JP2008020478A - Method of manufacturing toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems that heating and fusion are needed for forming a core/shell structure, internally added wax is exposed to the surface of each toner particle, coarse particles are generated and the shell is peeled, in a method of manufacturing an electrostatic charge image developing toner with a core/shell structure. <P>SOLUTION: The method comprises: a stage where a binding resin, wax and a coloring agent are dissolved or dispersed into an organic solvent, for obtaining a colored resin solution; a stage where a basic compound and water are successively added to the colored resin solution, and the colored resin solution is emulsified into the aqueous medium; a stage for forming particles, where an electrolytic aqueous solution is added to the emulsified suspension, and a dispersoid in the emulsified suspension is consolidated, so that colored resin fine particles are produced; a stage where an emulsified suspension obtained by emulsifying a resin for shell formation into an aqueous medium containing methylethyl ketone in the range of 25 to 35 mass% is added two or more times to the colored resin fine particle-containing dispersion liquid, and an electrolytic aqueous solution is added thereto, for forming particles with a core/shell structure; and a stage where the organic solvent is removed under the reduced pressure, thereafter, the particles with a core/shell structure are separated from the aqueous medium, and cleaning and drying are performed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a toner for developing an electrostatic charge image that is suitably used in a copying machine, a printer, a fax machine, and the like, and further used in a toner jet type printer.

In image output devices such as electrophotographic copiers, printers, fax machines, etc., the resolution of printed images is improved, the gradation is improved, the amount of waste toner is reduced, and the energy consumption is reduced by lowering the fixing temperature. Due to demands such as improvement in image characteristics in full-color images, toner particles used for image formation are becoming smaller.
In order to reduce the particle size by the conventional pulverization method, pulverization energy is applied. Therefore, a polymerization method, an emulsion dispersion method, or the like is used instead of the pulverization method.

As a method for producing a toner by a polymerization method, a so-called suspension polymerization method or an emulsion aggregation method in which fine particles obtained by an emulsion polymerization method are aggregated and heated and fused to form toner particles are proposed. However, the binder resin is not limited to a vinyl polymer that can be radically polymerized, and a toner cannot be produced using a polycondensation polyester resin having excellent fixing properties and transparency as a raw material. Further, the emulsion aggregation method has a problem that it is necessary to stir at a high temperature for a long time because it is fused after aggregation.
In addition, the polymerization method has a problem that volatile organic compounds composed of unreacted monomers remain.
On the other hand, as a method of using a polyester resin as a binder resin, a mixture of a binder resin and a colorant is dissolved / dispersed in an organic solvent, and then emulsified by mixing with an aqueous medium to generate particles. A dispersion method has been proposed. In this emulsification dispersion method, the organic resin oil droplets emulsified and dispersed such as a binder resin and a colorant in an aqueous medium are stirred at high speed to obtain a toner size with a shearing force, and then the solvent is removed, washed and dried. This is a method for obtaining particles. Therefore, there are problems that fine particles are easily generated and the particle size distribution of the toner is poor.

  For these methods, binder resin such as polyester resin, which is a self-dispersing resin, and wax or colorant are dissolved or dispersed in an organic solution, and the obtained oil phase component is neutralized in an aqueous medium. There has been proposed a toner manufacturing method called a phase inversion emulsification method in which a particle is grown by emulsification and precipitation at a submicron size together with a base. In this method, in order to obtain a sharp particle size distribution, an oil phase component is emulsified in an aqueous medium to form fine particles of the mixture in the aqueous medium, and then the electrolyte is sequentially added in the presence of the emulsifier. The toner is manufactured through a coalescing step for coalescing the fine particles by addition (see, for example, Patent Documents 1 and 2). The toner particles obtained by this production method have a problem that if the amount of the internally added wax is large, the toner particles are easily exposed on the surface and the development durability of the toner is lowered. Further, when a binder resin having a low glass transition temperature is used to lower the fixing temperature of the toner particles, there is a problem that the heat resistant storage stability of the toner is lowered.

On the other hand, in order to prevent the internally added wax from being exposed to the toner particle surface, an aggregated particle dispersion in which aggregated particles are formed is prepared, and a fine particle dispersion is added and mixed in the aggregated particle dispersion. A method for producing a toner for developing an electrostatic charge image having a core / shell structure in which the fine particles are adhered to the aggregated particles to form adhered particles, and the adhered particles are further heated (for example, Patent Document 3). reference). In this manufacturing method, since the core / shell structure is formed by heating and fusing the fine particles adhering to the surface of the agglomerated particles, a large amount of energy is required for heating and fusing. A cooling process was also required later, and temperature control was complicated. Further, the prevention of exposure of the internally added wax to the toner particle surface is not sufficient, and there is a problem that the toner particles are fused to generate coarse particles. Further, there is a problem that the shell peels off and the toner particles aggregate during storage.
JP 2003-122051 A JP 2004-198598 A JP-A-10-26842

  The present invention relates to a method for producing a toner for developing an electrostatic charge image having a core / shell structure, wherein heating and fusion are required to form the core / shell structure, and the internally added wax is applied to the toner particle surface. An object of the present invention is to solve the problems of toner development durability reduction due to exposure, generation of coarse particles, and shell peeling. It is another object of the present invention to provide a toner having both low-temperature fixability and heat-resistant storage stability.

The present invention relates to a method for producing a toner for developing an electrostatic charge image having a core / shell structure, wherein a binder resin, a wax and a colorant are dissolved or dispersed in an organic solvent to obtain a colored resin solution. A step of emulsifying the colored resin solution in an aqueous medium by sequentially adding a basic compound and water, adding an aqueous electrolyte solution to the emulsified suspension, and coloring the dispersoids in the emulsified suspension together A step of forming resin particles to form particles, and a dispersion containing colored resin particles, an emulsion in which a shell-forming resin is emulsified in an aqueous medium containing methyl ethyl ketone in the range of 25 to 35% by mass twice A step of adding an electrolyte aqueous solution to form particles having a core / shell structure, removing the organic solvent under reduced pressure, and then removing the particles having the core / shell structure from an aqueous medium Separated from, and washed, characterized in that drying is carried out.
The present invention provides a method for producing a toner for developing an electrostatic charge image having a core / shell structure, wherein a cross-linked polyester resin and a linear polyester resin are used as a binder resin, and a cross-linked polyester resin is used as a shell-forming resin. It is characterized by using.
In the method for producing a toner for developing an electrostatic charge image having a core / shell structure according to the present invention, heating is not required, energy for heating is saved, and cooling after heating is not required. it can. Further, according to the method for producing a toner for developing an electrostatic charge image having a core / shell structure of the present invention, the exposure of wax to the surface is prevented, the development durability is high, the content of coarse particles is small, and the shell is peeled off. It is possible to produce a toner for developing an electrostatic image having a core / shell structure that does not aggregate during storage and has both low-temperature fixability and heat-resistant storage stability.

The present invention will be described in detail below. The production method of the present invention comprises the following steps.
First step: Colored resin solution preparation step In this step, the binder resin, wax and colorant are dissolved or dispersed in an organic solvent to obtain a colored resin solution.
Second step: emulsification step In this step, a basic compound and water are sequentially added to the colored resin solution to emulsify the colored resin solution in the aqueous medium.
Third step: coalescence step At least one operation of forming colored resin fine particles by adding an aqueous electrolyte solution to the prepared emulsion suspension and coalescing the dispersoid in the emulsion suspension to form particles. It is a process to be performed.
Fourth Step: Shell Forming Step An emulsion suspension in which the shell forming resin is emulsified in an aqueous medium containing methyl ethyl ketone in the range of 25 to 35% by mass in the dispersion containing the colored resin fine particles obtained in the third step. Is added twice or more, and then an aqueous electrolyte solution is added to form particles having a core / shell structure.
Fifth step: separation / drying step In this step, after removing the organic solvent under reduced pressure, the particles having the core / shell structure are separated from the aqueous medium, washed and dried to obtain toner mother particles.

