JP2012032692A - Production method of toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of toner that can form an image with suppressed image blur.SOLUTION: The production method of toner includes steps of: preparing a hindered phenol compound solution by dissolving a hindered phenol compound in an organic solvent; preparing an aqueous dispersion liquid of the hindered phenol compound solution in which droplets of the hindered phenol compound solution are dispersed; preparing an aqueous dispersion liquid of hindered phenol compound fine particles in which fine particles of the hindered phenol compound having a median diameter of 50 to 500 nm on a volume basis is dispersed, by removing the organic solvent from the aqueous dispersion liquid of the hindered phenol compound by distillation; preparing a dispersion liquid of binder resin particles; preparing a dispersion liquid of colorant particles; and forming toner particles by aggregating the binder resin particles and the colorant particles to form aggregated particles, adding the aqueous dispersion liquid of the hindered phenol compound fine particles thereto, followed by aggregating and fusing the aggregated particles and the hindered phenol compound fine particles.

Description

  The present invention relates to a method for producing toner used for electrophotographic image formation.

  In an image forming apparatus used for electrophotographic image formation, a charging step for uniformly charging the surface of a cylindrical photosensitive member by a charging unit, and exposing the surface of the photosensitive member according to image information by an exposing unit. Performing an exposure process for forming an electrostatic latent image, developing the electrostatic latent image with a developer containing toner by a developing means to form a toner image, and converting the toner image into an image such as paper An image is formed on the image support by performing a transfer step of forming an image by transferring it to the support. Then, after the transfer process, a cleaning process is performed in which the toner remaining on the surface of the photoconductor is removed by a cleaning unit, and the photoconductor is used for the next image formation. That is, a series of processes such as a charging process, an exposure process, a developing process, a transfer process, and a cleaning process are repeatedly performed on the surface of the photoreceptor.

In general, in the charging process, ozone and nitrogen oxides are generated on the surface of the photoconductor. Also in the transfer process, ozone and nitrogen are generated due to peeling discharge when the charge amount of the toner is large. It is said that oxides are generated.
Such ozone and nitrogen oxides cause not only environmental hygiene problems, but also causes deterioration of the surface of the photoreceptor, and further causes image defects such as image blurring and image flow. In particular, when an image is formed in a high-temperature and high-humidity environment, an image defect due to image blur occurs remarkably. This is because ozone and nitrogen oxides generated on the surface of the photoconductor are combined with moisture in the environmental atmosphere, so that the electrical resistance of the surface of the photoconductor is reduced and it becomes difficult to hold the charge on the photoconductor. Therefore, it is considered that image blur occurs.

Therefore, in order to solve such problems, there are a method for adding an antioxidant such as a hindered phenol compound to the photoreceptor and a method for adding or externally adding an antioxidant such as a hindered phenol compound to the toner. Known (see, for example, Patent Document 1 and Patent Document 2).
However, depending on the method of adding a hindered phenol compound as an antioxidant to the photoreceptor, there is a problem that the photoreceptor becomes brittle and the surface of the photoreceptor is worn and high durability cannot be obtained. Further, even when a hindered phenol compound is internally or externally added as an antioxidant to the toner, the particle size of the hindered phenol compound powder is generally 20 to 40 μm, so that it is kneaded with the binder resin. As a result, it is not easy to uniformly disperse the hindered phenolic compound in the toner, so that its antioxidant effect cannot be sufficiently obtained, and the toner itself is oxidized when left for a long period of time. There is a problem that the charging property is affected by the action.

  On the other hand, in order to improve the fading and light resistance of the colorant, a technique for incorporating an antioxidant into the colorant in the toner has been disclosed (for example, see Patent Document 3). However, since it is necessary to contain an antioxidant for each colorant, there is a problem that the production facility is enlarged, and there is a problem that productivity is lowered due to an increase in the number of steps.

JP 2001-222134 A Japanese Unexamined Patent Publication No. 1-173061 JP 2007-212615 A

  The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to suppress the deterioration of the surface of the photoconductor, and to image images such as image blurring even in a high temperature and high humidity environment. An object of the present invention is to provide a toner manufacturing method in which the occurrence of defects is suppressed and a high-quality image can be formed.

The method for producing a toner of the present invention is a method for producing a toner comprising toner particles containing at least a binder resin, a colorant, and a hindered phenol compound.
A step (A) of preparing a hindered phenol compound solution by dissolving a hindered phenol compound in an organic solvent;
A step (B) of mixing the hindered phenolic compound solution with an aqueous medium, and preparing a hindered phenolic compound solution aqueous dispersion in which droplets of the hindered phenolic compound solution are dispersed in the aqueous medium; ,
The hindered phenolic compound fine particles are obtained by distilling off the organic solvent from the aqueous dispersion of the hindered phenolic compound solution and dispersing fine particles of a hindered phenolic compound having a dispersion diameter of 50 to 500 nm in terms of volume-based median diameter. A step (C) of preparing an aqueous dispersion;
A step (D) of preparing a binder resin particle dispersion in which binder resin particles are dispersed in an aqueous medium;
A step (E) of preparing a colorant particle dispersion in which colorant particles are dispersed in an aqueous medium;
The binder resin particle dispersion and the colorant particle dispersion are mixed, the binder resin particles and the colorant particles are aggregated to form aggregated particles, and then the hindered phenol compound fine particle aqueous dispersion And (F) forming a toner particle by adding a liquid to agglomerate and fuse the agglomerated particles and hindered phenol compound fine particles.

  In this toner production method, it is preferable to use a copolymer of styrene, (meth) acrylic acid ester or (meth) acrylic acid as the binder resin in the step (D).

