JP4365263B2 - Toner for developing electrostatic latent image and method for producing the same - Google Patents

Description

  The present invention relates to electrostatic latent image development used to develop an electrostatic latent image formed on an electrostatic latent image carrier such as a photoreceptor in an electrophotographic process and an electrostatic recording method such as an ion flow method. The present invention relates to a toner and a method for producing the same.

  For example, when an electrophotographic process is used in an image forming apparatus using an electrostatic recording system, an image is formed by a charging process, an exposure process, a developing process, a transfer process, a cleaning process, a fixing process, and the like. In the charging step, the surface of the photoreceptor is uniformly charged. In the exposure step, the charged photoconductor is exposed to form an electrostatic latent image on the surface of the photoconductor. In the development step, a visible image is formed by attaching a developer such as toner to the electrostatic latent image formed on the surface of the photoreceptor. In the transfer step, the visible image formed on the surface of the photoconductor is transferred to a recording medium such as paper or sheet. In the fixing step, the visible image transferred to the recording medium is fixed by means such as heating and pressing. In the cleaning process, the developer remaining on the surface of the photoreceptor without being transferred to the recording medium is collected. Through the above steps, an image forming apparatus using an electrophotographic process forms a desired image on a recording medium.

  As a method for producing toner used in such an image forming apparatus, a dry method and a wet method are known. Examples of the dry method include a pulverization method. The pulverization method is a method in which a toner component such as a thermoplastic resin, a colorant, a charge control agent and a wax is melt-kneaded and then solidified by cooling, and pulverized and classified to obtain a toner.

  Examples of the wet method include a suspension polymerization method, an emulsion aggregation method, and a suspension granulation method. In the suspension polymerization method, a polymerizable monomer, a polymerization initiator, a colorant, a wax and a charge control agent are mixed and suspended in water, and the polymerizable monomer is polymerized in the suspension. This is a method for obtaining toner. The emulsion aggregation method is a method in which toner particles are obtained by preparing resin fine particles by emulsion polymerization and aggregating the fine particles in a dispersion in which a colorant, wax and the like are dispersed. The suspension granulation method is a method in which a colorant, a wax and a charge control agent are mixed in a resin and melted, and the resulting melt is suspended in a medium that does not dissolve and granulated to obtain a toner. .

  In recent years, downsizing, digitization, and full color have been achieved in image forming apparatuses using electrostatic recording methods such as copying machines and printers. Therefore, a toner having a performance capable of realizing high image quality, color tone reproducibility, and the like is demanded for a toner used in an image forming apparatus using an electrostatic recording method. In other words, in the development process, the toner is uniform in shape and colored on the surface of the toner so that the toner can smoothly adhere to the electrostatic latent image on the photoreceptor and form a clear visible image. It is necessary to have excellent toner characteristics such as charging stability and storage stability such that the agent and wax are not exposed. However, the toner manufactured by the above manufacturing method has a non-uniform shape and inferior toner characteristics.

  The wet method is a method for producing a toner that has advantages such that it is easy to control the shape of the toner and that the colorant and wax can be encapsulated without being exposed to the surface of the toner. However, there are many restrictions on materials that can be used for resins, colorants, waxes, and the like, and since it is impossible to use optimal materials, it is difficult to realize high-definition and high coloring power of color images. Therefore, there is a problem that the amount of toner consumption increases.

  The pulverization method, which is a dry method, is an advantageous method for increasing the sharpness of a color image and increasing the coloring power because there are few restrictions on the materials that can be used and an optimum material can be used. However, since the shape is not uniform, the transfer rate is low, and the chargeability is not uniform, so the reproducibility of the formed image is also deteriorated. Further, since the wax and the colorant are exposed on the surface, there are many problems such as poor durability and poor storage stability and environmental stability such as generation of fine powder due to long-term running and environmental changes.

  Therefore, a typical conventional technique for solving the problem of the pulverization method is described in Patent Document 1. The method for producing a toner of Patent Document 1 is a method for producing a toner using a method in which a toner produced by a pulverization method is subjected to a heat treatment in a dry manner, in which inorganic fine particles are previously attached to the toner surface.

  As another conventional technique, Patent Document 2 describes a manufacturing method by dry heat treatment similar to Patent Document 1. The method for producing an electrophotographic toner of Patent Document 2 is a method in which toner particles are supplied into a heat treatment space, heat treated with hot air, and then the toner particles dispersed with hot air are cooled with cooling air. An electrophotographic toner manufacturing method that optimizes the positions of nozzles for supplying toner particles, hot air, and cooling air therein.

