JP6326896B2 - Sol-gel silica particles, electrostatic charge image developing toner, electrostatic charge image developer, toner cartridge, process cartridge, image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to sol-gel silica particles, an electrostatic charge image developing toner, an electrostatic charge image developer, a toner cartridge, a process cartridge, an image forming apparatus, and an image forming method.

  In recent years, the electrophotographic process has been widely used not only for copiers but also for office network printers, personal computer printers, on-demand printers, etc. due to the development of equipment in the information society and the enhancement of communication networks. Regardless of color, high image quality, high speed, high reliability, miniaturization, weight reduction, and energy saving performance are increasingly required.

  In an electrophotographic process, a latent image (electrostatic charge image) is usually formed on a photoconductor (image carrier) using a photoconductive substance by various means, and the latent image is developed using toner. Then, after the toner image on the photoconductor is transferred to a recording medium such as paper with or without an intermediate transfer body, a fixed image is formed through a plurality of steps of fixing the transferred image to the recording medium. doing.

Here, an invention is disclosed that provides silylated silica having a SiOH density per nm ² smaller than 0.6 with respect to the surface area according to the BET method (DIN 66131 and 66132) (for example, Patent Documents). 1).

Further, in order to provide a hydrophobic silica powder that is suitable as an external additive for toner for electrophotography and improves the fluidity and cleaning properties of the toner, it is a dry silica powder that has been subjected to a hydrophobic surface treatment with an organopolysiloxane, The ratio (A / D) of single silanol group integral value (A) and siloxane integral value (D) measured by ²⁹ Si solid state NMR is 0.25 <(A / D) <0. Hydrophobized surface-modified dry silica powder characterized in that it is .50 is disclosed (for example, see Patent Document 2).

A dry silica powder hydrophobized with organopolysiloxane, having a hydrophobicity of 85% or more, a single silanol group peak measured by ²⁹ Si solid state NMR, and a siloxane in the range of -10 ppm to -30 ppm Hydrophobized surface characterized in that the ratio (A / D) of single silanol group integral value (A) and siloxane integral value (D) based on the peak of 0.25 is (0.25) <(A / D) <0.50 Modified dry silica powder is disclosed (for example, see Patent Document 3).

In addition, a mixed slurry of metal silicon fine powder and water is sprayed into a flame, and at a portion where the temperature is 200 ° C. or higher in the course of collecting the obtained silica fine powder, first, alkylalkoxysilane is sprayed to the first stage. The alkylalkoxysilane-coated silica fine powder having an alkylalkoxysilane coating amount of 0.1 to 1 part by mass in terms of carbon to 100 parts by mass of the silica fine powder was collected, and then this alkyl was collected. Methanol titration characterized by forming a fluidized bed of alkoxysilane-coated silica fine powder and spraying and mixing alkylalkoxysilane and silicone oil while applying vibration from the outside to perform a second-stage hydrophobization treatment the degree of hydrophobicity at 40% to 90% by law, yet isolated silanol around wavenumber 3750cm ^-1 in FT-IR analysis Absorption band of groups are eliminated, the production method of the hydrophobic silica fine powder has been disclosed (e.g., refer to Patent Document 4.).

JP 2003-176122 A JP 2007-217249 A Japanese Patent No. 4793784 Japanese Patent No. 3886363

  An object of the present invention is to provide a sol-gel silica that improves the density stability of a toner image against changes in humidity when used as an external additive for toner.

Specific means for achieving the above object are as follows.
That is, the invention according to claim 1
A solvent removal step of circulating supercritical carbon dioxide in the sol-gel silica particle dispersion to remove the solvent of the sol-gel silica particle dispersion;
After the solvent removing step, a water applying step for applying water,
After the water application step, it was obtained through a hydrophobization treatment step of hydrophobizing with a hydrophobization treatment agent in supercritical carbon dioxide,
^A sol-gel silica particle having a ratio (S2 / S1) of a peak area S1 of a hydroxyl group to a peak area S2 of a trimethylsilyl group as measured by ¹ H MAS NMR of 0.5 or more.

The invention according to claim 2
The sol-gel silica particles according to claim 1, wherein the ratio (S2 / S1) is 0.5 or more and 0.9 or less.

The invention according to claim 3
An electrostatic charge image developing toner comprising toner particles and an external additive comprising the sol-gel silica particles according to claim 1.

The invention according to claim 4
An electrostatic charge image developer comprising the electrostatic charge image developing toner according to claim 3.

The invention according to claim 5
Containing the electrostatic image developing toner according to claim 3;
A toner cartridge to be attached to and detached from the image forming apparatus.

The invention according to claim 6
A developing means for containing the electrostatic charge image developer according to claim 4 and developing the electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer,
A process cartridge attached to and detached from the image forming apparatus.

The invention according to claim 7 provides:
An image carrier,
Charging means for charging the surface of the image carrier;
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier;
Development means for containing the electrostatic charge image developer according to claim 4 and developing the electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer;
Transfer means for transferring a toner image formed on the surface of the image carrier to the surface of a recording medium;
Fixing means for fixing the toner image transferred to the surface of the recording medium;
An image forming apparatus comprising:

The invention according to claim 8 provides:
A charging step for charging the surface of the image carrier;
An electrostatic charge image forming step of forming an electrostatic charge image on the surface of the charged image carrier;
A developing step of developing an electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer according to claim 4;
A transfer step of transferring a toner image formed on the surface of the image carrier to the surface of a recording medium;
A fixing step of fixing the toner image transferred to the surface of the recording medium;
An image forming method comprising:

According to the first aspect of the present invention, compared with the case where the ratio (S2 / S1) of the peak area S1 of the hydroxyl group to the peak area S2 of the trimethylsilyl group is less than 0.5, it is used as an external additive for the toner. In such a case, sol-gel silica is provided in which the density stability of the toner image with respect to humidity changes is improved.
According to the second aspect of the present invention, when the ratio (S2 / S1) is outside the range of 0.5 or more and 0.9 or less, the humidity change when used as an external additive for the toner. The density stability of the toner image with respect to the toner is further improved.
According to the third aspect of the present invention, compared to the case where the ratio (S2 / S1) between the peak area S1 of the hydroxyl group and the peak area S2 of the trimethylsilyl group is less than 0.5, the density of the toner image with respect to the humidity change. An electrostatic charge image developing toner having improved stability is provided.
According to the fourth aspect of the present invention, the density of the toner image with respect to a change in humidity is compared with the case where the ratio (S2 / S1) of the peak area S1 of the hydroxyl group to the peak area S2 of the trimethylsilyl group is less than 0.5. An electrostatic charge image developer with improved stability is provided.
According to the fifth aspect of the present invention, compared to the case where the ratio (S2 / S1) of the peak area S1 of the hydroxyl group to the peak area S2 of the trimethylsilyl group is less than 0.5, the density of the toner image with respect to the humidity change. Provided is a toner cartridge that accommodates toner for developing an electrostatic charge image with improved stability.
According to the sixth aspect of the present invention, compared to the case where the ratio (S2 / S1) of the peak area S1 of the hydroxyl group to the peak area S2 of the trimethylsilyl group is less than 0.5, the density of the toner image with respect to the humidity change. The electrostatic image developer having improved stability can be easily handled, and the adaptability to image forming apparatuses having various configurations can be enhanced.
According to the seventh aspect of the present invention, compared to the case where the ratio (S2 / S1) of the peak area S1 of the hydroxyl group to the peak area S2 of the trimethylsilyl group is less than 0.5, the density of the toner image with respect to the humidity change. An image forming apparatus using an electrostatic charge image developer with improved stability is provided.
According to the eighth aspect of the present invention, compared to the case where the ratio (S2 / S1) of the peak area S1 of the hydroxyl group to the peak area S2 of the trimethylsilyl group is less than 0.5, the density of the toner image with respect to the humidity change. There is provided an image forming method using an electrostatic charge image developer having improved stability.

It is a figure explaining the state of a screw about an example of a screw extruder used for manufacture of toner concerning this embodiment. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an exemplary embodiment. It is a schematic block diagram which shows the process cartridge which concerns on this embodiment.

  Hereinafter, embodiments of the sol-gel silica particles, electrostatic charge image developing toner, electrostatic charge image developer, toner cartridge, process cartridge, image forming apparatus, and image forming method of the present invention will be described in detail.

<Sol-gel silica particles>
In the sol-gel silica particles according to the present embodiment, the ratio (S2 / S1) of the peak area S1 of the hydroxyl group and the peak area S2 of the trimethylsilyl group, measured by ¹ H MAS (Magic Angle Spinning) NMR, is 0.5 or more. It is a sol-gel silica particle.
When the sol-gel silica particles according to the present embodiment are used as an external additive for the toner, the density stability of the toner image with respect to a change in humidity is improved. The reason is not clear, but is presumed as follows.

The sol-gel silica particles are characterized by having a high water content compared to general fumed silica particles produced by a gas phase method. This is because even after the hydrophobization treatment, the sol-gel silica particles have many hydroxyl groups having a high affinity for water on the surfaces and internal pores.
The amount of water adsorption of sol-gel silica particles is relatively small after drying treatment and stored for a long time at low temperature and low humidity. Become more. This is because the hydroxyl group has a high affinity with water, so that the moisture adsorption amount tends to be high in a high temperature and high humidity environment.
In particular, the presence of a large amount of hydroxyl groups in the sol-gel silica particles is affected by two effects: the amount of hydroxyl groups is large, and there are few hydrophobic groups such as trimethylsilyl groups that shield moisture adsorption on hydroxyl groups due to steric hindrance. The difference in the amount of adsorbed moisture in a high humidity environment tends to increase.
The amount of moisture adsorption of sol-gel silica under low temperature and low humidity or immediately after drying is small. In particular, when there are many hydroxyl groups in the sol-gel silica particles, the difference in the amount of moisture adsorption between a low temperature and low humidity environment and a high temperature and high humidity environment becomes large. The amount of water adsorbed on the sol-gel silica particles varies due to the variation in humidity, and may greatly affect the charge amount of toner containing such sol-gel silica particles as an external additive. In particular, regarding a toner containing sol-gel silica particles that are exposed to a low-temperature and low-humidity environment for a long period of time and have a small amount of moisture adsorbed on the surface as an external additive, the charge decrease when the humidity increases is large.

In recent years, humidifiers such as air purifiers equipped with a humidifying function have been used in general offices due to the spread of home appliances. In particular, the amount of water adsorbed on the hydroxyl groups on the surface of the sol-gel silica particles gradually increases and the charge amount gradually decreases until the humidity stabilizes from the non-operating state of the humidifier in winter. Concentration fluctuation sometimes occurred. As described above, the change in the amount of adsorbed water on the surface of the sol-gel silica particles accompanying the change in humidity sometimes makes the density of the toner image unstable.
Also, if the amount of hydroxyl groups is extremely reduced, the amount of moisture adsorbed increases greatly when the humidity reaches a certain level, and the density stability of the toner image may not be satisfied.
Furthermore, in order to improve the density stability of the toner image, even if the amount of the hydroxyl group is simply reduced, the effect of suppressing the fluctuation of the moisture adsorption amount due to the humidity fluctuation is not sufficient, and the density fluctuation of the toner image may occur. However, simply by the amount of hydroxyl group alone, the slight fluctuation in the amount of moisture adsorbed on the surface of the sol-gel silica particles cannot be controlled, and the density stability of the toner image may not be sufficiently adjusted.