First, the colored resin solution preparation step, which is the first step, will be described in detail. In the colored resin solution preparation step, first, the binder resin, wax and colorant are dissolved or dispersed in an organic solvent.
The binder resin, wax and colorant are preferably dissolved or dispersed in an organic solvent with a high-speed stirrer. In this case, the colorant may be pre-dispersed in advance to prepare a master kneading chip, and finely dispersed below the toner particle diameter to be prepared. Furthermore, wet dispersion may be performed using media, and the resin and the colorant may be dissolved and dispersed in the organic solvent. The wax may also be mixed after preparing the master kneading chip in advance. Alternatively, a wax master solution finely dispersed below the toner particle size by wet dispersion using media may be used. Or you may mix after preparing emulsion wax.

In the colored resin solution preparation step, Desper (manufactured by Asada Iron Works Co., Ltd.), T.M. K. A high-speed stirrer such as a homomixer (manufactured by PRIMIX Corporation) can be used. The blade tip speed at this time is preferably 4 to 30 m / s, and more preferably 8 to 25 m / s. By using the high-speed stirrer, the binder resin can be efficiently dissolved in the organic solvent, and uniform fine dispersion of the colorant in the binder resin solution can be achieved. That is, the state of the colorant finely dispersed in advance can be maintained in the binder resin solution by stirring at high speed.
When the blade tip speed is lower than 4 m / s, fine dispersion of the colorant, wax, etc. in the colored resin solution becomes insufficient. Or, the undissolved portion of the resin remains unfavorable. On the other hand, if it is higher than 30 m / s, heat generation due to shearing becomes large, and it is not preferable because uniform stirring becomes difficult in combination with volatilization of the solvent. Moreover, the temperature in the case of melt | dissolving or disperse | distributing has the preferable range of 20-60 degreeC, and the range of 30-50 degreeC is more preferable.

As an organic solvent, the thing whose solubility with respect to water in 25 degreeC is 0.1-30 mass% is preferable, and what is 0.1-25 mass% is more preferable. The boiling point at normal pressure is preferably lower than the boiling point of water. Further, the organic solvent is preferably a solvent having a low boiling point because it dissolves the binder resin and can be easily removed in a subsequent process.
As such an organic solvent, for example, ketones such as methyl ethyl ketone and methyl isopropyl ketone, and esters such as ethyl acetate and isopropyl acetate are used. Two or more organic solvents can be mixed and used, but from the viewpoint of solvent recovery, it is preferable to use the same type of solvent alone. Of these, methyl ethyl ketone is preferable.

In the step of preparing the colored resin solution, it is preferable to add an emulsifier.
In order for the emulsifier to function in the coalescing step, it is necessary to have a characteristic capable of maintaining dispersion stability even in the presence of an electrolyte added later. Examples of emulsifiers having such properties include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene Nonionic emulsifiers such as oxyethylene sorbitan fatty acid esters or various pluronics, alkyl sulfate ester type, alkyl sulfonate type anionic emulsifiers, and quaternary ammonium salt type cationic emulsifiers is there. Moreover, an alkylbenzene sulfonate type emulsifier and a linear alkyl benzene sulfonic acid type emulsifier can be mentioned.
The above-mentioned emulsifiers may be used alone or in combination of two or more. That is, in the production method of the present invention, it is possible to prevent non-uniform coalescence by adding an electrolyte in the presence of an emulsifier. Thereby, a preferable particle size distribution is obtained.
The amount of the emulsifier to be used is preferably 0.1 to 3.0% by mass, more preferably 0.3 to 2.0% by mass, and more preferably 0.3 to 1.5% by mass with respect to the solid content. It is particularly preferred that When the amount of the emulsifier to be used is less than 0.1% by mass with respect to the solid content, the desired effect of preventing the generation of coarse particles cannot be obtained. Further, when the amount of the emulsifier used is more than 3.0% by mass with respect to the solid content, the coalescence of the dispersoid in the emulsified suspension does not sufficiently proceed even if the amount of the electrolyte is increased, and the predetermined amount. As a result, fine particles remain and the yield decreases.

Next, in the emulsification step of the second step, a basic compound and water are sequentially added to the colored resin solution to emulsify the colored resin solution in the aqueous medium. Here, when the binder resin is polyester, it is preferable to gradually add water to the colored resin solution in which the carboxyl group of the binder resin is neutralized with a basic compound. By neutralizing the carboxyl group, the hydrophilicity of the binder resin is improved and the affinity with water is improved.
The added water is hydrated to the carboxyl group portion of the binder resin, and the binder resin is finely dispersed in combination with the stirring effect. On the other hand, the viscosity of the system containing the colored resin solution increases with the addition of water. When a certain amount of water is added, there is a point that the viscosity decreases, which is called a so-called phase inversion point. The viscosity increases until just before this, and the viscosity reaches the maximum value. The increase in viscosity correlates with the addition amount of the basic compound, and the increase in viscosity increases as the addition amount increases.

  On the other hand, the amount of the basic compound affects not only the emulsification step of the second step but also the uniformity and speed at the time of forming colored resin fine particles in the coalescence step of the third step described later. The range of 1-3 equivalent is preferable with respect to the carboxyl group of binder resin. Moreover, the range of 1-2 equivalent is still more preferable. By adding in excess of the amount required to neutralize all the carboxyl groups of the binder resin in this way, it is possible to prevent the formation of irregularly shaped particles in the coalescing step, and toner particles The particle size distribution can be made narrow.

  The ratio of the organic solvent to the total amount of the organic solvent and water after the emulsification step is preferably in the range of 20 to 35% by mass, and more preferably in the range of 20 to 30% by mass. As described above, the amount of water up to the phase inversion point decreases as the amount of organic solvent in the colored resin solution preparation step decreases, and increases as the amount of basic compound increases. At the phase inversion point, the viscosity of the emulsified suspension may be high, and the colored resin solution may not be completely finely dispersed in the aqueous medium. Therefore, it is preferable to add water. The amount of water added up to the phase inversion point is preferably in the range of 50 to 80% by mass of the total amount of water used up to the preparation of the phase inversion emulsion suspension.

  The binder resin used in the present invention is not particularly limited, but is preferably a polyester resin having an acid value of 3 to 30 KOHmg / g, and more preferably 5 to 20 KOHmg / g. When the acid value of the polyester resin is less than 3, toner particles cannot be produced. On the other hand, if the acid value of the polyester resin is greater than 30, the charge amount under the toner use environment is not stable.

  Examples of the basic compound for neutralization include inorganic bases such as sodium hydroxide, potassium hydroxide, and ammonia, and organic bases such as diethylamine, triethylamine, and isopropylamine. In particular, an aqueous solution of an inorganic base such as sodium hydroxide, potassium hydroxide or ammonia is preferred.

  The emulsified suspension produced by the above-described method exists in a state where the colored resin solution is emulsified and dispersed in an aqueous medium. The state varies depending on the type of organic solvent, the amount used, the acid value of the binder resin, the amount of basic compound used, the stirring conditions, etc. It is preferable to be emulsified and dispersed with an average particle size of less than 1 μm. Such a state is preferable because the stability of the emulsified suspension, the unitary stability in the subsequent steps, the particle size distribution of the colored resin fine particles, and the like are improved.

