JP4818946B2 - Toner for electrophotography and method for producing the same - Google Patents

Description

  The present invention relates to an electrophotographic toner and a method for producing the same.

  An image forming apparatus that forms an image using an electrophotographic system includes a photoconductor, a charging unit, an exposure unit, a developing unit, a transfer unit, and a fixing unit. The charging unit charges the surface of the photoreceptor. The exposure unit irradiates the charged photosensitive member surface with signal light to form an electrostatic latent image corresponding to the image information. The developing unit supplies toner for electrophotography (hereinafter simply referred to as “toner”) in the developer to the electrostatic latent image formed on the surface of the photoreceptor to form a toner image. The transfer unit transfers the toner image formed on the surface of the photoreceptor to a recording medium. The fixing unit fixes the transferred toner image on the recording medium. The cleaning unit cleans the surface of the photoconductor after the toner image is transferred. In such an image forming apparatus, an electrostatic latent image is developed using a one-component developer containing toner or a two-component developer containing toner and a carrier as a developer to form an image. The toner used here is resin particles granulated by dispersing a colorant, a wax as a release agent, etc. in a binder resin as a matrix.

  An image forming apparatus using an electrophotographic system can form an image with good image quality at a high speed and at a low cost. Therefore, the image forming apparatus is used in copying machines, printers, facsimiles, and the like, and has recently been remarkably popular. As a result, the demands on image forming apparatuses have become more severe. In particular, the emphasis is on high definition, high resolution, stable image quality, and high image forming speed of an image formed by the image forming apparatus. In order to achieve these, studies from both the image forming process and the developer are indispensable.

  From the standpoint of developing a high-definition and high-resolution image, it is important to faithfully reproduce the electrostatic latent image from the viewpoint of the developer. It has become. Known methods for producing small-diameter toner particles include wet methods such as suspension polymerization and dissolution suspension. According to the suspension polymerization method, a polymerizable monomer composition in which a binder resin monomer, a colorant, a polymerization initiator and the like are uniformly dissolved or dispersed is put into an aqueous dispersion medium containing a dispersion stabilizer. The toner is manufactured by dispersing and granulating using a mixing device having a high shearing force and then subjecting the granulated polymerizable monomer composition to suspension polymerization. According to the dissolution suspension method, a toner material containing a binder resin and a colorant is dissolved or dispersed in an organic solvent in which the binder resin can be dissolved, and the obtained solution or dispersion and an aqueous dispersion are mixed. After mixing and granulating, the toner is manufactured by removing the organic solvent.

  In the production of a toner by such a wet method, an aqueous dispersion medium or an organic solvent (hereinafter also referred to as “dispersion liquid”) containing a dispersion stabilizer together with a binder resin monomer or a binder resin for constituting the binder resin. A colorant is dispersed. At this time, if the dispersibility of the colorant in the dispersion liquid is poor, the dispersibility of the colorant also deteriorates in the finally obtained toner particles, and the coloring performance and charging performance are not good among the individual toner particles. It becomes uniform. Therefore, a method has been proposed in which the colorant is atomized in advance before the colorant is added to the dispersion (for example, see Patent Document 1).

  In Patent Document 1, the colorant is dispersed in the dispersion by utilizing collision and shear caused by an injection pressure of 30 MPa to 150 MPa, whereby the colorant is atomized and the dispersibility of the colorant in the dispersion is uniform. A method for producing a toner to be converted is disclosed. In Patent Document 1, a dispersion liquid containing a colorant supplied to a tank is supplied to an ultrahigh pressure generator by a supply pump while being stirred by a stirring device. The ultrahigh pressure generator pressurizes the supplied dispersion and injects it into the chamber, and atomizes the colorant in the dispersion by the effects of collision, shearing, cavitation, and the like.

  However, in the dispersion step of the toner production method disclosed in Patent Document 1, bubbles are generated along with cavitation, and the bubbles adhere to the surface of the colorant to disperse the colorant in the dispersion. There is a problem that the colorant cannot act on the colorant surface and the colorant cannot be sufficiently dispersed in the dispersion. As a result, the colorant cannot be sufficiently atomized and the dispersibility of the colorant in the toner particles cannot be improved. Further, it is not possible to obtain a toner excellent in uniformity of coloring performance and charging performance.

JP 2004-325697 A

  An object of the present invention is to provide an electrophotographic toner that improves the dispersibility of a colorant in toner particles and is excellent in the uniformity of coloring performance and charging performance, and a method for producing the same.

The present invention relates to a method for producing an electrophotographic toner using a dispersion of a colorant to obtain an electrophotographic toner containing a binder resin and a colorant.
The dispersion of the colorant is a dispersion obtained by treating a mixture of the colorant and the liquid medium with a high-pressure homogenizer equipped with a decompression unit, and the finely divided colorant is dispersed in the liquid medium. A feature of the present invention is a method for producing an electrophotographic toner.

  The present invention is also characterized in that an electrophotographic toner is obtained by suspension polymerization of a binder resin monomer in the presence of a colorant dispersion.

  The present invention is also characterized in that an electrophotographic toner is obtained by dissolving and suspending a binder resin in the presence of a colorant dispersion.

  The present invention also provides an electrophotographic toner produced by the method for producing an electrophotographic toner of the present invention.

  According to the present invention, in the method for producing an electrophotographic toner that obtains an electrophotographic toner containing a binder resin and a colorant (hereinafter simply referred to as “toner”) using a dispersion of the colorant, A dispersion of a colorant, which is a dispersion obtained by processing with a high-pressure homogenizer provided and dispersed in a liquid medium, is used. The treatment with the high-pressure homogenizer is performed by passing a mixture of the colorant and the liquid medium under pressure and heating through a pulverizing nozzle, and the colorant in the liquid medium is finely divided by this treatment. Furthermore, since the high-pressure homogenizer includes a pressure reducing means, the mixture of the colorant and the liquid medium after passing through the pulverizing nozzle can be decompressed, thereby suppressing the generation of cavitation and the generation of bubbles accompanying cavitation. it can. When the generation of bubbles is suppressed, a sufficient working point between the colorant surface and the liquid medium can be secured, and the colorant can be finely and stably granulated in the liquid medium. The dispersibility of the colorant can be further improved. Further, when a colorant that exhibits excellent dispersibility in such a liquid medium is used in the production of toner, the dispersibility of the colorant in the toner particles is improved, and a toner having excellent uniformity in coloring performance and charging performance is obtained. Obtainable.

  According to the present invention, an electrophotographic toner is obtained by suspension polymerization of a binder resin monomer in the presence of a dispersion of a colorant obtained by the above-described treatment with a high-pressure homogenizer. In such a production method, a polymerizable monomer composition in which a binder resin monomer, a colorant dispersion, a polymerization initiator, and the like are uniformly dissolved or dispersed is placed in an aqueous dispersion medium containing a dispersion stabilizer. The toner is then manufactured by dispersing and granulating using a mixing device having a high shearing force and then subjecting the granulated polymerizable monomer composition to suspension polymerization. In the suspension polymerization method in which the binder resin monomer is subjected to suspension polymerization, a colorant dispersion obtained by the treatment with the high-pressure homogenizer as described above, wherein the colorant has excellent dispersibility in a liquid medium. The use of a colorant dispersion that produces a colorant enables uniform dispersion of the colorant in an aqueous dispersion medium containing a dispersion stabilizer, which has been extremely difficult in the past. can do.

  According to the present invention, an electrophotographic toner is obtained by dissolving and suspending a binder resin in the presence of a dispersion of a colorant obtained by the treatment with a high-pressure homogenizer as described above. In such a production method, a toner material containing a dispersion of a colorant and a binder resin is dissolved or dispersed in an organic solvent in which the binder resin can be dissolved or dispersed, and the resulting solution or dispersion, for example, A dispersion stabilizer and an aqueous solution in which an emulsifier is dissolved are mixed and granulated, and then an organic solvent is removed to produce a toner. In the dissolution suspension method in which the binder resin is dissolved and suspended, the colorant dispersion obtained by the treatment with the high-pressure homogenizer as described above exhibits excellent dispersibility in the liquid medium. When the colorant dispersion liquid is used, it is possible to uniformly disperse the colorant in the organic solvent, which has been extremely difficult in the past, and it is possible to produce a toner that is further excellent in the uniform dispersibility of the colorant.