  According to the method for producing a toner of the present invention, fine particles of a hindered phenol compound (hereinafter referred to as “hindered phenol fine particle dispersion”) in the hindered phenol compound fine particle aqueous dispersion (hereinafter also referred to as “hindered phenol fine particle dispersion”) in the step (C). In the step (F), the hindered phenol fine particles are contained or held in a state of high dispersibility in the step (F). As the toner particles are formed, oxidizing substances such as ozone and nitrogen oxides generated on the surface of the photoreceptor are removed or reduced. Therefore, even in a high-temperature and high-humidity environment, image blurring or the like may occur. Occurrence of image defects is suppressed, and a toner capable of forming a high-quality image is obtained.

  Further, according to the method for producing a toner of the present invention, since the generated ozone and nitrogen oxides are removed or reduced without containing an antioxidant such as a hindered phenol compound in the photoreceptor itself, The occurrence of image defects such as image blurring can be suppressed without impairing the expected durability of the photoreceptor, and a toner capable of forming a high-quality image can be obtained.

  Furthermore, according to the method for producing a toner of the present invention, since the hindered phenol fine particles are contained or held in the toner particles in a highly dispersible state to form the toner particles, the toner particles themselves are prevented from being oxidized. As a result, the desired chargeability is maintained, resulting in the stable formation of high-quality images over a long period of time, and the formation of images with excellent light resistance. A toner that can be obtained is obtained.

  Hereinafter, the present invention will be described in detail.

[Toner Production Method]
The method for producing a toner of the present invention is a method for producing a toner comprising toner particles containing at least a binder resin, a colorant and a hindered phenol compound, and includes the following steps (A) to (H). It is a method to have. In the toner production method of the present invention, for example, an emulsion polymerization aggregation method or a suspension polymerization method can be used.

Step (A): Step of preparing a hindered phenolic compound solution by dissolving a hindered phenolic compound in an organic solvent Step (B): Mixing the hindered phenolic compound solution and the aqueous medium, Step of preparing hindered phenolic compound solution aqueous dispersion in which droplets of hindered phenolic compound solution are dispersed Step (C): Disperse by distilling off organic solvent from hindered phenolic compound solution aqueous dispersion A step of preparing a hindered phenol fine particle dispersion in which hindered phenol fine particles having a diameter of 50 to 500 nm as a volume-based median diameter are dispersed Step (D): a result of binding resin particles dispersed in an aqueous medium Step of preparing a colored resin particle dispersion Step (E): A colorant particle dispersion in which colorant particles are dispersed in an aqueous medium. Step of preparing Step (F): The binder resin particle dispersion and the colorant particle dispersion are mixed, and the binder resin particles and the colorant particles are aggregated to form aggregated particles, and then the hindered phenol fine particles are dispersed. A step of adding toner and aggregating and fusing the agglomerated particles and the hindered phenol fine particles to form toner particles Step (G): separating the toner particles from the toner particle dispersion (aqueous medium) and filtering the toner Step of removing surfactant and the like from particles Step (H): Step of drying washed toner particles The following step (I) can be added as necessary.
Step (I): Step of adding an external additive to the dried toner particles

  By preparing the hindered phenol fine particle dispersion through the steps (A) to (C), the hindered phenol fine particles dispersed in the hindered phenol fine particle dispersion have a small particle size and a particle size distribution. Becomes sharp.

  In the present invention, the “aqueous medium” refers to a medium comprising 50 to 100% by mass of water and 0 to 50% by mass of a water-soluble organic solvent. Examples of the water-soluble organic solvent include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran.

[Process (A)]
In this step (A), the liquid temperature when the hindered phenol-based compound is dissolved in the organic solvent is preferably about 40 ° C. Further, the concentration of the hindered phenol compound in the hindered phenol compound solution is not particularly limited as long as the hindered phenol compound is dissolved, but it is preferably 5 to 10% by mass.

  Examples of the organic solvent used in the step (A) include toluene, hexane, cyclohexane, 2-butanone, ethyl acetate and the like.

(Hindered phenolic compounds)
In the present invention, the hindered phenol compound refers to a compound having one or more t-butyl groups in the ortho position with respect to the hydroxyl group of the phenol compound and a derivative thereof, and includes a group represented by the following general formula (1). The compound which has. The hindered phenol compound may have an organic group in addition to the hydroxyl group of the phenol compound and the t-butyl group at the ortho position.

[In the said General formula (1), R < ¹ > and R < ² > shows a hydrogen atom or an organic group. ]

In the said General formula (1), it is preferable that any ^one of R < ¹ > and R < ² > is a t-butyl group.

  Specific examples of the hindered phenol compound in the toner production method of the present invention include those represented by the following formulas (A-1) to (A-11).

[Process (B)]
In this process (B), the hindered phenolic compound solution is added to the aqueous medium while stirring, or the aqueous medium is added to the hindered phenolic compound solution for phase inversion emulsification. It is preferable to prepare a phenol compound solution aqueous dispersion. Specifically, a method of preparing an aqueous dispersion of a hindered phenolic compound solution by phase inversion emulsification includes dissolving or dispersing a surfactant in a hindered phenolic compound solution, adding an aqueous medium, and adding water-in-oil droplets. In this method, an emulsion (W / O type) is obtained, and the continuous phase changes from the oil phase to the aqueous phase (phase inversion) during the emulsification to obtain an oil-in-water emulsion (O / W type).

[Process (C)]
In this step (C), it is preferable to prepare a hindered phenol fine particle dispersion using a rotary evaporator under reduced pressure, for example.