In this embodiment, toner is controlled by controlling the ratio of hydroxyl groups and trimethylsilyl groups, which are surface functional groups of sol-gel silica particles, to suppress the amount of moisture adsorbed on silica particles due to humidity changes caused by the effects of air conditioning and humidifiers. The toner image is stabilized, and the density stability of the toner image against a change in humidity is obtained.
About the water | moisture-content adsorption | suction mechanism to the sol-gel silica particle in a low-temperature low-humidity environment, it guesses as follows. Water molecules are first locally adsorbed on hydroxyl groups that have a high affinity for water. Next, co-adsorption occurs mainly at the location where water molecules are adsorbed locally, and the adsorbed layer develops into an island shape. Furthermore, when island-shaped adsorption layers contact each other, they develop into a continuous layer. Note that the amount of moisture adsorbed on the sol-gel silica particles depends on the amount of trimethylsilyl groups that shield the moisture adsorption on the sol-gel silica particles due to the amount of hydroxyl groups and steric hindrance. In other words, the amount of moisture adsorption varies depending on the amount of hydroxyl groups on the silica particle surface and the amount of trimethylsilyl groups. The density stability of the toner image can be adjusted. In addition, by controlling the amount of hydroxyl groups and the amount of trimethylsilyl groups within a certain range, it is possible to suppress fluctuations in the amount of moisture adsorbed when the humidity rises from a low humidity state, and the charge amount can be stabilized over time. It is possible to ensure sufficient concentration stability.
Further, by arranging the hydroxyl group and the trimethylsilyl group on the surface of the sol-gel silica particle without deviation, the effect of the present embodiment can be more easily obtained. An example of a method for arranging hydroxyl groups and trimethylsilyl groups on the surface of the sol-gel silica particles without bias is a hydrophobic treatment using supercritical carbon dioxide, which will be described later.

In this embodiment, “low humidity” refers to a humidity of 10% RH, “medium humidity” refers to a humidity of 30% RH, and “high humidity” refers to a humidity of 50% RH. Say.
In this embodiment, “low temperature” means that the temperature is 10 ° C., and “high temperature” means that the temperature is 30 ° C.

In the sol-gel silica particles according to the present embodiment, the ratio (S2 / S1) between the peak area S1 of the hydroxyl group and the peak area S2 of the trimethylsilyl group measured by ¹ H MAS NMR is 0.5 or more. When the ratio (S2 / S1) is less than 0.5, the amount of hydroxyl groups on the surface of the sol-gel silica particles is large, and the amount of trimethylsilyl groups relative to the amount of hydroxyl groups is small. Therefore, when the humidity rises from a low temperature and low humidity state, it is difficult to obtain an effect of shielding moisture adsorption on the hydroxyl group due to steric hindrance of the trimethylsilyl group. Further, due to the large amount of hydroxyl groups, moisture adsorption to the hydroxyl groups is likely to occur. Therefore, when sol-gel silica particles are used as an external additive for toner, the charge amount may decrease according to the amount of moisture adsorbed, and the concentration may increase accordingly.
If the ratio (S2 / S1) is 0.5 or more, the amount of hydroxyl groups on the surface of the silica particles is small, and the amount of trimethylsilyl groups is large relative to the amount of hydroxyl groups. Therefore, when the humidity rises from a low temperature and low humidity state, the effect of shielding moisture adsorption on the hydroxyl group due to the steric hindrance of the trimethylsilyl group tends to appear. Further, since the amount of hydroxyl group is small, moisture adsorption on the hydroxyl group can be blocked. Therefore, when the sol-gel silica particles are used as an external additive for the toner, the toner charge amount is stabilized over time, so that density stability can be ensured.

  In the present embodiment, the ratio (S2 / S1) is preferably 0.5 or more and 0.9 or less. When the ratio (S2 / S1) is 0.9 or less, even if the humidity increases from the low humidity state, a state where the amount of moisture adsorbed on the surface is small is maintained for a while. In addition, when the humidity is higher than the medium humidity, an excessive increase in the amount of adsorbed water is suppressed, and a rapid increase in toner concentration is likely to be suppressed.

In this embodiment, the peak area S1 of the hydroxyl group and the peak area S2 of the trimethylsilyl group are measured by ¹ H MAS NMR.
In this embodiment, the measurement conditions of S1 and S2 by ¹ H MAS NMR are as follows.
First, sol-gel silica particles are vacuum-dried overnight at 100 ° C. as a pretreatment. Next, a 4 mm zirconia rotor is fully filled with the sample, and ¹ H MAS NMR measurement is performed using AVANCE III400 manufactured by Bruker Biospin. At that time, measurement is performed at MAS rotation speed 8 kHz, 1H 90 ° pulse 2 μs, and number of integrations 16 times. The peak area S1 of the hydroxyl group and the peak area S2 of the trimethylsilyl group are calculated by separating the ¹ H MAS NMR spectrum from the peak.
Based on the measured S1 and S2, the ratio (S2 / S1) is calculated.

The method for producing sol-gel silica particles according to this embodiment is not particularly limited as long as it is based on the sol-gel method. Below, an example of the manufacturing method of the sol-gel silica particle which concerns on this embodiment is demonstrated.
In the present embodiment, the sol-gel silica particles refer to so-called wet silica particles produced by a sol-gel method.

  Examples of the method for producing silica particles by the sol-gel method include the following method (hereinafter referred to as a method for producing sol-gel silica particles).

  The method for producing sol-gel silica particles includes a step of preparing an alkali catalyst solution containing an alkali catalyst at a concentration of 0.6 mol / L or more and 0.85 mol / L or less in a solvent containing alcohol (hereinafter referred to as “alkali catalyst solution preparation”). In some cases, tetraalkoxysilane is supplied into the alkali catalyst solution, and 0.1 mol or more per 1 mol of the total amount of tetraalkoxysilane supplied per minute is 0. And a step of supplying an alkali catalyst at 4 mol or less (hereinafter sometimes referred to as “particle generation step”).

That is, in the method for producing sol-gel silica particles, in the presence of the alcohol containing the alkali catalyst at the above concentration, while supplying the raw material tetraalkoxysilane and the alkali catalyst as a catalyst separately in the above relationship, In this method, silica particles are produced by reacting tetraalkoxysilane.
In the method for producing sol-gel silica particles, by the above method, the generation of coarse aggregates is reduced, and irregular-shaped silica particles are obtained. Although this reason is not certain, it is thought to be due to the following reasons.

First, when an alkali catalyst solution containing an alkali catalyst is prepared in a solvent containing alcohol, and tetraalkoxysilane and an alkali catalyst are respectively supplied to this solution, the tetraalkoxysilane supplied in the alkali catalyst solution reacts. Thus, nuclear particles are generated. At this time, if the alkali catalyst concentration in the alkali catalyst solution is in the above range, it is considered that irregular-shaped core particles are generated while suppressing the formation of coarse aggregates such as secondary aggregates. This is because the alkali catalyst is coordinated to the surface of the generated core particle in addition to the catalytic action, and contributes to the shape and dispersion stability of the core particle. If the amount is within the above range, the alkali catalyst Does not cover the surface of the core particles uniformly (that is, because the alkali catalyst is unevenly distributed and adheres to the surface of the core particles), while maintaining the dispersion stability of the core particles, the surface tension and chemical affinity of the core particles This is because a partial bias occurs in the nuclei and atypical core particles are considered to be generated.
When the tetraalkoxysilane and the alkali catalyst are continuously supplied, the produced core particles grow by the reaction of the tetraalkoxysilane, and silica particles are obtained.
Here, by supplying the tetraalkoxysilane and the alkali catalyst while maintaining the supply amount in the above relationship, the generation of coarse aggregates such as secondary agglomerates is suppressed, and atypical nuclear particles However, it is considered that the particles grow while maintaining the atypical shape, and as a result, atypical silica particles are generated. This is because the supply amount of the tetraalkoxysilane and the alkali catalyst is in the above relationship, so that the partial distribution of the tension and chemical affinity on the surface of the core particle is maintained while maintaining the dispersion of the core particle. This is because it is considered that the core particles grow while maintaining the atypical shape.

From the above, it is considered that in the method for producing sol-gel silica particles, the generation of coarse aggregates is small and atypical silica particles can be obtained.
The irregular-shaped silica particles are, for example, silica particles having an average circularity of 0.5 or more and 0.85 or less.
The circularity of the silica particles is “100 / SF2” calculated by the following equation by observing the silica particles with a scanning electron microscope and obtaining the following I and A from the image analysis.
Circularity (100 / SF2) = 4π × (A / I ² )
Here, I is the peripheral length of the silica particles, A is the projected area of the silica particles, π is the circumference, and SF2 is the shape factor.
The average circularity of the silica particles is obtained as 50% circularity in the cumulative frequency of the equivalent circle diameter of 100 silica particles obtained from the image analysis.

Also, in the method for producing sol-gel silica particles, it is thought that silica particles are produced by generating irregularly shaped core particles and growing the nucleus particles while maintaining this atypical shape. It is considered that atypical silica particles having high properties and little variation in shape distribution can be obtained.
In addition, in the method for producing sol-gel silica particles, it is considered that the generated irregular core particles are grown while maintaining the irregular shape, so that silica particles are obtained. It is thought that it is obtained.
Further, in the method for producing sol-gel silica particles, particles are generated by causing a reaction of tetraalkoxysilane by supplying a tetraalkoxysilane and an alkali catalyst, respectively, into the alkali catalyst solution. Compared to the case of producing atypical silica particles by the conventional sol-gel method, the total amount of alkali catalyst used is reduced, and as a result, the step of removing the alkali catalyst can be omitted. This is particularly advantageous when silica particles are applied to products that require high purity.

The alkali catalyst solution preparation step will be described.
In the alkali catalyst solution preparation step, a solvent containing alcohol is prepared, and an alkali catalyst is added thereto to prepare an alkali catalyst solution.

The solvent containing alcohol may be a solvent of alcohol alone or, if necessary, a mixed solvent with other solvents such as water, ketone, ester, halogenated hydrocarbon, ether and the like. In the case of a mixed solvent, the amount of alcohol relative to the other solvent is preferably 80% by mass or more (desirably 90% by mass or more).
Examples of the alcohol include lower alcohols such as methanol and ethanol.

  On the other hand, the alkali catalyst is a catalyst for accelerating the reaction (hydrolysis reaction, condensation reaction) of tetraalkoxysilane, and examples thereof include basic catalysts such as ammonia, urea, monoamine, quaternary ammonium salts, Ammonia is particularly desirable.

The concentration (content) of the alkali catalyst is 0.6 mol / L or more and 0.85 mol / L, and preferably 0.65 mol / L or more and 0.78 mol / L.
If the concentration of the alkali catalyst is less than 0.6 mol / L, the dispersibility of the core particles in the growth process of the generated core particles becomes unstable, and coarse aggregates such as secondary aggregates are generated or gelled. The particle size distribution may deteriorate.
On the other hand, if the concentration of the alkali catalyst is more than 0.85 mol / L, the stability of the generated core particles becomes excessive, and spherical particles are generated, and atypical core particles cannot be obtained. Atypical silica particles cannot be obtained.
In addition, the density | concentration of an alkali catalyst is a density | concentration with respect to an alcohol catalyst solution (an alkali catalyst + solvent containing alcohol).

The particle generation process will be described.
In the particle generation step, tetraalkoxysilane and an alkali catalyst are respectively supplied to an alkali catalyst solution, and the tetraalkoxysilane is reacted (hydrolysis reaction, condensation reaction) in the alkali catalyst solution to obtain silica particles. Is a step of generating.
In this particle generation process, after the core particles are generated by the reaction of tetraalkoxysilane at the initial stage of supply of tetraalkoxysilane (core particle generation stage), the core particles are grown (core particle growth stage), and then the silica particles are Generate.

