developer can be obtained by appropriately mixing the toner particles and carrier particles so that the toner particle content (toner concentration) is 4.0 to 8.0% by mass. Examples of the mixing apparatus used for the mixing include a Nauta mixer, a W cone, and a V-type mixer.

<Carrier particles>
The carrier particles according to the present invention are made of a magnetic material. Examples of the carrier particles include coated carrier particles having a carrier core (core material particles) made of the magnetic material and a carrier coat resin (coating material) layer covering the surface, and magnetic in the resin. Resin-dispersed carrier particles in which fine body powder is dispersed. The carrier particles are preferably coated carrier particles from the viewpoint of suppressing the adhesion of carrier particles to the photoreceptor.

<Carrier core (core particle)>
The core particle is composed of a magnetic material, for example, a substance that is strongly magnetized in the direction by a magnetic field. The magnetic substance may be one kind or more, and examples thereof include metals exhibiting ferromagnetism such as iron, nickel and cobalt, alloys or compounds containing these metals, and exhibit ferromagnetism by heat treatment. Alloys.

Examples of the metal exhibiting ferromagnetism or a compound containing the same include iron, ferrite represented by the following formula (a), and magnetite represented by the following formula (b). M in the following formulas (a) and (b) represents one or more monovalent or divalent metals selected from the group consisting of Mn, Fe, Ni, Co, Cu, Mg, Zn, Cd, and Li. .
Formula (a): MO · Fe ₂ O ₃
Formula (b): MFe ₂ O ₄
Examples of alloys that exhibit ferromagnetism upon heat treatment include Heusler alloys such as manganese-copper-aluminum and manganese-copper-tin, and chromium dioxide.
The core particles are preferably various ferrites. This is because the specific gravity of the coated carrier particles is smaller than the specific gravity of the metal constituting the core material particles, so that the impact force of stirring in the developing device can be further reduced.

<Carrier coat resin (coating material)>
As the coating material, a known resin used for coating the core particles of the carrier particles can be used. It is preferable that the coating material is a resin having a cycloalkyl group from the viewpoint of reducing the moisture adsorptivity of the carrier particles and increasing the adhesion of the coating layer to the core material particles. Examples of the cycloalkyl group include a cyclohexyl group, a cyclopentyl group, a cyclopropyl group, a cyclobutyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, and a cyclodecyl group. Among these, a cyclohexyl group or a cyclopentyl group is preferable, and a cyclohexyl group is more preferable from the viewpoint of adhesion between the coating layer and the ferrite particles. The weight average molecular weight Mw of the resin is, for example, 10,000 to 800,000, and more preferably 100,000 to 750000. Content of the said cycloalkyl group in the said resin is 10-90 mass%, for example. The content of the cycloalkyl group in the resin can be determined by, for example, pyrolysis-gas chromatography / mass spectrometry (Py-GC / MS), ¹ H-NMR, or the like.

[Method for producing toner for developing electrostatic latent image]
The method for producing the toner of the present invention is not particularly limited, and examples thereof include known methods such as a kneading and pulverizing method, a suspension polymerization method, an emulsion aggregation method, a dissolution suspension method, a polyester elongation method, and a dispersion polymerization method. Among these, it is preferable to employ an emulsion aggregation method from the viewpoints of particle size uniformity and shape controllability.

In addition, the emulsion aggregation method is a method in which a poor solvent is dropped into a binder resin solution dissolved in a solvent to perform phase inversion emulsification, and then the solvent is removed to obtain a resin particle dispersion. The resin particle dispersion and the colorant The dispersion liquid and a release agent dispersion liquid such as wax are mixed, aggregated until a desired toner particle diameter is obtained, and further, the shape is controlled by fusing the binder resin particles, thereby controlling the toner particles. It is a manufacturing method.
An example of a method for producing toner particles by the emulsion aggregation method is shown below. The toner particles are manufactured by performing the following steps (1) to (6).
(1) Step of preparing a dispersion liquid in which colorant particles are dispersed in an aqueous medium (2) Dispersion liquid in which binder resin particles containing an internal additive are dispersed in an aqueous medium as necessary (3) The dispersion of the colorant particles and the dispersion of the binder resin particles are mixed, and the toner base particles are formed by aggregating, associating and fusing the colorant particles and the binder resin particles. (4) The step of filtering the toner base particles from the dispersion (aqueous medium) of the toner base particles to remove the surfactant and the like (5) The step of drying the toner base particles (6) The step of removing the toner base particles from the toner base particles Step of adding an additive