In the obtained hindered phenol fine particle dispersion, the hindered phenol fine particle has a volume-based median diameter of 50 to 500 nm, more preferably 100 to 300 nm.
When the dispersion diameter of the hindered phenol fine particles is less than 50 nm, the resulting toner has a low degree of hydrophobicity, and image defects such as image blur cannot be sufficiently suppressed. On the other hand, when the dispersion diameter of the hindered phenol fine particles exceeds 500 nm, the hindered phenol fine particles are aggregated and the resulting toner does not have good dispersibility with respect to the toner particles of the hindered phenol fine particles.

In the present invention, the dispersion diameter of the hindered phenol fine particles is measured using “UPA-150” (manufactured by Nikkiso Co., Ltd.).
Specifically, a few drops of a hindered phenol fine particle dispersion is dropped into a 50 ml graduated cylinder, added with 25 ml of pure water, and dispersed for 3 minutes using an ultrasonic cleaner “US-1” (manufactured by asone). A measurement sample was prepared, 3 ml of this measurement sample was put into “UPA-150” (manufactured by Nikkiso Co., Ltd.), and it was confirmed that the value of Sample Loading was in the range of 0.1 to 100. Measured by
-Measurement conditions-
Transparency (transparency): Yes
Refractive Index (refractive index): 1.59
Particle Density (particle specific gravity): 1.05 / cm ³
Spherical Particulate (spherical particles): Yes
-Solvent conditions-
Refractive Index (refractive index): 1.33
Viscosity:
High (temp) 0.797 × 10 ⁻³ Pa · S
Low (temp) 1.002 × 10 ⁻³ Pa · S

[Process (D)]
In this step (D), the binder resin particles in the binder resin particle dispersion are preferably formed by an emulsion polymerization method. In this emulsion polymerization method, a polymerizable monomer for forming a binder resin is dispersed in an aqueous medium to form emulsion particles (oil droplets), and then a polymerization initiator is added to the polymerizable monomer. By polymerizing, binder resin particles are formed.

The glass transition point of the binder resin particles is preferably 28 to 55 ° C, more preferably 38 to 50 ° C.
The glass transition point of the binder resin particles is measured using a differential scanning calorimeter “Diamond DSC” (manufactured by Perkin Elmer).
Specifically, 4.5 mg of a measurement sample (binder resin particles) is precisely weighed to two digits after the decimal point, sealed in an aluminum pan, and set in a sample holder. For the reference, an empty aluminum pan was used, and heat-cool-heat temperature control was performed at a measurement temperature of 0 to 200 ° C., a temperature increase rate of 10 ° C./min, and a temperature decrease rate of 10 ° C./min. Analysis is performed based on the data in Heat. The glass transition point is the value of the intersection of the baseline extension before the first endothermic peak rises and the tangent line that shows the maximum slope between the first endothermic peak rising portion and the peak apex.

(Polymerization initiator)
As a polymerization initiator used in the step (D), any suitable water-soluble polymerization initiator can be used. Specific examples of the polymerization initiator include persulfates (potassium persulfate, ammonium persulfate, etc.), azo compounds (4,4′-azobis-4-cyanovaleric acid and its salts, 2,2′-azobis (2 -Amidinopropane) salts), peroxide compounds and the like.

(Chain transfer agent)
In the step (D), a generally used chain transfer agent can be used for the purpose of adjusting the molecular weight of the binder resin. The chain transfer agent is not particularly limited, and examples thereof include mercaptans such as 2-chloroethanol, octyl mercaptan, dodecyl mercaptan, and t-dodecyl mercaptan, and styrene dimers.

  The binder resin particles may have a structure of two or more layers made of resins having different compositions. In this case, the resin particle dispersion prepared by emulsion polymerization treatment (first-stage polymerization) according to a conventional method is used. A method of adding a polymerization initiator and a polymerizable monomer and polymerizing this system (second stage polymerization) can be employed.

(Binder resin)
The binder resin used in the toner production method of the present invention is not particularly limited, and a known resin can be used.
Examples of the polymerizable monomer that should form the binder resin include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2, Styrene such as 4-dimethyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, or the like Styrene derivatives; 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, meta It can be mentioned acrylonitrile, methacrylonitrile, vinyl monomers such as acrylic acid or methacrylic acid derivatives such as acrylamide; diethylaminoethyl acrylic acid, methacrylic acid ester derivatives such as dimethylaminoethyl methacrylate. These vinyl monomers can be used alone or in combination of two or more.

Further, it is preferable to use a combination of the polymerizable monomer having an ionic dissociation group as the polymerizable monomer for forming the binder resin. The polymerizable monomer having an ionic dissociation group has, for example, a substituent such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group as a constituent group, and specifically includes acrylic acid, methacrylic acid, maleic acid. Acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrenesulfonic acid, allylsulfosuccinic acid, 2-acrylamido-2-methylpropanesulfonic acid, acid phosphooxyethyl methacrylate And 3-chloro-2-acid phosphooxypropyl methacrylate.
Furthermore, as a polymerizable monomer, divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl A binder resin having a crosslinked structure can also be obtained using a polyfunctional vinyl such as glycol diacrylate.

  Among these, it is preferable to use a copolymer of styrene, (meth) acrylic acid ester and (meth) acrylic acid as the binder resin.

[Process (E)]
In this step (E), the dispersion diameter of the colorant particles in the colorant particle dispersion is preferably 10 to 300 nm in terms of volume-based median diameter.
The dispersion diameter of the colorant particles is measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.).

(Coloring agent)
Examples of the colorant used in the toner production method of the present invention include generally known dyes and pigments.
As a colorant for obtaining a black toner, various known ones such as carbon black, a magnetic material, a dye, and a composite iron oxide pigment can be arbitrarily used.
As the colorant for obtaining a color toner, various known materials such as dyes and organic pigments can be arbitrarily used.
The colorant for obtaining the toner of each color can be used alone or in combination of two or more for each color.