  According to the invention, the toner is manufactured by a method for manufacturing a toner having the above-described effects. In such a toner, the colorant is uniformly dispersed in the toner, and the uniformity of the coloring performance and the charging performance is excellent. Therefore, when an image is formed using such a toner, a high-quality image with high coloring power and no density unevenness can be obtained.

  In the production method of the toner of the present invention, when the electrophotographic toner containing the binder resin and the colorant is produced using the colorant dispersion, the colorant and the liquid medium are used as the colorant dispersion. It is characterized by using a dispersion obtained by treating the mixture with a high-pressure homogenizer equipped with a decompression means and having a finely divided colorant dispersed in a liquid medium. Hereinafter, the dispersion of the colorant may be referred to as “colorant slurry”.

  The method for producing the electrophotographic toner using the colorant slurry is not particularly limited as long as it is a conventionally known wet toner production method. Examples of wet toner manufacturing methods include suspension polymerization and dissolution suspension. That is, as a method for producing the toner of the present invention, for example, a production method including a step of dispersing a finely divided colorant in a liquid medium to obtain a colorant slurry (hereinafter referred to as “dispersion step”) and a suspension polymerization step. Examples thereof include a method, a production method including a dispersion step and a dissolution suspension step.

[Dispersing process]
In the dispersion step, a colorant slurry in which the finely divided colorant is dispersed in a liquid medium is obtained.

  The colorant is not particularly limited, and for example, organic dyes, organic pigments, inorganic dyes, inorganic pigments, and the like can be used.

  Examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, nonmagnetic ferrite, magnetic ferrite, and magnetite.

  Examples of yellow colorants include chrome yellow, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, and Benzidine Yellow. GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, and the like.

  Examples of the orange colorant include red chrome yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK, C.I. I. Pigment orange 31, C.I. I. And CI Pigment Orange 43.

  Examples of red colorants include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risor red, pyrazolone red, watching red, calcium salt, lake red C, lake red D, brilliant carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B, C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

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

  Examples of the blue colorant include bitumen, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated product, first sky blue, indanthrene blue BC, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. And CI Pigment Blue 60.

  Examples of the green colorant include chrome green, chromium oxide, pigment green B, micalite green lake, final yellow green G, and C.I. I. And CI Pigment Green 7.

  Examples of the white colorant include compounds such as zinc white, titanium oxide, antimony white, and zinc sulfide.

  One colorant can be used alone, or two or more different colorants can be used in combination. Moreover, even if it is the same color, 2 or more types can be used together.

  As the liquid medium, for example, an aqueous medium containing an inorganic or organic dispersant can be used. Although it does not restrict | limit especially as an aqueous medium, Water is preferable when the ease of process control, the waste liquid process after all the processes, the ease of handling, etc. are considered. As water, ion-exchanged water, distilled water, pure water or the like can be used. The inorganic or organic dispersant is preferably added to the aqueous medium before the coarse powder of the colorant is added to the aqueous medium.

  The colorant is preferably used in a proportion of 5 to 50 parts by weight, more preferably 20 to 40 parts by weight, based on 100 parts by weight of the aqueous medium. When the use ratio of the colorant is less than 5 parts by weight, the amount of the colorant with respect to the aqueous medium is too small, so that the dispersion uniformity is lowered. If the proportion of the colorant used exceeds 50 parts by weight, the amount of the colorant relative to the aqueous medium is too large, so that the viscosity of the liquid medium becomes too high, and this also reduces the dispersibility.

  The inorganic dispersant is preferably a hydrophilic inorganic dispersant. By using a hydrophilic inorganic dispersant, the particle size of the fine powder of the colorant in the liquid medium can be made more uniform. Examples of the hydrophilic inorganic dispersant include silica, alumina, titania, calcium carbonate, magnesium carbonate, tricalcium phosphate, clay, diatomaceous earth, and bentonite. Among these, calcium carbonate is preferable.

  The inorganic dispersant preferably has a number average particle size of primary particles of 1 nm to 1000 nm, more preferably 5 nm to 500 nm, and still more preferably 10 nm to 300 nm. When the number average particle size of the primary particles of the inorganic dispersant is less than 1 nm, it is difficult to disperse the inorganic dispersant in the aqueous medium. If the number average particle size of the primary particles of the inorganic dispersant exceeds 1000 nm, the difference between the particle size of the colorant coarse powder and the particle size of the inorganic dispersant becomes small, and the colorant coarse powder is stable in the liquid. Thus, it becomes difficult to maintain the dispersion.

  The inorganic dispersant is preferably used in the range of 1 part by weight to 300 parts by weight and more preferably in the range of 4 parts by weight to 100 parts by weight with respect to 100 parts by weight of the colorant. When the amount of the inorganic dispersant used is less than 1 part by weight, it is difficult to disperse the inorganic dispersant in the aqueous medium. When the usage-amount of an inorganic dispersing agent exceeds 300 weight part, there exists a possibility that the viscosity of a liquid medium may become high too much and a dispersibility may fall.

  In addition, a polymer dispersant may be added to the aqueous medium together with the inorganic dispersant. As the polymer dispersant, for example, a hydrophilic one is preferably used, one having a carboxyl group is more preferable, and one having no lipophilic group such as a hydroxypropoxyl group or a methoxyl group is particularly preferable. Examples of such a polymer dispersant include water-soluble cellulose ethers such as carboxymethyl cellulose and carboxyethyl cellulose. Among these, carboxymethyl cellulose is particularly preferable. The polymer dispersant is preferably used in a proportion of 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the colorant.

  The organic dispersant is preferably an anionic dispersant. Anionic dispersants are excellent in the ability to improve the dispersibility of colorant particles in water. Examples of the anionic dispersant include a sulfonic acid type anionic dispersant, a sulfate ester type anionic dispersant, a polyoxyethylene ether type anionic dispersant, a phosphate ester type anionic dispersant, and a polyacrylate. Can be mentioned. As specific examples of the anionic dispersant, for example, sodium dodecylbenzenesulfonate, sodium polyacrylate, polyoxyethylene phenyl ether and the like can be preferably used. An anionic dispersing agent can be used individually by 1 type, or can use 2 or more types together.

  Moreover, as a dispersing agent, it is not limited to an anionic dispersing agent, A cationic dispersing agent may be sufficient. Examples of the cationic dispersant include alkyltrimethylammonium type cationic dispersants, alkylamidoamine type cationic dispersants, alkyldimethylbenzylammonium type cationic dispersants, cationized polysaccharide type cationic dispersants, and alkylbetaine type cationic dispersants. Dispersants, alkylamide betaine type cationic dispersants, sulfobetaine type cationic dispersants, amine oxide type cationic dispersants, metal salts and the like are preferable. Examples of the metal salt include chlorides such as sodium, potassium, calcium, and magnesium, and sulfates.

  Among these, alkyltrimethylammonium cationic dispersants are more preferable. Specific examples of the alkyl trimethyl ammonium type cationic dispersant include stearyl trimethyl ammonium chloride, tri (polyoxyethylene) stearyl ammonium chloride, lauryl trimethyl ammonium chloride and the like. A cationic dispersing agent can be used individually by 1 type, or can use 2 or more types together.

  The addition amount of the organic dispersant is not particularly limited and can be appropriately selected from a wide range, but is preferably 0.1 parts by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the colorant. When the addition amount is less than 0.1 parts by weight, the effect of dispersing the colorant by the dispersant becomes insufficient and aggregation may occur. Even if the organic dispersant is added in an amount exceeding 5 parts by weight, the dispersion effect is not further improved, and the dispersibility of the colorant is lowered by increasing the viscosity of the colorant slurry. As a result, aggregation may occur.

  A commercially available thing can also be used as a dispersing agent. Examples of commercially available dispersants include BYK-182, BYK-161, BYK-116, BYK-111, BYK-2000 (manufactured by Big Chemie Japan Co., Ltd.), Solsperse-2000, Solsperse-38500 (above Avicia Corporation). Product), EFKA-4046, EFKA-4047 (manufactured by Efcar Chemicals), Surfynol GA (manufactured by Air Products), and the like. One of these commercially available dispersants may be used alone, or two or more thereof may be mixed and used.