(Flocculant)
Although it does not specifically limit as a flocculant which can be used at the process of (3) mentioned above, The thing selected from the salt of a metal is used suitably. For example, salts of monovalent metals such as alkali metal salts such as sodium, potassium and lithium, salts of divalent metals such as calcium, magnesium, manganese and copper, salts of trivalent metals such as iron and aluminum Specific examples of the salt include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, and manganese sulfate. A divalent metal salt is preferred. When a divalent metal salt is used, agglomeration can be promoted with a smaller amount. These may be used alone or in combination of two or more.

  The binder resin particles containing an internal additive as necessary in the above (2) may be produced to have a multilayer structure of two or more layers. For example, when producing binder resin particles having a three-layer structure, it is divided into three stages: first-stage polymerization (inner layer formation), second-stage polymerization (intermediate layer formation), and third-stage polymerization (outer layer formation). It can be produced by carrying out a polymerization reaction for synthesizing the binder resin particles. Here, in each polymerization reaction of the first stage polymerization to the third stage polymerization, binder resin particles having a three-layer structure having different compositions can be produced by changing the composition of the polymerizable monomer. Further, for example, in any of the first-stage polymerization to the third-stage polymerization, by performing a synthesis reaction of the binder resin in a state containing an appropriate internal additive such as a release agent, an appropriate internal additive is obtained. The binder resin particles having a three-layer structure can be formed.

<External processing>
For the external additive mixing process on the toner base particles, a mechanical mixing device can be used. As the mechanical mixing device, a Henschel mixer, a nauter mixer, a turbuler mixer, or the like can be used. Among these, a mixing process such as increasing the mixing time or increasing the rotational peripheral speed of the stirring blade may be performed using a mixing apparatus that can apply a shearing force to the particles to be processed, such as a Henschel mixer. When multiple types of external additives are used, all external additives are mixed with toner particles at once, or divided into multiple times according to the external additive and mixed. Also good.
The external additive is mixed using the mechanical mixing device described above to control the mixing strength, that is, the peripheral speed of the stirring blade, the mixing time, the mixing temperature, etc. Can be controlled.

[Image forming method]
The toner for developing an electrostatic latent image of the present invention can be suitably applied to an image forming method including a step of charging the surface of a photoconductor with a charging roller provided so as to be in contact with the photoconductor. In an image forming method including a step of charging the surface of a photoreceptor with a charging roller, the lubricant on the surface of the photoreceptor is generally easily decomposed and an image density difference is likely to increase. The image density difference can be reduced.
Hereinafter, an example of a suitable electrophotographic image forming method performed using the toner for developing an electrostatic latent image of the present invention will be described using the image forming apparatus shown in FIG. The electrophotographic image forming method forms an image on a substrate using the electrostatic latent image developing toner of the present invention. Specifically, it is an electrophotographic image forming method having at least a charging step, an exposure step, a developing step, and a transfer step. In the transfer step, an intermediate transfer member is formed on the electrostatic latent image carrier (photosensitive drum 413). It is preferable to have a primary transfer step of transferring a toner image onto the (intermediate transfer belt 421) and a secondary transfer step of transferring the toner image on the intermediate transfer member onto a transfer material (paper S).

  An image forming apparatus 100 illustrated in FIG. 1 includes an image reading unit 110, an image processing unit 30, an image forming unit 40, a paper transport unit 50, a fixing device 60, and the like.

  The image forming unit 40 includes image forming units 41Y, 41M, 41C, and 41K that form images of toners of Y (yellow), M (magenta), C (cyan), and K (black). Since these have the same configuration except for the toner to be accommodated, the symbols representing the colors may be omitted hereinafter. The image forming unit 40 further includes an intermediate transfer unit 42 and a secondary transfer unit 43. These correspond to a transfer device.