Next, the unification process which is the 3rd process is explained. By adding an electrolyte to the obtained emulsion suspension while stirring, the dispersoid in the emulsion suspension is salted out or destabilized. At this time, by stirring the emulsified suspension, the dispersoids collide with each other to be integrated. Finely dispersed resin oil droplets, wax dispersoids, colorant dispersoids and the like that are dispersoids are integrated into colored resin fine particles. Thereafter, the colored resin fine particles collide with each other, coalescence proceeds, and larger colored resin fine particles are generated. Thereby, the colored resin fine particles become particles having almost the same composition. By controlling the coalescing speed, colored resin fine particles having a desired size and particle size distribution can be obtained.
These colored resin fine particles are in a kind of swollen state containing an organic solvent, and so-called coalescence occurs in which fusion occurs simultaneously with the collision. For this reason, the colored resin fine particles after solvent removal in the subsequent step have sufficient strength, and it is not necessary to provide a separate fusion step by heating.
Examples of the electrolyte used here include sodium sulfate, ammonium sulfate, potassium sulfate, magnesium sulfate, sodium phosphate, sodium dihydrogen phosphate, sodium chloride, potassium chloride, ammonium chloride, calcium chloride, sodium acetate, sodium bicarbonate, etc. Organic and inorganic water-soluble salts can be effectively used as the electrolyte. These electrolytes to be added for unity may be used alone or in combination of two or more kinds. Among them, monovalent cation sulfates such as sodium sulfate and ammonium sulfate are preferable for promoting uniform coalescence.

Moreover, the colored resin fine particles obtained are swollen by a solvent, and it is preferable that the particles collide with each other by stirring with a low shearing force to advance the coalescence. Unlike the so-called dissolution suspension method, it is not necessary to finely disperse oil droplets by high-speed stirring, so that no fine powder is generated and the toner particle size distribution can be narrow and good.
It is preferable to select an agitation speed so as to obtain a low shearing force in such a range that only coalescence in which the colored resin fine particles are not split proceeds.

  In order to promote uniform coalescence, agitation conditions at the same time are important. For example, anchor blade, turbine blade, fowler blade, full zone blade, max blend blade (registered trademark, manufactured by Sumitomo Heavy Industries, Ltd.), half moon blade, etc. Is used. Among them, it is preferable to use a large wing that is excellent in uniform mixing properties even at a low rotation, such as a Max blend wing or a full zone wing.

The peripheral speed of the stirring blade for generating uniform colored resin fine particles is preferably 0.2 to 10 m / s, and more preferably stirring at a low shear of 0.2 to 8 m / s. In particular, 0.2 to 6 m / s is preferable. If the peripheral speed of the stirring blade is higher than 10 m / s, fine particles remain, which is not preferable. On the other hand, if the peripheral speed is less than 0.2 m / s, stirring is not uniform and coarse particles are generated, which is not preferable. Under the above-described conditions, coalescence proceeds only by collision between the colored resin fine particles, and the colored resin fine particles are not dissociated and dispersed. In particular, in the coalescing process, the generation of fine particles is small and a narrow particle size distribution can be obtained.
That is, it is preferable to stir with a high-speed stirrer such as a desper in the colored resin solution preparation step and the emulsification step, and a large blade that can be uniformly mixed at a low speed such as a max blend blade is suitable in the coalescence step. For this reason, it is preferable to carry out the coalescing step by transferring the emulsified suspension obtained in the emulsifying step to another container attached to the large blade.

Moreover, 0.5-15 mass% is preferable with respect to solid content, and, as for the quantity of the electrolyte to be used, it is more preferable that it is 1-12 mass%, and it is especially preferable that it is 1-6 mass%. When the amount of the electrolyte is less than 0.5% by mass, coalescence does not proceed sufficiently. If the amount is more than 15% by mass, it is not preferable because a large amount of stop water is required in the subsequent process, and it takes time for washing and drying.
Moreover, 1-15 mass% is preferable and, as for the density | concentration of electrolyte solution, it is more preferable that it is 3-10 mass%. If the amount is less than 1% by mass, the effect of the electrolyte is not sufficiently exhibited, and a large amount of electrolyte is required for salting out and coalescence. Or, colored resin fine particles may not be generated. On the other hand, if it is higher than 15% by mass, unevenness is likely to occur in the system, and in particular, aggregates and coarse particles are likely to be generated during the formation of colored resin fine particles in the initial stage of coalescence, which is not preferable.

  In the coalescence process, when adding the aqueous electrolyte solution, it is preferable to increase the stirring speed in order to mix the electrolyte uniformly and quickly in the system. The temporary temperature is preferably in the range of 10 to 50 ° C. More preferably, it exists in the range of 20-40 degreeC, and it is especially preferable that it is 20-35 degreeC. When the temperature is lower than 10 ° C., it is difficult to perform coalescence, which is not preferable. On the other hand, when the temperature is higher than 50 ° C., the coalescence speed is increased, and aggregates and coarse particles are easily generated, which is not preferable. In the production method of the present invention, for example, colored resin fine particles can be produced by coalescence under a low temperature condition of 20 to 40 ° C.

  Next, the shell formation process which is a 4th process is demonstrated. The emulsion suspension of the shell-forming resin used in the shell-forming step may be only the resin from which the colorant and wax have been removed, or may contain a charge control agent and the like. The preparation method may be any method as long as the shell resin is emulsified, but from the compatibility with the colored resin fine particles, the same operation as in the first step and the second step of the present invention is performed. It is preferable to create. That is, an emulsifier, a basic compound, and water are sequentially added to a resin solution obtained by dissolving a shell-forming resin in methyl ethyl ketone, so that the shell-forming resin is contained in an aqueous medium containing methyl ethyl ketone in the range of 25 to 35% by mass. An emulsified suspension in which the resin is emulsified is prepared. This ratio indicates the ratio of methyl ethyl ketone in the aqueous medium, and can be adjusted by the amount of methyl ethyl ketone at the time of dissolution and the amount of water added in the emulsification step. If it is less than 25% by mass, the shell portion of the toner base particles having a core / shell structure obtained is difficult to adhere to the colored resin fine particles, which is not preferable. If the amount of methyl ethyl ketone exceeds 35% by mass, phase inversion emulsification is not carried out uniformly, and unphase inversion products may remain or phase inversion emulsification may not occur.

This invention exists in the place which adds the emulsification suspension of the resin for shell formation adjusted to the colored resin fine particle dispersion obtained at the coalescing process twice or more.
The ratio of the shell is preferably 2 to 40% by mass as a shell weight ratio in the toner. When the amount is less than 2% by mass, the shell thickness is not sufficiently formed, and the shell effect is not exhibited. On the other hand, when the content is more than 40% by mass, the function of the colored resin fine particles is hidden, which is not preferable.
Further, the shell ratio to be added at one time is preferably 1 to 6% by mass in terms of the shell ratio in the toner. It is preferable to add in two or more divided portions up to a predetermined amount.
The shell resin oil droplets in the shell emulsified suspension are preferably submicron in size. These oil droplets adhere to the surface of the colored resin fine particles to form a shell structure. The size ratio between the colored resin fine particles and the shell resin oil droplets is about 30: 1 to 50: 1, and the number ratio is 1: 5, assuming that the shell ratio in the toner is about 5% by mass, although it depends on the amount of shell input. 150 to 1: 250. Therefore, when the shell emulsification suspension is added and stirred and dispersed, there are about 150 to 250 shell resin oil droplets around one colored resin fine particle, and when stirring is performed under the coalescence conditions, The colored resin fine particles first collide with and adhere to the shell resin oil droplets. At this time, coalescence proceeds due to the effect of the electrolyte in the colored resin particle dispersion.
On the other hand, when there are too many shell resin oil droplets, many of the oil droplets collide with each other and remain without adhering to the colored resin fine particles, or even if adhering to the colored resin fine particles, they remain as large particles. The structure tends to be non-uniform and easily peeled off.
By adding the shell emulsified suspension in a divided manner, the above problems are eliminated, and the shell resin is adhered to the colored resin fine particles with the small size of the shell resin, and it is adhered in at least two layers by repeating it. Thus, a uniform shell structure can be constructed.
Therefore, when a predetermined amount of an emulsion suspension of the shell-forming resin is added to the colored resin fine particle dispersion at a time, the resulting toner particle shells having a core / shell structure are easily peeled off.
Next, an aqueous electrolyte solution is further added and stirred. The stirring conditions and the electrolyte used are the same as in the coalescing step. By adding the electrolyte aqueous solution, the shell-forming resin fine particles are further destabilized, and the shell-forming resin oil droplets remaining in the liquid that cannot be adhered in the previous stage are increased, and the surface of the colored resin fine particles is fixed. A shell is formed.