  Such a commercially available dispersant is preferably used in a ratio of 10 parts by weight or more and 100 parts by weight or less, and in a ratio of 20 parts by weight or more and 50 parts by weight or less with respect to 100 parts by weight of the colorant. Is more preferable. If the ratio of the commercially available dispersant used is less than 10 parts by weight, the effect of dispersing the colorant by the dispersant becomes insufficient, and aggregation may occur. When the use ratio of the commercially available dispersant exceeds 100 parts by weight, the dispersibility of the colorant is lowered due to an increase in the viscosity of the colorant slurry. As a result, aggregation may occur.

  Mixing with an aqueous medium and a dispersing agent can be performed by a well-known method, without being specifically limited. When mixing an inorganic dispersant and an aqueous medium, the inorganic dispersant can be dispersed in water in an aqueous medium using a disperser containing a medium such as a ball mill or a sand mill, a high-pressure disperser, an ultrasonic disperser, or the like. . When the organic dispersant and the aqueous medium are mixed, the addition and dispersion may be performed by any method as long as the dispersant can be uniformly dissolved in water. The liquid medium and the colorant obtained by mixing the aqueous medium and the dispersant are treated with a high-pressure homogenizer as shown in FIG. Thereby, the colorant is finely divided, and a colorant slurry in which the colorant is dispersed in the liquid medium, that is, a dispersion of the colorant can be obtained.

  FIG. 1 is a system diagram showing a simplified configuration of a high-pressure homogenizer 1 used in the toner manufacturing method of the present invention. The high-pressure homogenizer 1 includes a tank 2, a feed pump 3, a pressurizing unit 4, a heater 5, a crushing nozzle 6, a decompression module 7, a cooler 8, a pipe 9, and an outlet 10. Including. In the high-pressure homogenizer 1, the tank 2, the feed pump 3, the pressurizing unit 4, the heater 5, the crushing nozzle 6, the decompression module 7 and the cooler 8 are connected by a pipe 9 in this order. In the system connected by the pipe 9, the colorant slurry, which is a mixture of the colorant and the liquid medium after being cooled by the cooler 8, may be taken out of the system from the takeout port 10. The coarse slurry after being cooled may be returned to the tank 2 again and repeatedly circulated in the direction of the arrow 11.

  The tank 2 is a container-like member having an internal space, and stores a coarse powder slurry that is a mixture of coarse colorant powder and a liquid medium. Colorant coarse powder is colorant particles before being processed by a high-pressure homogenizer, and is colorant particles having a size of 1 μm or more in which a plurality of primary particles of the colorant are aggregated. The feed pump 3 feeds the coarse powder slurry stored in the tank 2 toward the pressurizing unit 4. The pressurizing unit 4 pressurizes the coarse powder slurry supplied from the feed pump 3 and feeds it to the heater 5. For the pressurizing unit 4, for example, a plunger pump including a plunger and a pump driven by suction and discharge by the plunger can be used. The heater 5 is supplied from the pressure unit 4 and heats the coarse powder slurry in a pressurized state. As the heater 5, for example, a heater including a coiled (or spiral) pipe (not shown) and a heating means (not shown) can be used. The coiled pipe is a member having a flow path (not shown) therein and a pipe-shaped member for allowing the mixture to flow around, which is wound in a coil shape (or a spiral shape). The heating means is provided along the outer peripheral surface of the coiled pipe, and includes a pipe through which water vapor, a heat medium and the like can flow, and a heating medium supply means for supplying the water vapor, the heat medium and the like to the pipe. The heating medium supply means is, for example, a boiler.

  The pulverizing nozzle 6 allows the coarse powder slurry supplied from the piping of the heater 5 to flow through a flow path formed therein, thereby allowing the colorant coarse powder to have a volume average particle diameter of, for example, 50 nm or more. Grind to a fine powder of 200 nm or less. As the pulverizing nozzle 6, a general pressure-resistant nozzle capable of liquid flow can be used. For example, a multiple nozzle having a plurality of flow paths can be preferably used. The flow paths of the multiple nozzles may be formed on concentric circles centering on the axis of the multiple nozzle, and the plurality of flow paths may be formed substantially parallel to the longitudinal direction of the multiple nozzles. Specific examples of the multi-nozzle include an inlet diameter and an outlet diameter of about 0.05 to 0.35 mm, and one or more, preferably about 1 to 2, channels having a length of 0.5 to 5 cm. It is done. A pressure-resistant nozzle in which the flow path is not formed linearly inside the nozzle can also be used. An example of such a pressure-resistant nozzle is shown in FIG.

  FIG. 2 is a cross-sectional view schematically showing the configuration of the pressure-resistant nozzle 21. The pressure-resistant nozzle 21 has a flow path 22 therein. In the present embodiment, the channel 22 has a small channel cross section in the direction perpendicular to the direction of the arrow 23 that is the flow direction of the mixture on the inlet 24 side and the outlet 25 side. Big in the middle part between. The flow path 22 is formed so that the diameter of the inlet 24 and the diameter of the outlet 25 are equal. The length related to the arrow 23 of the flow path 22 in the portion where the flow path cross section is small is longer on the inlet 24 side than on the outlet 25 side. The center of the cross section perpendicular to the arrow 23 which is the flow direction of the mixture in the flow path 22 exists on the same axis parallel to the flow direction of the slurry.

  FIG. 3 is a cross-sectional view schematically showing the configuration of another embodiment of the pressure-resistant nozzle 31. The pressure-resistant nozzle 31 has a flow path 32 therein. The flow path 32 is bent like a bowl and has at least one collision wall 34 on which the mixture entering the flow path 32 from the direction of the arrow 33 collides. The mixture collides with the collision wall 34 substantially at right angles, whereby the melt-kneaded material containing the synthetic resin is coarsely pulverized, and becomes, for example, a fine powder of a colorant having a volume average particle size reduced to 50 nm or more and 200 nm or less. And discharged from the outlet of the pressure-resistant nozzle 31. In the pressure-resistant nozzle 31, the inlet diameter and the outlet diameter are formed to be the same size, but the present invention is not limited to this, and the outlet diameter may be formed smaller than the inlet diameter. The outlet and the inlet are normally formed in a perfect circle shape, but are not limited thereto, and may be formed in a regular polygonal shape or the like. One pressure-resistant nozzle may be provided, or a plurality of pressure-resistant nozzles may be provided.

  By passing through the pulverizing nozzle 6 constituted by the pressure-resistant nozzle 21 or 31 as described above, the coarse powder of the colorant is finely divided, contains fine powder of the colorant, and the fine powder of the colorant is contained in the liquid medium. A uniformly dispersed colorant slurry is obtained.

  The decompression module 7 is decompression means for reducing the pressure applied to the colorant slurry. As the decompression module 7, it is preferable to use a multistage decompression device described in International Publication No. 03/059497. The multistage pressure reducing device includes an inlet passage, an outlet passage, and a multistage pressure reducing passage. One end of the inlet passage is connected to the pipe 9 and the other end is connected to the multistage decompression passage, and introduces the colorant slurry containing the colorant coarse powder in a pressurized state into the multistage decompression passage. The multistage depressurization passage has one end connected to the inlet passage and the other end connected to the outlet passage, and bubbles are generated by bubbling the colorant slurry in a heated and pressurized state introduced into the inside through the inlet passage (bubbling). ) Reduce the pressure so that it does not occur. The multistage decompression passage includes, for example, a plurality of decompression members and a plurality of connecting members. For example, a pipe-shaped member is used as the decompression member. For example, a ring-shaped seal member is used as the connecting member. A multistage decompression passage is configured by connecting a plurality of pipe-shaped members having different inner diameters with a ring-shaped seal member. For example, two to four pipe-shaped members A having the same inner diameter are connected by a ring-shaped seal member from the inlet passage to the outlet passage, and the pipe-shaped member B having an inner diameter about twice as large as the next pipe-shaped member A. Are connected by a ring-shaped seal member, and a multi-stage decompression passage is formed by connecting about 1-3 pipe-shaped members C having an inner diameter smaller than that of the pipe-shaped member B by about 5 to 20%. It is done. When the colorant slurry in a pressurized state is allowed to flow through such a multistage pressure reducing passage, the colorant slurry can be reduced to atmospheric pressure or a pressurized state close thereto without causing bubbling. A heat exchange means for circulating a refrigerant or a heat medium may be provided around the multistage decompression passage, and cooling or heating may be performed simultaneously with the decompression according to the pressure value applied to the colorant slurry. One end of the outlet passage is connected to the multistage decompression passage, the other end is connected to the pipe 9, and the coarse powder slurry depressurized by the multistage decompression passage is supplied to the pipe 9. In this multistage pressure reducing device, the inlet diameter and the outlet diameter may be the same, or the outlet diameter may be larger than the inlet diameter.