The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413, a charging device 414, and a drum cleaning device 415.
The photoreceptor drum 413 is, for example, a negatively charged organic photoreceptor. The surface of the photosensitive drum 413 has photoconductivity. The photoconductor drum 413 corresponds to a photoconductor.

The charging device 414 is preferably a charging roller type in which the surface of the photosensitive drum 413 is charged by a charging roller provided so as to be in contact with the photosensitive drum 413. In image formation using a charging roller system, the lubricant on the surface of the photoreceptor is generally easily decomposed, and the difference in image density tends to increase. However, if the toner for developing an electrostatic latent image of the present invention is used, the difference in image density is suppressed. be able to. The charging device 414 may be a contact charging device in which a contact charging member such as a corona charger, a charging brush, or a charging blade is brought into contact with the photosensitive drum 413 to be charged.
The exposure device 411 includes, for example, a semiconductor laser as a light source, and a light deflection device (polygon motor) that irradiates the photosensitive drum 413 with laser light corresponding to an image to be formed.

  The developing device 412 is a two-component developing type developing device. The developing device 412 includes, for example, a developing container that contains a two-component developer, a developing roller (magnetic roller) that is rotatably disposed in an opening of the developing container, and a developing container that allows the two-component developer to communicate with each other. A partition partitioning the inside, a transport roller for transporting the two-component developer on the opening side of the developing container toward the developing roller, and an agitation roller for stirring the two-component developer in the developing container . The developer container contains the toner as a two-component developer.

  The intermediate transfer unit 42 includes a primary transfer roller 422 that presses the intermediate transfer belt 421 against the photosensitive drum 413, a plurality of support rollers 423 including a backup roller 423A, and a belt cleaning device 426. The intermediate transfer belt 421 is looped around the plurality of support rollers 423. When at least one drive roller of the plurality of support rollers 423 rotates, the intermediate transfer belt 421 travels at a constant speed in the arrow A direction.

  The secondary transfer unit 43 has a plurality of support rollers 431 including an endless secondary transfer belt 432 and a secondary transfer roller 431A. The secondary transfer belt 432 is stretched in a loop by a secondary transfer roller 431A and a support roller 431.

  The fixing device 60 fixes, for example, the fixing roller 62, an endless heating belt 63 that covers the outer peripheral surface of the fixing roller 62, and heats and melts the toner constituting the toner image on the paper S, and the paper S. And a pressure roller 64 that presses toward the roller 62 and the heat generating belt 63.

  The image forming apparatus 100 further includes an image reading unit 110, an image processing unit 30, and a paper transport unit 50. The image reading unit 110 includes a paper feeding device 111 and a scanner 112. The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, and a transport path unit 53. In the three paper feed tray units 51a to 51c constituting the paper feed unit 51, paper S (standard paper, special paper) identified based on basis weight, size, or the like is stored for each preset type. . The conveyance path unit 53 includes a plurality of conveyance roller pairs such as registration roller pairs 53a.

An example of an image forming method by the image forming apparatus 100 will be described.
The scanner 112 optically scans and reads the document D on the contact glass. Reflected light from the document D is read by the CCD sensor 112a and becomes input image data. The input image data is subjected to predetermined image processing in the image processing unit 30 and sent to the exposure device 411.

  The photosensitive drum 413 rotates at a constant peripheral speed. The charging device 414 uniformly charges the surface of the photosensitive drum 413 to a negative polarity. In the exposure apparatus 411, the polygon mirror of the polygon motor rotates at high speed, and the laser beam corresponding to the input image data of each color component is developed along the axial direction of the photosensitive drum 413, and the photosensitive member along the axial direction. The drum 413 is irradiated on the outer peripheral surface. Thus, an electrostatic latent image is formed on the surface of the photosensitive drum 413.

  In the developing device 412, the toner particles are charged by stirring and transporting the two-component developer in the developing container, and the two-component developer is transported to the developing roller, and forms a magnetic brush on the surface of the developing roller. The charged toner particles are electrostatically attached to the electrostatic latent image portion on the photosensitive drum 413 from the magnetic brush. In this way, the electrostatic latent image on the surface of the photosensitive drum 413 is visualized, and a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum 413.