  The content ratio of the colorant is preferably 1 to 10% by mass in the toner particles, and more preferably 2 to 8% by mass. When the content ratio of the colorant is less than 1% by mass, the toner may be insufficient in coloring power. On the other hand, when the content ratio of the colorant exceeds 10% by mass, the colorant is liberated. Adhesion to a carrier may occur, which may affect the chargeability.

In the toner particles according to the present invention, in addition to the binder resin, the colorant, and the hindered phenol compound, an internal additive such as a release agent or a charge control agent may be contained as necessary. Such an internal additive is prepared, for example, by preparing an internal additive particle dispersion of internal additive particles consisting only of the internal additive before the step (F), and in the step (F), a hindered phenol fine particle dispersion and a binder. In the toner particles, the internal additive particle dispersion is mixed together with the resin particle dispersion and the colorant particle dispersion, and the internal additive particles are aggregated together with the hindered phenol fine particles, the binder resin particles, and the colorant particles. Can be introduced.
Further, for example, in the step (F), the binder resin and the internal additive can be introduced into the toner particles by using them as a mixture at the molecular level. The binder resin particles in which the binder resin and the internal additive are mixed at the molecular level are prepared by dissolving the internal additive in advance in the polymerizable monomer that should form the binder resin. It can be produced by polymerizing the polymerizable monomer.

(Release agent)
The release agent used in the method for producing the toner of the present invention is not particularly limited, and examples thereof include polyethylene wax, oxidized polyethylene wax, polypropylene wax, oxidized polypropylene wax, paraffin wax, microcrystalline wax, and fisher. Tropsch wax, carnauba wax, rice wax, candelilla wax and the like can be mentioned.
The content ratio of the release agent is usually 0.5 to 25 parts by mass, preferably 3 to 15 parts by mass with respect to 100 parts by mass of the binder resin.

(Charge control agent)
Examples of the charge control agent used in the toner production method of the present invention include various known compounds such as metal complexes, ammonium salts, and calixarene.
The content ratio of the charge control agent is usually 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the binder resin.

[Process (F)]
In this step (F), the coagulant is added and the temperature is raised, whereby the binder resin particles and the colorant particles are aggregated to form aggregated particles, and the aggregation of the aggregated particles is continued. By adding the hindered phenol fine particle dispersion to this system, the hindered phenol fine particles and the aggregated particles are aggregated to form aggregates, and toner particles are formed by heat fusion. In the toner particles, the hindered phenol fine particles are contained in the toner particles in a highly dispersed state and are also held on the surface of the toner particles. In particular, the toner particles obtained by the toner manufacturing method of the present invention are in a state where the hindered phenol fine particles are unevenly distributed on the surface of the toner particles.

(Flocculant)
Examples of the flocculant used in the step (F) include alkali metal salts and alkaline earth metal salts. Examples of the alkali metal constituting the flocculant include lithium, potassium, and sodium, and examples of the alkaline earth metal constituting the flocculant include magnesium, calcium, strontium, and barium. Of these, potassium, sodium, magnesium, calcium, and barium are preferable. Examples of the counter ion (anion constituting the salt) of the alkali metal or alkaline earth metal include chloride ion, bromide ion, iodide ion, carbonate ion and sulfate ion.

(Surfactant)
In the step (F), a surfactant may be added in order to stably disperse each particle in the agglomerated system, and such a surfactant is not particularly limited and various known ones are used. For example, sulfonates such as sodium dodecylbenzenesulfonate, sodium arylalkylpolyethersulfonate; sulfate esters such as sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate; sodium oleate; Examples of suitable ionic surfactants include fatty acid salts such as sodium laurate, sodium caprate, sodium caprylate, sodium caproate, potassium stearate, calcium oleate and the like.
Also, polyethylene oxide, polypropylene oxide, combination of polypropylene oxide and polyethylene oxide, ester of polyethylene glycol and higher fatty acid, alkylphenol polyethylene oxide, ester of higher fatty acid and polyethylene glycol, ester of higher fatty acid and propylenoxide, sorbitan ester Nonionic surfactants such as can also be used.
The above surfactants can be used alone or in combination of two or more as desired.

  In the step (F), the hindered phenol fine particle dispersion is preferably added at a ratio of 0.1 to 10 parts by mass (solid content conversion) with respect to 100 parts by mass of the binder resin. It is more preferable to add at a ratio of ˜5 parts by mass (in terms of solid content).

  In the step (F), the dispersion diameter of the aggregate is set to 4.0 to 11.0 μm, preferably 4.5 to 7.5 μm, based on the volume-based median diameter.

  In the present invention, the dispersion diameter of the aggregates is measured using a measuring apparatus in which a computer system equipped with data processing software “Software V3.51” is connected to “Coulter Multisizer 3” (manufactured by Beckman Coulter, Inc.).・ Calculated. Specifically, a measurement sample (aggregate 0.02 g) was added to 20 mL of a surfactant solution (a surfactant solution obtained by diluting a neutral detergent containing a surfactant component 10 times with pure water), and became accustomed. After that, ultrasonic dispersion was performed for 1 minute to prepare a dispersion, and this dispersion was placed in a beaker containing “ISOTONII” (manufactured by Beckman Coulter) in the sample stand and the display concentration of the measuring device was 8 Pipette until%. Here, a reproducible measurement value can be obtained by setting the concentration range. In the measurement apparatus, the measurement particle count is 25000, the aperture diameter is 50 μm, the frequency value is calculated by dividing the measurement range of 1 to 30 μm into 256, and the volume integrated fraction is 50 % Particle diameter is defined as the volume-based median diameter.