  Further, as another conventional technique, Patent Document 3 describes a manufacturing method by wet heat treatment. In the method for producing a dry developer for electrophotography of Patent Document 3, water is mixed with the granular composition obtained by the pulverization method to form a slurry, and a shear stress of 10 m / sec or more is applied to the slurry. And a method for producing a dry developer for electrophotography, wherein the granular composition is further pulverized.

JP-A-3-179363 JP 2000-29241 A JP 59-159176

  The method for producing a toner for an electrostatic latent image needs to be able to produce a toner that has a uniform shape and does not expose wax and colorant on the toner surface.

  According to the toner manufacturing method disclosed in Patent Document 1, since the toner having inorganic fine particles attached to the surface is heat-treated, the toner can be spheroidized while preventing aggregation between the toners. However, since the obtained toner is a toner whose surface is covered with inorganic fine particles, a decrease in fixing property to a recording medium such as a paper surface and a decrease in the effect of preventing offset are inevitable.

  According to the method for producing toner for electrophotography disclosed in Patent Document 2, the position of the nozzle for supplying toner particles, hot air and cooling air into the heat treatment space is optimized, so that the toner particles are uniformly dispersed in the hot air. The toner particles can also be prevented from agglomerating when cooled by cooling air. Therefore, the toner particles can be spheroidized without adding an external additive or the like to the toner particles. However, in order to obtain sufficient sphericity, heat treatment conditions such as a long heat treatment time and a high heat treatment temperature are necessary, so that the wax is transferred to the surface by heat and the dispersion state in the toner changes, Fusion of toner particles occurs, and the particle diameter increases.

  According to the dry development method for electrophotography disclosed in Patent Document 3, the granular composition obtained by the pulverization method is mixed with water to form a slurry, and the slurry is further subjected to shear stress to further form the granular composition. Since it is pulverized into a spherical shape, the toner particles can be spheroidized without adding an external additive or the like to the toner particles. However, the obtained toner cannot remove the colorant and wax existing on the surface.

  An object of the present invention is to provide a toner for developing an electrostatic latent image that can control the shape of the toner and that does not expose the colorant and wax to the surface of the toner, and a method for producing the same.

The present invention comprises a preparation step of preparing fine particles containing a binder resin, a colorant and a wax;
A dispersion step of stirring and dispersing the fine particles in a solvent containing an organic solvent under normal pressure at a temperature of 30 ° C. or higher and lower than the melting point of the wax;
Have a separation step of separating the fine particles and a solvent,
The organic solvent includes a solvent that does not dissolve the binder resin, and acetone that is a solvent that dissolves the binder resin,
The content of acetone is 30 parts by weight or less with respect to 100 parts by weight of the solvent that does not dissolve the binder resin .

In the preparation step, the present invention prepares fine particles by pulverizing a kneaded product containing a binder resin, a colorant and a wax,
Wherein in the dispersion step, the fine particles are dispersed by 攪拌in a solvent comprising an organic solvent, it characterized and Turkey to spherical the particle.

Or the present invention, the solvent does not dissolve the binder resin, characterized in that an alcohol.
The present invention is further characterized by further comprising an external addition step of externally adding inorganic fine particles to the fine particles.

The present invention, alcohol, characterized in that ethanol.

Or the present invention is a toner for electrostatic latent image development which is characterized in that produced by the manufacturing method of the.

According to the present invention, fine particles containing a binder resin, a colorant and a wax are prepared, and the fine particles obtained in a solvent containing an organic solvent are stirred at a temperature lower than the melting point of the wax at 30 ° C. or higher under normal pressure. To do. By doing so, the colorant and wax present near the surface of the fine particles can be dissolved in the solvent. Thereafter, by separating the fine particles and the solvent, it is possible to produce a toner in which the colorant and the wax are not exposed on the surface of the toner. Further, since stirring is performed at a temperature lower than the melting point of the wax, the wax does not elute (bleed) on the surface of the toner, and the wax can be prevented from being exposed on the surface of the toner.
The organic solvent includes a solvent that does not dissolve the binder resin and acetone that is a solvent that dissolves the binder resin, and the content of acetone is 30 parts by weight with respect to 100 parts by weight of the solvent that does not dissolve the binder resin. Less than parts by weight. By doing so, the colorant and wax present on the surface of the toner can be removed without changing the binder resin. Therefore, it is possible to prevent the colorant and the wax from being exposed on the surface of the toner while keeping the shape of the toner uniform.

According to the invention, in the preparation step, the kneaded product containing the binder resin, the colorant and the wax is pulverized to prepare fine particles . Then, in the dispersion step, the solvent comprising an organic solvent and fine particles are dispersed in 攪 拌, made spherical microparticles.