  Examples of the tetraalkoxysilane supplied into the alkali catalyst solution include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and the like. From the viewpoints of diameter, particle size distribution, etc., tetramethoxysilane and tetraethoxysilane are preferable.

The supply amount of tetraalkoxysilane is preferably 0.001 mol / mol · min or more and 0.01 mol / mol · min or less with respect to the number of moles of alcohol in the alkali catalyst solution, for example.
By setting the supply amount of the tetraalkoxysilane within the above range, the generation of coarse aggregates is small and atypical silica particles are easily generated.
The supply amount of tetraalkoxysilane indicates the number of moles of tetraalkoxysilane supplied per minute with respect to 1 mol of alcohol in the alkali catalyst solution.

  On the other hand, examples of the alkali catalyst supplied into the alkali catalyst solution include those exemplified above. The alkali catalyst to be supplied may be of the same type as the alkali catalyst previously contained in the alkali catalyst solution, or may be of a different type, but is preferably of the same type.

The supply amount of the alkali catalyst is 0.1 mol or more and 0.4 mol or less, preferably 0.14 mol or more and 0.35 mol or less, per 1 mol of the total supply amount of tetraalkoxysilane supplied per minute.
If the supply amount of the alkali catalyst is less than 0.1 mol, the dispersibility of the core particles in the growth process of the generated core particles becomes unstable, and coarse aggregates such as secondary aggregates are generated, The particle size distribution may deteriorate.
On the other hand, if the supply amount of the alkali catalyst is more than 0.4 mol, the stability of the generated core particles becomes excessive, and even if atypical core particles are generated at the core particle generation stage, In some cases, the particles grow in a spherical shape, and irregular-shaped silica particles cannot be obtained.

  Here, in the particle generation step, tetraalkoxysilane and an alkali catalyst are supplied to the alkali catalyst solution, respectively, but this supply method may be a continuous supply method or intermittently. A supply method may be used.

  In the particle generation step, the temperature in the alkaline catalyst solution (temperature at the time of supply) is, for example, preferably 5 ° C. or more and 50 ° C. or less, and desirably 15 ° C. or more and 40 ° C. or less.

  Through the above steps, hydrophilic sol-gel silica particles are obtained in the method for producing sol-gel silica particles.

  In the dispersion preparation step described above, for example, when sol-gel silica particles are obtained by a wet process, the sol-gel silica particles are obtained in a state of dispersion (sol-gel silica particle dispersion) in which the sol-gel silica particles are dispersed in a solvent.

The sol-gel silica particles according to the present embodiment have a ratio (S2 / S1) of 0.5 or more. In order to set the ratio (S2 / S1) to 0.5 or more, it is desirable to subject the surfaces of the sol-gel silica particles to a hydrophobic treatment. The method for hydrophobizing sol-gel silica particles is not particularly limited. Hereinafter, a method using supercritical carbon dioxide will be described in detail as an example of a method for hydrophobizing sol-gel silica particles.
Examples of the hydrophobization method using supercritical carbon dioxide include, for example, a dispersion preparation step for preparing a silica particle dispersion containing sol-gel silica particles and a solvent containing alcohol and water, and circulating supercritical carbon dioxide. Solvent removal step of removing the solvent of the silica particle dispersion, water application step of applying water to the sol-gel silica particles from which the solvent has been removed, and the sol-gel using a hydrophobizing agent in the supercritical carbon dioxide And a method having a hydrophobizing step of hydrophobizing the surface of silica particles.
In the above method, the dispersion preparing step includes a step of preparing the above-mentioned sol-gel silica particle dispersion.

When shifting to the solvent removal step, the prepared sol-gel silica particle dispersion preferably has a mass ratio of water to alcohol of, for example, 0.1 to 1.0, preferably 0.15 to 0.5. More preferably, it is 0.2 or more and 0.3 or less.
In the sol-gel silica particle dispersion, when the mass ratio of water to alcohol is in the above range, the generation of hydrophobic sol-gel silica particle coarse powder after hydrophobization treatment is small, and the hydrophobicity has a high degree of hydrophobicity and good electrical resistance. Sol-gel silica particles are easily obtained.
When the mass ratio of water to alcohol is less than 0.1, the condensation of hydroxyl groups (silanol groups) on the surface of the sol-gel silica particles when removing the solvent is extremely reduced in the solvent removal step. When the moisture adsorbed on the surface of the silica particles increases, the electrical resistance of the sol-gel silica particles after the hydrophobization treatment may become too low. In addition, when the water mass ratio exceeds 1.0, in the solvent removal step, a large amount of water remains near the end point of the solvent removal in the sol-gel silica particle dispersion, and the sol-gel silica particles aggregate due to the liquid crosslinking force. Easily present as a coarse powder after hydrophobization treatment.

In addition, when shifting to the solvent removal step, the prepared sol-gel silica particle dispersion preferably has a mass ratio of water to the sol-gel silica particles of, for example, 0.02 to 3, preferably 0.05 to 1. More preferably, it is 0.1 or more and 0.5 or less.
In the sol-gel silica particle dispersion, when the mass ratio of water to the sol-gel silica particles is within the above range, sol-gel silica particles having a high degree of hydrophobicity and good electrical resistance are obtained with less generation of coarse sol-gel silica particles. It becomes easy.
If the mass ratio of water to the sol-gel silica particles is less than 0.02, the condensation of the hydroxyl groups (silanol groups) on the surface of the sol-gel silica particles when removing the solvent is extremely reduced in the solvent removal step. As the amount of moisture adsorbed on the surface of the sol-gel silica particles increases, the electrical resistance of the sol-gel silica particles may become too low.
When the water mass ratio exceeds 3, in the solvent removal step, a large amount of water remains in the vicinity of the end point of solvent removal in the sol-gel silica particle dispersion, and the sol-gel silica particles tend to aggregate with each other due to the liquid crosslinking force. Sometimes.

In addition, when shifting to the solvent removal step, the prepared sol-gel silica particle dispersion preferably has a mass ratio of sol-gel silica particles to the sol-gel silica particle dispersion of, for example, 0.05 to 0.7, preferably 0.2. It is 0.65 or less, more preferably 0.3 or more and 0.6 or less.
When the mass ratio of the sol-gel silica particles to the sol-gel silica particle dispersion is less than 0.05, the amount of supercritical carbon dioxide used in the solvent removal step increases, and productivity may deteriorate.
In addition, when the mass ratio of the sol-gel silica particles to the sol-gel silica particle dispersion exceeds 0.7, the distance between the sol-gel silica particles becomes closer in the sol-gel silica particle dispersion, and coarse particles due to aggregation or gelation of the sol-gel silica particles are generated. May occur easily.

-Solvent removal step-
The solvent removal step is a step of removing the solvent of the silica particle dispersion by circulating supercritical carbon dioxide.
In other words, this step is a step of removing the solvent by bringing the supercritical carbon dioxide into contact with the silica particle dispersion by circulating the supercritical carbon dioxide.
Specifically, in this step, for example, a sol-gel silica particle dispersion is introduced into a closed reactor. Thereafter, liquefied carbon dioxide is added to the sealed reactor and heated, and the pressure in the reactor is increased by a high-pressure pump to bring the carbon dioxide into a supercritical state. Then, the supercritical carbon dioxide is introduced into the closed reactor and discharged, and is passed through the closed reactor, that is, the sol-gel silica particle dispersion.
As a result, the supercritical carbon dioxide dissolves the solvent (alcohol and water) and accompanies it to the outside of the silica particle dispersion (outside of the sealed reactor), and the solvent is removed.

  Here, supercritical carbon dioxide is carbon dioxide in a state of temperature and pressure above the critical point, and has both gas diffusibility and liquid solubility.

The temperature condition for removing the solvent, that is, the temperature of supercritical carbon dioxide is, for example, 31 ° C. or higher and 350 ° C. or lower, preferably 60 ° C. or higher and 300 ° C. or lower, and more preferably 80 ° C. or higher and 250 ° C. or lower.
When this temperature is less than the above range, the solvent is difficult to dissolve in supercritical carbon dioxide, and thus it may be difficult to remove the solvent. In addition, it is considered that coarse powder is likely to be generated due to the liquid crosslinking force of a solvent or supercritical carbon dioxide. On the other hand, when this temperature exceeds the above range, it is considered that coarse powder such as secondary aggregates may be easily generated due to condensation of hydroxyl groups (silanol groups) on the surface of the sol-gel silica particles.

Moreover, the temperature conditions for solvent removal vary depending on the mass ratio of water to alcohol in the sol-gel silica particle dispersion. Water tends to be less soluble in supercritical carbon dioxide than alcohol, but the solubility tends to increase by increasing the temperature of supercritical carbon dioxide.
Therefore, y represented by the following formula (11) is within the range of the following formula (12) (preferably within the range of the following formula (12-1), more preferably within the range of the formula (12-2)). The solvent may be removed by bringing supercritical carbon dioxide into contact with the sol-gel silica particle dispersion.
Formula (11): y = ((Water mass ratio of sol-gel silica particle dispersion / Alcohol mass ratio of sol-gel silica particle dispersion) / Temperature (° C.)) “This temperature is the temperature for solvent removal. "
Formula (12): 0.0001 ≦ y ≦ 0.0016
Formula (12-1): 0.0003 ≦ y ≦ 0.0012
Formula (12-2): 0.0005 ≦ y ≦ 0.001

  When y represented by the above formula (11) is less than the above range, condensation of hydroxyl groups (silanol groups) on the surface of the sol-gel silica particles when removing the solvent is extremely reduced. When the moisture adsorbed on the surface of the silica particles increases, the electrical resistance of the sol-gel silica particles after the hydrophobization treatment may become too low. On the other hand, when y represented by the above formula (11) exceeds the above range, a large amount of water remains in the vicinity of the end point of solvent removal, and aggregation of sol-gel silica particles due to liquid crosslinking force may easily occur.

On the other hand, the pressure condition for removing the solvent, that is, the pressure of supercritical carbon dioxide is, for example, 7.38 MPa or more and 40 MPa or less, desirably 10 MPa or more and 35 MPa or less, more desirably 15 MPa or more and 25 MPa or less.
If this pressure is less than the above range, the solvent tends to be difficult to dissolve in supercritical carbon dioxide. On the other hand, if the pressure exceeds the above range, the equipment tends to be expensive.

The amount of supercritical carbon dioxide introduced into and discharged from the closed reactor is, for example, preferably from 15.4 L / min / m ^{3 to} 1540 L / min / m ³ , and preferably 77 L / min / m. ³ or more and 770 L / min / m ³ or less.
When the introduction / discharge amount is less than 15.4 L / min / m ³ , it takes time to remove the solvent, and the productivity tends to deteriorate.
On the other hand, when the introduction / discharge amount is 1540 L / min / m ³ or more, the supercritical carbon dioxide has a short path, the contact time of the silica particle dispersion is shortened, and the solvent cannot be efficiently removed. It becomes.