[Step (G) to Step (H)]
These steps can be performed according to generally known steps.

[Step (I)]
The toner obtained by the method for producing a toner of the present invention can be used as it is as it is. However, in order to improve fluidity, chargeability, cleaning properties, etc., so-called fluidizing agents and cleaning aids are added to the toner particles. An external additive such as can be added.
Examples of the fluidizing agent include silica, alumina, titanium oxide, zinc oxide, iron oxide, copper oxide, lead oxide, antimony oxide, yttrium oxide, magnesium oxide, barium titanate, ferrite, bengara, magnesium fluoride, silicon carbide. Inorganic fine particles made of boron carbide, silicon nitride, zirconium nitride, magnetite, magnesium stearate and the like.
These inorganic fine particles are preferably subjected to a surface treatment with a silane coupling agent, a titanium coupling agent, a higher fatty acid, silicone oil or the like in order to improve the dispersibility of the toner particles on the surface and the environmental stability. .
Examples of the cleaning aid include polystyrene fine particles and polymethyl methacrylate fine particles.
Various external additives may be used in combination.
The total addition amount of these external additives is preferably 0.1 to 20% by mass in the toner.

The toner comprising the toner particles obtained as described above contains at least a binder resin, a colorant, and a hindered phenol compound, and the toner particles are dispersed in a highly dispersed state. It is contained inside and is also held on the surface of the toner particles. In particular, the toner particles obtained by the toner production method of the present invention are in a state where the hindered phenol fine particles are unevenly distributed on the surface of the toner particles.
The hindered phenolic compound present inside and on the surface of the toner particles is an antioxidant that prevents or suppresses the oxidizing action caused by oxidizing substances such as ozone and nitrogen oxide generated on the surface of the photoreceptor in the image forming apparatus. Function as.

(Toner particle size)
The toner obtained by the method for producing a toner of the present invention preferably has a toner particle diameter of 3 to 9 μm, more preferably 3 to 8 μm in terms of volume-based median diameter. This particle size can be controlled by the concentration of the aggregating agent used in the production of the toner, the amount of organic solvent added, the fusing time, and the composition of the polymer.
When the particle size of the toner particles is in the above range, the transfer efficiency is increased, the image quality of halftone is improved, and the image quality of fine lines and dots is improved.

The particle size of the toner particles is measured and calculated using a measuring device in which a computer system equipped with data processing software “Software V3.51” is connected to “Coulter Multisizer 3” (manufactured by Beckman Coulter). .
Specifically, 0.02 g of a sample for measurement (toner particles) was added to 20 mL of a surfactant solution (for example, a neutral detergent containing a surfactant component diluted 10-fold with pure water for the purpose of dispersing toner particles). And added to the activator solution), followed by ultrasonic dispersion for 1 minute to prepare a dispersion, and this dispersion is a beaker containing “ISOTONII” (manufactured by Beckman Coulter) in the sample stand. Then, inject with a pipette until the displayed concentration of the measuring device is 8%. Here, a reproducible measurement value can be obtained by setting the concentration range. In the measurement apparatus, the measurement particle count is 25000, the aperture diameter is 50 μm, the frequency value is calculated by dividing the measurement range of 1 to 30 μm into 256, and the volume integrated fraction is 50 % Particle size is the volume-based median diameter.

(Average circularity of toner particles)
In the toner obtained by the toner production method of the present invention, the average circularity of the toner particles is preferably 0.930 to 1.000, preferably 0.950 to 0.995, from the viewpoint of improving transfer efficiency. It is more preferable that The average circularity indicates an average value of circularity calculated by the following formula (T).
Formula (T): Circularity = circumference of circle obtained from equivalent circle diameter / perimeter of particle projection image

The circularity of the toner particles is measured using “FPIA-2100” (manufactured by Sysmex).
Specifically, after adding a measurement sample (toner particles) to a commercially available special sheath solution in which a surfactant is dissolved, the dispersion is prepared by performing ultrasonic dispersion for 1 minute. For this dispersion, using “FPIA-2100”, the measurement conditions are set to the HPF (high magnification imaging) mode, and measurement is performed at an appropriate concentration of 3000 to 10,000 HPF detections.

(Developer)
The toner obtained by the toner production method of the present invention can be used as a magnetic or non-magnetic one-component developer, but may be mixed with a carrier and used as a two-component developer. In the case where the toner according to the present invention is used as a two-component developer, the carrier may be a conventionally known material such as a metal such as iron, ferrite, or magnetite, or an alloy of such a metal with a metal such as aluminum or lead. Magnetic particles can be used, and ferrite particles are particularly preferable. Further, as the carrier, a coated carrier in which the surface of magnetic particles is coated with a coating agent such as a resin, a dispersion type carrier in which a magnetic fine powder is dispersed in a binder resin, or the like may be used.
About the particle size of a carrier, it is preferable that it is 15-100 micrometers by the median diameter of a volume basis, and it is more preferable that it is 20-80 micrometers. The volume-based median diameter of the carrier can be measured by a laser diffraction type particle size distribution measuring apparatus “HELOS” (manufactured by Sympathec) equipped with a wet disperser.

  Preferred carriers include a resin-coated carrier in which the surface of magnetic particles is coated with a resin, and a so-called resin-dispersed carrier in which magnetic particles are dispersed in a resin. The resin constituting the resin-coated carrier is not particularly limited, and examples thereof include olefin resins, styrene resins, styrene / acrylic resins, silicone resins, ester resins, and fluorine-containing polymer resins. Moreover, it does not specifically limit as resin which comprises a resin dispersion type carrier, A well-known thing can be used, For example, a styrene acrylic resin, a polyester resin, a fluorine resin, a phenol resin etc. can be used.