According to the present invention, an organic solvent which does not dissolve the binder resin is alcohol. Alcohol can be softened without dissolving the binder resin, and further, the colorant and wax can be dissolved, so that the colorant and wax present on the toner surface can be more efficiently removed. . Therefore, it is possible to further prevent the colorant and the wax from being exposed on the surface of the toner while maintaining the shape of the toner.
According to the present invention, the method further includes an external addition step of externally adding inorganic fine particles to the fine particles. By doing so, it is possible to prevent fusion between the toners, so that a toner having a more uniform shape can be obtained.

  According to the invention, the alcohol is ethanol. Since ethanol is an environmentally friendly solvent compared to other organic solvents, no special wastewater treatment is required and the burden on the environment is reduced.

  Further, according to the present invention, since the toner for developing an electrostatic latent image is produced by the above production method, the toner has a uniform shape and a small amount of colorant and wax exposed on the surface of the toner.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a process diagram showing a toner manufacturing method according to the present invention. In the pulverization step S1, which is a preparation step, finely shaped particles having a non-uniform shape are prepared by pulverizing a kneaded product containing a binder resin, a colorant and a wax. In the spheronization step S2, which is a dispersion step, the fine particles are stirred at a predetermined temperature in a solvent containing an organic solvent. By doing so, the fine particles are spheroidized to have a uniform shape, and further, the colorant and wax existing near the surface of the fine particles are dissolved in the solvent and removed. In the separation step S3, the solvent containing the colorant and wax removed from the surface of the fine particles is separated from the fine particles, and the separated fine particles are dried. By doing so, fine particles with little colorant and wax exposed on the surface can be obtained. These fine particles are the electrostatic latent image developing toner according to the present invention.

  As described above, in the method for producing a toner for developing an electrostatic latent image according to the present invention, the non-uniform fine particles obtained by pulverization are spheroidized while the colorant and wax existing near the surface are formed. Can be removed.

[Crushing process]
The method for producing a toner for developing an electrostatic latent image according to the present invention includes a pulverizing step S1. In the pulverization step S1, the kneaded material containing the binder resin, the colorant and the wax is pulverized.

  The kneaded product can be obtained by using a known method. For example, a kneading machine having a binder resin, a colorant and a wax added with additives as necessary at a melting point or softening point of the binder resin or higher. It can be obtained by melt kneading using

  The binder resin may be any thermoplastic resin, for example, styrene resins such as polystyrene, styrene-butadiene copolymer and styrene-acrylic copolymer, polyethylene, polyethylene-polyvinyl acetate copolymer and polyethylene- Ethylene resins such as polyvinyl alcohol copolymers, acrylic resins such as polymethyl methacrylate, phenol resins, epoxy resins, allyl phthalate resins, polyamide resins, polyester resins, polyether resins, and male resins Is mentioned. Among these, polyester resins are more preferable in terms of fixing properties and transparency.

  As the colorant, a masterbatch that has been subjected to a flushing treatment so as to be uniformly dispersed in the binder resin, or a masterbatch that is melt-kneaded at a high concentration with the resin may be used. The colorant may be a pigment having any color such as black, cyan, magenta and yellow. Examples of the black color pigment include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, nonmagnetic ferrite, magnetic ferrite, and magnetite. Examples of cyan pigments include bitumen, cobalt blue, alkali blue lake, and Victoria blue lake. Examples of the magenta color pigment include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, resol red, pyrazolone red, watching red, lake red C, lake red D, brilliant carmine 6B, eosin lake, Rhodamine lake B, alizarin lake, brilliant carmine 3B, and the like. Yellow pigments include, for example, yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, quinoline yellow lake, permanent yellow NCG and tartrazine lake.

  These pigments may be used alone or in combination. The content of the colorant in 100 parts by weight of the toner is preferably 2 parts by weight or more and 20 parts by weight or less, and more preferably 6 parts by weight or more and 15 parts by weight or less. When the amount is less than 2 parts by weight, the image density is lowered. When the amount is more than 20 parts by weight, the fixing property and the charging stability are deteriorated.

  As waxes, petroleum waxes such as paraffin wax, oxidized paraffin wax and microcrystalline wax, mineral waxes such as montan wax, animal and plant waxes such as beeswax and carnauba wax, polyolefin (polyethylene, polypropylene, etc.) wax, oxidized polyolefin wax, Fischer-Tropsch Synthetic waxes such as waxes may be mentioned. These waxes may be used alone or in combination. The content of the wax in 100 parts by weight of the toner is preferably 2 parts by weight or more and 15 parts by weight or less, and more preferably 5 parts by weight or more and 10 parts by weight or less. When the amount is less than 2 parts by weight, offset occurs, and when the amount is more than 15 parts by weight, the storage stability is lowered.