  In the present embodiment, the decompression module 7 is not limited to the multistage decompression device having the above-described configuration, and for example, a decompression nozzle can be used.

  FIG. 4 is a longitudinal sectional view schematically showing the configuration of the decompression nozzle 41. The decompression nozzle 41 is formed with a flow path 42 penetrating the inside thereof in the longitudinal direction. An inlet 41a and an outlet 41b of the flow path 42 are connected to the pipe 9, respectively. The flow path 42 is formed so that the diameter of the inlet 41a is larger than the diameter of the outlet 41b. Further, in the present embodiment, the flow path 42 has a cross-section in a direction perpendicular to the direction of the arrow 43 that is the flow direction of the colorant slurry, gradually decreases as it approaches the outlet 41b from the inlet 41a. Is located on the same axis (axis of the pressure reducing nozzle 41) parallel to the direction of the arrow 43. According to the pressure reducing nozzle 41, the colorant slurry in a pressurized and heated state is introduced into the flow path 42 from the inlet 41a, and after being reduced in pressure, is discharged toward the pipe 9 from the outlet 41b. One or more multistage pressure reducing devices or pressure reducing nozzles as described above can be provided. In the case of providing a plurality, they may be provided in series or in parallel.

  For the cooler 8, a general liquid cooler having a pressure-resistant structure can be used. For example, a pipe for circulating cooling water is provided around the pipe through which the colorant slurry flows, and coloring is performed by circulating the cooling water. A cooler for cooling the agent slurry can be used. Among them, a cooler having a large cooling area such as a serpentine cooler is preferable. When the temperature of the colorant slurry is normal temperature (25 ° C.) or less, the colorant slurry does not necessarily have to be cooled. Further, it is preferable that the cooling gradient is reduced (or the cooling capacity is lowered) from the cooler inlet toward the cooler outlet. This further prevents reagglomeration of the finely divided coarse powder, so that the diameter of the colorant particles can be reduced more efficiently and the yield of the colorant particles can be improved. One cooler 8 or a plurality of coolers 8 may be provided. When providing two or more, you may provide in series or in parallel. When provided in series, it is preferable to provide a cooler so that the cooling capacity gradually decreases in the flow direction of the colorant slurry. The colorant slurry discharged from the decompression module 7 and containing the colorant particles and in a heated state is introduced into the cooler 8 from an inlet 8a connected to the pipe 9 of the cooler 8, for example, and has a cooling gradient. The inside of the machine 8 is cooled and discharged from the outlet 8 b of the cooler 8 to the pipe 9.

  The high pressure homogenizer 1 is commercially available. Specific examples thereof include NANO3000 (trade name, manufactured by Migrain Co., Ltd.). According to the high-pressure homogenizer 1, the coarse powder slurry stored in the tank 2 is introduced into the pulverization nozzle 6 in a heated and pressurized state, and the coarse powder is pulverized to a fine powder having a volume average particle diameter of 50 nm to 200 nm. The colorant slurry containing the fine powder that has been discharged from the pulverizing nozzle 6 and is in a pressurized state is introduced into the vacuum module 7 to reduce pressure so that no bubbling occurs, and the mixture discharged from the vacuum module 7 is cooled 8 and cooled to obtain a colorant slurry. The colorant slurry is discharged from the take-out port 10 or circulated again in the tank 2 and subjected to the same pulverization treatment.

  According to such a high-pressure homogenizer 1, the coarse powder slurry, which is a mixture of the coarse powder of the colorant and the liquid medium, is processed to make the coarse powder of the colorant fine, and the fine powder is fined to 50 nm to 200 nm. The obtained colorant is dispersed in a liquid medium. In the dispersion step using the high-pressure homogenizer 1, the high-pressure homogenizer includes the decompression module 7 that serves as a decompression means and the cooler 8 that serves as a cooling means. Therefore, the mixture of the colorant and the liquid medium after passing through the pulverizing nozzle 6 is decompressed and reduced. Cooling can be performed, and thereby generation of cavitation and generation of bubbles accompanying cavitation can be suppressed. When the generation of bubbles is suppressed, a sufficient working point between the colorant surface and the liquid medium can be secured, and the colorant can be finely and stably granulated in the liquid medium. The dispersibility of the colorant can be improved.

  In the dispersion step, the coarse powder slurry, which is a mixture of the colorant coarse powder and the liquid medium, is pressurized by the pressure unit 4 to 120 MPa or more and 250 MPa or less. When the coarse powder slurry is passed through the pulverizing nozzle 6 under such a range of pressure, a large collision force can be imparted to the coarse powder of the colorant in the coarse powder slurry. Fine graining can be performed. If the pressure is less than 120 MPa, the shear energy becomes small and the pulverization may not proceed sufficiently. If it exceeds 250 MPa, the danger is too great in an actual production line, which is not realistic. The coarse powder slurry is preferably pressurized to 100 MPa to 230 MPa, more preferably 150 MPa to 200 MPa.

  The coarse powder slurry is introduced into the pulverizing nozzle 6 from the inlet of the pulverizing nozzle 6 at a pressure and temperature in the above-mentioned range. The colorant slurry discharged from the outlet of the pulverizing nozzle 6 is, for example, 0 ° C. or higher and 100 ° C. or lower. When the temperature of the colorant slurry is less than 0 ° C., energy for cooling to a temperature lower than room temperature is required. When the temperature of the colorant slurry exceeds 100 ° C., problems such as volatilization of the liquid medium due to temperature rise occur. The colorant slurry is preferably 10 ° C. or higher and 70 ° C. or lower, and more preferably 20 ° C. or higher and 40 ° C. or lower. In addition, the colorant slurry is cooled by the cooler 8 as needed after being decompressed by the decompression module 7. By this cooling, the colorant slurry is set to about 20 to 40 ° C.

  Through such a dispersion step, the coarse powder slurry can be passed through a pressure-resistant nozzle, and the colorant can be finely divided. Preferably, the fine powder can be finely divided into fine powder of a colorant having a diameter of 50 nm to 200 nm. When the colorant is dispersed under the above-mentioned conditions, fine powder of about 50 to 100 nm for carbon black, fine powder of about 50 to 200 nm for phthalocyanine, and about 100 to 200 nm for other organic pigments. It can be refined to a fine powder. By dispersing the colorant coarse powder to such a size, the dispersibility of the colorant in the liquid in the suspension polymerization step or dissolution suspension step, which is the next toner preparation step, can be improved. Thus, it is possible to produce a toner having excellent dispersion uniformity of the colorant in the toner particles.

  If the particle size of the fine powder of the colorant is less than 50 nm, it takes a long time to make fine particles with a high-pressure homogenizer, and there is a possibility that re-aggregation of the fine powder may occur. When the particle size of the fine powder of the colorant exceeds 200 nm, the dispersibility of the colorant in the toner particles may be reduced. The particle diameter of the fine powder of the colorant can be measured using, for example, a laser light scattering microscope (trade name: DLS-700, manufactured by Otsuka Electronics Co., Ltd.).

  When the colorant is dispersed in the above dispersion step, either the suspension polymerization step or the dissolution suspension step is performed using the colorant slurry to produce a toner.