-Water application process-
In the hydrophobization process, after removing the solvent from the silica particle dispersion by circulating supercritical carbon dioxide, in order to promote hydrolysis of the hydrophobizing agent in the hydrophobization process described later, You may provide the water provision process which provides water to sol-gel silica particle before.
By providing a water application step, the sol-gel silica particles are made rich in water before the hydrophobization treatment step, so that hydrolysis of the hydrophobization agent is promoted and the hydroxyl group is hydrophobized in the hydrophobization treatment step. It becomes easy to crush with the agent. For this reason, when the sol-gel silica particles hydrophobized are used as an external additive for the toner, the environmental stability of the toner image with respect to a change in humidity is superior to that in the case where no water application step is provided.
In the water application step, water may be added to the supercritical carbon dioxide in the solvent removal step.
In the water application step, the amount of water applied to the sol-gel silica particles is preferably 5 parts by mass or more and 30 parts by mass or less, more preferably 5 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the sol-gel silica particles. More preferably, it is more than 20 parts by weight.

-Hydrophobization process-
The hydrophobizing treatment step is a step of hydrophobizing the surface of the sol-gel silica particles with a hydrophobizing agent in supercritical carbon dioxide.
That is, in this step, the surface of the sol-gel silica particles is hydrophobized with a hydrophobizing agent in supercritical carbon dioxide.
Specifically, in this step, for example, after stopping and introducing supercritical carbon dioxide into the closed reactor in the solvent removal step, the temperature and pressure in the closed reactor are adjusted, In a state where supercritical carbon dioxide is present, a certain proportion of the hydrophobizing agent is added to the sol-gel silica particles. The sol-gel silica particles are hydrophobized by reacting the hydrophobizing agent in a state in which this state is maintained, that is, in supercritical carbon dioxide. After completion of the reaction, the inside of the sealed reactor is depressurized and cooled.
Here, in this process, the hydrophobization treatment may be performed in supercritical carbon dioxide (that is, in the atmosphere of supercritical carbon dioxide), and supercritical carbon dioxide is circulated (that is, supercritical carbon dioxide into the closed reactor). Hydrophobic treatment may be performed while introducing and discharging carbon), or non-circulating hydrophobic treatment may be performed.

  When the sol-gel silica particles are subjected to a hydrophobization treatment in supercritical carbon dioxide, it is considered that the hydrophobization agent is dissolved in the supercritical carbon dioxide. Since supercritical carbon dioxide has a characteristic of extremely low interfacial tension, the hydrophobizing agent in a state dissolved in supercritical carbon dioxide can easily reach the surface of the silica particles evenly, and the hydroxyl group is uniformly hydrophobic. It is thought that it will be processed. Therefore, it is estimated that a hydroxyl group and a trimethylsilyl group are arranged on the sol-gel silica surface with a good balance.

In the hydrophobization treatment step, the amount of sol-gel silica particles relative to the reactor volume (that is, the charged amount) is, for example, preferably 50 g / L or more and 600 g / L or less, preferably 100 g / L or more and 500 g / L or less, more preferably 150 g / L or more and 400 g / L or less.
When this amount is less than the above range, the concentration of the hydrophobic treatment agent with respect to supercritical carbon dioxide is lowered, the contact probability with the silica surface is lowered, and the hydrophobic reaction is difficult to proceed. On the other hand, if this amount is larger than the above range, the concentration of the hydrophobic treatment agent with respect to supercritical carbon dioxide becomes high, and the hydrophobic treatment agent cannot be completely dissolved in supercritical carbon dioxide, resulting in poor dispersion and easy generation of coarse aggregates. Become.

The density of supercritical carbon dioxide is, for example, 0.10 g / ml or more and 0.60 g / ml or less, preferably 0.10 g / ml or more and 0.50 g / ml or less, more preferably 0.2 g / ml or more and 0 or less. .30 g / ml or less.
When this density is lower than the above range, the solubility of the hydrophobic treating agent in supercritical carbon dioxide tends to decrease, and aggregates tend to be generated. On the other hand, when the density is higher than the above range, the diffusibility to the silica pores is lowered, and thus the hydrophobization treatment may be insufficient. In particular, the sol-gel silica containing a large amount of hydroxyl groups is preferably subjected to a hydrophobization treatment in the above density range.
The density of supercritical carbon dioxide is adjusted by temperature, pressure, and the like.

Examples of the hydrophobizing agent include known organosilicon compounds having an alkyl group (for example, a methyl group, an ethyl group, a propyl group, a butyl group). Specific examples include, for example, a silazane compound (for example, a methyltrimethyl group). Silane compounds such as methoxysilane, dimethyldimethoxysilane, trimethylchlorosilane, and trimethylmethoxysilane, hexamethyldisilazane, tetramethyldisilazane, and the like. The hydrophobizing agent may be used alone or in combination.
Among these hydrophobizing agents, organosilicon compounds having a trimethyl group such as trimethylmethoxysilane and hexamethyldisilazane are preferable, and hexamethyldisilazane is more preferable.

  The amount of the hydrophobizing agent used is not particularly limited, but in order to obtain the effect of hydrophobizing, for example, it is preferably 1% by mass to 60% by mass, and preferably 5% by mass with respect to the sol-gel silica particles. % To 40% by mass, more preferably 10% to 30% by mass.

Here, the temperature condition of the hydrophobization treatment (temperature condition under reaction), that is, the temperature of supercritical carbon dioxide is, for example, 80 ° C. or more and 300 ° C. or less, preferably 100 ° C. or more and 300 ° C. or less, more preferably 150 ° C. It is at least 250 ° C.
When this temperature is less than the above range, the reactivity between the hydrophobizing agent and the surface of the sol-gel silica particles may be lowered. On the other hand, when the temperature exceeds the above range, the condensation reaction between the hydroxyl groups of the sol-gel silica particles proceeds, and as a result, the reaction sites are reduced and the degree of hydrophobicity may be difficult to improve.

  On the other hand, the pressure condition (temperature condition under reaction) of the hydrophobization treatment, that is, the pressure of supercritical carbon dioxide may be a condition that satisfies the above-mentioned density. For example, it is preferably 8 MPa or more and 30 MPa or less, and preferably 10 MPa or more 25 MPa or less, more desirably 15 MPa or more and 20 MPa or less.

  Hydrophobic sol-gel silica particles can be obtained through the hydrophobization process described above.

<Toner for electrostatic image development>
The electrostatic image developing toner according to the present embodiment (hereinafter referred to as toner according to the present embodiment) includes toner particles and an external additive including the sol-gel silica particles according to the present embodiment.

  In the present embodiment, other external additives other than the sol-gel silica particles according to the present embodiment may be used in combination. As other external additives other than the sol-gel silica particles according to the present embodiment, resin particles (resin particles such as polystyrene, polymethyl methacrylate (PMMA) and melamine resin) and cleaning activators (for example, zinc stearate) are representative. Higher fatty acid metal salts, fluorine-based high molecular weight particles) and the like.

The external addition amount of the external additive is, for example, preferably 0.01% by mass or more and 5% by mass or less, and more preferably 0.01% by mass or more and 2.0% by mass or less with respect to the toner particles.
In the toner according to the exemplary embodiment, the ratio of the sol-gel silica particles according to the exemplary embodiment is preferably 0.5% by mass or more and 2.5% by mass or less, and more preferably 1.0% by mass or more and 2.5% by mass or less. Desirably, 1.0 mass% or more and 2.0 mass% or less is still more desirable.

(Toner particles)
The toner particles include, for example, a binder resin and, if necessary, a colorant, a release agent, and other additives.

-Binder resin-
Examples of the binder resin include styrenes (eg, styrene, parachlorostyrene, α-methylstyrene, etc.), (meth) acrylic acid esters (eg, methyl acrylate, ethyl acrylate, n-propyl acrylate, acrylic acid). n-butyl, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (for example, acrylonitrile, Methacrylonitrile, etc.), vinyl ethers (eg, vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), olefins (eg, ethylene, propylene, etc.) Emissions, a homopolymer of a monomer such as butadiene) and the like, or a vinyl-based resin composed of these monomers with two or more combinations copolymer.
As the binder resin, for example, epoxy resin, polyester resin, polyurethane resin, polyamide resin, cellulose resin, polyether resin, non-vinyl resin such as modified rosin, a mixture of these with the vinyl resin, or these Examples also include a graft polymer obtained by polymerizing a vinyl monomer in the coexistence.
These binder resins may be used alone or in combination of two or more.

The glass transition temperature (Tg) of the binder resin is preferably 50 ° C. or higher and 80 ° C. or lower, and more preferably 50 ° C. or higher and 65 ° C. or lower.
The glass transition temperature is obtained from a DSC curve obtained by differential scanning calorimetry (DSC), more specifically, according to JIS K-7121-1987 “Method for measuring glass transition temperature”. It is calculated | required by description "extrapolated glass transition start temperature" of description.

The weight average molecular weight (Mw) of the binder resin is preferably from 5,000 to 1,000,000, more preferably from 7,000 to 500,000.
The number average molecular weight (Mn) of the binder resin is preferably 2000 or more and 100,000 or less.
The molecular weight distribution Mw / Mn of the binder resin is preferably 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less.
The weight average molecular weight and the number average molecular weight are measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC is performed with a THF solvent using a Tosoh GPC / HLC-8120GPC as a measuring device and a Tosoh column / TSKgel SuperHM-M (15 cm). The weight average molecular weight and the number average molecular weight are calculated using a molecular weight calibration curve prepared from a monodisperse polystyrene standard sample from this measurement result.

  The content of the binder resin is, for example, preferably 40% by weight to 95% by weight, more preferably 50% by weight to 90% by weight, and more preferably 60% by weight to 85% by weight with respect to the entire toner particles. Further preferred.

-Colorant-
Examples of the colorant include carbon black, chrome yellow, hansa yellow, benzidine yellow, selenium yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, vulcan orange, watch young red, permanent red, brilliantamine 3B, brilliant. Carmine 6B, Dupont Oil Red, Pyrazolone Red, Resol Red, Rhodamine B Lake, Lake Red C, Pigment Red, Rose Bengal, Aniline Blue, Ultramarine Blue, Calco Oil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Pigment Blue, Phthalocyanine Green, Various pigments such as malachite green oxalate, or acridine series, xanthene series, azo series Various dyes such as benzoquinone, azine, anthraquinone, thioindico, dioxazine, thiazine, azomethine, indico, phthalocyanine, aniline black, polymethine, triphenylmethane, diphenylmethane, and thiazole Can be mentioned.
A colorant may be used individually by 1 type and may use 2 or more types together.

  As the colorant, a surface-treated colorant may be used as necessary, or it may be used in combination with a dispersant. A plurality of colorants may be used in combination.

  The content of the colorant is, for example, preferably 1% by mass or more and 30% by mass or less, and more preferably 3% by mass or more and 15% by mass or less with respect to the entire toner particles.

-Release agent-
Examples of mold release agents include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax, and candelilla wax; synthetic or mineral / petroleum waxes such as montan wax; and ester waxes such as fatty acid esters and montanic acid esters. And so on. The release agent is not limited to this.

The melting temperature of the release agent is preferably 50 ° C. or higher and 110 ° C. or lower, and more preferably 60 ° C. or higher and 100 ° C. or lower.
The melting temperature is determined by the “melting peak temperature” described in the method for determining the melting temperature in JIS K-7121-1987 “Method for measuring the transition temperature of plastic” from the DSC curve obtained by differential scanning calorimetry (DSC). Ask.

  The content of the release agent is, for example, preferably 1% by mass to 20% by mass and more preferably 5% by mass to 15% by mass with respect to the entire toner particles.

-Other additives-
Examples of other additives include known additives such as a magnetic material, a charge control agent, and inorganic powder. These additives are contained in the toner particles as internal additives.

-Toner particle characteristics-
The toner particles may be toner particles having a single layer structure, or toner particles having a so-called core / shell structure composed of a core (core particle) and a coating layer (shell layer) covering the core. May be.
Here, the core / shell structure toner particles include, for example, a core portion including a binder resin and, if necessary, other additives such as a colorant and a release agent, and a binder resin. It is good to be comprised with the comprised coating layer.