In order to fix the shell-forming resin to the surface of the colored resin particles, in addition to the amount of methyl ethyl ketone in the emulsion suspension for shell, the amount of methyl ethyl ketone in the second step, in other words, the color before dropping the emulsion suspension for shell The amount of methyl ethyl ketone in the resin fine particle dispersion also has an effect. The colored fine resin particles are swollen by methyl ethyl ketone. When the concentration of methyl ethyl ketone is low, the particles are difficult to adhere to each other and shell fine particles are easily left behind. On the other hand, if the concentration is too high, fixing is likely to proceed, but the colored resin fine particles are further united with each other, causing problems such as deterioration in particle size distribution and generation of coarse particles. Therefore, when the amount of methyl ethyl ketone in the second step is low, it is preferable to increase the amount of methyl ethyl ketone in the shell emulsified suspension and decrease it when the opposite is the case.
In order to fix the shell-forming resin fine particles to the surface of the colored resin fine particles, it is preferable to add a basic compound before adding the shell emulsion suspension. By adding the basic compound, there is an effect that the colored resin fine particles are further swollen and the shell-forming resin fine particles are easily fixed.

  In the shell forming step, the colored resin fine particles swollen by the organic solvent and the shell forming resin oil droplets collide with each other to grow the particles. Therefore, the shell can be formed even if it is lower than the glass transition temperature of the shell-forming resin. Depending on the glass transition temperature of the shell-forming resin, a shell can be formed even at 30 ° C. or lower. Therefore, heating is not required in the shell forming step, and naturally, cooling after heating is not required, so that a great deal of energy is not consumed and temperature management becomes simple.

  Particle growth can be expressed by creating a blotted particle growth curve from time and particle size to maintain a nearly constant growth rate under certain conditions. As a result, the arrival time of the target particle diameter can be estimated from the curve. Moreover, it is preferable to stop shell formation by adding water. The amount of water when the shell formation is stopped is related to the amount of the organic solvent added during the preparation of the colored resin solution and the emulsion suspension of the shell forming resin. As the amount of the organic solvent relative to the solid content is larger, the amount of the organic solvent taken into the particles is relatively larger, so that it is necessary to suppress swelling with a larger amount of water.

  The shelled colored resin fine particle dispersion is desolvated and proceeds to the next step. The solvent removal is preferably carried out with stirring under reduced pressure in order to carry out quickly under low temperature conditions. In removing the solvent, an antifoaming agent is preferably added. The antifoaming agent is preferably in the form of a silicone emulsion. Examples of silicone-based antifoaming agents include BY22-517, SH5503, SM5572F, BY28-503 (manufactured by Toray Dow Corning Silicone), KM75, KM89, KM98, KS604, KS538 (manufactured by Shin-Etsu Chemical Co., Ltd.), and the like. . Of these, BY22-517 is preferred as having little influence on physical properties and a high defoaming effect. The amount of the antifoaming agent is preferably 30 to 100 ppm with respect to the solid content.

  The toner particles produced by the production method of the present invention are characterized in that a colorant, wax, etc. are encapsulated in a binder resin, and the colorant, wax, etc. are observed by observation with a transmission electron microscope or the like. It can be confirmed that the particles are contained in the particles and are dispersed almost uniformly.

The shape of the toner particles is determined by a particle image analyzer (Sysmex flow type particle image analyzer FPIA-1000) or the like, and the degree of circularity is the circumference of a circle corresponding to the projected area of the observed particle image. It is expressed as an average circularity which is an average value of numerical values expressed as a ratio to the perimeter of the projected image of the observed particle.
Regarding the shape of the toner particles, the average circularity is preferably 0.95 or more, more preferably 0.96 or more, and further preferably 0.97 or more. This is because powder fluidity is improved and transfer efficiency is improved by making the average circularity into a substantially spherical shape or a spherical shape with 0.97 or more.

  Next, in the separation / drying step, which is the fifth step, the particles having a core / shell structure are separated, washed and dehydrated. Separation and dehydration from the aqueous medium can be performed by a separation means such as a centrifugal separator, a filter press, or a belt filter. Washing is performed by stirring and solidifying the solid content using ion exchange water or the like and repeating dehydration. Next, toner particles can be obtained by drying the particles. Drying is a fluidized bed dryer such as a ribocorn dryer (Okawara Seisakusho), a mixed vacuum dryer such as Nauta Mixer (Hosokawa Micron), a fluidized bed dryer (Okawara Seisakusho), or a vibrating fluidized bed dryer (central processing machine). However, it is not limited to these dryers.

  As for the particle size distribution of the toner, it is preferable that the 50% volume particle size / 50% number particle size is 1.25 or less as measured by a multisizer type II (aperture tube diameter: 100 μm) manufactured by Beckman Coulter. More preferably, it is 20 or less. This is because a good image is easily obtained when the ratio is 1.25 or less.

  The toner preferably has a 50% volume average particle diameter of 3 to 8 μm. The use of a toner having a small particle diameter not only improves the resolution and gradation, but also the thickness of the toner layer for forming a printed image. The amount of heat required for fixing can be reduced, and at the same time, the toner consumption can be reduced.

  In the present invention, the binder resin and the shell forming resin are not particularly limited, but a polyester resin is preferably used. The polyester resin used in the present invention is a cross-linked polyester resin or a linear polyester resin, and is obtained by reacting a compound selected from the following raw materials.

The crosslinked polyester is preferably produced by reacting a divalent basic acid or derivative thereof, a divalent alcohol, and a polyvalent compound as a crosslinking agent. In particular, it is preferable to produce by reacting a divalent basic acid or a derivative thereof, a divalent aliphatic polyhydric alcohol, and a polyvalent epoxy compound as a crosslinking agent.
The linear polyester resin is produced by reacting a divalent basic acid with a dihydric alcohol.

  Examples of the divalent basic acid compound used for producing the crosslinked polyester resin and the linear polyester resin include phthalic anhydride, terephthalic acid, isophthalic acid, orthophthalic acid, adipic acid, maleic acid, and maleic anhydride. , Fumaric acid, itaconic acid, citraconic acid, hexahydrophthalic anhydride, cyclohexanedicarboxylic acid, succinic acid, malonic acid, glutaric acid, azelaic acid, sebacic acid and other dicarboxylic acids or derivatives thereof.

  Examples of the divalent aliphatic alcohol include 1,4-cyclohexanedimethanol, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, neopentyl glycol, butanediol, pentanediol, Diols such as hexanediol, polyethylene glycol, polypropylene glycol, ethylene oxide-propylene oxide random copolymer diol, ethylene oxide-propylene oxide block copolymer diol, ethylene oxide-tetrahydrofuran copolymer diol, polycaprocactone diol Is mentioned.