[Suspension polymerization process]
In the suspension polymerization step, the binder resin monomer is subjected to suspension polymerization in the presence of a colorant dispersion to obtain an electrophotographic toner. The suspension polymerization method in the suspension polymerization step is not particularly limited as long as a colorant dispersion is used, and a conventionally known suspension polymerization method can be used. For example, in the suspension polymerization step, a polymerizable monomer composition in which the colorant slurry, the binder resin monomer, the polymerization initiator and the like obtained as described above are uniformly dissolved or dispersed is prepared. Next, the polymerizable monomer composition is put into an aqueous dispersion medium containing a dispersion stabilizer, dispersed and granulated using a mixing apparatus having a high shearing force, and the like. A toner is produced by suspension polymerization of the monomer composition.

  The binder resin monomer constitutes the binder resin by suspension polymerization. Examples of the binder resin monomer include aromatic vinyl monomers such as styrene, α-methylstyrene, p-methylstyrene, and p-chlorostyrene, unsaturated nitriles such as acrylonitrile, methyl (meth) acrylate, and ethyl. Unsaturated (meth) acrylates such as (meth) acrylate, butyl (meth) acrylate, ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, conjugated diolefins such as butadiene and isoprene, etc. Is mentioned. These binder resin monomers can be used alone or in combination of two or more.

  In addition, the polymerizable monomer composition containing the colorant slurry and the binder resin monomer includes an oil-soluble polymerization initiator, a molecular weight regulator, a crosslinkable monomer, a release agent, a charge control agent and the like as necessary. Additives can be added. Any oil-soluble polymerization initiator may be used as long as it is soluble in the monomers used. Examples thereof include methyl ethyl peroxide, di-t-butyl peroxide, acetyl peroxide, dicumyl peroxide, and lauroyl peroxide. Peroxides such as oxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, di-isopropylperoxydicarbonate, di-t-butyldiperoxyisophthalate, 2,2'-azobis Examples thereof include azo compounds such as (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azubis (1-cyclohexanecarbonitrile), and the like. The oil-soluble polymerization initiator is usually used in a proportion of 0.1 to 20 parts by weight, preferably 1 to 10 parts by weight, with respect to 100 parts by weight of the binder resin monomer. The polymerization initiator can be added in advance to the polymerizable monomer composition, and in some cases, can also be added to the liquid after granulation.

  Examples of the molecular weight modifier include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan and n-octyl mercaptan, and halogenated hydrocarbons such as carbon tetrachloride and carbon tetrabromide. These molecular weight regulators can be added before the start of polymerization or during the polymerization. The molecular weight modifier is usually used in a proportion of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, with respect to 100 parts by weight of the binder resin monomer.

  Examples of the crosslinkable monomer include polyfunctional monomers such as divinylbenzene, ethylene glycol di (meth) acrylate, glycidyl (meth) acrylate, and trimethylolpropane tri (meth) acrylate. These crosslinkable monomers can be added before the start of polymerization or during the polymerization. The crosslinkable monomer is usually used in a proportion of 0.01 to 10 parts by weight, preferably 0.5 to 5 parts by weight, with respect to 100 parts by weight of the binder resin monomer.

  Examples of the release agent include petroleum wax such as paraffin wax and derivatives thereof, microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin wax and derivatives thereof, low molecular weight polypropylene wax and derivatives thereof, polyolefin Hydrocarbon synthetic waxes such as polymer wax (low molecular weight polyethylene wax, etc.) and derivatives thereof, carnauba wax and derivatives thereof, rice wax and derivatives thereof, candelilla wax and derivatives thereof, plant waxes such as wood wax, beeswax, whales Animal waxes such as waxes, oils and fats synthetic waxes such as fatty acid amides and phenol fatty acid esters, long chain carboxylic acids and their derivatives, long chain alcohols and their derivatives, silicone polymers, higher fatty acids, etc. . Derivatives include oxides, block copolymers of vinyl monomers and waxes, graft modified products of vinyl monomers and waxes, and the like. Among these, a wax having a melting point equal to or higher than the liquid temperature of the aqueous water-soluble dispersant solution in the granulation step is preferable. The content of the release agent is not particularly limited and can be appropriately selected from a wide range, but is usually 0.1 to 20 parts by weight, preferably 1 to 10 parts by weight with respect to 100 parts by weight of the binder resin monomer. It is done.

  The charge control agent is not particularly limited, and those for positive charge control and negative charge control can be used. Examples of charge control agents for positive charge control include nigrosine dyes, basic dyes, quaternary ammonium salts, quaternary phosphonium salts, aminopyrines, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, nigrosine dyes and derivatives thereof, and triphenylmethane. Derivatives, guanidine salts, amidine salts and the like can be mentioned. As charge control agents for controlling negative charges, oil-soluble dyes such as oil black and spiron black, metal-containing azo compounds, azo complex dyes, metal salts of naphthenic acid, salicylic acid and its derivatives, metal complexes and metal salts (metal is Chromium, zinc, zirconium, etc.), fatty acid soaps, long-chain alkyl carboxylates, resin acid soaps, and the like. The charge control agent can be used alone or in combination of two or more as required. The content of the charge control agent is not particularly limited and can be appropriately selected from a wide range, but is preferably 0.5 to 3 parts by weight with respect to 100 parts by weight of the binder resin monomer.

  The binder resin monomer as described above, various additives added as necessary, and a colorant slurry are mixed to obtain a polymerizable monomer composition. Mixing can be performed by a known mixer.

  As the aqueous dispersion medium into which the polymerizable monomer composition is charged, water or an aqueous liquid containing water as a main component can be used. Examples of the dispersion stabilizer include water-soluble polymers such as polyvinyl alcohol, methylcellulose, and gelatin; poorly water-soluble salts such as calcium phosphate, barium sulfate, calcium sulfate, barium carbonate, calcium carbonate, and magnesium carbonate; and inorganic substances such as silicic acid. Examples thereof include polymer substances, metal oxides such as aluminum oxide and titanium oxide, metal hydroxides such as aluminum hydroxide, magnesium hydroxide, and ferric hydroxide. The dispersion stabilizers can be used alone or in combination of two or more. The dispersion stabilizer is usually used at a ratio of 0.1 to 20 parts by weight, preferably 0.5 to 18 parts by weight, with respect to 100 parts by weight of the aqueous dispersion medium.

  The ratio of the polymerizable monomer composition to the aqueous dispersion medium is not particularly limited, but considering the ease of granulation in the aqueous dispersion medium and the dispersion stability of the particles during the polymerization reaction, A range in which the concentration of the polymerizable monomer composition is 5 to 50% by weight, preferably 10 to 40% by weight, more preferably about 20 to 35% by weight is preferable.

  The production of the toner by the suspension polymerization method is performed by a known method. Specifically, a polymerizable monomer composition in which a binder resin monomer, a polymerization initiator and the like are uniformly dissolved or dispersed is prepared. The colorant slurry is used in an amount of 0.1 to 20 parts by weight, more preferably 0.2 to 10 parts by weight, based on 100 parts by weight of the binder resin monomer. The amount is less than parts by weight. Next, the prepared polymerizable monomer composition is put into an aqueous dispersion medium containing a dispersion stabilizer, and dispersed and granulated using a mixing device having a high shearing force. In the present invention, at this time, the colorant slurry is introduced into the aqueous dispersion medium together with the polymerizable monomer composition. Thereafter, the granulated polymerizable monomer composition is subjected to suspension polymerization.

  Examples of the mixing device having a high shearing force include a stirrer generally called a homomixer, a homogenizer, or the like. Such a stirrer includes a specially shaped turbine or rotor that rotates at high speed, and a stator or screen that is installed on the outer periphery of the rotating portion with a clearance of 2 mm or less. Then, stirring is performed by mechanical energy such as shearing force, pressure fluctuation, cavitation, collision force generated between the turbine or rotor rotating at a peripheral speed of about 1 m / second to about 40 m / second and the stator or screen. . Suspension polymerization is carried out by placing in a reactor equipped with a stirring blade and stirring the mixture at 65 ° C. for 8 hours to cause a polymerization reaction.

  A commercially available stirrer can be used as the mixing device having a high shearing force. Examples of commercially available agitators include T.I. K homomixer (made by Special Machine Industry Co., Ltd.), Claremix (made by M Technique Co., Ltd.), Polytron homogenizer (made by KINEMATICA), Supraton (made by Tsukishima Kikai Co., Ltd.), etc. are mentioned.