  As an additive, a charge control agent may be used. A known charge control agent can be used as the charge control agent, and it may be a low molecular compound or a high molecular compound. Examples thereof include quaternary ammonium salt compounds, nigrosine compounds, organometallic complexes, chelate compounds, polymer compounds obtained by homopolymerizing monomers having amino groups, and polymer compounds obtained by copolymerizing monomers having amino groups. These charge control agents may be used alone or in combination.

  As the kneader, known ones can be used, and examples thereof include a twin screw extruder, a three roll mill, a lab blast mill, and an open roll type extruder. For example, TEM-100B (manufactured by Toshiba Machine Co., Ltd.) and PCM-65 / 87 (manufactured by Ikegai Co., Ltd.) can be cited as the twin-screw extruder. Manufactured). Among them, particularly in the melt kneading operation, in order to disperse the additive efficiently, high shear kneading at a low temperature is desirable so that the resin viscosity at the time of melting does not decrease too much, and an open roll type extruder is particularly preferable. At this time, the colorant may be uniformly dispersed in the resin, and the melt-kneading conditions are not particularly limited, but are usually 80 ° C. or higher and 180 ° C. or lower and preferably 10 minutes or longer and 2 hours or shorter.

  A well-known thing can be used as a grinder, for example, a jet mill etc. can be mentioned. The kneaded product obtained by the kneader is cooled and then finely pulverized by the pulverizer. Thereafter, the finely pulverized product is classified by an air classifier or the like, whereby fine particles containing a binder resin, a colorant and a wax can be obtained.

[Spheronization process]
The method for producing a toner for developing an electrostatic latent image according to the present invention includes a spheronization step S2. In the spheronization step S2, fine particles are stirred and dispersed in a solvent at a predetermined temperature.

  The solvent is a solvent containing an organic solvent. As the organic solvent, those which do not dissolve the binder resin are desirable, and there are a hydrophilic solvent and a hydrophobic solvent than the binder resin. As solvents more hydrophilic than the binder resin, alcohols such as methanol, ethanol, isopropanol, n-butanol and t-butanol, glycols such as ethylene glycol, diethylene glycol and triethylene glycol, acids such as formic acid and acetic acid, triethylamine and triethylamine Examples include amines such as ethanolamine and ethers such as diethyl ether. Examples of hydrophobic solvents that are more hydrophobic than the binder resin include aliphatic hydrocarbons such as n-hexane, cyclohexane, heptane, octane, isooctane, 1-heptene, 1-octene, and kerosene, and silicone oils such as dimethyl silicone oil. Can be mentioned. When a polyester resin that is preferably used in color and low-temperature fixing toners is used, low molecular weight components such as diols and dibasic acids are often contained as impurities and are more hydrophilic than hydrophobic solvents. Since the solvent can be removed, a hydrophilic solvent is preferable. Further, among these, alcohols, particularly ethanol, which have little adverse effects even when remaining in the toner, have excellent drying properties, and have low odor and toxicity are particularly preferable.

  The organic solvent may contain an organic solvent that dissolves the binder resin. For example, acetone, toluene, xylene, tetrahydrofuran, etc. are mentioned. By doing so, it becomes easy to remove the colorant, wax, and the like present near the surface of the toner. The organic solvent that dissolves the binder resin is preferably 30 parts by weight or less with respect to 100 parts by weight of the organic solvent that does not dissolve the binder resin such as ethanol. More preferably, it is 20 parts by weight or less. When the amount is more than 30 parts by weight, the solvent dissolves the binder resin, so that the particles are not formed or the particles are easily aggregated to become a toner having a wide particle size distribution.

  Furthermore, water may be included as a solvent. By doing so, aggregation of toners can be further prevented. The amount of water is preferably 70 parts by weight or less with respect to 100 parts by weight of the organic solvent. More preferably, it is 50 parts by weight or less. When the amount is more than 70 parts by weight, it becomes difficult to remove the colorant and wax existing near the surface of the toner.

  The stirrer is not particularly limited, and known devices can be used. Examples thereof include a media stirrer such as a sand grinder and a paint shaker, an ultrasonic stirrer, a rotary blade stirrer equipped with paddle blades, and the like. It is done. When the rotary blade type agitator and the ultrasonic type agitator are used in combination, the colorant and wax existing near the surface of the fine particles can be effectively removed, and further, fusion between the aggregates can be prevented. .

Further, spheronization process, intends row at a temperature below the melting point of the wax. When the melting point is higher than the melting point of the wax, the wax is eluted (bleeded) on the surface of the toner. In addition, it intends line at 30 ℃ or more. If the temperature is lower than 30 ° C., the processing time becomes long and a cooling device is required, so that the operation becomes complicated.