  The toner image on the surface of the photosensitive drum 413 is transferred to the intermediate transfer belt 421 by the intermediate transfer unit 42. Transfer residual toner remaining on the surface of the photosensitive drum 413 after the transfer is removed by a drum cleaning device 415 having a drum cleaning blade that is in sliding contact with the surface of the photosensitive drum 413.

  When the intermediate transfer belt 421 is pressed against the photosensitive drum 413 by the primary transfer roller 422, a primary transfer nip is formed for each photosensitive drum by the photosensitive drum 413 and the intermediate transfer belt 421. In the primary transfer nip, the toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 421.

  On the other hand, the secondary transfer roller 431A is pressed against the backup roller 423A via the intermediate transfer belt 421 and the secondary transfer belt 432. Accordingly, a secondary transfer nip is formed by the intermediate transfer belt 421 and the secondary transfer belt 432. The sheet S passes through the secondary transfer nip. The sheet S is conveyed to the secondary transfer nip by the sheet conveying unit 50. The correction of the inclination of the sheet S and the adjustment of the conveyance timing are performed by a registration roller unit in which the registration roller pair 53a is provided.

  When the sheet S is conveyed to the secondary transfer nip, a transfer bias is applied to the secondary transfer roller 431A. By applying the transfer bias, the toner image carried on the intermediate transfer belt 421 is transferred onto the paper S. The sheet S on which the toner image is transferred is conveyed toward the fixing device 60 by the secondary transfer belt 432.

  The fixing device 60 forms a fixing nip by the heat generating belt 63 and the pressure roller 64, and heats and presses the conveyed paper S at the fixing nip portion. The toner particles constituting the toner image on the paper S are heated, and the crystalline resin melts quickly in the inside thereof. As a result, the entire toner particles are quickly melted with a relatively small amount of heat, and the toner component is transferred to the paper S. Adhere to. Thus, the toner image is quickly fixed on the paper S with a relatively small amount of heat. The paper S on which the toner image has been fixed is discharged out of the apparatus by a paper discharge unit 52 having a paper discharge roller 52a. Thus, a high-quality image is formed.

  Note that transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer is removed by a belt cleaning device 426 having a belt cleaning blade that is in sliding contact with the surface of the intermediate transfer belt 421.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[Preparation of Colorant Particle Dispersion 1]
11.5 parts by mass of sodium n-dodecyl sulfate was dissolved in 160 parts by mass of ion-exchanged water. Next, 24.5 parts by mass of copper phthalocyanine was gradually added to the solution while stirring the solution. Subsequently, the colorant particle dispersion liquid 1 having a volume-based median diameter of 126 nm is obtained by carrying out a dispersion treatment using a stirrer “Clearmix W Motion CLM-0.8” (manufactured by M Technique Co., Ltd.). Prepared.

[Preparation of binder resin particle dispersion 1]
(1) First-stage polymerization Into a reaction vessel equipped with a stirrer, temperature sensor, cooling pipe and nitrogen introducing device, 4 parts by mass of polyoxyethylene (2) sodium dodecyl ether sulfate and 3000 parts by mass of ion-exchanged water are charged, and nitrogen is added. The internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under an air flow. After raising the temperature, 10 parts by mass of potassium persulfate dissolved in 200 parts by mass of ion-exchanged water was added to the reaction vessel. Next, the liquid temperature in the reaction vessel is 75 ° C.,
-Styrene 584 parts by mass-N-butyl acrylate 160 parts by mass-A monomer mixture consisting of 56 parts by mass of methacrylic acid is added dropwise over 1 hour, followed by polymerization while heating and stirring at 75 ° C for 2 hours. Thus, a dispersion of resin particles [1] was prepared.

(2) Second-stage polymerization 2 parts by mass of polyoxyethylene (2) sodium dodecyl ether sulfate was dissolved in 3000 parts by mass of ion-exchanged water in a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe and a nitrogen introducing device. The solution was charged and heated to 80 ° C. Next, 42 parts by mass of the resin particles [1] (in terms of solid content) and 70 parts by mass of microcrystalline wax “HNP-0190” (manufactured by Nippon Seiwa Co., Ltd.)
・ Styrene 239 parts by mass ・ N-butyl acrylate 111 parts by mass ・ Methacrylic acid 26 parts by mass ・ n-octyl mercaptan 3 parts by mass A solution dissolved at 80 ° C. was added to the circulation route. A dispersion liquid containing emulsified particles (oil droplets) was prepared by mixing and dispersing for 1 hour using a mechanical disperser “CLEARMIX” (manufactured by M Technique Co., Ltd.).
Next, an initiator solution in which 5 parts by mass of potassium persulfate is dissolved in 100 parts by mass of ion-exchanged water is added to this dispersion, and this system is heated and stirred at 80 ° C. for 1 hour to perform polymerization. A dispersion of resin particles [2] was prepared.