  In the suspension polymerization step, an aqueous system that has been extremely difficult in the past by using a colorant slurry obtained by the above-described dispersion step, in which the colorant exhibits excellent dispersibility in a liquid medium. It is possible to uniformly disperse the colorant in the dispersion medium, and it is possible to produce a toner having excellent colorant uniform dispersibility.

[Dissolution suspension process]
In the dissolution suspension step, the binder resin is dissolved and suspended in the presence of a colorant dispersion to obtain an electrophotographic toner. The dissolution suspension method in the dissolution suspension step is not particularly limited as long as a colorant dispersion is used, and a conventionally known dissolution suspension method can be used. For example, in the dissolution suspension step, a resin emulsion in which a binder resin is dissolved or dispersed in an organic solvent is prepared, and the resin emulsion and the colorant slurry are mixed. The obtained mixture is further mixed with an aqueous dispersion to dissolve and suspend the binder resin, granulate, and the toner is manufactured by removing the organic solvent after the separation.

  As the binder resin, known toner resins can be used. For example, polystyrene, poly-α-methylstyrene, chloropolystyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer. Polymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-acrylic acid ester -Styrene resins such as methacrylic acid ester copolymer, styrene-α-methyl chloroacrylate copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, styrene-vinyl methyl ether copolymer, etc. Homopolymers or copolymers containing Reester, epoxy resin, urethane modified epoxy resin, silicone modified epoxy resin, vinyl chloride resin, rosin modified maleic acid resin, phenol resin, polyethylene, polypropylene, ionomer resin, polyurethane, silicone resin, ketone resin, ethylene-ethyl acrylate copolymer , Xylene resin, polyvinyl butyral resin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, etc., alone or in combination. In the present invention, styrene-acrylic acid ester resins, styrene-methacrylic acid ester resins, and polyesters are particularly preferable. As the binder resin, those having a glass transition temperature of 50 to 75 ° C. and a flow softening temperature of 100 to 150 ° C. are preferable.

  To the toner material, additives other than the binder resin and the colorant such as a release agent and a charge control agent may be added. For example, various additives exemplified in the above-described suspension polymerization method may be used. .

  Organic solvents include hydrocarbons such as toluene, xylene, hexane, halogenated hydrocarbons such as methylene chloride, chloroform, dichloroethane, trichloroethane, carbon tetrachloride, alcohols such as ethanol, butanol, isopropyl alcohol, acetone, methyl ethyl ketone, Examples include ketones such as methyl isobutyl ketone, ethers such as benzyl alcohol ethyl ether, benzyl alcohol isopropyl ether, and tetrahydrofuran, and esters such as methyl acetate, ethyl acetate, and butyl acetate. Can do. The organic solvent is preferably 40 to 300 parts by weight, more preferably 60 to 140 parts by weight, and more preferably 80 to 120 parts by weight with respect to 100 parts by weight of the toner material. More preferably it is. By setting the amount of the organic solvent in such a range, the viscosity of the resin emulsion in which the toner material is dissolved or dispersed in the organic solvent is 20 to 500 mP · s (cps) at 25 ° C., preferably 30 to 300 mP. It can be set to s (cps). Viscosity can be measured by using a rotary viscometer.

  Mixing of the colorant slurry and the resin emulsion can be performed by a known mixer. The colorant slurry is used in an amount of 0.1 to 20 parts by weight, more preferably 0.2 to 10 parts by weight, based on 100 parts by weight of the binder resin monomer. The amount is less than parts by weight.

  As the aqueous dispersion, an aqueous solution in which a dispersion stabilizer and an emulsifier are dissolved or dispersed in water can be used. Examples of the dispersion stabilizer include various metal oxides such as tricalcium phosphate, hydroxyapatite, calcium carbonate, and silica, polyvinyl alcohol, polyvinyl pyrrolidone, hydroxyethyl cellulose, carboxymethyl cellulose, and sodium polyacrylate.

  Examples of the emulsifier used in combination with the dispersion stabilizer include sodium alkylbenzene sulfonate such as sodium oleate and sodium dodecylbenzene sulfonate, sodium α-olefin sulfonate, sodium alkyl sulfonate, sodium alkyl diphenyl ether disulfonate, and the like.

  The addition amount of the dispersion stabilizer is preferably 0.01 parts by weight or more and 10 parts by weight or less, more preferably 0.1 parts by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the toner material mixed in the aqueous dispersion. . The addition amount of the emulsifier is preferably 0.01 parts by weight or more and 10 parts by weight or less, and more preferably 0.1 parts by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the toner material mixed in the aqueous dispersion.

  The dissolution suspension method can be carried out by a known method. Specifically, a solution or dispersion obtained by dissolving or dispersing a mixture containing a resin emulsion and a colorant slurry in an organic solvent is pressed into an aqueous dispersion through the pores of porous glass to form emulsion oil droplets. To do. At this time, the emulsion oil droplets are vibrated to form emulsion fine particles corresponding to the toner particle size, the emulsion fine particles and the aqueous dispersion are separated by a method such as water washing, and the organic solvent is removed from the obtained emulsion fine particles. To obtain toner particles. The removal of the organic solvent is performed by heating the obtained emulsion solution to a temperature not lower than the boiling point of the organic solvent or by spraying the emulsion solution in an atmosphere not lower than the boiling point of the organic solvent by a spray drying apparatus or the like. At this time, aggregation of the toner particles can be prevented by performing the heating temperature below the glass transition temperature of the binder resin.

  In the dissolution and suspension process, the colorant obtained by the dispersion process, which exhibits excellent dispersibility in a liquid medium, makes it possible to achieve uniform coloration in an organic solvent, which has been extremely difficult in the past. Can be dispersed and a toner excellent in uniform dispersibility of the colorant can be produced.

  By the suspension polymerization step or the dissolution suspension step as described above, a toner having a volume average particle size of 3 μm or more and 8 μm or less, preferably 4 μm or more and 7 μm or less is obtained. When the volume average particle size is 3 μm, the particle size of the toner becomes too small, and there is a possibility that high charge and low fluidity may occur. When this high charging and low fluidization occur, it becomes impossible to stably supply the toner to the photoreceptor, and there is a possibility that background fogging and a decrease in image density may occur. When the volume average particle diameter exceeds 8 μm, the particle diameter of the toner is large, so that a high-definition image cannot be obtained. Further, as the toner particle size increases, the specific surface area decreases and the charge amount of the toner decreases. When the charge amount of the toner is small, the toner is not stably supplied to the photoconductor, and there is a possibility that in-machine contamination due to toner scattering occurs.

  In the toner of the present invention obtained as described above, the colorant is uniformly dispersed in the toner, and is excellent in the uniformity of coloring performance and charging performance. Therefore, when an image is formed using such a toner, a high-quality image with high coloring power and no density unevenness can be obtained.

  An external additive may be added to the toner of the present invention. Known external additives can be used, such as silicon oxide, titanium oxide, silicon carbide, aluminum oxide, calcium carbonate, barium titanate, strontium titanate, metal stearate particles, fluorine resin particles, acrylic Resin particles and the like. One type of external additive can be used alone, or two or more types can be used in combination. The amount of the external additive used is not particularly limited, but is preferably 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the toner.

  The toner of the present invention can be used as a one-component developer or a two-component developer. When used as a one-component developer, the toner is used only without using a carrier. When used as a one-component developer, a blade and a fur brush are used, and the toner is conveyed by friction charging with a developing sleeve to adhere the toner onto the sleeve, thereby forming an image. When used as a two-component developer, the toner of the present invention is used with a carrier. As the carrier, a known carrier can be used, and examples thereof include a single or composite ferrite composed of iron, copper, zinc, nickel, cobalt, manganese, chromium, etc. and carrier core particles whose surface is coated with a coating substance. A known material can be used as the coating material, for example, polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin, polyester, metal compound of ditertiary butyl salicylic acid, styrene resin, acrylic resin, Polyacids, polyvinyllarls, nigrosine, aminoacrylate resins, basic dyes, lakes of basic dyes, silica fine powders, alumina fine powders, and the like can be mentioned, and these are preferably selected according to the toner components. Moreover, a coating substance can be used individually by 1 type, or can use 2 or more types together. The volume average particle diameter of the carrier is preferably 10 to 100 μm, more preferably 20 to 50 μm.