(Toner glass transition point)
The toner obtained by the toner manufacturing method of the present invention preferably has a glass transition point of 28 to 55 ° C, more preferably 38 to 55 ° C.

The glass transition point of the toner is measured using a differential scanning calorimeter “DSC8500” (manufactured by Perkin Elmer).
Specifically, 4.5 mg of a measurement sample (toner) is precisely weighed to two digits after the decimal point, sealed in an aluminum pan, and set in a DSC-7 sample holder. For the reference, an empty aluminum pan was used, and heat-cool-heat temperature control was performed at a measurement temperature of 0 to 200 ° C., a temperature increase rate of 10 ° C./min, and a temperature decrease rate of 10 ° C./min. Analysis is performed based on the data in Heat. The glass transition point is defined as the value of the intersection of the extension line of the base line before the rise of the first endothermic peak and the tangent line indicating the maximum slope between the rising portion of the first endothermic peak and the peak apex.

(Image forming device)
The toner obtained by the toner manufacturing method of the present invention is used in a general electrophotographic image forming apparatus.
The photoreceptor in such an image forming apparatus includes, for example, a cylindrical conductive substrate and a photosensitive layer formed on the outer peripheral surface of the conductive substrate. The photosensitive layer includes a charge generation layer and a photosensitive layer. It is preferable that the layered photosensitive layer is formed by laminating the layer and the charge transport layer. Moreover, the thing of the structure by which the protective layer is provided in the outer peripheral surface of the photosensitive layer may be sufficient as needed. However, when such a protective layer is provided, it is preferable to use a protective layer that does not contain an antioxidant such as a hindered phenol compound.

  Examples of the conductive substrate constituting the photosensitive member include those obtained by molding a metal such as aluminum, copper, chromium, nickel, zinc and stainless steel into a drum or sheet, and those obtained by laminating a metal foil such as aluminum and copper on a plastic film. , Aluminum, indium oxide, tin oxide and the like deposited on a plastic film, a metal, a plastic film, paper, and the like provided with a conductive layer by applying a conductive substance alone or with a binder resin.

The charge generation layer constituting the photoreceptor is preferably formed by dispersing a charge generation material in a binder resin solution and applying the dispersion.
Examples of the charge generating substance include azo pigments, quinone pigments, quinocyanine pigments, perylene pigments indigo pigments, and phthalocyanine pigments.
Examples of the binder resin for the charge generation layer include known resins such as polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, vinyl chloride resin, and vinyl acetate resin.

The charge transport layer constituting the photoreceptor is preferably formed by dispersing a charge transport material in a binder resin solution and applying the dispersion.
Examples of the charge transport material include carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, and the like.
Examples of the binder resin for the charge transport layer include known resins such as polycarbonate resin, polyacrylate resin, polyester resin, polystyrene resin, and styrene-acrylonitrile copolymer resin.

According to the method for producing a toner of the present invention, the hindered phenol fine particle dispersion in the step (C) has a dispersion diameter of the hindered phenol fine particles within a specific range. Since the toner particles are formed by being contained or held in the toner particles in a highly dispersible state, oxidizing substances such as ozone and nitrogen oxide generated on the surface of the photoreceptor are removed or reduced. Therefore, even in a high-temperature and high-humidity environment, the occurrence of image defects such as image blur is suppressed, and a toner capable of forming a high-quality image is obtained.
In addition, since the generated ozone and nitrogen oxides are removed or reduced without containing an antioxidant such as a hindered phenol compound in the photoreceptor itself, the intended durability of the photoreceptor is impaired. Therefore, the occurrence of image defects such as image blurring is suppressed, and a toner capable of forming a high-quality image is obtained.
Furthermore, since the toner particles are formed by being contained or held in the toner particles in a state where the hindered phenol fine particles have high dispersibility, the antioxidant function of the toner particles themselves is improved, and as a result, the expected charging By maintaining the property, it is possible to stably form a high-quality image over a long period of time, and to obtain a toner capable of forming an image with excellent light resistance.

  Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

[Example 1]
<Process (A): Preparation of hindered phenol compound solution [A]>
A hindered phenol compound solution [A] was prepared by dissolving 3 parts by mass of the hindered phenol compound represented by the above formula (A-5) in 35 parts by mass of toluene.

<Process (B): Preparation of hindered phenol compound solution aqueous dispersion [A]>
A surfactant solution in which 2.2 parts by mass of sodium polyoxyethylene (2) dodecyl ether sulfate was dissolved in 84 parts by mass of ion-exchanged water was added to a flask equipped with a stirrer. The hindered phenol compound solution [A] was added to this surfactant solution.
And it was made to disperse | distribute for 10 minutes using ultrasonic disperser "US-1" (made by asone), and the hindered phenol type compound solution aqueous dispersion [A] was prepared.

<Step (C): Preparation of hindered phenol fine particle dispersion [A]]
About hindered phenolic compound solution aqueous dispersion [A], using a rotary evaporator, toluene is distilled off at 35 ° C. under reduced pressure, and hindered phenol fine particle dispersion [A] is dispersed. A] was prepared. The hindered phenol fine particles [A] had a dispersion diameter of 150 nm in terms of volume-based median diameter. In addition, this dispersion diameter is measured by the measuring method mentioned above.

<Process (D): Preparation of binder resin particle dispersion [D]>
By performing the following operations (I) to (III), a binder resin particle dispersion [D] in which the binder resin particles [D] having a dispersion diameter of 140 nm in terms of volume-based median diameter are prepared is prepared. did. The binder resin particles [D] contain paraffin wax as a release agent.