(3) Third-stage polymerization Further, a solution obtained by dissolving 10 parts by mass of potassium persulfate in 200 parts by mass of ion-exchanged water is added to the dispersion of the resin particles [2], and the temperature is set to 80 ° C. ,
-Styrene 380 mass parts-N-butyl acrylate 132 mass parts-Methacrylic acid 39 mass parts-n-octyl mercaptan 6 mass parts monomer mixture liquid was dripped over 1 hour. After completion of the dropwise addition, polymerization was carried out by heating and stirring for 2 hours, and then cooled to 28 ° C. to obtain a binder resin particle dispersion 1.

[Synthesis of Crystalline Resin Particles 1]
As a material for the polyester polymerization segment, 220 parts by mass of sebacic acid (molecular weight 202.25) as a polyvalent carboxylic acid compound and 298 parts by mass of 1,12-dodecanediol (molecular weight 202.33) as a polyhydric alcohol compound were introduced into nitrogen. It put into the reaction container equipped with the pipe | tube, the dehydration pipe | tube, the stirrer, and the thermocouple, and it heated at 160 degreeC and made it melt | dissolve. Thereafter, 2.5 parts by mass of tin (II) 2-ethylhexanoate and 0.2 parts by mass of gallic acid were added, the temperature was raised to 210 ° C., and the reaction was performed for 8 hours. Furthermore, reaction was performed at 8.3 kPa for 1 hour to obtain crystalline resin particles 1.
The obtained crystalline resin particles 1 were obtained by using a differential scanning calorimeter “Diamond DSC” (manufactured by PerkinElmer Co., Ltd.) to obtain a DSC curve under the condition of a heating rate of 10 ° C./min. The melting point (Tm) measured by the method of measuring the endothermic peak top temperature was 82.8 ° C., and the molecular weight was measured by GPC “HLC-8120GPC” (manufactured by Tosoh Corporation). The molecular weight Mw was 28000.

[Preparation of crystalline resin particle dispersion 1]
The crystalline resin particles 1 were dissolved in 100 parts by mass and 400 parts by mass of ethyl acetate. Subsequently, 25 mass parts of 5.0 mass% sodium hydroxide aqueous solution was added, and the resin solution was prepared. This resin solution was put into a container having a stirring device, and 638 parts by mass of a 0.26% by mass aqueous sodium lauryl sulfate solution was dropped and mixed over 30 minutes while stirring the resin solution. During the dropwise addition of the aqueous sodium lauryl sulfate solution, the liquid in the reaction vessel became cloudy. Further, after the entire amount of the aqueous sodium lauryl sulfate solution was dropped, an emulsion was prepared in which the resin solution particles were uniformly dispersed. Next, the emulsion is heated to 40 ° C., and ethyl acetate is distilled off under a reduced pressure of 150 hPa using a diaphragm vacuum pump “V-700” (manufactured by BUCHI). A crystalline resin particle dispersion 1 was obtained.

[Preparation of toner base particles 1]
(Aggregation / fusion process)
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing device, 300 parts by mass (in terms of solid content) of a dispersion of the binder resin particle dispersion 1 and a dispersion 60 of the crystalline resin particle dispersion 1 are obtained. After 5 parts by mass (solid content conversion), 1100 parts by mass of ion-exchanged water, and 40 parts by mass (converted to solid content) of the colorant particle dispersion 1, the liquid temperature was adjusted to 30 ° C. A sodium aqueous solution was added to adjust the pH to 10. Next, an aqueous solution in which 60 parts by mass of magnesium chloride was dissolved in 60 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. The temperature was raised after holding for 3 minutes, and the temperature of the system was raised to 85 ° C. over 60 minutes, agglomerating while maintaining 85 ° C., and the particle growth reaction was continued. In this state, the particle size of the aggregated particles was measured with “Coulter Multisizer 3” (manufactured by Beckman Coulter), and when the volume-based median diameter reached 6.5 μm, 40 parts by mass of sodium chloride was ionized. An aqueous solution dissolved in 160 parts by mass of the exchange water is added to stop the particle growth, and further, the fusion between the particles proceeds by heating and stirring at a liquid temperature of 80 ° C. for 1 hour as a ripening step. A dispersion of toner base particles 1 was prepared.