  The volume average particle diameter (D50v) of the toner particles is preferably 2 μm or more and 10 μm or less, and more preferably 4 μm or more and 8 μm or less.

The various average particle diameters and various particle size distribution indexes of the toner particles are measured using Coulter Multisizer II (manufactured by Beckman-Coulter), and the electrolyte is measured using ISOTON-II (manufactured by Beckman-Coulter). The
In the measurement, 0.5 mg to 50 mg of a measurement sample is added as a dispersant to 2 ml of a 5% aqueous solution of a surfactant (preferably sodium alkylbenzenesulfonate). This is added to 100 ml or more and 150 ml or less of the electrolytic solution.
The electrolyte in which the sample is suspended is dispersed for 1 minute with an ultrasonic disperser, and the particle size distribution of particles having a particle size in the range of 2 μm to 60 μm is measured using a 100 μm aperture with a Coulter Multisizer II. taking measurement. The number of particles to be sampled is 50,000.
A cumulative distribution is drawn from the smaller diameter side to the particle size range (channel) divided based on the measured particle size distribution, and the cumulative particle size of 16% is the volume particle size D16v. D16p, a particle size that is 50% cumulative is defined as a volume average particle size D50v, a cumulative number average particle size D50p, and a particle size that is 84% cumulative is defined as a volume particle size D84v and a number particle size D84p.
Using these, the volume average particle size distribution index (GSDv) is calculated as (D84v / D16v) ^1/2 and the number average particle size distribution index (GSDp) is calculated as (D84p / D16p) ^1/2 .

  The shape factor SF1 of the toner particles is preferably 110 or more and 150 or less, and more preferably 120 or more and 140 or less.

The shape factor SF1 is obtained by the following formula.
Formula: SF1 = (ML ² / A) × (π / 4) × 100
In the above formula, ML represents the absolute maximum length of the toner, and A represents the projected area of the toner.
Specifically, the shape factor SF1 is quantified mainly by analyzing a microscope image or a scanning electron microscope (SEM) image using an image analyzer, and is calculated as follows. That is, by capturing an optical microscope image of particles dispersed on the surface of a slide glass into a Luzex image analyzer using a video camera, obtaining the maximum length and projected area of 100 particles, calculating by the above formula, and obtaining the average value can get.

(Toner production method)
Next, a toner manufacturing method according to this embodiment will be described.
The toner according to the exemplary embodiment can be obtained by externally adding an external additive to the toner particles after the toner particles are manufactured.

  The toner particles may be produced by any of a dry production method (for example, a kneading and pulverizing method) and a wet production method (for example, an aggregation coalescence method, a suspension polymerization method, a dissolution suspension method, etc.). The production method of the toner particles is not particularly limited, and a known production method is adopted.

Specifically, for example, when toner particles are produced by an aggregation coalescence method,
A step of preparing a resin particle dispersion in which resin particles to be a binder resin are dispersed (resin particle dispersion preparation step), and a resin particle dispersion (after mixing other particle dispersions as necessary) In the dispersion), the resin particles (other particles as necessary) are aggregated to form aggregated particles (aggregated particle formation step), and the aggregated particle dispersion in which the aggregated particles are dispersed is heated. Then, toner particles are manufactured through a process of fusing and coalescing the aggregated particles to form toner particles (fusing and coalescing process).

Details of each step will be described below.
In the following description, a method of obtaining toner particles containing a colorant and a release agent will be described. However, the colorant and the release agent are used as necessary. Of course, you may use other additives other than a coloring agent and a mold release agent.

-Preparation step of resin particle dispersion-
First, together with a resin particle dispersion in which resin particles serving as a binder resin are dispersed, for example, a colorant particle dispersion in which colorant particles are dispersed and a release agent particle dispersion in which release agent particles are dispersed are prepared. To do.

  Here, the resin particle dispersion is prepared, for example, by dispersing resin particles in a dispersion medium using a surfactant.

Examples of the dispersion medium used for the resin particle dispersion include an aqueous medium.
Examples of the aqueous medium include water such as distilled water and ion exchange water, and alcohols. These may be used individually by 1 type and may use 2 or more types together.

Examples of the surfactant include anionic surfactants such as sulfate ester, sulfonate, phosphate, and soap; cationic surfactants such as amine salt type and quaternary ammonium salt type; polyethylene glycol And nonionic surfactants such as polyphenols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, an anionic surfactant and a cationic surfactant are particularly mentioned. The nonionic surfactant may be used in combination with an anionic surfactant or a cationic surfactant.
Surfactant may be used individually by 1 type and may use 2 or more types together.

Examples of the method for dispersing the resin particles in the dispersion medium in the resin particle dispersion include a general dispersion method such as a rotary shear homogenizer, a ball mill having media, a sand mill, and a dyno mill. Depending on the type of resin particles, the resin particles may be dispersed in the resin particle dispersion using, for example, a phase inversion emulsification method.
The phase inversion emulsification method is a method in which a resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, and a base is added to the organic continuous phase (O phase) to neutralize the aqueous medium. (W phase) is added to convert the resin from W / O to O / W (so-called phase inversion) to form a discontinuous phase and disperse the resin in an aqueous medium in the form of particles. It is.

The volume average particle size of the resin particles dispersed in the resin particle dispersion is, for example, preferably 0.01 μm or more and 1 μm or less, more preferably 0.08 μm or more and 0.8 μm or less, and further preferably 0.1 μm or more and 0.6 μm or less. .
In addition, the volume average particle diameter of the resin particles is based on the particle size range (channel) divided by using the particle size distribution obtained by measurement with a laser diffraction particle size distribution measuring apparatus (for example, LA-700 manufactured by Horiba, Ltd.). The cumulative distribution is subtracted from the small particle diameter side with respect to the volume, and the particle diameter that becomes 50% cumulative with respect to all the particles is measured as the volume average particle diameter D50v. The volume average particle size of particles in other dispersions is also measured in the same manner.

  As content of the resin particle contained in a resin particle dispersion liquid, 5 to 50 mass% is preferable, for example, and 10 to 40 mass% is more preferable.

  For example, a colorant particle dispersion and a release agent particle dispersion are also prepared in the same manner as the resin particle dispersion. In other words, regarding the volume average particle diameter of the particles in the resin particle dispersion, the dispersion medium, the dispersion method, and the content of the particles, the colorant particles dispersed in the colorant particle dispersion and the release agent particle dispersion The same applies to the release agent particles to be dispersed.

-Aggregated particle formation process-
Next, the colorant particle dispersion and the release agent particle dispersion are mixed together with the resin particle dispersion.
Then, in the mixed dispersion, resin particles, colorant particles, and release agent particles are hetero-aggregated to have resin particles, colorant particles, and release agent particles having a diameter close to the diameter of the target toner particles. Aggregated particles are formed.

Specifically, for example, the flocculant is added to the mixed dispersion, and the pH of the mixed dispersion is adjusted to acidic (for example, the pH is 2 or more and 5 or less), and a dispersion stabilizer is added as necessary. The resin particles are heated to a glass transition temperature (specifically, for example, the glass transition temperature of the resin particles −30 ° C. or more and the glass transition temperature −10 ° C. or less), and the particles dispersed in the mixed dispersion liquid are aggregated. , Forming aggregated particles.
In the agglomerated particle forming step, for example, the above-mentioned flocculant is added at room temperature (for example, 25 ° C.) while stirring the mixed dispersion with a rotary shearing homogenizer, and the pH of the mixed dispersion is acidic (for example, the pH is 2 or more and 5 or less) ), And after adding a dispersion stabilizer as necessary, the heating may be performed.

Examples of the flocculant include surfactants having a polarity opposite to that of the surfactant used as the dispersant added to the mixed dispersion, for example, inorganic metal salts and divalent or higher-valent metal complexes. In particular, when a metal complex is used as the flocculant, the amount of the surfactant used is reduced, and the charging characteristics are improved.
If necessary, an additive that forms a complex or a similar bond with the metal ion of the flocculant may be used. As this additive, a chelating agent is preferably used.

Examples of inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate, and inorganic substances such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. Examples thereof include metal salt polymers.
A water-soluble chelating agent may be used as the chelating agent. Examples of the chelating agent include oxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid, iminodiacid (IDA), nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), and the like.
As addition amount of a chelating agent, 0.01 mass part or more and 5.0 mass part or less are preferable with respect to 100 mass parts of resin particles, for example, and 0.1 mass part or more and less than 3.0 mass parts are more preferable.

-Fusion / unification process-
Next, the aggregated particle dispersion in which the aggregated particles are dispersed is heated to, for example, a glass transition temperature or higher of the resin particles (for example, a temperature of 10 to 30 ° C. higher than the glass transition temperature of the resin particles). Are fused and united to form toner particles.

Through the above steps, toner particles are obtained.
In addition, after obtaining the aggregated particle dispersion liquid in which the aggregated particles are dispersed, the aggregated particle dispersion liquid and the resin particle dispersion liquid in which the resin particles are dispersed are further mixed, and the resin particles are further added to the surface of the aggregated particles. A process of aggregating to adhere to form second aggregated particles, and heating the second aggregated particle dispersion in which the second aggregated particles are dispersed to fuse and coalesce the second aggregated particles. The toner particles may be manufactured through a step of forming toner particles having a core / shell structure.

Here, after completion of the fusion / unification process, toner particles formed in the solution are dried through a known washing process, solid-liquid separation process, and drying process to obtain toner particles.
In the washing step, it is preferable to sufficiently carry out substitution washing with ion-exchanged water from the viewpoint of chargeability. The solid-liquid separation step is not particularly limited, but suction filtration, pressure filtration, etc. are preferably performed from the viewpoint of productivity. Also, the drying process is not particularly limited, but from the viewpoint of productivity, freeze drying, flash jet drying, fluidized drying, vibration fluidized drying, or the like is preferably performed.

  The toner according to the exemplary embodiment is manufactured, for example, by adding an external additive to the obtained dry toner particles and mixing them. Mixing may be performed, for example, with a V blender, a Henschel mixer, a Ladyge mixer, or the like. Furthermore, if necessary, coarse toner particles may be removed using a vibration classifier, a wind classifier, or the like.

In the kneading and pulverization method, after mixing materials such as a binder resin, the above materials are melt-kneaded using a kneader, an extruder, etc., and the resulting melt-kneaded material is roughly crushed and then pulverized with a jet mill or the like. In this method, toner particles having a target particle size are obtained using an air classifier.
More specifically, the kneading and pulverizing method is divided into a kneading step for kneading a toner forming material containing a binder resin and a pulverizing step for pulverizing the kneaded product. As needed, you may have other processes, such as a cooling process of cooling the kneaded material formed by the kneading process.
Each step related to the kneading and pulverizing method will be described in detail.

-Kneading process-
In the kneading step, the toner forming material containing the binder resin is kneaded.
In the kneading step, it is desirable to add 0.5 to 5 parts by mass of an aqueous medium (for example, water such as distilled water or ion exchange water, alcohols, etc.) to 100 parts by mass of the toner forming material. .

  Examples of the kneader used in the kneading step include a single screw extruder, a twin screw extruder, and the like. Hereinafter, as an example of a kneader, a kneader having a feed screw portion and two kneading portions will be described with reference to the drawings, but the present invention is not limited to this.