[Separation process]
The method for producing a toner for developing an electrostatic latent image according to the present invention includes a separation step S3. In the separation step S3, the fine particles and the solvent are separated. A known method can be used as the separation method, and examples thereof include a natural sedimentation method and a centrifugal separation method. Thereafter, only fine particles can be obtained by decantation.

[External additive addition process]
The method for producing a toner for developing an electrostatic latent image according to the present invention may include an external additive adding step. The external additive addition step may be performed between the pulverization step S1 and the spheronization step S2, or may be performed after the separation step S3, or between and between the pulverization step S1 and the spheronization step S2. You may perform twice after process S3. By adding an external additive to the fine particles, aggregation of the fine particles becomes difficult to occur. Examples of the external additive are inorganic fine particles, and examples include silicon dioxide (silica) and hydrophobic silica surface-treated with polyorganosilane and a silane coupling agent. Are listed. AEROSIL R972, AEROSIL R974, AEROSIL R202, AEROSIL R805, AEROSIL R812, AEROSIL RY200, AEROSIL R809, AEROSIL RX50 (above, manufactured by Nippon Aerosil Co., Ltd.), Wacker HDK H2000, Wacker East Nipsil SS-10, Nipsil SS-15, Nipsil SS-20, Nipsil SS-50, Nipsil SS-60, Nipsil SS-100, Nipsil SS-50B, Nipsil SS-50F, Nipsil SS-10F, Nipsil SS -40, Nipsil SS-70, Nipsil SS-7 2F (manufactured by Nippon Silica Kogyo Co., Ltd.).

  The external addition amount is 0.1 parts by weight or more and 5.0 parts by weight with respect to 100 parts by weight of the toner in consideration of imparting a necessary charge amount to the toner, influence on the photosensitive drum, and environmental characteristics of the toner. The following is preferred.

  As a method for adding the external additive to the fine particles, a known mixer can be used, and examples thereof include so-called surface reformers such as a Henschel mixer and a hybridizer. The external additive may be attached to the surface of the fine particles, or a part of the external additive may be embedded in the fine particles.

[Supercritical carbon dioxide]
In the method for producing a toner for developing an electrostatic latent image according to the present invention, the following solvent different from the above solvent may be used. Specifically, it is a supercritical fluid, for example, carbon dioxide in a supercritical state. By setting the temperature and pressure of the substance to a certain condition (critical point) or more, the density in the gas phase and the liquid phase becomes equal, and such a state is a supercritical state.

  Supercritical fluids exhibit both gas and liquid properties. For example, the density of a supercritical fluid is several hundred times that of a gas and is close to the density of a liquid. The viscosity is 1/10 to 1/100 of the viscosity of the liquid and is close to the viscosity of the gas. The thermal conductivity is about 100 times the thermal conductivity of gas and is close to the thermal conductivity of liquid.

  As described above, the supercritical fluid has the same thermal conductivity as that of a normal liquid, but is superior in terms of permeability to the resin because of its low viscosity. Among the supercritical fluids, carbon dioxide in a supercritical state is preferable because the critical point is relatively low pressure and low temperature and excellent in safety. The critical point is relatively low pressure and low temperature, which is excellent in terms of safety.

  However, when only the supercritical carbon dioxide is used as a solvent, since carbon dioxide is a gas at room temperature and normal pressure, it is difficult to separate the colorant and wax removed from the fine particles from the fine particles. . Therefore, it is preferably used in combination with alcohol. Furthermore, for the reasons described above, the alcohol is more preferably ethanol. By doing so, since the colorant and wax removed from the fine particles can be contained in a solvent such as ethanol, the colorant and wax removed from the fine particles can be easily separated from the fine particles. The mixing ratio of carbon dioxide and ethanol (carbon dioxide / ethanol) is preferably more than 0/10 and not more than 5/5, and more preferably not less than 2/8 and not more than 3/7. If the carbon dioxide / ethanol is larger than 5/5, the carbon dioxide penetrates into the toner and foams when the pressure is reduced, resulting in cavities in the particles. Further, the spheronization step is preferably performed at a temperature not lower than the critical point of carbon dioxide and lower than the melting point of the wax. When the melting point is higher than the melting point of the wax, the wax is eluted (bleeded) on the surface of the toner. Furthermore, it is preferably higher than the critical temperature of carbon dioxide. If it is lower than around 31 ° C., which is the critical temperature of carbon dioxide, carbon dioxide will not be in a supercritical state.

  FIG. 2 is a schematic diagram showing a manufacturing apparatus 1 that manufactures toner using carbon dioxide in a supercritical state as a solvent. The manufacturing apparatus 1 includes a gas cylinder 2 filled with carbon dioxide, a solvent tank 3 filled with ethanol, pressure pumps 4 and 5, a processing vessel 6, valves 7 and 8, a heater 9, a thermometer 10, and a pressure gauge 11. A pressure reducing valve 12 and a stirring means 13 are included.