(Washing / drying process)
The produced dispersion of toner base particles 1 was subjected to solid-liquid separation with a basket-type centrifuge “MARK III model number 60 × 40 + M” (manufactured by Matsumoto Machinery Co., Ltd.) to form a wet cake of toner base particles 1. The wet cake was washed with ion exchange water at 40 ° C. until the electric conductivity of the filtrate reached 5 μS / cm with the basket-type centrifuge, and then transferred to “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.) The toner base particles 1 were produced by drying until the water content reached 0.5% by mass.

The content of the crystalline resin in the toner base particles 1 obtained by the above method is 15% by mass, and this value can be calculated by the following formula. In addition, the mass of each material is the value converted into solid content.
Content of crystalline resin in toner base particles (mass%) = crystalline resin amount / (styrene-acrylic resin amount + crystalline resin amount + colorant amount) × 100
Similarly, styrene-acrylic resin content (mass%) is calculated by the following formula. The mass of each material is a value in terms of solid content.
Styrene-acrylic resin content (mass%) in toner base particles = styrene-acrylic resin amount / (styrene-acrylic resin amount + crystalline resin amount + colorant amount) × 100
For example, in the case of toner base particles 1, the crystalline resin content is
60 / (300 + 60 + 40) × 100 = 15%
Styrene-acrylic resin content is
300 / (300 + 60 + 40) × 100 = 75%
Can be calculated respectively.

[External additive addition process]
(Production of toners 1 to 21)
Each inorganic particle described in Table I and Table II is added to toner base particle 1, and the blade tip peripheral speed is 40 m / s using Henschel mixer model “FM20C / I” (manufactured by Nippon Coke Industries, Ltd.). In this manner, the number of rotations of the stirring blade was set, and stirring was performed for 20 minutes to prepare toners 1 to 21 shown in Table III. The amount of each external additive particle added was 0.50 parts by mass of inorganic particles (see Table I) and 0.20 parts by mass of fatty acid metal salt particles (see Table II) with respect to the toner base particles 1. . In addition, the temperature of the mixed powder at the time of external additive mixing was set to be 40 ° C. ± 1 ° C.
In the “presence / absence of a planar portion of the surface shape” described in Table I, the flatness defined in JIS B 0621-1984 (maximum value and minimum value measured when sandwiched between two straight lines parallel to the reference surface) When a portion where the difference in the values is 0 nm or more and 1/10 nm or less of the number average particle diameter of the inorganic particles is a planar portion, the planar portion is 1/6 or more of the number average surface area of the inorganic particles. The thing is described as “present” as “the surface shape has a planar portion”.
Moreover, the silane coupling agent described in Table I is a surface modifier for inorganic particles. X in the structure of the silane coupling agent represents the carbon number of the alkyl group of X in the following general formula (1). Moreover, R of the structure of a silane coupling agent represents the kind of substituent represented by R in following General formula (1).
General formula (1): X-Si (OR) ₃
In addition, inorganic particles No. 1 shown in Table I were used. 6 is surface-modified with HMDS (hexamethyldisilazane). In addition, inorganic particles No. 1 shown in Table I were used. 7 and no. 9 is surface-modified with PDMS (polydimethylsiloxane).

(Measurement method of number average particle diameter)
The number average particle diameter of the inorganic particles and the fatty acid metal salt particles described later was measured by the following method.
Using a scanning electron microscope (SEM) “JSM-7401F” (manufactured by JEOL Ltd.), an SEM photograph magnified 50,000 times was taken, and the SEM photograph was taken as an image processing analyzer “LUZEX AP” (manufactured by Nireco). ), The ferret diameter in the horizontal direction for 100 particles was calculated, and the average value was taken as the number average particle diameter.