(Example)
EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not particularly limited as long as it does not exceed the gist thereof. In the examples and comparative examples, the dispersed particle diameter of the colorant, the volume average particle diameter of the toner, and the coefficient of variation (CV value) were obtained as follows.

<Dispersed particle size of colorant>
Measurement was performed using a laser light scattering microscope (trade name: DLS-700, manufactured by Otsuka Electronics Co., Ltd.), and the dispersed particle size, which is the number average particle size of the colorant, was calculated from the number particle size distribution of the sample particles.

<Volume average particle size and coefficient of variation>
20 ml of a sample and 1 ml of sodium alkyl ether sulfate are added to 50 ml of an electrolytic solution (trade name: ISOTON-II, manufactured by Beckman Coulter, Inc.), and ultrasonic waves are applied using an ultrasonic disperser (trade name: UH-50, manufactured by STM). A sample for measurement was prepared by dispersion treatment at a frequency of 20 kHz for 3 minutes. This sample for measurement was measured using a particle size distribution measuring device (trade name: Multisizer 3, manufactured by Beckman Coulter, Inc.) under the conditions of aperture diameter: 20 μm, number of measured particles: 50000 count, and volume particle size distribution of sample particles. Were used to determine the standard deviation in volume average particle size and volume particle size distribution. The coefficient of variation (CV value,%) was calculated based on the following formula.
CV value (%) = (standard deviation in volume particle size distribution / volume average particle size) × 100

Example 1
[Dispersing process]
It was obtained by mixing 5 parts of carbon black, 3.5 parts of sodium dodecylbenzenesulfonate (trade name: LUNOX S-100, surfactant, manufactured by Toho Chemical Co., Ltd.) and 96.5 parts of water. The coarse powder slurry was put into a tank of a high-pressure homogenizer (trade name: NANO3000, manufactured by Miki Co., Ltd.), pressurized and heated to 210 MPa and 70 ° C., and supplied to the pressure-resistant nozzle through a pipe. The pressure-resistant nozzle is a pressure-resistant multiple nozzle having a length of 0.2 cm formed so that two liquid flow holes having a hole diameter of 0.085 mm are substantially parallel in the longitudinal direction of the nozzle. The temperature of the aqueous slurry at the nozzle inlet was 70 ° C., the pressure applied to the aqueous slurry was 210 MPa, and the temperature of the aqueous slurry at the nozzle outlet was 120 ° C. The aqueous slurry discharged from the pressure-resistant nozzle was introduced into a serpentine type cooler connected to the outlet of the pressure-resistant nozzle and cooled. The temperature of the aqueous slurry at the cooler outlet was 30 ° C. The aqueous slurry discharged from the cooler outlet was introduced into a multistage pressure reducing device connected to the cooler outlet for decompression. The above treatment with the high-pressure homogenizer was repeated three times to obtain a colorant slurry containing finely divided carbon black. The colorant dispersed particle size in this colorant slurry was 0.2 μm.

[Polymerizable monomer composition preparation step]
Styrene (binder resin monomer) 70 parts n-butyl methacrylate (binder resin monomer) 30 parts Charge control agent (trade name: TRH, manufactured by Hodogaya Chemical Co., Ltd.) 1 part Divinylbenzene (crosslinkable monomer) 1 part 2,2'-azobisisobutyronitrile (polymerization initiator) 2 parts Colorant slurry 100 parts

  The above materials were stirred and mixed at a rotational speed of 6000 rpm by a TK homomixer (manufactured by PRIMIX Co., Ltd.), which is a mixer having high shearing force, to prepare a polymerizable monomer composition in which the above materials were uniformly dispersed. .

[Suspension polymerization process]
The prepared polymerizable monomer composition was charged into a dispersion stabilizer-containing aqueous solution in which 2.5 parts of polyvinyl alcohol was dissolved in 250 parts of ion-exchanged water, and the mixture was stirred and mixed using a propeller-type stirrer. A mixed solution obtained by using a pump in a granulator (CLEAMIX, manufactured by M Technique Co., Ltd.) equipped with a 500cc pressurized vacuum attachment, a rotor, and a screen, and operating at a rotor speed of 21,000 rpm. Was supplied at a flow rate of 30 kg / Hr. Thus, the continuous process was performed and the droplet (particle | grains) of the polymerizable monomer composition was granulated.

  An aqueous dispersion containing the granulated polymerizable monomer composition is placed in a reactor equipped with a stirring blade, and stirred at 65 ° C. for 8 hours to conduct a polymerization reaction. A polymer (polymerized toner) is then added to the aqueous dispersion. An aqueous dispersion obtained by dispersing particles) was obtained.

  The obtained polymer aqueous dispersion was filtered to separate water, and 500 parts of ion-exchanged water was newly added, heated to 50 ° C., reslurried, and washed with water for 10 minutes. This water washing was repeated 5 times, and the solid content was separated by filtration, followed by drying at 40 ° C. all day and night in a dryer to obtain toner particles. The obtained toner particles had a volume average particle diameter of 5.7 μm and a coefficient of variation (CV value) of 22. 0.2 parts by weight of hydrophobic silica (trade name: R-974, manufactured by Nippon Aerosil Co., Ltd.) and hydrophobic titanium (trade name: T-805, manufactured by Nippon Aerosil Co., Ltd.) with respect to 100 parts by weight of the toner particles. The toner of Example 1 was obtained by adding 0.3 part by weight and mixing with a Henschel mixer.

(Example 2)
[Resin emulsion preparation process]
A monomer mixture containing 80 parts by weight of styrene monomer, 20 parts by weight of butyl acrylate, and 5 parts by weight of acrylic acid was added to 105 parts by weight of water, 1 part by weight of a nonionic emulsifier, 1.5 parts by weight of an anionic emulsifier, and 0. It added to the water-soluble mixture in which 55 weight part was mixed, and it stirred under 70 degreeC nitrogen stream for 8 hours, and made the polymerization reaction. After the polymerization reaction, the mixture was cooled to obtain a milky white resin emulsion having a particle size of 0.25 μm.

[Dispersing process]
It was obtained by mixing 7 parts of phthalocyanine blue, 3.5 parts of sodium dodecylbenzenesulfonate (trade name: LUNOX S-100, surfactant, manufactured by Toho Chemical Co., Ltd.) and 96.5 parts of water. The coarse powder slurry was put into a tank of a high-pressure homogenizer (trade name: NANO3000, manufactured by Miki Co., Ltd.), pressurized and heated to 210 MPa and 70 ° C., and supplied to the pressure-resistant nozzle through a pipe. The pressure-resistant nozzle is a pressure-resistant multiple nozzle having a length of 0.2 cm formed so that two liquid flow holes having a hole diameter of 0.085 mm are substantially parallel in the longitudinal direction of the nozzle. The temperature of the aqueous slurry at the nozzle inlet was 70 ° C., the pressure applied to the aqueous slurry was 210 MPa, and the temperature of the aqueous slurry at the nozzle outlet was 120 ° C. The aqueous slurry discharged from the pressure-resistant nozzle was introduced into a serpentine type cooler connected to the outlet of the pressure-resistant nozzle and cooled. The temperature of the aqueous slurry at the cooler outlet was 30 ° C. The aqueous slurry discharged from the cooler outlet was introduced into a multistage pressure reducing device connected to the cooler outlet for decompression. The above treatment with the high-pressure homogenizer was repeated three times to obtain a colorant slurry containing finely divided phthalocyanine blue. The colorant dispersed particle size in this colorant slurry was 0.2 μm.

[Dissolution suspension process]
A slurry containing 200 parts of resin emulsion obtained in the resin emulsion preparation step, 20 parts of polyethylene wax emulsion, and 100 parts of colorant slurry was added to sodium dodecylbenzenesulfonate (trade name: LUNOX S-100, surfactant, Made by Toho Chemical Co., Ltd.) Dispersed in 0.2 parts by weight of water, added diethylamine to adjust the pH to 5.5, and then added 0.3 parts by weight of aluminum sulfate as the electrolyte with stirring. Then, the mixture was stirred at high speed with a TK homomixer and dispersed in water.