  First, carbon dioxide pressurized to a predetermined pressure from the gas cylinder 2 by the pressure pump 4 is supplied to the processing container 6. Further, ethanol pressurized to a predetermined pressure by the pressure pump 5 from the solvent tank 3 is supplied to the processing container 6. These carbon dioxide and ethanol are supplied through valves 7 and 8. When supplying these carbon dioxide and ethanol, the temperature may be adjusted near a predetermined temperature by a preheating coil (not shown) or the like. Moreover, before supplying to the processing container 6, you may mix the carbon dioxide and ethanol of a supercritical state beforehand in another container.

  In the processing container 6, fine particles 14 and inorganic fine particles 15 such as silica fine particles are enclosed. The processing container 6 is a high-pressure processing container configured with, for example, a heater 9 or a constant temperature water tank (not shown) so as to reach a predetermined temperature. Further, the inside of the processing container 6 is adjusted to a predetermined pressure by valves 7 and 8. These temperatures and pressures are monitored by a thermometer 10 and a pressure gauge 11. Thus, carbon dioxide, ethanol, fine particles 14 and inorganic fine particles 15 in a supercritical state are mixed in the processing vessel 6. At this time, the stirrer 16 as the stirrer 13 is rotated by the motor 17 to stir the inside of the processing container 6 to process the toner.

  Thereafter, by opening the pressure reducing valve 12, the fine particles 14 are collected in the processing container 6 in a state dispersed in ethanol. From this, the toner and the colorant and wax separated from the toner can be separated by the method described above.

[Other manufacturing methods]
In the method for producing a toner for developing an electrostatic latent image according to the present invention, fine particles obtained by another method may be used instead of using fine particles obtained by pulverizing the kneaded material as described above. . For example, fine particles obtained by wet methods such as suspension polymerization method, emulsion aggregation method and suspension granulation method, and fine particles obtained by pulverizing fine particles obtained by pulverization by methods other than those described above can be used. By doing so, similarly to the toner obtained by the above-described manufacturing method, a toner having a uniform shape and a small amount of colorant and wax exposed on the surface can be obtained.

  The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples unless it exceeds the gist.

[Creation of fine particles]
Polyester resin (manufactured by Sanyo Chemical Co., Ltd .: EP208, softening point: 117 ° C.) 4000 parts by weight as binder resin, carbon black (manufactured by Cabot: MOGAL-L) 500 parts by weight, polyolefin wax (Toyo Petrolite as wax) Co., Ltd .: Polywax 655, melting point: 99 ° C.) 450 parts by weight, and 50 parts by weight of aluminum salicylate as a charge control agent are put into a Henschel mixer (Mitsui Mining Co., Ltd .: FM-20 type) and mixed for 10 minutes. Then, after being melt-kneaded and dispersed at a temperature of 130 ° C. or less with a Nidicus (Mitsui Mining Co., Ltd .: MOS140-800), fine particles are prepared by finely dispersing and classifying with a jet mill (NPK Co., Ltd .: IDS-5). .

( Test Example 1)
200 parts by weight of the obtained fine particles and 1500 ml of methanol were put into a 2000 ml treatment container having a stirrer having comb-shaped wings, a throwing-type ultrasonic transmitter, a heater and a thermometer. Thereafter, stirring was performed at 400 rpm for about 1 h while maintaining the temperature in the processing container at 45 ° C. Next, stirring was stopped and the mixture was allowed to settle naturally, and then the supernatant was removed by decantation and then dried. A toner was manufactured by adding 1.5 parts by weight of hydrophobic silica fine particles (manufactured by Nippon Aerosil Co., Ltd .: RX-100) to 100 parts by weight of the fine particles and processing with a Henschel mixer.

( Test Example 2)
A toner was manufactured in the same manner as in Test Example 1 except that ethanol was used instead of methanol and the temperature in the processing container was set to 40 ° C.

( Test Example 3)
To 100 parts by weight of the obtained fine particles, 1.0 part by weight of hydrophobic silica fine particles (manufactured by Nippon Aerosil Co., Ltd .: RX-100) was added and subjected to external addition treatment with a Henschel mixer. 200 parts by weight of externally added fine particles and 1500 ml of ethanol were charged into a 2000 ml treatment container having a stirrer having comb-shaped wings, a throwing-type ultrasonic transmitter, a heater and a thermometer. Thereafter, stirring was performed at 400 rpm for about 1 h while maintaining the temperature in the processing container at 45 ° C. Next, stirring was stopped and the mixture was allowed to settle naturally, and then the supernatant was removed by decantation and then dried. A toner was manufactured by adding 1.0 part by weight of hydrophobic silica fine particles (manufactured by Nippon Aerosil Co., Ltd .: RX-100) to 100 parts by weight of the fine particles and processing with a Henschel mixer.