Use of an aliphatic alcohol in the cross-linked polyester resin and the linear polyester resin is preferable because compatibility with waxes is improved and offset resistance is improved. Moreover, fixing property at low temperature is improved by softening the polyester main chain. When producing a crosslinked polyester resin, a polyvalent epoxy compound is further used as a crosslinking agent. Examples of such compounds include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, ethylene glycol diglycidyl ether, hydroquinone diglycidyl ether, N, N-diglycidyl aniline lysine triglycidyl ester, Trimethylolpropane triglycidyl ether, trimethylolethane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetrakis 1,1,2,2 (P-hydroxyphenyl) ethane tetraglycidyl ether, cresol novolac type epoxy resin, phenol novolac type epoxy resin A polymer or copolymer of an epoxy group-containing vinyl compound, an epoxidized resorcinol-acetone condensate, a partial epoxy Polybutadiene, polymers of vinyl compounds having an epoxy group, or a copolymer, such as semi-drying or drying fatty acid ester epoxy compound. Among the above compounds, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, cresol novolac type epoxy resin, phenol novolac type epoxy resin, glycerin / triglycidyl ether, trimethylolpropane triglycidyl ether, trimethylol Ethanetriglycidyl ether and pentaerythritol tetraglycidyl ether are more preferably used.
Specific examples of bisphenol A type epoxy resins include Dainippon Ink Chemical Co., Ltd. Epicron 850, Epicron 1050, Epicron 2055, Epicron 3050, and the like. Epicron 830, Epicron 520, etc. manufactured by Dainippon Ink & Chemicals, Inc. as examples of orthocresol novolac type epoxy resins, N-660, N-665, N-667, N-670, N- 673, N-680, N-690, N-695, etc. are examples of phenol novolac type epoxy resins. Epiklon N-740, N-770, N-775, N-manufactured by Dainippon Ink & Chemicals, Inc. 865 etc. As a polymer or copolymer of a vinyl compound having an epoxy group, Examples thereof include a homopolymer of glycidyl (meth) acrylate, an acrylic copolymer, and a copolymer with styrene.

Moreover, the epoxy compound mentioned above can also be used in combination of 2 or more types, Furthermore, the mono epoxy compound described below can also be used together as a modifier | denaturant of resin. Examples of the monoepoxy compound that can be used at the same time include phenyl glycidyl ether, alkylphenyl glycidyl ether, alkyl glycidyl ether, alkyl glycidyl ester, glycidyl ether of alkylphenol alkylene oxide adduct, α-olefin oxide, monoepoxy fatty acid alkyl ester, etc. Is mentioned.
By using these monoepoxy compounds in combination, fixability and resistance to offset at high temperatures are improved. Among these, alkyl glycidyl esters are particularly preferably used. A specific example is Cardura E (Neodecanoic acid glycidyl ester manufactured by Shell Japan).

The cross-linked polyester resin and the linear polyester resin can be obtained, for example, by performing a dehydration condensation reaction or a transesterification reaction in the presence of a catalyst using the raw material components described above. The reaction temperature and reaction time at this time are not particularly limited, but are usually 150 to 300 ° C. and 2 to 24 hours.
As the catalyst for performing the above reaction, for example, tetrabutyl titanate, zinc oxide, stannous oxide, dibutyltin oxide, dibutyltin dilaurate, paratoluenesulfonic acid, and the like can be used as appropriate.

  When a mixture of a crosslinked polyester resin and a linear polyester resin is used in the present invention, the mixing ratio is not particularly limited, but (mass of crosslinked polyester resin) / (mass of linear polyester resin) = 5 / 95 to 60/40 is preferable, 10/90 to 40/60 is more preferable, and 20/80 to 40/60 is particularly preferable. When the ratio of the cross-linked polyester resin is less than 5% by mass, the hot offset resistance, the coalescence speed, and the dispersibility of wax, colorant and the like are not preferable. On the other hand, when the ratio of the cross-linked polyester resin is more than 60% by mass, the melt viscosity (T1 / 2 temperature) increases and the low-temperature fixability decreases, which is not preferable.

  The glass transition temperature (Tg) of the cross-linked polyester resin is not particularly limited, but is preferably 40 to 90 ° C, and particularly preferably 40 to 80 ° C. When the glass transition temperature (Tg) is lower than 40 ° C., a blocking phenomenon (thermal aggregation) tends to occur when the toner is stored, transported, or exposed to a high temperature inside the developing device of the machine. On the other hand, a glass transition temperature (Tg) higher than 90 ° C. is not preferable because the low-temperature fixability is lowered.

  Although the glass transition temperature (Tg) of a linear polyester resin is not specifically limited, It is preferable that it is 35-70 degreeC, and it is especially preferable that it is 40-65 degreeC. When the glass transition temperature (Tg) is lower than 35 ° C., a blocking phenomenon (thermal aggregation) tends to occur when the toner is stored, transported, or exposed to a high temperature inside the developing device of the machine. On the other hand, a glass transition temperature (Tg) higher than 70 ° C. is not preferable because the low wrinkle fixing property is lowered.

  The softening point of the cross-linked polyester resin is not particularly limited, but is preferably 150 ° C or higher, more preferably 150 ° C to 220 ° C, and particularly preferably 170 ° C to 190 ° C. This is because when the softening point is less than 150 ° C., the toner tends to cause an aggregation phenomenon, so that trouble is likely to occur during storage or printing, and when it exceeds 220 ° C., the fixability is likely to deteriorate. is there.

  The softening point of the linear polyester resin is not particularly limited, but is preferably 90 ° C. or higher, more preferably 90 ° C. to 130 ° C., and particularly preferably 90 ° C. to 110 ° C. . As with the cross-linked polyester resin, when the softening point is less than 90 ° C., the glass transition temperature is lowered, and the toner tends to cause aggregation phenomenon, which is likely to cause trouble during storage or printing. If the temperature exceeds 130 ° C., the fixability tends to deteriorate.

The softening point of the polyester resin in the present invention is a T1 / 2 temperature measured using a constant load extrusion capillary type rheometer (Shimadzu Corporation flow tester CFT-500). The measurement is performed under the conditions of a piston cross-sectional area of 1 cm ² , a cylinder pressure of 0.98 MPa, a die hole length of 1 mm, a die hole diameter of 1 mm, a measurement start temperature of 50 ° C., a temperature increase rate of 6 ° C./min, and a sample mass of 1.5 g. It was.
Moreover, the measurement of the glass transition temperature (Tg) of a polyester resin is measured using DSC (Shimadzu DSC-60A). 20 mg of sample is put in an aluminum crimp cell, heated to 180 ° C. at a heating rate of 10 ° C./min, cooled to room temperature at a cooling rate of 10 ° C./min from 180 ° C., and again to 180 ° C. at a heating rate of 10 ° C./min. The value of the softening point in the temperature rise and second run profile is defined as Tg.

  In the production method of the present invention, waxes that can be introduced in the colored resin solution preparation step include hydrocarbon waxes such as polypropylene wax, polyethylene wax, and Fischer-Trofisch wax, synthetic ester waxes, carnauba wax, and rice. Mention may be made of waxes selected from natural ester waxes such as waxes. Of these, natural ester waxes such as carnauba wax and rice wax, synthetic ester waxes obtained from a high alcohol and a long-chain monocarboxylic acid, and hydrocarbon waxes such as Fischer-Trofisch wax are suitable. Examples of the synthetic ester wax include WEP-5 and WEP-7 (manufactured by NOF Corporation). The wax content is preferably in the range of 1 to 40% by mass with respect to the total toner. If the wax content is less than 1% by mass with respect to the whole toner, the releasability becomes insufficient. It becomes easy to do.

  The colored resin solution can be prepared by mixing a charge control agent. The positively chargeable charge control agent is not particularly limited, and known and commonly used nigrosine dyes, quaternary ammonium compounds, onium compounds, triphenylmethane compounds and the like can be used for toners. In addition, basic group-containing compounds such as amino groups, imino groups, and N-heterocycles, such as tertiary amino group-containing styrene acrylic resins, are also effective as a positively chargeable charge control agent. As a control agent, it can be used alone or in combination with the positively chargeable charge control agent. Depending on the application, a small amount of a negative charge control agent such as an azo dye metal complex or a salicylic acid derivative metal complex salt may be used in combination with these positively chargeable charge control agents. In addition, as the negatively chargeable charge control agent, heavy metals such as trimethylethane dyes, salicylic acid metal complexes, benzylic acid metal complexes, copper phthalocyanine, perylene, quinacridone, azo pigments, metal complex azo dyes, azochrome complexes, etc. Examples thereof include acidic dyes, calixarene-type phenol condensates, cyclic polysaccharides, resins containing carboxyl groups and / or sulfonyl groups, and the like. The content of the charge control agent is preferably 0.01 to 10% by mass, and particularly preferably 0.1 to 6% by mass with respect to the whole toner.