(I) First stage polymerization 8 parts by mass of sodium dodecyl sulfate and 3000 parts by mass of ion-exchanged water are added to a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction device, and the stirring speed is 230 rpm under a nitrogen stream. The internal temperature was raised to 80 ° C. with stirring. After the temperature increase, a polymerization initiator solution in which 10 parts by mass of potassium persulfate was dissolved in 200 parts by mass of ion-exchanged water was added to adjust the liquid temperature to 80 ° C.
Next, after a polymerizable monomer mixture composed of the compounds shown below was added dropwise to the reaction vessel over 1 hour, polymerization was performed by heating and stirring at 80 ° C. for 2 hours to obtain resin particles [1H A dispersion was prepared.
Styrene 480 parts by weight n-butyl acrylate 250 parts by weight Methacrylic acid 68 parts by weight n-octyl-3-mercaptopropionate 16 parts by weight

(II) Second-stage polymerization 7 parts by mass of polyoxyethylene (2) sodium dodecyl ether sulfate was dissolved in 800 parts by mass of ion-exchanged water in a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction device. A surfactant solution was added. After heating the reaction vessel to 98 ° C., 260 parts by mass (in terms of solid content) of a dispersion of resin particles [1H] and a polymerizable monomer mixture composed of the compounds shown below are added to have a circulation path. A dispersion liquid in which emulsified particles (oil droplets) were dispersed was prepared by mixing and dispersing for 1 hour using a mechanical disperser “CLEAMIX” (manufactured by M Technique Co., Ltd.).
Styrene 245 parts by mass n-butyl acrylate 120 parts by mass n-octyl-3-mercaptopropionate 1.5 parts by mass polyethylene wax (melting point 81 ° C.) 190 parts by mass Next, 6 parts by mass of potassium persulfate is added to this dispersion. A polymerization initiator solution in which 200 parts by mass of ion exchange water was dissolved was added, and polymerization was performed by heating and stirring at 82 ° C. for 1 hour to prepare a dispersion of resin particles [1HM].

(III) Third-stage polymerization A polymerization initiator solution in which 11 parts by mass of potassium persulfate is dissolved in 400 parts by mass of ion-exchanged water is added to the dispersion of the above resin particles [1HM], and at a temperature of 82 ° C. Then, a polymerizable monomer solution comprising the compound shown below was added dropwise over 1 hour. After dropping, polymerization was carried out by heating and stirring for 2 hours, followed by cooling to 28 ° C. to prepare a binder resin particle dispersion [D] in which the binder resin particles [D] were dispersed. The binder resin particles [D] had a glass transition point of 28 ° C. In addition, this glass transition point is measured by the measuring method mentioned above.
Styrene 435 parts by weight n-butyl acrylate 130 parts by weight Methacrylic acid 33 parts by weight n-octyl-3-mercaptopropionate 8 parts by weight

<Process (E): Preparation of colorant particle dispersion [E]>
While stirring a solution obtained by adding 90 parts by mass of sodium dodecyl sulfate to 1600 parts by mass of ion-exchanged water, 420 parts by mass of “Red No. 215” as a rhodamine dye was gradually added, and then a mechanical disperser having a circulation path By performing a dispersion treatment using “CLEAMIX” (manufactured by M Technique), a colorant particle dispersion liquid [E] in which the colorant particles [E] are dispersed was prepared.
The dispersion diameter of the colorant particles [E] was 110 nm as a volume-based median diameter. The dispersion diameter was measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.).

<Step (F): Formation of toner particles [1]>
The following materials were added to a reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introducing device, and the liquid temperature was adjusted to 30 ° C.
Binder resin particle dispersion [D] 300 parts by mass (solid content conversion)
Ion-exchanged water 1400 parts by weight Colorant particle dispersion [E] 120 parts by weight To this, a surfactant solution in which 3 parts by weight of polyoxyethylene (2) sodium dodecyl ether sulfate was dissolved in 120 parts by weight of ion-exchanged water was added. did.
Next, a 5 mol / liter sodium hydroxide aqueous solution is added to adjust the pH to 10, and a 30 ° C. flocculant solution in which 35 parts by mass of magnesium chloride is dissolved in 35 parts by mass of ion-exchanged water is in a stirring state. It added over 10 minutes in the reaction system. After 3 minutes, the temperature was started to rise, and the temperature of the reaction system was raised to 90 ° C. over 60 minutes to advance the aggregation. Next, 9 parts by mass of the hindered phenol fine particle dispersion [A] (in terms of solid content) was added, and when the aggregation was continued until the volume-based median diameter was 6.5 μm, a 20% aqueous sodium chloride solution Aggregation was stopped by adding 750 parts by mass.
Thereafter, the liquid temperature was set to 98 ° C., and the stirring was continued, and fusion was allowed to proceed while confirming the average circularity using a flow type particle image analyzer “FPIA-2100” (manufactured by Sysmex). When the average circularity reached 0.965, the liquid temperature was cooled to 30 ° C., hydrochloric acid was added to adjust the pH to 4, stirring was stopped, and toner particles [1] were produced. The toner particles [1] had a volume-based median diameter of 6.5 μm. In addition, this particle size is measured by the measuring method mentioned above.

<Step (G) and Step (H): Washing and drying>
The toner particles [1] are solid-liquid separated with a basket type centrifuge “MARK III Model No. 60 × 40” (manufactured by Matsumoto Kikai Co., Ltd.) to form a wet cake of toner particles [1], which is separated from the basket type centrifuge. The filtrate is washed with ion exchange water at 45 ° C. until the electrical conductivity of the filtrate reaches 5 μS / cm, and then transferred to “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.) until the water content becomes 0.5 mass%. Dried.