( Test Example 4)
A toner was manufactured in the same manner as in Test Example 3 except that a mixture of 1300 ml of ethanol and 200 ml of water was used instead of 1500 ml of ethanol.

( Test Example 5)
A toner was manufactured in the same manner as in Test Example 1 except that a mixture of 1000 ml of ethanol and 500 ml of water was used instead of 1500 ml of ethanol.

(Example 1 )
A toner was manufactured in the same manner as in Test Example 3 except that a mixture of 1400 ml of ethanol and 100 ml of acetone was used instead of 1500 ml of ethanol.

(Example 2 )
A toner was manufactured in the same manner as in Test Example 3 except that a mixture of 1300 ml of ethanol and 200 ml of acetone was used instead of 1500 ml of ethanol.

( Test Example 6 )
750 ml of ethanol, 100 parts by weight of fine particles and 1 weight of hydrophobic silica fine particles (RX-100, manufactured by Nippon Aerosil Kogyo Co., Ltd.) in a 1000 ml high-pressure treatment vessel incorporating a stirrer having a comb-shaped wing, a heater, a temperature monitor and a pressure monitor Department was put in. While stirring at 100 rpm, carbon dioxide was supplied by a pressure pump until the pressure reached 25 MPa. The set temperature was changed to 85 ° C., and the mixture was stirred until the temperature in the high-pressure processing vessel reached 50 ° C. Thereafter, the temperature in the high-pressure treatment vessel was set to 40 ° C., the stirring speed was increased to 2000 rpm, and stirring was performed for about 1 hour. After the stirring was stopped, the decompression valve was opened, and the ethanol dispersion remaining in the reaction vessel was recovered. Next, after allowing the dispersion to settle naturally, the supernatant was removed by decantation, followed by drying. To 100 parts by weight of the fine particles, 1.0 part by weight of hydrophobic silica fine particles (manufactured by Nippon Aerosil Kogyo Co., Ltd .: RX-100) was added and treated with a Henschel mixer to obtain a toner.

(Comparative Example 1)
A toner was obtained by externally adding 1.2 parts by weight of hydrophobic silica (manufactured by Nippon Aerosil Kogyo Co., Ltd .: RX-100) to 100 parts by weight of the fine particles.

(Comparative Example 2)
A toner was manufactured in the same manner as in Example 3 except that the supernatant was directly dried without decantation.

(Comparative Example 3)
It was produced in the same manner as in Example 1 except that methanol was changed to water.

(Comparative Example 4)
It was produced in the same manner as in Example 1 except that methanol was changed to acetone.

(Comparative Example 5)
Manufactured in the same manner as in Example 8 except that the temperature in the high-pressure treatment vessel was changed to 100 ° C.

[Evaluation methods]
For Examples 1 to 8 and Comparative Examples 1 to 5, the volume average particle diameter of the toner, its coefficient of variation, shape evaluation, storage stability evaluation, charging stability evaluation and transferability evaluation were performed as follows. The physical properties of the toner prepared by the above method were evaluated by the following evaluation methods, and the results are shown in Table 1.

  Symbols such as “◯”, “Δ”, and “X” described in the description of the evaluation items below are symbols indicating evaluation results used in Table 1. “◯” indicates that it is very excellent, “Δ” indicates that it is practical, and “×” indicates that practical use is difficult.

(Volume average particle size and coefficient of variation)
The volume average particle size of the toner and the coefficient of variation thereof were measured using a laser diffraction particle size measuring device (Horiba, Ltd .: LA-920).

(shape)
The shape of the toner was measured by observation with a reflection electron microscope (REM) as an average value of the ratio of the minor axis to the major axis of 25 toners as a shape factor. The shape factor is expressed by the minor axis / major axis, and the closer to 1, the closer to a true sphere.

  In addition, the exposure property of the wax and the colorant near the surface of the toner was evaluated by observing a thin film sliced sample with a transmission electron microscope (TEM) after encapsulating the toner with a resin.

(Storage stability)
The storage stability was evaluated according to the following criteria by putting 10 g of the obtained toner in a 100 ml glass bottle and leaving it in a thermostatic bath at a temperature of 50 ° C. for 3 days.
○: No blocking is observed in the toner.
Δ: The toner is in a soft caking state.
X: The toner is in a hard caking state.