FIG. 1 is a diagram illustrating a screw state of an example of a screw extruder used in a kneading step in the toner manufacturing method according to the present embodiment.
The screw extruder 11 includes a barrel 12 having a screw (not shown), an inlet 14 for injecting a toner forming material as a raw material of the toner into the barrel 12, and an aqueous medium added to the toner forming material in the barrel 12. A liquid addition port 16 for discharging the toner, and a discharge port 18 for discharging the kneaded material formed by kneading the toner forming material in the barrel 12.

  The barrel 12 is a feed screw portion SA that transports the toner forming material injected from the injection port 14 to the kneading portion NA in order from the side closer to the injection port 14, and melt-kneading the toner forming material in the first kneading step. The kneading part NA, the feed screw part SB for transporting the toner forming material melted and kneaded in the kneading part NA to the kneading part NB, and the knee for melting and kneading the toner forming material in the second kneading step to form a kneaded product. It is divided into a ding part NB and a feed screw part SC that transports the formed kneaded material to the discharge port 18.

  The barrel 12 is provided with temperature control means (not shown) that is different for each block. That is, the temperature may be controlled at different temperatures from the block 12A to the block 12J. FIG. 1 shows a state in which the temperatures of the block 12A and the block 12B are controlled to t0 ° C., the temperatures of the blocks 12C to 12E are controlled to t1 ° C., and the temperatures of the blocks 12F to 12J are controlled to t2 ° C. Yes. Therefore, the toner forming material of the kneading part NA is heated to t1 ° C., and the toner forming material of the kneading part NB is heated to t2 ° C.

  When a toner forming material containing a binder resin, a colorant, a release agent and the like is supplied from the injection port 14 to the barrel 12, the toner forming material is sent to the kneading portion NA by the feed screw portion SA. At this time, since the temperature of the block 12C is set to t1 ° C., the toner forming material is fed into the kneading portion NA in a state of being heated and changed into a molten state. Since the temperatures of the block 12D and the block 12E are also set to t1 ° C., the toner forming material is melt-kneaded at the temperature of t1 ° C. in the kneading portion NA. The binder resin and the release agent are in a molten state at the kneading portion NA and are subjected to shearing by the screw.

Next, the toner forming material that has been kneaded in the kneading part NA is sent to the kneading part NB by the feed screw part SB.
Next, the aqueous medium is added to the toner forming material by injecting the aqueous medium into the barrel 12 from the liquid addition port 16 in the feed screw portion SB. Moreover, although the form which inject | pours an aqueous medium in the feed screw part SB is shown in FIG. 1, it is not restricted to this, An aqueous medium may be inject | poured in the kneading part NB, The feed screw part SB and the kneading part NB In both cases, an aqueous medium may be injected. That is, the position and the injection location for injecting the aqueous medium are selected as necessary.

As described above, when the aqueous medium is injected into the barrel 12 from the liquid addition port 16, the toner forming material and the aqueous medium in the barrel 12 are mixed, and the toner forming material is cooled by the latent heat of vaporization of the aqueous medium, The temperature of the toner forming material is maintained.
Finally, the kneaded material formed by being melt-kneaded by the kneading part NB is transported to the discharge port 18 by the feed screw part SC and discharged from the discharge port 18.
As described above, the kneading step using the screw extruder 11 shown in FIG. 1 is performed.

-Cooling process-
The cooling step is a step of cooling the kneaded product formed in the kneading step. In the cooling step, cooling is performed from the temperature of the kneaded product at the end of the kneading step to 40 ° C. or lower at an average temperature decrease rate of 4 ° C./sec or higher. It is preferable to do. When the cooling rate of the kneaded product is slow, the mixture finely dispersed in the binder resin in the kneading step (a mixture of internal additives such as a colorant and a release agent) may be recrystallized and the dispersion diameter may increase. . On the other hand, quenching at the above average temperature drop rate is preferable because the dispersion state immediately after the end of the kneading process is maintained as it is. The average temperature decreasing rate refers to the average value of the temperature decreasing rate from the temperature of the kneaded product at the end of the kneading step (for example, t2 ° C. when using the screw extruder 11 in FIG. 1) to 40 ° C.
Specific examples of the cooling method in the cooling step include a method using a rolling roll in which cold water or brine is circulated, a sandwiching cooling belt, and the like. When cooling is performed by the above method, the cooling rate is determined by the speed of the rolling roll, the flow rate of brine, the supply amount of the kneaded material, the slab thickness at the time of rolling the kneaded material, and the like. The slab thickness is preferably 1 mm or more and 3 mm or less.

-Crushing process-
The kneaded product cooled in the cooling step is pulverized in the pulverization step, and particles are formed. In the pulverization step, for example, a mechanical pulverizer or a jet pulverizer is used.

-Classification process-
The particles obtained by the pulverization step may be classified by a classification step in order to obtain toner particles having a volume average particle diameter in a target range, if necessary. In the classification process, conventionally used centrifugal classifiers, inertia classifiers, etc. are used, and fine powder (particles smaller than the target particle size) and coarse powder (target particle size). Larger particles) are removed.

-External addition process-
External toner is added to the obtained toner particles in the same manner as in the aggregation and coalescence method, and the toner according to the exemplary embodiment is manufactured by mixing.

<Electrostatic image developer>
The electrostatic charge image developer according to the exemplary embodiment includes at least the toner according to the exemplary embodiment.
The electrostatic image developer according to this embodiment may be a one-component developer including only the toner according to this embodiment, or may be a two-component developer mixed with the toner and a carrier.

There is no restriction | limiting in particular as a carrier, A well-known carrier is mentioned. As a carrier, for example, a coated carrier in which the surface of a core made of magnetic powder is coated with a coating resin; a magnetic powder dispersion type carrier in which magnetic powder is dispersed and mixed in a matrix resin; a porous magnetic powder is impregnated with a resin Resin impregnated type carriers; and the like.
Note that the magnetic powder-dispersed carrier and the resin-impregnated carrier may be a carrier in which the constituent particles of the carrier are used as a core material and coated with a coating resin.

  Examples of the magnetic powder include magnetic metals such as iron, nickel, and cobalt, and magnetic oxides such as ferrite and magnetite.

  Examples of the conductive particles include particles of metals such as gold, silver, and copper, carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate.

Examples of the coating resin and matrix resin include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid copolymer. Examples thereof include a polymer, a straight silicone resin containing an organosiloxane bond or a modified product thereof, a fluororesin, a polyester, a polycarbonate, a phenol resin, and an epoxy resin.
Note that the coating resin and the matrix resin may contain other additives such as a conductive material.

Here, in order to coat the surface of the core material with the coating resin, a method of coating with a coating layer forming solution obtained by dissolving the coating resin and, if necessary, various additives in an appropriate solvent may be mentioned. The solvent is not particularly limited, and may be selected in consideration of the coating resin to be used, coating suitability, and the like.
Specific resin coating methods include a dipping method in which the core material is immersed in the coating layer forming solution, a spray method in which the coating layer forming solution is sprayed on the surface of the core material, and a state in which the core material is suspended by flowing air. Examples thereof include a fluidized bed method in which a coating layer forming solution is sprayed, a kneader coater method in which a carrier core material and a coating layer forming solution are mixed in a kneader coater, and the solvent is removed.

  The mixing ratio (mass ratio) of the toner and the carrier in the two-component developer is preferably toner: carrier = 1: 100 to 30: 100, and more preferably 3: 100 to 20: 100.

<Image Forming Apparatus / Image Forming Method>
The image forming apparatus / image forming method according to the present embodiment will be described.
The image forming apparatus according to the present embodiment includes an image carrier, a charging unit that charges the surface of the image carrier, an electrostatic image forming unit that forms an electrostatic image on the surface of the charged image carrier, and an electrostatic charge. Development means for containing an image developer and developing the electrostatic image formed on the surface of the image carrier as a toner image with the electrostatic image developer, and the toner image formed on the surface of the image carrier as a recording medium Transfer means for transferring to the surface of the recording medium, and fixing means for fixing the toner image transferred to the surface of the recording medium. The electrostatic charge image developer according to this embodiment is applied as the electrostatic charge image developer.

  In the image forming apparatus according to this embodiment, a charging process for charging the surface of the image carrier, an electrostatic charge image forming process for forming an electrostatic image on the surface of the charged image carrier, and an electrostatic charge according to this embodiment. A developing step of developing an electrostatic charge image formed on the surface of the image carrier as a toner image with an image developer; a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of the recording medium; An image forming method (an image forming method according to the present embodiment) including a fixing step of fixing the toner image transferred onto the surface of the recording medium is performed.

The image forming apparatus according to the present embodiment is a direct transfer type apparatus that directly transfers a toner image formed on the surface of an image carrier to a recording medium; the toner image formed on the surface of the image carrier is transferred to an intermediate transfer member An intermediate transfer type apparatus that primarily transfers the toner image transferred to the surface of the intermediate transfer body and then secondary transfer the toner image to the surface of the recording medium; after the toner image is transferred, the surface of the image carrier before charging is cleaned. An apparatus provided with a cleaning unit; a known image forming apparatus such as an apparatus provided with a charge removing unit that discharges the surface of an image holding member by irradiating a discharge light after charging a toner image and before charging is applied.
In the case of an intermediate transfer type apparatus, the transfer means includes, for example, an intermediate transfer body on which a toner image is transferred to the surface, and a primary transfer that primarily transfers the toner image formed on the surface of the image holding body to the surface of the intermediate transfer body. And a secondary transfer unit that secondarily transfers the toner image transferred onto the surface of the intermediate transfer member onto the surface of the recording medium.

  In the image forming apparatus according to the present embodiment, for example, the part including the developing unit may have a cartridge structure (process cartridge) that is detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge that accommodates the electrostatic charge image developer according to this embodiment and includes a developing unit is preferably used.

  Hereinafter, an example of the image forming apparatus according to the present embodiment will be described, but the present invention is not limited thereto. The main parts shown in the figure will be described, and the description of the other parts will be omitted.

FIG. 2 is a schematic configuration diagram illustrating the image forming apparatus according to the present embodiment.
The image forming apparatus shown in FIG. 2 is a first to first electrophotographic method that outputs yellow (Y), magenta (M), cyan (C), and black (K) images based on color-separated image data. Fourth image forming units 10Y, 10M, 10C, and 10K (image forming means) are provided. These image forming units (hereinafter sometimes simply referred to as “units”) 10Y, 10M, 10C, and 10K are arranged in parallel at a predetermined distance from each other in the horizontal direction. The units 10Y, 10M, 10C, and 10K may be process cartridges that are detachable from the image forming apparatus.

Above each of the units 10Y, 10M, 10C, and 10K, an intermediate transfer belt 20 as an intermediate transfer member is extended through each unit. The intermediate transfer belt 20 is provided by being wound around a drive roll 22 and a support roll 24 that are in contact with the inner surface of the intermediate transfer belt 20 that are spaced apart from each other in the left to right direction in the drawing. The vehicle travels in the direction toward the unit 10K. The support roll 24 is applied with a force in a direction away from the drive roll 22 by a spring or the like (not shown), and tension is applied to the intermediate transfer belt 20 wound around the support roll 24. An intermediate transfer member cleaning device 30 is provided on the side of the image carrier of the intermediate transfer belt 20 so as to face the drive roll 22.
Further, each of the developing devices (developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K has yellow, magenta, cyan, and black contained in the toner cartridges 8Y, 8M, 8C, and 8K. The toner including the four color toners is supplied.

  Since the first to fourth units 10Y, 10M, 10C, and 10K have the same configuration, here, the first unit that forms a yellow image disposed on the upstream side in the intermediate transfer belt traveling direction. 10Y will be described as a representative. It should be noted that reference numerals with magenta (M), cyan (C), and black (K) are attached to the same parts as those of the first unit 10Y instead of yellow (Y). Description of the units 10M, 10C, and 10K will be omitted.