  Examples of the colorant that can be added in the colored resin solution preparation step include C.I. I. Pigment Black 11 and other iron oxide pigments, C.I. I. Examples thereof include iron-titanium complex oxide pigments such as Pigment Black 12, and carbon black such as furnace black, channel black, acetylene black, thermal black, and lamp black.

  Examples of blue colorants include phthalocyanine C.I. I. Pigment Blue 1, 2, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 15, 16, 17: 1, 27, 28, 29, 56, 60, 63 and the like. Among these, C.I. I. Pigment Blue 15: 3, 15, 16, 60 are preferable. I. Pigment Blue 15: 3, 60 is more preferable.

  Examples of yellow colorants include C.I. I. Pigment Yellow 1, 3, 4, 5, 6, 12, 13, 14, 15, 16, 17, 18, 24, 55, 65, 73, 74, 81, 83, 87, 93, 94, 95, 97, 98 , 100, 101, 104, 108, 109, 110, 113, 116, 117, 120, 123, 128, 129, 133, 138, 139, 147, 151, 153, 154, 155, 156, 168, 169, 170 , 171, 172, 173, 180, 184, 185 and the like. Among these, C.I. I. Pigment Yellow 17, 74, 93, 97, 110, 155 and 180 are preferable. I. Pigment Yellow 74, 93, 97, 180, and 184 are more preferable. I. Pigment Yellow 93, 97, 180, and 184 are more preferable.

  Examples of red colorants include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 17, 18, 22, 23, 31, 37, 38, 41, 42, 48: 1, 48 : 2, 48: 3, 48: 4, 49: 1, 49: 2, 50: 1, 52: 1, 52: 2, 53: 1, 54, 57: 1, 58: 4, 60: 1, 63 : 1, 63: 2, 64: 1, 65, 66, 67, 68, 81, 83, 88, 90, 90: 1, 112, 114, 115, 122, 123, 133, 144, 146, 147, 149 , 150, 151, 166, 168, 170, 171, 172, 174, 175, 176, 177, 178, 179, 184, 185, 187, 188, 189, 190, 193, 194, 202, 208, 209, 214 216, 220, 221, 2 4,242,243,243: 1,245,246,247, and the like. Among these, C.I. I. Pigment Red 48: 1, 48: 2, 48: 3, 48: 4, 53: 1, 57: 1, 122, 184, 209 are preferred. I. Pigment Red 57: 1, 122, 184, and 209 are more preferable.

  The content of the colorant is preferably 1 to 20% by mass, more preferably 2 to 18% by mass, and still more preferably 2 to 15% by mass with respect to the whole toner. These colorants can be used alone or in combination of two or more.

  The toner particles produced by the production method of the present invention can be adjusted in fluidity, electrostatic property, etc. by adding fine particles such as silica and titania or those hydrophobized to these as external additives. The obtained toner particles can be used as a one-component toner, but can also be used as a two-component toner by mixing a carrier.

(Synthesis of cross-linked polyester resin 1)
Terephthalic acid 9.06 parts by mass Isophthalic acid 3.90 parts by mass Neopentyl glycol 4.26 parts by mass Ethylene glycol 2.54 parts by mass Tetrabutyl titanate 0.10 parts by mass Epicron 830 0.30 parts by mass (Dainippon Ink & Chemicals, Inc. Bisphenol F type epoxy resin (Epoxy equivalent 170g / eq)
0.10 parts by weight of Cardura E (Shell Japan alkyl glycidyl ester epoxy equivalent 250 g / eq)
The above raw materials were put into a stainless steel 50 L reaction kettle and reacted at 240 ° C. for 12 hours under a normal pressure nitrogen stream. Thereafter, the pressure was reduced successively and the reaction was continued at 10 mmHg. The reaction was followed by the softening point specified in ASTM E28-517, and the reaction was terminated when the softening point reached 160 ° C. The obtained polymer was a colorless solid, and had a glass transition temperature of 65 ° C. by a DSC measurement method and a softening point (T1 / 2) by a flow tester of 178 ° C. The polymer is hereinafter referred to as “H1”.

(Synthesis of cross-linked polyester resin 2)
Terephthalic acid 3.90 parts by mass Isophthalic acid 9.06 parts by mass Neopentyl glycol 4.26 parts by mass Ethylene glycol 2.54 parts by mass Tetrabutyl titanate 0.10 parts by mass Epicron 830 0.30 parts by mass (Dainippon Ink & Chemicals, Inc. Bisphenol F type epoxy resin (Epoxy equivalent 170g / eq)
0.10 parts by weight of Cardura E (Shell Japan alkyl glycidyl ester epoxy equivalent 250 g / eq)
The above raw materials were put into a stainless steel 50 L reaction kettle and reacted at 240 ° C. for 12 hours under a normal pressure nitrogen stream. Thereafter, the pressure was reduced successively and the reaction was continued at 10 mmHg. The reaction was followed by the softening point specified in ASTM E28-517, and the reaction was terminated when the softening point reached 160 ° C. The obtained polymer was a colorless solid, and had a glass transition temperature of 60 ° C. by a DSC measurement method and a softening point (T1 / 2) by a flow tester of 178 ° C. The polymer is hereinafter referred to as “H2”.

(Synthesis of linear polyester resin)
Terephthalic acid 5.31 parts by mass Isophthalic acid 7.97 parts by mass Neopentyl glycol 4.37 parts by mass Ethylene glycol 2.6 parts by mass Tetrabutyl titanate 0.1 parts by mass or more of raw materials are placed in a stainless steel 50 L reaction kettle, After reacting at 210 ° C. for 10 hours under a normal nitrogen stream, the pressure was reduced successively and the reaction was continued at 10 mmHg. The reaction was followed by the softening point specified in ASTM E28-517, and the reaction was terminated when the softening point reached 82 ° C. The obtained polymer was a colorless solid, and had a glass transition temperature of 40 ° C. by a DSC measurement method and a softening point (T1 / 2) by a flow tester of 90 ° C. The polymer is hereinafter referred to as “L11”.

(Preparation of wax master solution)
Carnauba wax (Carnauba wax No. 1, imported by Yoko Kato) 30 parts by mass, linear polyester resin L11 70 parts by mass and methyl ethyl ketone 150 parts by mass were premixed with Desper, and then Starmill LMZ-10 (Ashizawa Finedeck) The wax master solution W-1 having a solid content of 40% by mass was prepared. The composition of W-1 is L11 / wax / methyl ethyl ketone = 28/12/60.

(Preparation of colorant master chip)
20L Henschel set with 2000 parts by mass of Ket Blue 111 (Cyan Pigment manufactured by Dainippon Ink and Chemicals, Inc., CI Pigment B-15: 3) and 2000 parts by mass of a linear polyester resin L2 The mixture was put into a mixer (Mitsui Mine Co., Ltd.) and stirred at 698 min ⁻¹ for 2 minutes to obtain a mixture. The mixture was melt-kneaded using a kneedex MOS140-800 (an open roll continuous extrusion kneader manufactured by Mitsui Mining Co., Ltd.) to prepare a master chip. The obtained master chip was diluted with the linear polyester resin L11 and methyl ethyl ketone, and when the dispersion state of the colorant and the presence or absence of coarse particles were observed with a 400 × optical microscope, the colorant was uniformly dispersed and coarse particles There was no.