<Step (I): Addition of external additive>
1% by mass of hydrophobic silica (number average primary particle size = 12 nm) and 0.3% by mass of hydrophobic titania (number average primary particle size = 20 nm) are added to the washed and dried toner particles [1]. The toner [1] was obtained by mixing with a “Henschel mixer” (manufactured by Mitsui Miike Chemical Co., Ltd.).
Note that the particle size and average circularity of the toner particles did not change depending on the addition of the external additive.

[Examples 2-6, Comparative Examples 1-3]
In the preparation of the hindered phenol compound solution [A] in the step (A) in Example 1, the kind of the hindered phenol compound and / or the dispersion diameter of the hindered phenol fine particles and / or the hindered phenol fine particles in the step (F). Toners [2] to [9] were obtained in the same manner except that the amount of the dispersion added was changed according to Table 1 below.

[Developer Preparation Examples 1 to 9]
Each of the toners [1] to [9] is mixed with a volume-based median diameter 60 μm ferrite carrier coated with a silicone resin so that the toner concentration becomes 6% by mass, and the developers [1] to [9]. ] Was produced.

[Evaluation 1: Image blur]
Developers [1] to [9] are put in magenta toner containers of an image forming apparatus “bizhub PRO C65hc” (manufactured by Konica Minolta Business Technologies), respectively, and are in a high temperature and high humidity environment (temperature 30 ° C., humidity 85% RH). In FIG. 2, after continuous printing of 2 million sheets at a magenta color 5% printing rate, the sheet was left for 12 hours, and then 7 halftone images were printed, and the halftone images were visually evaluated. Evaluation was performed according to the following evaluation criteria. The results are shown in Table 1.
A: No streaks are generated on the halftone image.
B: Some streaks were generated on the halftone image, but there is no practical problem.
C: Streaks are generated on the halftone image, which causes a practical problem.

[Evaluation 2: Image stability]
Developers [1] to [9] are put into magenta toner containers of an image forming apparatus “bizhub PRO C65hc” (manufactured by Konica Minolta Business Technologies), respectively, in a low temperature and low humidity environment (temperature 10 ° C., humidity 10% RH) and In a high temperature and high humidity environment (temperature 30 ° C., humidity 85% RH), after continuous printing of 2 million sheets with a magenta color 5% printing rate, the image density decreases at the beginning and end of continuous printing and on the photoreceptor. The fog was visually observed and evaluated according to the following evaluation criteria. The results are shown in Table 1.
A: Neither image density reduction nor fogging occurs in the initial and final stages of continuous printing in either a low-temperature, low-humidity environment or a high-temperature, high-humidity environment.
B: In either a low temperature and low humidity environment or a high temperature and high humidity environment, there was a slight decrease in image density and / or fogging at the initial and final stages of continuous printing, but there is no practical problem.
C: In either a low-temperature and low-humidity environment or a high-temperature and high-humidity environment, image density lowering and fogging at the initial stage and the final stage of continuous printing occur, and there is a practical problem.

[Evaluation 3: Light resistance]
Developers [1] to [9] are respectively charged into magenta toner containers of an image forming apparatus “bizhub PRO C65hc” (manufactured by Konica Minolta Business Technologies), and a magenta toner image having a toner adhesion amount of 8 g / m ² After conducting a 7-day exposure test using a “Xenon Long Life Weather Meter” (manufactured by Suga Test Instruments Co., Ltd .; xenon arc lamp, 70,000 lux, 44.0 ° C.), “Macbeth Color Eye 7000” (Gretag Macbeth) Chromaticity before and after the exposure test was measured using a CMC (2: 1) color difference formula, and the color differences calculated by the CMC (2: 1) color difference formula were compared. In addition, the thing with a small change of chromaticity before and after an exposure test, ie, a thing with a small color difference, is excellent in light resistance, and if the color difference which is the limit which a human eye distinguishes is 3 or less, light resistance is favorable. As evaluated. The results are shown in Table 1.

  According to the first to sixth embodiments of the present invention, the occurrence of image blur is suppressed, a high-quality image can be stably formed over a long period of time, and an image with excellent light resistance can be formed. It was confirmed that it was possible.

Claims (2)

In a method for producing a toner comprising toner particles containing at least a binder resin, a colorant, and a hindered phenol compound,
A step (A) of preparing a hindered phenol compound solution by dissolving a hindered phenol compound in an organic solvent;
A step (B) of mixing the hindered phenolic compound solution with an aqueous medium, and preparing a hindered phenolic compound solution aqueous dispersion in which droplets of the hindered phenolic compound solution are dispersed in the aqueous medium; ,
The hindered phenolic compound fine particles are obtained by distilling off the organic solvent from the aqueous dispersion of the hindered phenolic compound solution and dispersing fine particles of a hindered phenolic compound having a dispersion diameter of 50 to 500 nm in terms of volume-based median diameter. A step (C) of preparing an aqueous dispersion;
A step (D) of preparing a binder resin particle dispersion in which binder resin particles are dispersed in an aqueous medium;
A step (E) of preparing a colorant particle dispersion in which colorant particles are dispersed in an aqueous medium;
The binder resin particle dispersion and the colorant particle dispersion are mixed, the binder resin particles and the colorant particles are aggregated to form aggregated particles, and then the hindered phenol compound fine particle aqueous dispersion And (F) forming a toner particle by adding a liquid to agglomerate and fuse the agglomerated particles and hindered phenol compound fine particles.   The toner production method according to claim 1, wherein in the step (D), a copolymer of styrene, (meth) acrylic acid ester, and (meth) acrylic acid is used as the binder resin.