[Preparation of developers 1 to 21]
A ferrite carrier having a volume average particle diameter of 60 μm was added to the toners 1 to 21 to obtain a two-component developer. Here, by adjusting the addition amount of the ferrite carrier, the toner content (toner concentration) in the two-component developer was set to 7% by mass. Then, it mixed for 30 minutes with the V-type mixer, and obtained the two-component developers 1-21 corresponding to each.

[Evaluation]
Using the toners 1 to 21 corresponding to the developers 1 to 21 obtained as described above, an electrophotographic image was formed by the following method and evaluated.

Using a commercially available color multifunction peripheral “bizhub C754” (manufactured by Konica Minolta), a test image on high-quality paper (65 g / m ² ) of A4 size in a normal temperature and humidity environment (temperature 20 ° C., humidity 50% RH). As a result, 10,000 images were continuously printed in which the right half of the image was vertically divided into two (image portion) and the left half was white (non-image portion). Thereafter, a full solid image is output, and the density of the five points corresponding to the image portion (right half) and the five points corresponding to the non-image portion (left half) at the time of printing 10,000 sheets is determined as a Macbeth reflection densitometer. Measurement was performed with “RD907” (manufactured by Macbeth). Then, the maximum image density difference was calculated by the following equation.
Maximum density difference = (“Image density at the point where the image density is the highest among the five image densities of the part corresponding to the belt part during durability” − “Image density of the part corresponding to the non-band part”)
Based on the calculated maximum image density difference, 0.10 or less was determined to be practical according to the following criteria, and the result was accepted. The image density is an absolute density.

A: Maximum density difference is 0.03 or less. O: Maximum density difference is larger than 0.03 and 0.06 or less. Δ: Maximum density difference is larger than 0.06 and 0.10 or less. X: Maximum density difference is from 0.10. large

<Summary>
From the results shown in Table III above, it has been found that when an image is formed using the electrostatic latent image developing toner according to the present invention, a density difference hardly occurs in the output image. This is considered to be because the difference in the density of the lubricant on the surface of the photoconductor is small, so that the density difference between the image area and the non-image area can be reduced.
On the other hand, when an image was formed using the electrostatic latent image developing toner according to the comparative example, the density difference of the output image was large. This is probably because the difference in the density of the lubricant on the surface of the photoreceptor is large, and thus the density difference between the image area and the non-image area is large.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 30 Image processing part 40 Image forming part 50 Paper conveyance part 60 Fixing apparatus 411 Exposure apparatus 412 Developing apparatus 413 Photosensitive drum 414 Charging apparatus 42 Intermediate transfer unit 421 Intermediate transfer belt (intermediate transfer body)
110 Image reading unit

Claims (6)

An electrostatic latent image developing toner containing toner base particles having an external additive on the surface,
The external additive contains inorganic particles and fatty acid metal salt particles,
The number average particle diameter of the inorganic particles is in the range of 10 to 50 nm,
The surface shape of the inorganic particles has a planar portion, and
The toner for developing an electrostatic latent image, wherein the number average particle diameter of the fatty acid metal salt particles is in a range of 0.4 to 2.0 μm.   The electrostatic latent image developing toner according to claim 1, wherein the inorganic particles are alumina particles.   3. The electrostatic latent image developing toner according to claim 1, wherein the fatty acid metal salt particles are at least one selected from zinc stearate particles, lithium stearate particles, and calcium stearate particles. .   The electrostatic latent image developing toner according to claim 1, wherein the fatty acid metal salt particles are zinc stearate particles. The inorganic particles are surface-modified with a silane coupling agent,
The toner for developing an electrostatic latent image according to any one of claims 1 to 4, wherein the silane coupling agent has a structure represented by the following general formula (1).
General formula (1): X-Si (OR) ₃
[In said general formula (1), X represents a C4-C12 alkyl group. R represents a methyl group or an ethyl group. ]   The image forming method using the electrostatic latent image developing toner according to claim 1, further comprising a step of charging the surface of the photoconductor with a charging roller provided so as to be in contact with the photoconductor. Method.

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