(Preparation of colored resin solution)
11.25 parts by weight of the above wax master solution, 3.78 parts by weight of the colorant master chip, 4.75 parts by weight of the cross-linked polyester resin H2, 13.97 parts by weight of the linear polyester resin L11 and 7.79 parts by weight of methyl ethyl ketone. Using a desper (manufactured by Asada Iron Works Co., Ltd.) having a blade diameter of 230 mm in the range of 40 to 45 ° C., the mixture was mixed at 777 min ⁻¹ for 2 hours for dissolution and dispersion. The resulting mixture was further added methyl ethyl ketone, the solid content was adjusted to 65% by mass, and 0.22 parts by mass of dodecylbenzenesulfonic acid-based emulsifier (Daiichi Kogyo Seiyaku Neogen SC-F) was added as an emulsifier. A colored resin solution was prepared by dissolving and dispersing (Step A).

(Example 1)
(Emulsification process)
A cylindrical container having a blade with a blade diameter of 230 mm as a stirring blade was charged with 41.54 parts by mass (27 parts by mass of solid content) of the colored resin solution, and then 4.5 parts by mass of 1N ammonia water was added to 777 min ^−1. And the temperature was adjusted to 35 ° C. Subsequently, the stirring speed was changed to 1100 min ⁻¹ and 41.4 parts by mass of deionized water was added dropwise at 10 parts by mass / min to prepare an emulsified suspension. The peripheral speed of the stirring blade at this time was 13.2 m / s. As deionized water was added, the viscosity of the system increased, but water was taken into the system at the same time as the dropwise addition, and stirring and mixing were uniform. After adding 26 parts by weight of deionized water, a sharp drop in viscosity was observed (phase inversion emulsification). Further, when a predetermined amount of the remaining deionized water was added and the emulsion suspension was observed with an optical microscope, it was observed that the resin was dissolved and the pigment and wax fine particles were dispersed (step B). . No unemulsified material was observed. Since the pigment and wax fine particles are stably dispersed in the aqueous medium, it is considered that the resin is adsorbed on the surfaces of the fine particles.

(Joint process)
Next, after the suspension was transferred to a cylindrical container attached to a Max Blend blade (registered trademark, manufactured by Sumitomo Heavy Industries) with a blade diameter of 340 mm, the temperature was maintained at 26 ° C. while maintaining the stirring speed at 85 min ^−1. It was adjusted. Thereafter, the rotational speed was adjusted to 120 min ⁻¹ , 10.8 parts by mass of a 3.5 mass% sodium sulfate aqueous solution was added dropwise at 1 part by mass / min, and 5 minutes after the completion of dropping, the rotational speed was 85 min ⁻¹ for 5 minutes. , 65 min ⁻¹ for 5 minutes, and 47 min ⁻¹ for 20 minutes. The peripheral speed of the stirring blade at this time was 0.47 m / s. Subsequently, the rotational speed was adjusted to 120 min ⁻¹ , 2 parts by mass of a sodium sulfate aqueous solution having a concentration of 5.0 mass% was dropped at 1 part by mass / min, and 5 minutes after the completion of dropping, the rotational speed was 85 min ⁻¹ for 5 minutes. The mixture was stirred at 65 min ⁻¹ for 5 minutes and then continued at 47 min ⁻¹ . When the particle size became 4.5 μm, the mixture was stirred at 85 min ⁻¹ for 30 minutes.

(Preparation process of emulsion suspension for shell)
Mixing 7.33 parts by mass of methyl ethyl ketone and 6 parts by mass of cross-linked polyester resin H1 in a range of 35 to 40 ° C. using a desper with a blade diameter of 135 mm (manufactured by Asada Iron Works Co., Ltd.) at 1200 min ⁻¹ for 30 minutes, then 0.033 parts by mass of anionic emulsifier Neogen SC-F (Daiichi Kogyo Seiyaku Co., Ltd.) was added and mixed for 30 minutes to obtain a solution / dispersion. Next, 1.765 parts by mass of 1N aqueous ammonia was added and stirred, and the temperature was adjusted to 35 ° C. Next, the stirring speed was changed to 1550 min ⁻¹ and 13.83 parts by mass of deionized water was added dropwise at 0.6 parts by mass / min to prepare an emulsified suspension. The peripheral speed of the stirring blade at this time was 11 m / s. As deionized water was added, the viscosity of the system increased, but water was taken into the system at the same time as the dropwise addition, and stirring and mixing were uniform. After adding 10 parts by weight of deionized water, a sharp drop in viscosity was observed (phase inversion emulsification). Further, when a predetermined amount of the remaining deionized water was added and the emulsion suspension was observed with an optical microscope, the resin was dissolved and no unemulsified material was observed. The ratio of methyl ethyl ketone (MEK ratio) in the aqueous medium of the emulsified suspension was 31.95% by mass (Step C).

(Shelling process)
In Step B, the rotational speed was 120 min ⁻¹ , and 5.2 parts by mass of the emulsion suspension for shell obtained in Step C was added dropwise to the 4.5 μm colored resin fine particles at 0.5 kg / min, and the rotational speed was 75 min ^{−. Held} at ¹ for 10 minutes. Next, the number of revolutions was set to 120 min ⁻¹ and the above was repeated twice (added three times in total). Thereafter, the rotational speed was adjusted to 120 min ⁻¹ , 1.2 parts by mass of a 5 mass% sodium sulfate aqueous solution was dropped at 1 part by mass / min, and 5 minutes after the completion of the dropping, the rotational speed was 85 min ⁻¹ for 5 minutes. and stirred at 65min ^-1 5 minutes, the mixture was stirred at 47min ^-1 15 minutes to stop the combined deionized water were added 10 parts by weight. The particle size at this time was 5.71 μm.

(Molecular / Drying process)
Thereafter, after adding 0.006 parts by mass of antifoaming agent BY22-517 (manufactured by Toray Dow Corning Silicone Co., Ltd.), methyl ethyl ketone and water were distilled off under reduced pressure until the recovered amount became 35 parts by mass. The slurry after the solvent removal was repeatedly washed by solid-liquid separation and redispersion, and then a colored resin fine particle dispersion obtained by removing the solvent with a basket type centrifuge was obtained. Thereafter, drying was performed with a mixing vacuum dryer to obtain toner mother particles. A core / shell structure was confirmed by observing a cross-section of the toner base particles with a microtome with a transmission electron microscope. The centrifuge filtrate was clear.

(Example 2)
In Example 1, toner mother particles were obtained in the same manner as in Example 1 except that 5.2 parts by mass of the emulsion suspension for shell prepared in Step C was added twice.

(Example 3)
In Example 1, toner mother particles were obtained in the same manner as in Example 1 except that 5.2 parts by mass of the emulsion suspension for shell prepared in Step C was added 5 times.

Example 4
In Example 1, a toner was prepared in the same manner as in Example 1 except that 5.2 parts by mass of the emulsion suspension for shell prepared in Step C was added 8 times and 2 parts by mass of a 5% by mass aqueous sodium sulfate solution was added. Mother particles were obtained.

(Example 5)
In Example 1, the ratio of methyl ethyl ketone in the aqueous medium of the emulsified suspension for shell prepared in Step C was 35.00% by mass, and 4.85 parts by mass of the emulsified suspension for shell was added three times. Obtained toner base particles in the same manner as in Example 1.

(Example 6)
In Example 1, 2 parts by mass of 2.3N-NH ₄ OH aqueous solution was added before the emulsion suspension prepared in Step C was added, and 3.9 parts by mass of the emulsion suspension for shell was added 4 times. Toner mother particles were obtained in the same manner as in Example 1 except for the addition.

(Example 7)
In Example 1, 2.6 parts by mass of the emulsified suspension prepared in Step C was added four times, and the aqueous sodium bicarbonate solution was used instead of the aqueous sodium sulfate solution added after mixing the emulsified suspension for shell. Toner mother particles were obtained in the same manner as in Example 1 except that was added.

(Example 8)
In Example 1, the ratio of methyl ethyl ketone in the aqueous medium of the emulsion suspension for shell prepared in Step C was 26.0 mass%, 6.15 parts by mass of the emulsion suspension for shell was added three times, Toner mother particles were obtained in the same manner as in Example 1 except that 1.5 parts by mass of a subsequent 5% by mass aqueous sodium sulfate solution was added.