(Charge stability)
Charging stability is achieved by mixing ferrite particles (manufactured by Powder Tech Co., Ltd.) having a particle size of 60 μm and toner at a weight ratio of 95: 5, temperature 30 ° C., humidity 80% (hereinafter, this environment is referred to as HH), and After stirring for 30 minutes with a ball mill in an environment with an air temperature of 10 ° C. and a humidity of 20% (hereinafter referred to as LL), the charge amount was measured with a blow-off charge amount measuring device (manufactured by Toshiba Chemical Corporation), Evaluation was carried out by the ratio of the charge amount at LL to the charge amount at environment LL [(charge amount at HH) / (charge amount at LL)].
A: (Charge amount at HH) / (Charge amount at LL) is 0.8 or more.
Δ: (Charge amount at HH) / (Charge amount at LL) is 0.7 or more and less than 0.8.
X: (Charge amount at HH) / (Charge amount at LL) is less than 0.7.

(Transferability)
The transfer rate T (%) is determined based on the toner weight Mp on the recording medium on which a predetermined image is formed by using an improved machine of a copying machine (manufactured by Sharp Corporation: ARC-150) having a process speed of 88 mm / sec and on the photoreceptor. The toner weight Md remaining in the toner was measured, calculated from the following formula, and evaluated according to the following criteria based on the calculated transfer rate T (%). Note that 75 g / m ² of paper was used as the recording medium.
Transcription rate T = Mp / (Md + Mp)
○: Transfer rate T is 0.9 or more.
Δ: Transfer rate T is 0.8 or more and less than 0.9.
X: Transfer rate T is less than 0.8.

Test Examples 1 to 6, Examples 1 and 2, and Comparative Examples 1 to 5 were comparatively evaluated according to the above methods. The results are shown in Table 1.

As is evident from Table 1, the toner over produced by the production method of the toner is present invention has a narrow particle size distribution, a toner substantially spherical greater circularity, storage stability, charge stability and It has been found that a toner having excellent toner characteristics such as transferability can be produced.

  If the stirring process is not performed in a solvent containing an organic solvent (Comparative Example 1), the toner obtained by the pulverization method has a non-uniform shape, so that the storage stability, charging stability and transferability are poor. A toner was obtained.

  If the solvent and fine particles are not separated (Comparative Example 2), the colorant and wax removed from the fine particles contained in the solvent will adhere to the fine particles, so that the storage stability and charging stability are poor. A toner was obtained.

  When only water is used as the solvent (Comparative Example 3), the pigment and wax cannot be dissolved with water, and therefore the pigment and wax present in the vicinity of the surface of the fine particles cannot be sufficiently removed. Therefore, a toner having inferior storage stability, charging stability and transferability was obtained.

  When only acetone was used as the solvent (Comparative Example 4), the acetone could not form the toner because the binder resin was dissolved. Therefore, it was judged that there was no need to evaluate.

  When the predetermined temperature was higher than the melting point of the wax (Comparative Example 5), the wax was eluted (bleeded), so that a toner having poor storage stability was obtained.

It is process drawing which shows the manufacturing method of the toner which is this invention. It is the schematic which shows the manufacturing apparatus 1 which manufactures a toner using the carbon dioxide of a supercritical state as a solvent.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 2 Gas cylinder 3 Solvent tank 4,5 Pressure pump 6 Processing container 7,8 Valve 9 Heater 10 Thermometer 11 Pressure gauge 12 Pressure-reducing valve 13 Agitation means 14 Fine particle 15 Inorganic fine particle 16 Stirring rod 17 Motor

Claims (6)

A preparation step of preparing fine particles containing a binder resin, a colorant and a wax;
A dispersion step of stirring and dispersing the fine particles in a solvent containing an organic solvent under normal pressure at a temperature of 30 ° C. or higher and lower than the melting point of the wax;
Have a separation step of separating the fine particles and a solvent,
The organic solvent includes a solvent that does not dissolve the binder resin, and acetone that is a solvent that dissolves the binder resin,
The method for producing a toner for developing an electrostatic latent image , wherein the content of acetone is 30 parts by weight or less with respect to 100 parts by weight of a solvent that does not dissolve the binder resin . In the preparation step, fine particles are prepared by pulverizing a kneaded product containing a binder resin, a colorant and a wax,
2. The method for producing a toner for developing an electrostatic latent image according to claim 1, wherein, in the dispersing step, the fine particles are stirred and dispersed in a solvent containing an organic solvent to make the fine particles spherical. The solvent that does not dissolve the binder resin, an electrostatic latent image producing method of the developing toner according to claim 1 or 2, characterized in that an alcohol. An electrostatic latent image producing method of the developing toner according to any one of claims 1-3, characterized in that it further comprises an external addition step of externally added inorganic fine particles to the microparticles. The method for producing a toner for developing an electrostatic latent image according to claim 3, wherein the alcohol is ethanol. An electrostatic latent image developing toner, characterized by manufactured by the method according to any one of claims 1-5.

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