The first unit 10Y includes a photoreceptor 1Y that functions as an image holding member. Around the photoreceptor 1Y, a charging roll (an example of a charging unit) 2Y for charging the surface of the photoreceptor 1Y to a predetermined potential, and the charged surface is exposed by a laser beam 3Y based on a color-separated image signal. Then, an exposure device (an example of an electrostatic image forming unit) 3 that forms an electrostatic image, and a developing device (an example of a developing unit) 4Y that develops the electrostatic image by supplying toner charged to the electrostatic image, developed A primary transfer roll 5Y (an example of a primary transfer unit) that transfers a toner image onto the intermediate transfer belt 20, and a photoconductor cleaning device (an example of a cleaning unit) 6Y that removes toner remaining on the surface of the photoconductor 1Y after the primary transfer. Are arranged in order.
The primary transfer roll 5Y is disposed inside the intermediate transfer belt 20, and is provided at a position facing the photoreceptor 1Y. Further, a bias power source (not shown) for applying a primary transfer bias is connected to each of the primary transfer rolls 5Y, 5M, 5C, and 5K. Each bias power source varies the transfer bias applied to each primary transfer roll under the control of a control unit (not shown).

Hereinafter, an operation of forming a yellow image in the first unit 10Y will be described.
First, prior to operation, the surface of the photoreceptor 1Y is charged to a potential of −600V to −800V by the charging roll 2Y.
The photoreceptor 1Y is formed by laminating a photosensitive layer on a conductive substrate (for example, volume resistivity at 20 ° C .: 1 × 10 ⁻⁶ Ωcm or less). This photosensitive layer usually has a high resistance (general resin resistance), but has a property that the specific resistance of the portion irradiated with the laser beam changes when irradiated with the laser beam 3Y. Therefore, a laser beam 3Y is output to the surface of the charged photoreceptor 1Y via the exposure device 3 in accordance with yellow image data sent from a control unit (not shown). The laser beam 3Y is applied to the photosensitive layer on the surface of the photoreceptor 1Y, whereby an electrostatic charge image having a yellow image pattern is formed on the surface of the photoreceptor 1Y.

The electrostatic charge image is an image formed on the surface of the photoreceptor 1Y by charging, and the specific resistance of the irradiated portion of the photosensitive layer is lowered by the laser beam 3Y, and the charged charge on the surface of the photoreceptor 1Y flows. On the other hand, this is a so-called negative latent image formed by the charge remaining in the portion not irradiated with the laser beam 3Y.
The electrostatic charge image formed on the photoreceptor 1Y is rotated to a predetermined development position as the photoreceptor 1Y travels. At this development position, the electrostatic charge image on the photoreceptor 1Y is visualized (developed image) as a toner image by the developing device 4Y.

  In the developing device 4Y, for example, an electrostatic charge image developer containing at least yellow toner and a carrier is accommodated. The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y, has a charge of the same polarity (negative polarity) as the charged electric charge on the photoreceptor 1Y, and has a developer roll (of the developer holder). Example) is held on. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner is electrostatically attached to the latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. . The photoreceptor 1Y on which the yellow toner image is formed continues to run at a predetermined speed, and the toner image developed on the photoreceptor 1Y is conveyed to a predetermined primary transfer position.

When the yellow toner image on the photoreceptor 1Y is conveyed to the primary transfer, a primary transfer bias is applied to the primary transfer roll 5Y, and an electrostatic force from the photoreceptor 1Y toward the primary transfer roll 5Y is applied to the toner image, so that the photoreceptor is exposed. The toner image on 1Y is transferred onto the intermediate transfer belt 20. The transfer bias applied at this time has a (+) polarity opposite to the polarity (−) of the toner, and is controlled to +10 μA by the control unit (not shown) in the first unit 10Y, for example.
On the other hand, the toner remaining on the photoreceptor 1Y is removed and collected by the photoreceptor cleaning device 6Y.

Further, the primary transfer bias applied to the primary transfer rolls 5M, 5C, and 5K after the second unit 10M is also controlled in accordance with the first unit.
Thus, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and the toner images of the respective colors are superimposed and transferred in a multiple manner. The

  The intermediate transfer belt 20 on which the four color toner images are transferred in multiple ways through the first to fourth units is disposed on the image transfer surface side of the intermediate transfer belt 20, the support roll 24 in contact with the inner surface of the intermediate transfer belt 20. The secondary transfer roll (an example of a secondary transfer unit) 26 is formed to a secondary transfer portion configured. On the other hand, recording paper (an example of a recording medium) P is fed at a predetermined timing into a gap where the secondary transfer roll 26 and the intermediate transfer belt 20 are in contact with each other via a supply mechanism, and the secondary transfer bias is supplied to the support roll. 24. The transfer bias applied at this time is a (−) polarity that is the same polarity as the polarity (−) of the toner, and an electrostatic force from the intermediate transfer belt 20 toward the recording paper P is applied to the toner image, so The toner image is transferred onto the recording paper P. The secondary transfer bias at this time is determined according to the resistance detected by a resistance detection means (not shown) for detecting the resistance of the secondary transfer portion, and is voltage-controlled.

  Thereafter, the recording paper P is fed into the pressure contact portions (nip portions) of a pair of fixing rolls in a fixing device (an example of a fixing unit) 28, and the toner image is fixed on the recording paper P to form a fixed image.

Examples of the recording paper P to which the toner image is transferred include plain paper used in electrophotographic copying machines, printers, and the like. In addition to the recording paper P, the recording medium may be an OHP sheet.
In order to further improve the smoothness of the image surface after fixing, the surface of the recording paper P is also preferably smooth. For example, coated paper with the surface of plain paper coated with resin, art paper for printing, etc. are preferably used. Is done.

  The recording paper P on which the color image has been fixed is carried out toward the discharge unit, and a series of color image forming operations is completed.

<Process cartridge / toner cartridge>
The process cartridge according to this embodiment will be described.
The process cartridge according to the present embodiment accommodates the electrostatic image developer according to the present embodiment, and develops the electrostatic image formed on the surface of the image carrier as a toner image by the electrostatic image developer. And a process cartridge that can be attached to and detached from the image forming apparatus.

  Note that the process cartridge according to the present embodiment is not limited to the above-described configuration, and other means such as a developing device and other units such as an image carrier, a charging unit, an electrostatic charge image forming unit, and a transfer unit, if necessary. And at least one selected from the above.

  Hereinafter, an example of the process cartridge according to the present embodiment will be shown, but the present invention is not limited to this. The main parts shown in the figure will be described, and the description of the other parts will be omitted.

FIG. 3 is a schematic configuration diagram showing a process cartridge according to the present embodiment.
The process cartridge 200 shown in FIG. 3 is provided around the photosensitive member 107 and the photosensitive member 107 by, for example, a housing 117 provided with an attachment rail 116 and an opening 118 for exposure. A charging roller 108 (an example of a charging unit), a developing device 111 (an example of a developing unit), and a photoconductor cleaning device 113 (an example of a cleaning unit) are integrally combined and held to form a cartridge. Yes.
In FIG. 3, reference numeral 109 denotes an exposure device (an example of an electrostatic charge image forming unit), 112 denotes a transfer device (an example of a transfer unit), 115 denotes a fixing device (an example of a fixing unit), and 300 denotes a recording paper (a recording medium). An example).

Next, the toner cartridge according to this embodiment will be described.
The toner cartridge according to the present exemplary embodiment is a toner cartridge that accommodates the toner according to the present exemplary embodiment and is detachable from the image forming apparatus. The toner cartridge contains toner for replenishment to be supplied to the developing means provided in the image forming apparatus.

  The image forming apparatus shown in FIG. 2 is an image forming apparatus having a configuration in which the toner cartridges 8Y, 8M, 8C, and 8K are attached and detached. The developing devices 4Y, 4M, 4C, and 4K each have their respective developing devices (colors). And a toner supply pipe (not shown). Further, when the amount of toner stored in the toner cartridge becomes low, the toner cartridge is replaced.

  Hereinafter, although an example and a comparative example are given and this embodiment is described more concretely, this embodiment is not limited to the following examples. Unless otherwise specified, “part” and “%” are based on mass.

[Preparation of sol-gel silica particle dispersion]
(Silica particle dispersion 1)
To a 1.5 L glass reaction vessel equipped with a stirrer, a dropping nozzle and a thermometer, 255 parts of methanol and 40 parts of 10% aqueous ammonia were added and mixed. After this mixed liquid was adjusted to 25 ° C., 149 parts of tetramethoxysilane and 48 parts of 5.2% aqueous ammonia were simultaneously added while stirring, and dripped over 60 minutes, and 487 parts of a sol-gel silica particle dispersion was added. Obtained.
Thus, a silica particle dispersion 1 in which sol-gel silica particles were dispersed was obtained.

(Silica particle dispersion 2)
In the preparation of the silica particle dispersion 1, a silica particle dispersion 2 in which the sol-gel silica particles were dispersed was obtained in the same manner as the preparation of the silica particle dispersion 1, except that 40 parts of 10% ammonia water was changed to 35 parts. .

[Example A1]
The obtained silica particle dispersion 1 was dried by spray drying to remove the solvent to obtain hydrophilic sol-gel silica particles. The obtained sol-gel silica particles are put into a mixer and stirred at 200 rpm while heating to 200 ° C. in a nitrogen atmosphere, and hexamethyldisilazane (Wako Pure Chemical Industries, Ltd., hereinafter referred to as HMDS) is added to the amount of sol-gel silica particles as a hydrophobizing agent. On the other hand, an amount of 30% by mass was added and reacted for 2 hours. Then, it was cooled to room temperature.
In this way, sol-gel silica particles 1 were obtained. The ratio (S2 / S1) value of the obtained sol-gel silica particles 1 was 0.5.

[Example A2]
As shown below, the sol-gel silica particles were hydrophobized together with the solvent removal treatment of the silica particle dispersion. In addition, the apparatus equipped with the carbon dioxide cylinder, the carbon dioxide pump, the autoclave with a stirrer (capacity 500 ml), and the back pressure valve was used for the solvent removal process and the hydrophobization process. A trap device for trapping the removed solvent and a gas flow meter (DC-5 manufactured by Shinagawa Co., Ltd.) for measuring the carbon dioxide flow rate were installed behind the back pressure valve.

First, an autoclave with a stirrer (capacity 500 ml) and a device equipped with a back pressure valve are prepared, and 400 parts of the silica particle dispersion 1 is charged into the autoclave. Thereafter, the autoclave is filled with liquefied carbon dioxide.
Next, the stirrer is operated at 200 rpm, heated to 150 ° C. with a heater, and then increased to 20 MPa with a carbon dioxide pump. Thereby, supercritical carbon dioxide is circulated in the autoclave to remove the solvent from the silica particle dispersion. The trap device is kept at 0 ° C. by the refrigerant and can remove the removed solvent from the carbon dioxide. Thereafter, the flow rate of carbon dioxide is measured through a gas flow meter.
Next, when the distribution amount of the supercritical carbon dioxide distributed (accumulated amount: measured as the distribution amount of carbon dioxide in the standard state) reaches 20 L, the supercritical carbon dioxide distribution is stopped, and then the hydrophobizing agent HMDS is charged in an amount of 30% by mass with respect to the amount of sol-gel silica particles.
Thereafter, the temperature was maintained at 150 ° C. with a heater, and the pressure was maintained at 20 MPa with a carbon dioxide pump. While maintaining the supercritical state of carbon dioxide in the autoclave, the stirrer was operated at 200 rpm and held for 30 minutes as the hydrophobization time. After maintaining for 30 minutes, supercritical carbon dioxide was circulated again, the pressure was released from the back pressure valve to atmospheric pressure, and cooled to room temperature. Then, the stirrer was stopped and the hydrophobic silica particle powder hydrophobized from the autoclave was taken out.
In this way, sol-gel silica particles 2 were obtained. The ratio (S2 / S1) value of the obtained sol-gel silica particles 2 was 0.5.