(Comparative Example 1)
In Example 1, the ratio of methyl ethyl ketone in the aqueous medium of the emulsion suspension for shell prepared in Step C was 23.0 mass%, and 6.82 parts by mass of the emulsion suspension for shell was added three times. Toner mother particles were obtained in the same manner as in Example 1 except that 2 parts by mass of a 5% by mass aqueous sodium sulfate solution was added thereafter.

(Comparative Example 2)
In Example 1, an attempt was made to prepare a solution in which the weight ratio of methyl ethyl ketone in the aqueous medium was 37.50% by mass in Step C. However, the crosslinked polyester resin H1 was not emulsified in the aqueous medium, and the emulsion suspension for shells was used. A liquid was not obtained.

(Comparative Example 3)
In Example 1, toner base particles are obtained in the same manner as in Example 1 except that the total amount of 15.6 parts by mass of the emulsion suspension for shell added in Step C is mixed with the colored resin fine particle dispersion at a time. It was.

  Table 1 shows the mixing and stirring conditions of the dispersion containing the colored resin fine particles and the emulsified suspension of the shell-forming resin in Examples 1 to 7 and Comparative Examples 1 to 3, and the electrolyte added thereafter.

  Table 2 shows the evaluation results of the toner base particles obtained in Examples 1 to 8 and Comparative Examples 1 to 3. The measuring method of each physical property shown in Table 2 is as follows.

(Particle size and particle size distribution)
Dv (50% volume average diameter) and Dn (50% number average diameter) were determined using a 100 micron aperture tube of Coulter Multisizer II (Coulter Beckman).

(Circularity and number frequency of 1.06 μm or less)
To 20 g of water, 0.1 g of ELCLEAR (surfactant manufactured by Chugai Photo Chemical Co., Ltd.) is added, 0.04 g of toner base particles as a sample is further added, and the toner base particles are put into water with an ultrasonic disperser. Samples are prepared by suspending. Next, the sample is allowed to flow down into a transparent and flat cell provided in a flow type particle image analyzer FPIA-1000 under conditions of 25 ° C. and humidity 60%. A light source that emits pulsed light is installed on one side of the cell, and an imaging camera is provided on the opposite side of the cell so as to face the light source. The toner particles in the sample flowing down in the FPIA-1000 cell are captured as a still image by a camera facing the light source across the cell when irradiated with pulsed light. Based on the image of the toner particle thus captured, the contour of each toner particle is extracted by the image analysis device, and the projected area and the perimeter of the toner particle image (peripheral length of the toner particle projected image) are calculated. The Further, from the calculated projected area of the toner particle image, the circumference of a circle having the same area (the circumference of the circle having the same area as the toner particle projected area) is calculated. The average circularity is obtained by dividing the circumference of the circle having the same area as the toner particle projection area calculated in this way by the circumference of the toner particle projection image.
Further, 1.06 μm> indicates the number frequency of 1.06 μm or less measured by FPIA-1000.

(Degree of cloudiness of filtrate)
The degree of white turbidity of the filtrate obtained by separating the colored resin fine particles after solvent removal with a centrifuge was visually observed. A transparent one is indicated by ◯, a cloudy one is indicated by Δ, and a white one is indicated by ×.

(Preservation test)
To the toner base particles, 0.5 part by weight of silica (RX50 manufactured by Nippon Aerosil Co., Ltd.) was externally mixed with a Henschel mixer for 1 minute at a peripheral speed of 30 m / s, and 10 g of the obtained toner was put into a glass bottle and 12 ° C. at 12 ° C. It was stored in a constant temperature bath for a time, and aggregation of toner mother particles was observed. A case where the toner base particles are not aggregated is indicated by ◯, a case where the toner base particles are partially aggregated is indicated by Δ, and a case where the toner base particles are aggregated is indicated by ×.

(Wax inclusion)
The sample in which the toner base particles were suspended in water was observed with an optical microscope. The case where the wax was encapsulated in the toner base particles is indicated by ○, the case where the wax is slightly exposed on the surface of the toner base particles is indicated by △, and the case where the wax is clearly exposed on the surface of the toner base particles is indicated by ×. Show.

(Fixability and image evaluation characteristics)
1.0 part by mass of large silica (RX50 manufactured by Nippon Aerosil Co., Ltd.), 1.0 part by mass of small silica (RX200 manufactured by Nippon Aerosil Co., Ltd.) as an external additive with respect to 100 parts by mass of the prepared toner base particles, Add 0.5 parts by mass of titanium oxide (STT30S manufactured by Titanium Industry Co., Ltd.), put it in a 10L Henschel mixer (manufactured by Mitsui Mining Co., Ltd.), mix for 2 minutes at a blade tip peripheral speed of 30 m / s, and add cyan toner. Produced.
The produced cyan toner is filled in a toner cut ridge of a color printer (LP7000 manufactured by Seiko Epson Corporation), and solid printing is performed using a coated paper for color laser printer (manufactured by Seiko Epson Corporation) as a recording medium. The degree of occurrence of unevenness was judged visually. ◯ indicates that no unevenness was observed, Δ indicates that some unevenness was observed (allowable range), and × indicates that unevenness was large (the occurrence of streaks and banding).
Further, an unfixed solid print was printed on the upper half of the A4 paper, and the stain due to the low temperature offset generated in the lower half was observed while adjusting the fixing roller temperature to 120-180 ° C. The temperature at which contamination occurs is the low temperature offset temperature.

The toner particles having the core / shell structure obtained in Examples 1 to 8 which are the production methods of the present invention do not contain coarse particles, the shell is difficult to peel off from the core, has high temperature storage stability, and is a wax toner particle. It can be seen that there is no surface exposure. Also, images obtained from these toner particles are good.
On the other hand, the toner particles of Comparative Example 1 prepared using the emulsion suspension for shell having a weight ratio of methyl ethyl ketone in the aqueous medium lower than 25% by mass do not adhere to the colored resin fine particles. They were united with each other, and a large amount of fine particles remained and flowed into the filtrate and became cloudy. In addition, the image obtained from the toner particles of Comparative Example 1 was greatly uneven.
The toner particles of Comparative Example 3 to which the shell emulsion suspension was added all at once have a slightly larger particle size distribution than the toner particles of the present invention, and fine particles remain in the filtrate as in the Comparative Example 1. It flowed out and became cloudy. Further, the images obtained from the toner particles of Comparative Example 3 were not good because the unevenness was seen from the images obtained from the toner particles of Examples 1 to 8.
Further, it can be seen that the toner particles of Comparative Examples 1 and 3 have low high-temperature storage stability, and the wax is easily exposed on the toner particle surface.

Claims (2)

A step of obtaining a colored resin solution by dissolving or dispersing a binder resin, a wax and a colorant in an organic solvent, a basic compound and water are sequentially added to the colored resin solution to emulsify the colored resin solution in an aqueous medium. A step of adding an aqueous electrolyte solution to the emulsified suspension and coalescing the dispersoid in the emulsified suspension to form colored resin fine particles to form particles; a dispersion containing the colored resin fine particles; Particles having a core / shell structure are added by adding an emulsion suspension in which a shell-forming resin is emulsified to an aqueous medium containing methyl ethyl ketone in a range of 25 to 35% by mass, and then adding an aqueous electrolyte solution. The core / shell is characterized in that the step of forming, the organic solvent is removed under reduced pressure, and then the particles having the core / shell structure are separated from the aqueous medium, washed, and dried. Method for producing a toner for developing electrostatic images having a structure. 2. The electrostatic charge image having a core / shell structure according to claim 1, wherein a cross-linked polyester resin and a linear polyester resin are used as a binder resin, and a cross-linked polyester resin is used as a shell forming resin. A method for producing a developing toner.