  Furthermore, 40 parts of styrene monomer, 10 parts of butyl acrylate, and 5 parts of zinc salicylate were added together with 40 parts of water, and the mixture was heated to 90 ° C. while stirring under a nitrogen stream, and hydrogen peroxide was added for polymerization for 5 hours. And let the particles grow. After the polymerization was stopped, the pH was raised to 95 ° C. and maintained for 5 hours without adjusting the pH to 5 or higher in order to increase the bond strength of the associated particles. Thereafter, the obtained particles were washed with water and vacuum-dried at 45 ° C. for 10 hours. Thus, toner particles were obtained. The obtained toner particles had a volume average particle size of 5.3 μm and a coefficient of variation (CV value) of 25. 0.2 parts by weight of hydrophobic silica (trade name: R-974, manufactured by Nippon Aerosil Co., Ltd.) and hydrophobic titanium (trade name: T-805, manufactured by Nippon Aerosil Co., Ltd.) with respect to 100 parts by weight of the toner particles. The toner of Example 2 was obtained by adding 0.3 part by weight and mixing with a Henschel mixer.

(Comparative Example 1)
[Resin emulsion preparation process]
A monomer mixture containing 80 parts by weight of styrene monomer, 20 parts by weight of butyl acrylate, and 5 parts by weight of acrylic acid was added to 105 parts by weight of water, 1 part by weight of a nonionic emulsifier, 1.5 parts by weight of an anionic emulsifier, and 0. It added to the water-soluble mixture in which 55 weight part was mixed, and it stirred under 70 degreeC nitrogen stream for 8 hours, and made the polymerization reaction. After the polymerization reaction, the mixture was cooled to obtain a milky white resin emulsion having a particle size of 0.25 μm.

[Dispersing process]
It was obtained by mixing 7 parts of phthalocyanine blue, 3.5 parts of sodium dodecylbenzenesulfonate (trade name: LUNOX S-100, surfactant, manufactured by Toho Chemical Co., Ltd.) and 96.5 parts of water. The coarse powder slurry was put into a tank of a high-pressure homogenizer (NANO3000, manufactured by Mie Co., Ltd.) that was replaced with a system not equipped with a decompression mechanism, heated to 210 MPa and 70 ° C., and supplied to the pressure-resistant nozzle through a pipe . The pressure-resistant nozzle is a pressure-resistant multiple nozzle having a length of 0.2 cm formed so that two liquid flow holes having a hole diameter of 0.085 mm are substantially parallel in the longitudinal direction of the nozzle. The temperature of the aqueous slurry at the nozzle inlet was 70 ° C., the pressure applied to the aqueous slurry was 210 MPa, and the temperature of the aqueous slurry at the nozzle outlet was 120 ° C. The aqueous slurry discharged from the pressure-resistant nozzle was introduced into a serpentine type cooler connected to the outlet of the pressure-resistant nozzle and cooled. The temperature of the aqueous slurry at the cooler outlet was 30 ° C. For aqueous slurry discharged from the outlet of the cooler, repeated 3 times a treatment with high pressure homogenizer, to obtain a colorant slurry containing phthalocyanine blue, which is comminuted. However, the dispersed particle diameter of the colorant in this colorant slurry was very large and was 3 μm.

[Dissolution suspension process]
A slurry containing 200 parts of resin emulsion obtained in the resin emulsion preparation step, 20 parts of polyethylene wax emulsion, and 100 parts of colorant slurry was added to sodium dodecylbenzenesulfonate (trade name: LUNOX S-100, surfactant, Made by Toho Chemical Co., Ltd.) Dispersed in 0.2 parts by weight of water, added diethylamine to adjust the pH to 5.5, and then added 0.3 parts by weight of aluminum sulfate as the electrolyte with stirring. Then, the mixture was stirred at high speed with a TK homomixer and dispersed in water.

  Furthermore, 40 parts of styrene monomer, 10 parts of butyl acrylate, and 5 parts of zinc salicylate were added together with 40 parts of water, and the mixture was heated to 90 ° C. while stirring under a nitrogen stream, and hydrogen peroxide was added for polymerization for 5 hours. And let the particles grow. After the polymerization was stopped, the pH was raised to 95 ° C. and maintained for 5 hours without adjusting the pH to 5 or higher in order to increase the bond strength of the associated particles. Thereafter, the obtained particles were washed with water and vacuum-dried at 45 ° C. for 10 hours. Thus, toner particles were obtained. The obtained toner particles had a volume average particle diameter of 7.1 μm and a coefficient of variation (CV value) of 26. 0.2 parts by weight of hydrophobic silica (trade name: R-974, manufactured by Nippon Aerosil Co., Ltd.) and hydrophobic titanium (trade name: T-805, manufactured by Nippon Aerosil Co., Ltd.) with respect to 100 parts by weight of the toner particles. The toner of Comparative Example 1 was obtained by adding 0.3 part by weight and mixing with a Henschel mixer.

  95 parts by weight of a ferrite core carrier having a volume average particle size of 45 μm as a carrier is added to 5 parts by weight of the toners of the examples and comparative examples, and a V-type mixer (trade name: V-5, manufactured by Tokuju Koujo Co., Ltd.) Was mixed for 20 minutes to prepare a two-component developer having a toner concentration of 5% by weight.

  The charging uniformity after forming an image using a two-component developer containing the toners of Examples and Comparative Examples was evaluated by the following method.

<Charge uniformity>
The two-component developer containing the toner of Example and Comparative Example was measured using a particle charge distribution measuring device E-SPART Analyzer model EST-1 (manufactured by Hosokawa Micron Corporation), and the half-value width of the maximum peak of the charge amount distribution (maximum in the distribution) It was evaluated by the size of the cut width when the distribution was cut at a value half the peak height. If the distribution is sharp, the full width at half maximum is small. Conversely, if the distribution is broad, the full width at half maximum is large. Table 1 shows the evaluation results of the charging uniformity.

  In the toners of Examples 1 and 2, the colorant was uniformly dispersed in the toner, and the uniformity in coloring performance and charging performance was excellent. Further, when an image was formed using the toner as in Examples 1 and 2, a high-quality image having high colorability and no uneven density could be obtained.

  In contrast, the toner of Comparative Example 1 had a large dispersion diameter of the colorant in the toner, poor dispersion, and low coloring power. Also, the charging performance was non-uniform, and when an image was formed using the toner of Comparative Example 1, the image was rough and the density was insufficient.

FIG. 2 is a system diagram showing a simplified configuration of a high-pressure homogenizer 1 used in the toner manufacturing method of the present invention. 2 is a cross-sectional view schematically showing a configuration of a pressure-resistant nozzle 21. FIG. It is sectional drawing which shows typically the structure of the pressure | voltage resistant nozzle 31 of another form. 3 is a longitudinal sectional view schematically showing a configuration of a decompression nozzle 41. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High pressure homogenizer 2 Tank 3 Feeding pump 4 Pressure unit 5 Heater 6 Grinding nozzle 7 Decompression module 8 Cooling machine 9 Piping 10 Extraction port 21, 31 Pressure-resistant nozzle 41 Pressure-reducing nozzle

Claims (4)

In the method for producing an electrophotographic toner, an electrophotographic toner comprising a binder resin and a colorant is obtained using a dispersion of the colorant.
The dispersion of the colorant is a dispersion obtained by treating a mixture of the colorant and the liquid medium with a high-pressure homogenizer equipped with a decompression unit, and the finely divided colorant is dispersed in the liquid medium. A method for producing an electrophotographic toner, which is characterized.   2. The method for producing an electrophotographic toner according to claim 1, wherein the binder resin monomer is subjected to suspension polymerization in the presence of a colorant dispersion to obtain an electrophotographic toner.   2. The method for producing an electrophotographic toner according to claim 1, wherein a binder resin is dissolved and suspended in the presence of a colorant dispersion to obtain an electrophotographic toner.   An electrophotographic toner produced by the method for producing an electrophotographic toner according to claim 1.

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