[Example A3]
In Example A2, sol-gel silica particles 3 were obtained in the same manner as in Example A2, except that after the flow of supercritical carbon dioxide was stopped, a step of adding 4.5 parts of water was added. The ratio (S2 / S1) value of the obtained sol-gel silica particles 3 was 0.5.

[Example A4]
In Example A3, sol-gel silica particles 4 were obtained in the same manner as in Example A3, except that the amount of water added was changed to 6.4 parts. The ratio (S2 / S1) value of the obtained sol-gel silica particles 4 was 0.7.

[Example A5]
In Example A3, sol-gel silica particles 5 were obtained in the same manner as in Example A3, except that the amount of water added was changed to 8.2 parts. The ratio (S2 / S1) value of the obtained sol-gel silica particles 5 was 0.9.

[Example A6]
In Example A3, sol-gel silica particles 6 were obtained in the same manner as in Example A3, except that the amount of water added was changed to 10 parts. The ratio (S2 / S1) value of the obtained sol-gel silica particles 6 was 1.1.

[Comparative Example A1]
Sol gel silica particles 7 were obtained in the same manner as in Example A2 except that the silica particle dispersion 2 was used. The ratio (S2 / S1) value of the obtained sol-gel silica particles 7 was 0.4.

[Example B1]
(Preparation of toner particles 1)
Extruder is a mixture of 100 parts of styrene-butyl acrylate copolymer (weight average molecular weight Mw = 150,000, copolymerization ratio 80:20), 5 parts of carbon black (Mogal L: manufactured by Cabot Corporation), and 6 parts of carnauba wax. After kneading and pulverizing with a jet mill, spheronization treatment with warm air was performed with Kryptron (manufactured by Kawasaki Heavy Industries), and classification was performed with an air classifier to obtain toner particles 1 having a particle size of 6.2 μm.
To 100 parts of the toner particles 1, 1.6 parts of the sol-gel silica particles 1 obtained in Example A1 were added and mixed with a Henschel mixer to obtain toner 1.

(Preparation of carrier 1)
2.8 parts of a styrene-methyl methacrylate copolymer (Mw: 35,000) and 0.2 part of carbon black were added to 50 parts of toluene and dispersed for 30 minutes using a sand mill to prepare a dispersion. 23 parts of this dispersion was mixed with 100 parts of ferrite particles (volume average particle size 30 μm), and this mixture was stirred for 30 minutes while heating to 90 ° C. with a vacuum degassing kneader. Thereafter, the mixture was stirred under reduced pressure to remove the solvent. The extracted mixture was sieved with a 75 μm mesh to remove coarse components, and carrier 1 was obtained.

(Preparation of electrostatic charge image developer)
40 parts of toner 1 and 350 parts of carrier 1 were stirred at 35 rpm for 30 minutes using a V-blender, sieved with a 212 μm mesh, and coarse particles were removed to remove an electrostatic charge image developer (hereinafter referred to as “the developer”). 1) (referred to as “developer”).

[Example B2]
(Preparation of toner particles 2)
Extruder is a mixture of 100 parts of styrene-butyl acrylate copolymer (weight average molecular weight Mw = 150,000, copolymerization ratio 80:20), 5 parts of carbon black (Mogal L: manufactured by Cabot Corporation), and 6 parts of carnauba wax. After kneading and pulverizing with a jet mill, spheronization treatment with hot air was performed with Kryptron (manufactured by Kawasaki Heavy Industries), and classification was carried out with an air classifier to obtain toner particles 2 having a particle diameter of 4.5 μm.
To 100 parts of the toner particles 2, 1.6 parts of the sol-gel silica particles 1 obtained in Example A1 were added and mixed with a Henschel mixer to obtain toner 2. A developer 2 was obtained in the same manner as in Example B1, except that the toner 2 was used instead of the toner 1.

[Example B3]
Toner 3 was obtained in the same manner as in Example B1, except that sol-gel silica particles 2 were used instead of sol-gel silica particles 1. A developer 3 was obtained in the same manner as in Example B1, except that the toner 3 was used instead of the toner 1.

[Example B4]
Toner 4 was obtained in the same manner as in Example B1, except that sol-gel silica particles 3 were used instead of sol-gel silica particles 1. A developer 4 was obtained in the same manner as in Example B1, except that the toner 4 was used instead of the toner 1.

[Example B5]
(Preparation of toner particles 3)
Extruder is a mixture of 100 parts of styrene-butyl acrylate copolymer (weight average molecular weight Mw = 150,000, copolymerization ratio 80:20), 5 parts of carbon black (Mogal L: manufactured by Cabot Corporation), and 6 parts of carnauba wax. After kneading and pulverizing with a jet mill, spheronization treatment with warm air was performed with Kryptron (manufactured by Kawasaki Heavy Industries), and classification was performed with an air classifier to obtain toner particles 3 having a particle diameter of 4.8 μm.
To 100 parts of the toner particles 3, 1.2 parts of the sol-gel silica particles 4 obtained in Example A4 were added and mixed with a Henschel mixer to obtain a toner 5. A developer 5 was obtained in the same manner as in Example B1, except that the toner 5 was used instead of the toner 1.

[Example B6]
Toner 6 was obtained in the same manner as in Example B1, except that sol-gel silica particles 4 were used instead of sol-gel silica particles 1. A developer 6 was obtained in the same manner as in Example B1, except that the toner 6 was used instead of the toner 1.

[Example B7]
Toner 7 was obtained in the same manner as in Example B1, except that sol-gel silica particles 5 were used instead of sol-gel silica particles 1. A developer 7 was obtained in the same manner as in Example B1, except that the toner 7 was used instead of the toner 1.

[Example B8]
Toner 8 was obtained in the same manner as in Example B1, except that sol-gel silica particles 5 were used instead of sol-gel silica particles 1 and toner particles 2 were used instead of toner particles 1. A developer 8 was obtained in the same manner as in Example B1, except that the toner 8 was used instead of the toner 1.

[Example B9]
Toner 9 was obtained in the same manner as in Example B1, except that sol-gel silica particles 6 were used instead of sol-gel silica particles 1. A developer 9 was obtained in the same manner as in Example B1, except that the toner 9 was used instead of the toner 1.

[Comparative Example B1]
A toner 10 was obtained in the same manner as in Example B1, except that the sol-gel silica particles 7 were used in place of the sol-gel silica particles 1. A developer 10 was obtained in the same manner as in Example B1, except that the toner 10 was used instead of the toner 1.

(Evaluation)
In an environment of 15 ° C./10% RH, the obtained toner and developer were filled in a toner cartridge and a developing device of an image forming apparatus (manufactured by Fuji Xerox Co., Ltd., DocuCenter Color 400CP), respectively.
Using P paper manufactured by Fuji Xerox Co., Ltd. as a recording medium, a solid image having a toner loading of 5.0 g / m ² was formed on the recording medium. The image density SAD10 of the solid image on the tenth recording medium when 10 solid images were output was measured with a reflection densitometer (X-Rite 404) manufactured by X-rite. Further, the image density SAD30 of the solid image was measured under the environment of 15 ° C./10% RH in the environment of 15 ° C./10% RH by increasing the humidity. Further, the image density SAD50 of the solid image was measured in the same manner as in the environment of 15 ° C./10% RH in the environment of 15 ° C./10% RH with the humidity increased.
The density difference ΔSAD (humidity 30%) between the solid image density SAD10 and SAD30 and the density difference ΔSAD (humidity 50%) between the solid image density SAD10 and SAD50 were calculated and digitized. Based on the density difference ΔSAD, the density stability of the toner image was evaluated according to the following criteria. If ΔSAD is less than 0.3, there is no practical problem.
◎: Less than 0.1 ○: 0.1 or more and less than 0.2 Δ: 0.2 or more and less than 0.3 ×: 0.3 or more

1Y, 1M, 1C, 1K, photoconductor (an example of an image carrier)
2Y, 2M, 2C, 2K, charging roll (an example of charging means)
3. Exposure device (an example of electrostatic charge image forming means)
3Y, 3M, 3C, 3K Laser beams 4Y, 4M, 4C, 4K Developing device (an example of developing means)
5Y, 5M, 5C, 5K primary transfer roll (an example of primary transfer means)
6Y, 6M, 6C, 6K Photoconductor cleaning device (an example of cleaning means)
8Y, 8M, 8C, 8K Toner cartridge 10Y, 10M, 10C, 10K Image forming unit 20 Intermediate transfer belt (an example of an intermediate transfer member)
22 Drive roll 24 Support roll 26 Secondary transfer roll (an example of secondary transfer means)
30 Intermediate transfer member cleaning device 107 Photosensitive member (an example of an image holding member)
108 Charging roll (an example of charging means)
109 Exposure apparatus (an example of electrostatic charge image forming means)
111 Developing device (an example of developing means)
112 Transfer device (an example of transfer means)
113 photoconductor cleaning device (an example of cleaning means)
115 Fixing device (an example of fixing means)
116 Mounting rail 117 Housing 118 Opening 200 for exposure Process cartridge 300 Recording paper (an example of a recording medium)
P Recording paper (an example of a recording medium)

Claims (8)

A solvent removal step of circulating supercritical carbon dioxide in the sol-gel silica particle dispersion to remove the solvent of the sol-gel silica particle dispersion;
After the solvent removing step, a water applying step for applying water,
After the water application step, it was obtained through a hydrophobization treatment step of hydrophobizing with a hydrophobization treatment agent in supercritical carbon dioxide,
^A sol-gel silica particle having a ratio (S2 / S1) of a peak area S1 of a hydroxyl group to a peak area S2 of a trimethylsilyl group as measured by ¹ H MAS NMR of 0.5 or more.   The sol-gel silica particles according to claim 1, wherein the ratio (S2 / S1) is 0.5 or more and 0.9 or less.   An electrostatic charge image developing toner comprising toner particles and an external additive comprising the sol-gel silica particles according to claim 1.   An electrostatic charge image developer comprising the electrostatic charge image developing toner according to claim 3. Containing the electrostatic image developing toner according to claim 3;
A toner cartridge to be attached to and detached from the image forming apparatus. A developing means for containing the electrostatic charge image developer according to claim 4 and developing the electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer,
A process cartridge attached to and detached from the image forming apparatus. An image carrier,
Charging means for charging the surface of the image carrier;
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier;
Development means for containing the electrostatic charge image developer according to claim 4 and developing the electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer;
Transfer means for transferring a toner image formed on the surface of the image carrier to the surface of a recording medium;
Fixing means for fixing the toner image transferred to the surface of the recording medium;
An image forming apparatus comprising: A charging step for charging the surface of the image carrier;
An electrostatic charge image forming step of forming an electrostatic charge image on the surface of the charged image carrier;
A developing step of developing an electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer according to claim 4;
A transfer step of transferring a toner image formed on the surface of the image carrier to the surface of a recording medium;
A fixing step of fixing the toner image transferred to the surface of the recording medium;
An image forming method comprising: