JP2010276754A - Method for producing toner and the toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing toner, with which a shell can be formed so that resin particles for forming the shell added to a core particle dispersion liquid can uniformly and completely coat the surface of the core particle. <P>SOLUTION: The method for producing the toner includes a step of forming the shell by adding resin particles having a volume-based median diameter of 60 nm or more and 110 nm or less to a core particle dispersion liquid when average circularity of the core particles reaches 0.87 or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a toner used in an electrophotographic image forming method, and more particularly to a toner having a core-shell structure.

  In recent years, in electrophotographic image forming apparatuses, so-called low-temperature fixing technology capable of fixing a toner image at a lower temperature than before has been studied in order to reduce power consumption and realize high-speed printing. It was. One of the performances required for toners that achieve low-temperature fixing is improved meltability at low temperatures. Examples of techniques for realizing this include, for example, resins having low glass transition temperatures and softening points of toner constituent resins, There is a method of using a low melting point wax.

  As described above, the toner using a resin having a low glass transition temperature and a softening point can be formed with a toner image at a fixing temperature lower than that of the conventional one. However, in order to sacrifice thermal stability to some extent, In addition, there is a problem called blocking in which unused toners adhere and aggregate. Therefore, a so-called core-shell structure toner has been developed in which the surface of particles composed of a resin having a low glass transition temperature or softening point is coated with a thermally stable resin so as to eliminate the blocking problem ( For example, see Patent Document 1).

  In the core-shell toner, after preparing core particles made of a resin that contributes to low-temperature fixing, thermally stable resin particles are added to the core particle dispersion together with a flocculant, and the resin particles are placed on the surface of the core particles. It can be produced by attaching and aggregating to form a shell. In addition to improving the storage stability of the toner due to the inclusion of the shell, a toner with a core-shell structure designed to improve the peelability and offset resistance of the toner image by controlling the amount of resin particles added to form the shell is also considered. (For example, refer to Patent Documents 2 and 3).

  The technology disclosed in the above-mentioned patent document has been used to study a technology for producing a toner having a core-shell structure. However, the present inventor has formed a uniform thickness shell on the surface of the core particles without any unevenness in the prior art. I have noticed that it is surprisingly difficult to do. That is, when resin particles are added to a core particle dispersion based on the prior art to form a shell, a toner with a sufficiently coated core particle surface is formed, but the shell formation is insufficient and storage properties are affected. A toner having core particles exposed at a given level was also formed. Therefore, the present inventor attempted to increase the amount of the resin particles for forming the shell to sufficiently form the shell by uniformly attaching the resin particles to the surface of the core particles. However, the formed toner has hindered effective expression of the performance of the core particles, for example, the shell thickness is increased and it is difficult to perform low-temperature fixing. It has also been found that the shell cannot be formed so as to completely cover the surface of all the core particles even if the amount of the resin particles for the shell is increased. From these results, the present inventor has recognized that it is unexpectedly difficult to form a uniform shell uniformly on all core particle surfaces. In fact, Patent Documents 2 and 3 described above disclose a technique for changing the amount of resin particles added so that the shell has a thickness within a specific range, but the thickness is uniform for all core particles. No description suggesting the formation of a shell that can be coated without any unevenness was found.

Japanese Patent Laid-Open No. 11-231570 JP 2004-191618 A JP 2004-271638 A

  The present invention provides a shell having a uniform thickness, in which the resin particles for forming a shell added to the core particle dispersion liquid uniformly coat the surface of all core particles when the core-shell structure toner is produced. An object of the present invention is to provide a method for producing a toner to be formed. In other words, even if the core particle surface is completely covered with a shell and stored in a harsh environment such as a high temperature environment, the toner particles do not adhere to each other, and the performance caused by the core particles such as low temperature fixing is stabilized during image formation. It is an object of the present invention to provide a toner having a core-shell structure that is excellent in offset resistance and does not generate image contamination in a wide fixing temperature range.

The present inventor has found that the above-described problems can be solved by any of the configurations described below after repeated studies. That is, the invention described in claim 1
“In a method for producing a toner, a toner having a core-shell structure is formed through a step of forming core particles containing at least a resin and a colorant and a step of forming a shell by adding resin particles around the core particles. There,
In the step of forming the core particles, when the average circularity of the core particles is 0.87 or more, the formation of the core particles is terminated,
In the step of forming the shell, the shell is formed by adding the resin particles having a volume-based median diameter of 60 nm to 110 nm in the dispersion of the core particles. ].

The invention described in claim 2
“The resin contained in the core particles constituting the toner and the resin particles forming the shell are formed using a polymerizable monomer having at least a carboxyl group,
The ratio of the content of the polymerizable monomer having a carboxyl group of the resin particle forming the shell to the content of the polymerizable monomer having a carboxyl group of the resin contained in the core particle is 1.5 or more and 3 The toner production method according to claim 1, wherein the toner production method is 0.0 or less. ].

The invention according to claim 3
“A core-shell toner having a shell formed by adding resin particles around core particles containing at least a resin and a colorant,
The toner is obtained by adding a resin particle having a volume-based median diameter of 60 nm or more and 110 nm or less to form a shell when the average circularity of the core particles is 0.87 or more.
A toner characterized in that a thickness of the shell constituting the toner is 30 nm or more and 80 nm or less. ].

  In the present invention, when preparing a toner having a core-shell structure, when the average circularity of the core particles in the core particle dispersion is within a specific range, the resin particles for forming a shell whose volume-based median diameter is within the specific range are added. By doing so, it was found that the effect of the present invention was expressed. That is, when forming the shell, by adding the shell-forming resin particles having the volume-based median diameter to the core particles having the average circularity, the shell-forming resin particles are uniformly distributed on all the core particle surfaces. It became possible to adhere to a uniform thickness.

  In particular, according to the configuration described in claims 1 and 3, since the resin particles are uniformly attached to the entire surface of the core particles without unevenness, for example, when the shell formation is performed with the addition amount of the resin particles reduced, the layer thickness is reduced. A thin shell can be formed. Therefore, it is possible to form a core-shell toner having a thin shell, which is difficult to produce by the prior art. For example, it is also possible to form a toner that completely covers the core surface with a shell having a thickness of 30 nm to 60 nm. Became.

  In this way, by forming a thin shell that completely covers the core, the core-shell structure toner is excellent in heat-resistant storage and realizes low-temperature fixability and offset resistance that does not cause image contamination in a wide fixing temperature range. It became possible to provide.

FIG. 3 is a schematic diagram illustrating an example of a core-shell toner having a structure in which the surface of core particles is completely covered with a shell and a mechanism of shell formation. 2 is an example of a monochrome type image forming apparatus in which the toner according to the present invention can be used. 2 is an example of a tandem type color image forming apparatus in which the toner according to the present invention can be used. It is another example of a color image forming apparatus in which the toner according to the present invention can be used.

  The present invention relates to a toner having a core-shell structure produced through a step of forming a shell by adding resin particles around core particles containing at least a resin and a colorant. In the present invention, the formation of the core particles is stopped when the average circularity of the core particles becomes 0.87 or more, and resin particles having a volume-based median diameter of 60 nm to 110 nm are added to the core particle dispersion. To form a shell. And it discovered that a shell could be uniformly formed on the surface of a core particle by passing through this process.

  The present inventor has studied to find out the conditions for adding the shell-forming resin particles so as to completely cover the surface of the core particles. We paid attention to the fact that there are places that are difficult to adhere. Then, focusing on the influence of the shape of the core particle as a factor that the shell-forming resin particles do not adhere uniformly and uniformly to the surface of the core particle, an investigation was made to find a shape in which the resin particles easily adhere.

  As a result, when the core particles are rounded to some extent, it has been found that if the resin particles for shell formation are added, the resin particles adhere uniformly to the surface of the core particles. This is because when the snowball is enlarged with snow that has accumulated on the ground, if the original snowball has a distorted shape, it will not adhere to the snow evenly, making it difficult to make a round snowball. If the core particle shape is rounded to some extent, the resin particles are considered to adhere uniformly. And after further investigation, it was found that if the average circularity is a core particle in the above range, the resin particles for shell formation can be attached to any part of the surface of the core particle with the same probability. is there.

  In addition, in order to form a uniform shell without unevenness on the surface of the core particle, the present inventor not only sets the conditions on the core particle side described above, but also defines the resin particles for forming the shell. Thought. The condition of the resin particles that minimizes the area of the gap formed between the adhering particles is considered that a gap is always formed between the resin particles even if the resin particles are uniformly adhered to the surface of the core particle. I tried to find out. That is, if the core particles are defined so that the adhesion probability of the resin particles on the surface of the core particles is the same, and the resin particles are uniformly adhered to the surface, the gap between the resin particles becomes large. I thought it would be impossible to cover with resin. Then, considering the gap area between the particles by defining the particle diameter of the shell-forming resin particles, and as a result of the study, if the volume-based median diameter is in the above range, the gap formed between the resin particles The shell was made uniform and uniform.

  Hereinafter, the present invention will be described in detail.

  In the present invention, a toner having a core-shell structure is prepared through a step of forming core particles containing at least a resin and a colorant and a step of forming resin shells around the core particles to form a shell. Here, the “core-shell toner” means that a thermally stable resin is added to the surface of particles called core particles, which are made by adding a toner component such as a colorant in a resin that can be melted at a low temperature. The toner has a structure in which a region called a shell is formed.

  In the present invention, the formation of the core particles is terminated when the average circularity of the core particles becomes 0.87 or more in the step of forming the core particles, and then the volume-based median diameter in the core particle dispersion liquid. Is added to the resin particles of 60 nm to 110 nm to form a shell. Through the step of forming the shell, a core-shell structure toner is manufactured.

  The core particles constituting the toner according to the present invention will be described. In the present invention, when the core particles are produced, when the resin particles for shell formation having a volume-based median diameter of 60 nm to 110 nm are added when the average circularity is 0.87 or more, the surface of the core particles It was found that the shell was uniformly formed without unevenness.

  The method for preparing the core particles constituting the toner according to the present invention is not particularly limited as long as the average circularity value of the core particles can be controlled in the above range in the particle preparation step. It can be handled by a known particle production method such as a pulverization method or a polymerization method. Among these, the particle production method by the polymerization method can perform polymerization, aggregation of the resin particles, shape control, etc. in a state where oil droplets of the polymerizable monomer and the formed resin particles are dispersed in an aqueous medium. This is a preferable method. In particular, a polymerizable monomer dispersed in a predetermined particle size in an aqueous medium is polymerized, the formed resin particles are dispersed in an aqueous medium together with the colorant particles, and an aggregating agent is added to the resin particles and the colorant particles. The emulsion association method in which the particles are aggregated and fused is preferable for producing core particles having a uniform shape and particle size.

  Examples of the method for adjusting the average circularity of the formed core particles to 0.87 or more include a method of heat-treating the core particle dispersion at a temperature higher than the glass transition temperature of the resin constituting the formed core particles. It is done. In this method, in the core particle formation step (aggregation / fusion / maturation step of resin fine particles and colorant fine particles) in the toner production method by the emulsion association method described later, the resin fine particles are agglomerated / fused when forming the core particles. The agglomeration and the fusion are stopped when the particle size reaches a predetermined particle size. Thereafter, the reaction system is heated to continue the aging treatment for softening the core particles, and the aging treatment is performed until the shape of the core particles reaches a desired average circularity. A specific method for preparing the core particles by the emulsion association method will be described later.

  In the present invention, a core-shell toner exhibiting the effects of the present invention is obtained by adding shell-forming resin particles having a volume-based median diameter of 60 nm to 110 nm to core particles having an average circularity of 0.87 or more. It is done. That is, a toner having a structure in which the shell is uniformly formed on the surface of the core particle and the core particle is completely covered with the shell is obtained, and adhesion of the toner due to the exposed portion of the core particle is avoided, so that the storage property of the toner is improved. Can be improved. This is presumably because the shell-forming resin particles can adhere to any part of the surface of the core particle with the same probability as the core particle becomes rounder. As a result, it is possible to form a structure in which the core particles are completely covered with the shell without causing dispersion of the adhesion such that the areas where the resin particles for the shell are sparsely attached and the areas where the particles are intensively attached are generated on the surface of the core particles. It is considered a thing. Accordingly, the higher the average circularity value of the core particles, the closer the shape of the core particles is to a sphere, so that the resin particles for shells are attached to any part of the surface of the core particles with the same probability. That is, it is considered that the higher the average circularity value of the core particles, the more uniform adhesion of the resin particles for the shell is realized.

  Further, in the present invention, since the shell-forming resin particles can be uniformly adhered to the surface of the core particles, it is possible to completely cover the core particles with a thin shell by reducing the addition amount of the shell-forming resin particles. Can be considered. When the thickness of the shell is reduced, the performance inherent to the core particles can be sufficiently exhibited. For example, if the core particles have the ability to melt and fix at a low heating temperature, a toner having sufficient low-temperature fixability and stable storage by the shell can be obtained. Further, if the toner has a core-shell structure in which a colorant is contained only in the core particles, the density and color tone of the formed toner image are improved. As described above, the core-shell toner having a structure in which the core particles are completely covered with the thin shell can greatly contribute to the quality improvement of the toner and the formed image.

  In the present invention, a toner having a shell thickness of 30 nm to 80 nm is prepared by adding shell-forming resin particles having a volume-based median diameter of 60 nm to 110 nm to core particles having an average circularity of 0.87 or more. can do.

The “average circularity of the core particles” is a value calculated by dividing the value obtained by adding up the “circularity of the core particles” defined by the following formula by the total number of core particles measured. That is,
Circularity of the core particle = (perimeter of a circle having the same projection area as the core particle projection image) / (perimeter of the core particle projection image)
The “average circularity of the core particles” can be calculated using, for example, a flow particle image analyzer represented by “FPIA-2100 (manufactured by Sysmex)”.

  Specifically, ultrasonic dispersion treatment is performed for 1 minute in the liquid in which the core particles are dispersed, so that the core particles are uniformly dispersed. Then, it measures using "FPIA-2100" mentioned above. Measurement conditions are set to HPF (high magnification imaging) mode, and the number of HPF detections is set to an appropriate density of 3000 to 10,000. By making this range, the same measurement value with reproducibility can be obtained.

  Next, the resin particles for forming a shell used in the present invention will be described. In the present invention, when the average circularity of the core particles is 0.87 or more and the shell-forming resin particles having a volume-based median diameter of 60 nm to 110 nm are added, the surface of the core particles is uniform and uniform with the resin particles. A toner having a structure coated on the surface is obtained.

  The method for producing the shell-forming resin particles is not particularly limited as long as it is possible to produce resin particles having a volume-based median diameter of 60 nm to 110 nm, such as a pulverization method or a polymerization method. This can be handled by a known manufacturing method. In the present invention, a uniform thickness shell is formed on the surface of the core particle, so that the particle size distribution is sharp, that is, the resin particles can be produced so that the particle sizes of the individual resin particles can be made uniform. A manufacturing method is required. Specifically, a method of producing resin particles in an aqueous medium by a polymerization method such as emulsion polymerization or suspension polymerization is preferable. The resin particle production method by the polymerization method is easy to control various conditions during production by a known method, and can be produced while measuring the particle size of the resin particles by a known method. This is a preferred method for producing resin particles having a diameter.

  In the present invention, by adding resin particles having a volume-based median diameter of 60 nm or more and 110 nm or less to the core particle surface having an average circularity of 0.87 or more, the core particle surface is completely covered with a shell. Toner is obtained. By making the volume-based median diameter of the shell-forming resin particles 60 nm or more and 110 nm or less, the gap area between the adhered shell-forming resin particles is minimized on the core particle surface, and a uniform shell without unevenness is formed. It is considered a thing. Therefore, if the resin particles for shell formation having a volume-based median diameter in the above range are formed, a shell having a thickness equivalent to one resin particle for shell formation is uniformly formed on the surface of the core particles by reducing the addition amount thereof. It is also possible to do this. Thus, in the present invention, the volume-based median diameter of the shell-forming resin particles in the above range may contribute to the formation of a thin shell.

  In the present invention, a toner having a shell thickness of 30 nm to 80 nm is prepared by adding resin particles having a volume-based median diameter of 60 nm to 110 nm to the surface of the core particles having an average circularity of 0.87 or more. can do. The thickness of the formed shell is smaller than the particle size of the supplied resin particles because the shell forming resin particles completely cover the core particle surface, and then the shell forming resin particles are melted by heating. This is considered to be caused by filling the gaps between the resin particles.

  If the volume-based median diameter of the shell-forming resin particles is smaller than 60 nm, the added resin particles may aggregate to form a uniform shell on the surface of the core particles. Further, if the volume-based median diameter of the shell-forming resin particles is larger than 110 nm, the gap formed between the resin particles when the shell-forming resin particles are attached to the core particle surface becomes large, and the core particle surface There is a risk that a uniform shell cannot be formed.

  The volume-based median diameter of the shell-forming resin particles can be measured in a state where the resin particles are dispersed in an aqueous surfactant solution. As a measuring means for realizing such a measuring method, for example, particle size analysis using a dynamic light scattering method such as a dynamic light scattering nanotrack particle size distribution measuring apparatus “Microtrack UPA150 (manufactured by Microtrack)”. There is a measurement method using an apparatus.

The measurement procedure when carrying out particle size measurement with “Microtrac UPA150” is shown below. The following measurement conditions are automatically set by the control program of the “Microtrack UPA150” main body.
(1) Measurement conditions Sample refractive index: 1.59
Sample specific gravity: 1.05 (in terms of spherical particles)
Solvent refractive index: 1.33
Solvent viscosity: 0.797 (30 ° C), 1.002 (20 ° C)
(2) Pour pure water into the measurement cell and adjust the zero point.
(3) 1 ml of the resin particle dispersion for shell formation is added to 50 ml of pure water. As the added shell-forming resin particle dispersion, the dispersion in the reaction system can be used as it is.
(4) The prepared dispersion is subjected to ultrasonic treatment for about 3 minutes using a commercially available ultrasonic cleaner “US-1 (manufactured by Asone)” or the like.
(5) The dispersion liquid after ultrasonic treatment is put into a measurement cell, and it is confirmed that the transmission density is within an appropriate range (0.1 to 10.0 in strength).
(6) When it is confirmed that the transmission density is within an appropriate range, measurement is started by the main body control program. If the transmission density is not within the proper range, pure water is further added to lower the toner content, and the transmission density is adjusted to fall within the proper range.

  (7) The measurement time is set to 180 seconds, the number of measurements is set to 1, and the volume-based median diameter is calculated by program processing.

  In the toner according to the present invention, it is preferable that both the resin contained in the core particles and the resin particles for shell formation are formed using a polymerizable monomer having a carboxyl group. In particular, paying attention to the content of the monomer having a carboxyl group constituting each resin, the content of the polymerizable monomer having a carboxyl group of the resin particle forming the shell is the carboxyl of the resin contained in the core particle. The content of the polymerizable monomer having a group is preferably 1.5 times or more and 3.0 times or less. The toner according to the present invention in which the ratio of the content of the monomer component having a carboxyl group constituting both resins is in the above range is considered to realize improvement in durability and stability of the core-shell structure.

  That is, in order to improve the durability of the core-shell structure, it is necessary to improve the adhesive force acting between the core particles and the shell-forming resin particles. The presence of a monomer component having a carboxyl group in both resins results in the formation of an environment in which hydrogen bonds and intermolecular attractive forces are easily imparted between the two via the carboxyl group. Improvement can be expected. As a result, a strong adhesive force is developed between the core particles and the shell, and even if the toner is repeatedly agitated in the developing device and continues to receive stress, the shell-shell structure does not detach unnecessarily. This is considered to improve the performance.

  On the other hand, in order to maintain a stable core-shell structure, it is necessary to impart some degree of incompatibility between the two so that the core particle component does not elute into the shell over time. When the adhesive force between the core particle and the shell becomes strong, it becomes difficult to maintain incompatibility. In the present invention, the content of the polymerizable monomer having a carboxyl group in the resin particles for shell formation is 1.5 times or more and 3.0 times the content of the polymerizable monomer having a carboxyl group in the core particle constituent resin. It is thought that the incompatibility between both is also ensured by setting it as the following.

  For this reason, the content of the polymerizable monomer having a carboxyl group in the shell-forming resin particles is 1.5 times or more the content of the polymerizable monomer having a carboxyl group in the core particle constituent resin. It is considered that the durability and stability of the core-shell structure can be improved by making it 0 times or less.

  Further, making the molar ratio as described above means that the molar ratio of the monomer component having a carboxyl group constituting the shell-forming resin particles is higher than the molar ratio in the core particles. This is considered to contribute to maintaining the stability of the toner. That is, it is considered that the higher the carboxyl group ratio, the higher the hydrophilicity, and it is easier to form a uniform shell when shell formation is performed with a highly hydrophilic resin. It is considered that the more uniform the shell, the more preferable it is to maintain the stability of the toner.

  According to the above configuration, it is considered that by reducing the number of carboxyl groups on the core particle side, carboxyl groups that are not involved in the bond with the shell are not generated, and toner deterioration from the core particle side can be suppressed. On the other hand, even if a lot of carboxyl groups are present in the shell, it is in contact with the outside, so that the activity is easily suppressed by binding with water molecules in the atmosphere, and it is considered that there is no problem.

  The core-shell toner will be further described.

  An example of a toner having a core-shell structure manufactured by the toner manufacturing method according to the present invention is shown in FIG. The toner T shown in FIG. 1A is composed of a core particle TA made of a resin R2 containing a colorant C1 and a shell TB formed by coating the surface of the core particle TA with the resin R3. It is. The toner T shown in FIG. 1 has a structure in which the surface of the core TA is completely covered with the shell TB.

  As described above, the toner having a core-shell structure in which the surface of the core particle TA is completely covered with the shell TB having a uniform thickness has a volume basis when the average circularity of the core particle TA becomes 0.87 or more. This is achieved by adding shell-forming resin particles having a median diameter of 60 nm to 110 nm.

  By the way, the cross-sectional structure of the core-shell structured toner and the shell coverage on the core particle surface can be detected by observation with a transmission electron microscope (TEM), a scanning probe microscope (SPM), or the like. The scanning probe microscope (SPM) can evaluate the physical properties such as the hardness of the resin constituting the toner in addition to the observation of the sectional shape of the toner.

  A method for observing the cross-sectional structure of the toner with a transmission electron microscope (TEM) will be described. Regarding the cross-sectional structure of the toner, the method for observing the cross-sectional structure of the toner with a transmission electron microscope can observe the prepared sample from a photographed image, for example, by the following procedure.

  First, after sufficiently dispersing the toner in a room temperature curable epoxy resin, embedding and dispersing in a fine styrene powder having a particle size of about 100 nm, and then performing pressure molding to form a block containing the toner. Make it. If necessary, the prepared block is dyed with ruthenium tetroxide or osmium tetroxide if necessary, and then a microtome with diamond teeth is used to form a flake shape having a thickness of 80 to 200 nm. The sample for a measurement is produced.

  The measurement sample thus thinned is set on a transmission electron microscope (TEM), and the cross-sectional structure of the toner is photographed. At this time, the magnification of the electron microscope is preferably a magnification that allows the cross section of one toner to enter the field of view, and specifically about 10,000 times. Further, the number of toners for taking a photograph with a transmission electron microscope is preferably 100 or more.

  Observation of the cross-sectional structure of the toner with a transmission electron microscope can be sufficiently handled by a model that is generally well known among those skilled in the art. For example, “LEM-2000 type (manufactured by Topcon)” And “JEM-2000FX (manufactured by JEOL Ltd.)”.

  The toner according to the present invention has a core-shell structure. When a photograph of the photographed cross-sectional structure is observed, a region where a colorant or the like is present and a region where these are not present are confirmed, and a boundary serving as an interface between the core and the shell. Can be confirmed.

  The coverage of the shell on the core surface is calculated by processing the captured image information with an image processing apparatus “Luzex F” (manufactured by Nireco) using a transmission electron microscope (TEM). That is, the areas of the core particle region and the shell region of the toner imaged by the arithmetic processing by “Luzex F” are calculated. Further, by confirming a photograph of a cross-sectional structure of at least 10 toners, it can be confirmed that the toner according to the present invention has a structure in which the surface of the core particles is completely covered with a shell.

  Next, a method for producing a toner having a core-shell structure according to the present invention will be described.

  As described above, the present invention produces a core-shell toner through a step of adding shell-forming resin particles having a volume-based median diameter of 60 nm to 110 nm to core particles having an average circularity of 0.87 or more. is there. That is, when the colored particles constituting the toner (toner particles before the external addition treatment) are produced, the core particles having a rounded shape having an average circularity in the above range are produced. Moreover, the resin particles for forming a shell having a volume-based median diameter in the above range are prepared. As described above, the polymerization method is preferable as a method for designing and producing the resin particles so that the shape and particle diameter are within a specific range.

  In other words, the polymerization method is preferable because when the resin particles for core particles or the resin particles for shells are produced, the shape and size of the particles can be controlled in the production process. Further, when the core resin particles and colored particles are produced by a polymerization method, the particles are formed through a process of forming resin particles of about 100 nm in advance by an emulsion polymerization method or a suspension polymerization method, and aggregating and fusing the formed resin particles. An emulsification association method for forming is a preferable production method. Thus, toner production by a polymerization method typified by an emulsion association method can easily form particles having a desired shape and size by controlling reaction conditions by a known method in the production process. Therefore, it is also optimal for producing a small-diameter toner that can faithfully reproduce a minute dot image formed by digital image formation.

Hereinafter, an example of preparing a toner having a core-shell structure by the emulsion association method will be described. In the emulsification association method, a toner is generally prepared through the following procedure. That is,
(1) Preparation step of resin fine particles (resin fine particles for core particle formation and fine resin particles for shell formation) dispersion (2) Preparation step of colorant fine particle dispersion (3) Formation step of core particles (resin fine particles and colorant fine particles Agglomeration, fusion, aging process)
(4) Shelling step (5) Aging step (6) Cooling step (7) Cleaning step (8) Drying step (9) External additive treatment step Hereinafter, each step will be described.

(1) Production process of resin fine particles (resin fine particles for core particle formation and resin fine particles for shell formation) dispersion This step is a polymerization reaction under the condition that a polymerizable monomer is charged and dispersed in an aqueous medium. This is a step of forming resin fine particles having a size of, for example, about 100 nm. In this step, when producing resin fine particles for forming core particles, it is possible to form the resin fine particles containing wax. In this case, resin particles containing wax can be formed by dissolving or dispersing the wax in a polymerizable monomer and polymerizing it in an aqueous medium.

  Further, when producing resin fine particles for shell formation, for example, when a polymerizable monomer is charged and dispersed in an aqueous medium, the volume-based median diameter is controlled by controlling the output of a known dispersion processor. An oil droplet of a polymerizable monomer is formed so as to be in a range of 60 nm to 110 nm. By performing polymerization in an aqueous medium in this state, shell-forming resin particles having a volume-based median diameter of 60 nm to 110 nm can be produced.

(2) Preparation Step of Colorant Fine Particle Dispersion This is a step of preparing a colorant fine particle dispersion having a size of about 100 nm by dispersing a known colorant in an aqueous medium.

(3) Core particle formation process (aggregation / fusion / aging process of resin fine particles and colorant fine particles)
In this step, the resin particles for the core particles and the colorant fine particles described above are aggregated in an aqueous medium, and the aggregate of fine particles aggregated by heating is fused to produce the core particles. Then, heating is continued even after the aggregate of the aggregated fine particles is fused, and aging treatment is performed until the core particles have a predetermined average circularity. That is, in this step, after adding an alkali metal salt, an alkaline earth metal salt, or the like as an aggregating agent to an aqueous medium in which resin fine particles and colorant fine particles are mixed, the mixture is heated at a temperature higher than the glass transition temperature of the resin particles. The mixture is heated below the melting peak temperature to cause agglomeration, and at the same time, the resin fine particles are fused together. Furthermore, the shape of the surface of the core particles is controlled by continuing heating even after the fusion of the resin fine particles is completed.

  Specifically, the resin fine particles for core particles and the colorant fine particles prepared by the above-described procedure are added to the reaction system, and the resin fine particles and the colorant particles are aggregated by adding an aggregating agent such as magnesium chloride. At the same time, the fine particles are fused together to form core particles. Then, when the size of the core particles reaches the target size, a salt such as saline is added to stop aggregation.

  By this step and the subsequent first aging step, the core particle TA having the structure shown in FIG. 1B can be formed. That is, the core particle TA is formed by aggregating and fusing the resin fine particles R2 for forming the core particles and the colorant fine particles C1 in the core particle forming step.

  In the agglomeration / fusion / ripening step, the reaction system is heat-treated by a known method so that the shape of the core particles is a desired shape, that is, in the present invention, the heat treatment is carried out until the average circularity becomes 0.87 or more. The shape of the core particle can be controlled continuously.

(4) Shelling step In this step, resin fine particles for shell formation are added to a dispersion of core particles having an average circularity of 0.87 or more by the aging treatment performed in the core particle forming step. This is a step of forming a shell on the surface of the core particle. That is, shell formation is performed on the surface of the core particle having an average circularity of 0.87 or more using resin fine particles having a volume-based median diameter of 60 nm or more and 110 nm or less as resin fine particles for shell formation. In the present invention, by adding the above-mentioned volume-based median diameter shell-forming resin fine particles to the core particle surface having the above-mentioned average circularity, the shell-forming resin particles uniformly adhere to the core particle surface. Thus, the core particles can be completely coated.

  In addition, the thickness of the shell can be controlled by controlling the amount of the resin fine particles for forming the shell in this step. Specifically, a thinner shell can be formed as the addition amount of the resin fine particles for shell formation is reduced. In the present invention, even if the addition amount of the shell-forming resin fine particles is reduced, the shell-forming resin fine particles can adhere to the core particle surface so as to completely cover the core particle surface.

  FIG. 1B is a schematic diagram schematically illustrating the shelling process. In FIG. 1B, first, resin particles R3 for shell formation having a volume-based median diameter of 60 nm or more and 110 nm or less are aggregated and adhered on the surface of the core particle TA having an average circularity of 0.87 or more. In the present invention, by using the core particles TA having an average circularity in the above range and the resin fine particles R3 for forming shells in which the volume-based median diameter is in the above range, the resin particles R3 are completely coated on the surface of the core particles TA. Can be attached. Moreover, in FIG.1 (b), the resin fine particle R3 for shell formation adhering to the core particle TA surface has adhered by the single layer.

  After the resin fine particles R3 for shell formation aggregate and adhere to the surface of the core particles TA, the resin fine particles R3 are fused with the surface of the core particles TA or the adjacent resin fine particles R3 by the action of heat treatment. Then, the heat treatment is continued, and through a second aging step described later, the interface between the resin fine particles R3 disappears to form a shell TB phase. In this way, as shown in FIG. 1A, the toner T having the shell TB on the surface of the core particle TA can be formed.

(5) Aging step This step is a step of heat-treating the reaction system following the shelling step, and enhances the adhesion and covering properties of the shell-forming resin fine particles adhering to the surface of the core particles, and also colors the core-shell structure. In this process, the heat treatment is continued until the particles have a desired shape.

  In this way, colored particles having a core-shell structure with a uniform shape and particle size can be produced in the aging step. In the present invention, colored particles having a core-shell structure are formed by completely covering the core particles with a shell having a thickness of 30 nm or more and 80 nm or less through an aging step.

(6) Cooling step This step is a step of cooling (rapid cooling) the dispersion of the colored particles. As a cooling treatment condition, cooling is performed at a cooling rate of 1 to 20 ° C./min. The cooling treatment method is not particularly limited, and examples thereof include a method of cooling by introducing a refrigerant from the outside of the reaction vessel, and a method of cooling by directly introducing cold water into the reaction system.

(7) Washing step This step comprises a step of solid-liquid separation of the colored particles from the colored particle dispersion cooled to the predetermined temperature in the above step, and a surface activity from the colored particles separated into a solid cake and wet cake. It consists of a cleaning step for removing deposits such as an agent and a flocculant.

  In the washing treatment, the filtrate is washed with water until the electric conductivity of the filtrate reaches 10 μS / cm. Examples of the filtration method include a centrifugal separation method, a vacuum filtration method using Nutsche and the like, and a filtration method using a filter press and the like, and are not particularly limited.

(8) Drying step This step is a step of obtaining dried colored particles by drying the washed colored particles. Examples of the drying apparatus that can be used in this step include a spray dryer, a vacuum freeze dryer, and a vacuum dryer, and a stationary shelf dryer, a mobile shelf dryer, a fluidized bed dryer, and a rotary dryer. It is preferable to use a stirring dryer or the like.

  The water content of the dried colored particles is preferably 5% by mass or less, and more preferably 2% by mass or less. In addition, when the dried colored particles are aggregated with weak interparticle attractive force, the aggregate can be pulverized using a known pulverization apparatus. As the crushing treatment apparatus, a known mechanical crushing apparatus such as a jet mill, a Henschel mixer, a coffee mill, or a food processor can be used.

(9) External additive treatment step This step is a step of preparing a toner by mixing the dried particles with an external additive as necessary. As an external additive mixing apparatus, a mechanical mixing apparatus such as a Henschel mixer or a coffee mill can be used.

  Through the above steps, the toner according to the present invention can be produced by an emulsion association method.

  Next, toner constituent materials such as a binder resin, a colorant, and wax that can be used in the toner according to the present invention will be described with specific examples.

  The toner according to the present invention has a core-shell structure in which a shell composed of a thermally stable resin is formed on the surface of a core particle containing a colorant or the like in a resin that can be melted at a relatively low heating temperature. It is.

  The resin that can be used in the toner according to the present invention is not particularly limited, but a polymer formed by polymerizing a polymerizable monomer called a vinyl monomer described below is a typical example. Is something. The polymer constituting the resin that can be used in the present invention is a polymer obtained by polymerizing at least one polymerizable monomer, and these vinyl monomers are used alone. Or it is the polymer produced combining multiple types.

Specific examples of vinyl polymerizable monomers are shown below. In addition, the styrene monomer used when forming resin using the polymer represented by General formula (1) by this invention can contain the styrene shown below or a styrene derivative. Moreover, a (meth) acryl monomer can contain the methacrylic acid ester derivative and acrylic acid ester derivative which are shown below other than an acrylic acid monomer and a methacrylic acid monomer. That is,
(1) Styrene or styrene derivatives Styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert- Butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, etc. (2) Methacrylate derivatives Methyl methacrylate, methacryl Ethyl acetate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethyl methacrylate Aminoethyl, dimethylaminoethyl methacrylate, etc. (3) Acrylic acid ester derivatives Methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, etc. (4) olefins ethylene, propylene, isobutylene, etc. (5) vinyl esters vinyl propionate, vinyl acetate, vinyl benzoate, etc. (6) vinyl ether (7) Vinyl ketones Vinyl methyl ketone, vinyl ethyl ketone, vinyl hexyl ketone, etc. (8) N-vinyl compounds N-vinyl carbazole, N-vinyl India (9) Others Vinyl compounds such as vinyl naphthalene and vinyl pyridine, acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide.

  Further, the vinyl-based polymerizable monomer constituting the resin usable in the toner according to the present invention includes those having an ionic dissociation group such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group shown below. It is preferable to use it. Among them, it is particularly preferable to use a vinyl polymerizable monomer having a carboxyl group.

  First, those having a carboxyl group include acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, and the like. Examples of those having a sulfonic acid group include styrene sulfonic acid, allyl sulfosuccinic acid, and 2-acrylamido-2-methylpropane sulfonic acid. Examples of those having a phosphoric acid group include acid phosphooxyethyl methacrylate. is there.

  Moreover, it is also possible to produce a resin having a crosslinked structure by using the following polyfunctional vinyls. Specific examples of polyfunctional vinyls are shown below.

  Ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, and the like.

  As described above, in the present invention, a vinyl polymerizable monomer having a carboxyl group, that is, a functional group represented by “—COOH” is particularly preferable as the vinyl polymerizable monomer forming the toner constituent resin. . That is, it is preferable that both the resin constituting the core particle and the resin constituting the shell are formed using a polymerizable monomer having a carboxyl group. In particular, when paying attention to the content of the polymerizable monomer having a carboxyl group constituting each resin, the content of the polymerizable monomer having a carboxyl group in the shell constituting resin has a carboxyl group in the core particle constituting resin. The content of the polymerizable monomer is preferably 1.5 times or more and 3.0 times or less.

  As described above, it is considered that the durability and stability of the core-shell structure are improved because the content of the polymerizable monomer having a carboxyl group in the shell constituent resin and the core particle constituent resin has the above relationship. That is, in order to improve the durability of the core-shell structure, it is preferable to improve the adhesive force between the core particles and the shell. It is considered that the presence of the carboxyl group-containing monomer component in both resins imparts a hydrogen bond, an intermolecular attractive force, or the like via the carboxyl group between them, thereby improving the adhesive force. In this way, by improving the adhesive force between the core particles and the shell, it is considered that the core-shell toner is not stirred up and the durability of the toner is improved even if the toner is repeatedly stirred in the developing device and continues to be stressed. It is done.

  Known colorants can be used for the toner according to the present invention. Specific colorants are shown below.

  As the black colorant, for example, carbon black such as furnace black, channel black, acetylene black, thermal black and lamp black, and magnetic powder such as magnetite and ferrite can be used.

  Examples of the colorant for magenta or red include C.I. I. Pigment Red 2, 3, 5, 6, 7, 15, 15, 48: 1, 53: 1, 57: 1, 60, 63, 64, 68, the same 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 139, 144, 149, 150, 163, 166, 170, 177, 178, 184, 202, 206, 207, 209, 222, 238, 269, and the like.

  Examples of the colorant for orange or yellow include C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment Yellow 12, 14, 15, 17, 74, 83, 93, 94, 138, 155, 162, 180, 185, and the like.

  Further, as a colorant for green or cyan, C.I. I. Pigment Blue 2, 3, 15, 15, 15: 2, 15: 3, 15: 4, 16, 17, 17, 60, 62, 66, C.I. I. Pigment Green 7 etc.

  Examples of the dye include C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 2, 6, 14, 15, 16, 19, 21, 21, 33, 44, 56, 61, 77, 79, 80, 81, 82, the same 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95, etc.

  These colorants can be used alone or in combination of two or more as required. Further, the amount of the colorant added is in the range of 1 to 30% by mass, preferably 2 to 20% by mass, based on the whole toner, and a mixture thereof can also be used. The number average primary particle size varies depending on the type, but is preferably about 10 to 200 nm.

  As a method for adding the colorant, the resin fine particles are added at the stage of agglomeration by the addition of the flocculant to color the polymer. The colorant can also be used by treating the surface with a coupling agent or the like.

Next, the wax that can be used for the toner according to the present invention will be described. The waxes that can be used in the toner according to the present invention include the following known waxes. That is,
(1) Polyolefin wax Polyethylene wax, polypropylene wax, etc. (2) Long-chain hydrocarbon wax, paraffin wax, sazol wax, etc. (3) Dialkyl ketone wax, distearyl ketone, etc. (4) Ester wax Carnauba wax, Montan Wax, trimethylolpropane tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerine tribehenate, 1,18-octadecanedioldi Stearate, Tristearyl trimellitic acid, Distearyl maleate, etc. (5) Amide wax Ethylenediamine dibehenyl amide, Trimellitic acid tris The melting point of the allyl amide such as wax is generally forty to one hundred twenty-five ° C., preferably from 50 to 120 ° C., more preferably from 60 to 90 ° C.. By setting the melting point within the above range, the heat-resistant storage stability of the toner is ensured, and stable toner image formation can be performed without causing cold offset or the like even when fixing at a low temperature. Further, the wax content in the toner is preferably 1% by mass to 30% by mass, and more preferably 5% by mass to 20% by mass.

  Next, the toner according to the present invention is prepared by adding particles such as inorganic fine particles and organic fine particles having a number average primary particle size of 4 to 800 nm as external additives (= external additives) in the production process. Is possible.

  By adding the external additive, the fluidity and chargeability of the toner are improved, and the cleaning property is improved. The type of external additive is not particularly limited, and examples thereof include inorganic fine particles, organic fine particles, and lubricants exemplified below.

  As the inorganic fine particles, conventionally known fine particles can be used. For example, silica, titania, alumina, strontium titanate fine particles and the like are preferable. Moreover, what hydrophobized these inorganic fine particles can also be used as needed.

  Specific examples of the silica fine particles include commercially available products R-805, R-976, R-974, R-972, R-812, R-809 manufactured by Nippon Aerosil Co., Ltd., HVK-2150 manufactured by Hoechst, H -200, commercially available products TS-720, TS-530, TS-610, H-5, MS-5, etc. manufactured by Cabot Corporation.

  As the titania fine particles, for example, commercially available products T-805 and T-604 manufactured by Nippon Aerosil Co., Ltd., commercially available products MT-100S, MT-100B, MT-500BS, MT-600, MT-600SS, JA- 1. Commercial products TA-300SI, TA-500, TAF-130, TAF-510, TAF-510T manufactured by Fuji Titanium Co., Ltd. Commercial products IT-S, IT-OA, IT-OB, IT- manufactured by Idemitsu Kosan Co., Ltd. OC etc.

  Examples of the alumina fine particles include commercial products RFY-C and C-604 manufactured by Nippon Aerosil Co., Ltd., and commercial products TTO-55 manufactured by Ishihara Sangyo Co., Ltd.

  As the organic fine particles, spherical organic fine particles having a number average primary particle diameter of about 10 to 2000 nm can be used. Specifically, homopolymers such as styrene and methyl methacrylate and copolymers thereof can be used.

  In addition, a lubricant can be used to further improve the cleaning property and transfer property, and examples thereof include the following higher fatty acid metal salts. That is, salts of zinc stearate, aluminum, copper, magnesium, calcium, etc., zinc oleate, salts of manganese, iron, copper, magnesium, etc., zinc palmitate, salts of copper, magnesium, calcium, etc., linoleic acid There are salts of zinc, calcium and the like, and zinc and calcium of ricinoleic acid.

  The addition amount of these external additives and lubricants is preferably 0.1 to 10.0% by mass with respect to the whole toner. As a method for adding external additives and lubricants, there is a method of adding using a known mixing apparatus such as a turbuler mixer, a Henschel mixer, a nauter mixer, a V-type mixer or the like.

  Next, a polymerization initiator, a dispersion stabilizer, a surfactant and the like used when the toner according to the present invention is produced by an emulsion association method will be described.

When the binder resin constituting the toner according to the present invention is formed using a vinyl polymerizable monomer, a known oil-soluble or water-soluble polymerization initiator can be used. Specific examples of the oil-soluble polymerization initiator include the following azo or diazo polymerization initiators and peroxide polymerization initiators. That is,
(1) Azo or diazo polymerization initiator 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1) -Carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile, etc. (2) peroxide-based polymerization initiators benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl Peroxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis- (4 4-t-butylperoxycyclohexyl) propane, tris (T-butylperoxy) triazine In the case of forming the resin particles by emulsion polymerization is a water-soluble radical polymerization initiators can be used. Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, hydrogen peroxide and the like.

  A known chain transfer agent can also be used for adjusting the molecular weight of the resin particles. Specific examples include octyl mercaptan, dodecyl mercaptan, tert-dodecyl mercaptan, n-octyl-3-mercaptopropionic acid ester, terpinolene, carbon tetrabromide, α-methylstyrene dimer and the like.

  In the present invention, the polymerizable monomer dispersed in the aqueous medium is polymerized, or the resin particles dispersed in the aqueous medium are aggregated and fused to produce a toner. It is preferable to use a dispersion stabilizer that is stably dispersed therein. Examples of the dispersion stabilizer include tricalcium phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, Examples include barium sulfate, bentonite, silica, and alumina. In addition, polyvinyl alcohol, gelatin, methylcellulose, sodium dodecylbenzenesulfonate, ethylene oxide adduct, higher alcohol sodium sulfate and the like that are generally used as surfactants can also be used as the dispersion stabilizer.

  Further, when polymerization is performed using a polymerizable monomer in an aqueous medium, it is necessary to uniformly disperse oil droplets of the polymerizable monomer in the aqueous medium using a surfactant. In this case, usable surfactants are not particularly limited, but for example, the following ionic surfactants can be used as preferable ones. Examples of the ionic surfactant include a sulfonate, a sulfate ester salt, and a fatty acid salt. Examples of the sulfonate include sodium dodecylbenzenesulfonate, sodium arylalkylpolyethersulfonate, and 3,3-disulfonediphenyl. Urea-4,4-diazo-bis-amino-8-naphthol-6-sulfonate sodium, ortho-carboxybenzene-azo-dimethylaniline, 2,2,5,5-tetramethyl-triphenylmethane-4,4 -Sodium diazo-bis-β-naphthol-6-sulfonate.

  Examples of sulfate salts include sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, and sodium octyl sulfate. Fatty acid salts include sodium oleate, sodium laurate, sodium caprate, sodium caprylate, Examples include sodium caproate, potassium stearate, calcium oleate, polyoxyethylene (2) dodecyl ether sulfate sodium salt.

  Nonionic surfactants can also be used. Specifically, polyethylene oxide, polypropylene oxide, a combination of polypropylene oxide and polyethylene oxide, esters of polyethylene glycol and higher fatty acids, alkylphenol polyethylene oxide, higher fatty acids and Examples include polyethylene glycol esters, higher fatty acid and polypropylene oxide esters, sorbitan esters, and the like.

  Next, physical properties such as the particle diameter of the toner according to the present invention will be described.

  The toner according to the present invention preferably has a volume-based median diameter (D50v) of 3 μm or more and 8 μm or less. By setting the volume reference median diameter in the above range, for example, it is possible to faithfully reproduce a very minute dot image at a level of 1200 dpi (dpi; number of dots per inch (2.54 cm)).

  The toner according to the present invention is one of the problems to be able to faithfully reproduce the color of a photographic image. By making the volume-based median diameter a small diameter level in the above range, a photographic image can be formed. The dot image to be reduced is miniaturized, and a high-definition photographic image equivalent to or better than the printed image is obtained. In particular, in a printing field called “on-demand printing” where a print order is received at a level of several hundred to several thousand copies, high-quality prints containing high-definition photographic images can be quickly delivered to the user.

  The volume-based median diameter (D50v) of the toner can be measured and calculated using an apparatus in which a computer system for data processing is connected to “Multisizer 3 (manufactured by Beckman Coulter)”.

  As a measurement procedure, 0.02 g of toner is blended with 20 ml of a surfactant solution (for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant component 10 times with pure water for the purpose of dispersing the toner). After that, ultrasonic dispersion is performed for 1 minute to prepare a toner dispersion. This toner dispersion is poured into a beaker containing “ISOTONII” (manufactured by Beckman Coulter) in the sample stand with a pipette until the measured concentration reaches 5 to 10%, and the measuring machine count is set to 2500 pieces. To measure. The aperture diameter of the multisizer 3 is 50 μm.

  The toner according to the present invention preferably has a coefficient of variation (CV value) in the volume-based particle size distribution of 2% to 21%, more preferably 5% to 15%.

  The coefficient of variation (CV value) in the volume-based particle size distribution represents the degree of dispersion in the particle size distribution of the toner particles on the volume basis, and is defined by the following equation.

CV value (%) = [(standard deviation in volume-based particle size distribution) / (median diameter in volume-based particle size distribution (D50v))] × 100
The smaller the CV value, the sharper the particle size distribution, and the larger the toner particle size. In other words, since toners with uniform sizes can be obtained, it is possible to reproduce a fine dot image and fine lines required for digital image formation with higher accuracy. Further, when printing photographic images, it is possible to create high-quality photographic images at the image level or higher made with printing ink by using small-diameter toners of uniform sizes.

  The toner according to the present invention preferably has a softening point temperature (Tsp) of 70 ° C. or higher and 110 ° C. or lower, more preferably 70 ° C. or higher and 100 ° C. or lower. The colorant used in the toner according to the present invention has a stable property that the spectrum does not change even under the influence of heat. However, by setting the softening point within the above range, The influence of the applied heat can be further reduced. Therefore, since image formation can be performed without imposing a burden on the colorant, it is expected that a wider and more stable color reproducibility is expressed.

  In addition, by setting the softening point of the toner within the above range, the toner image can be fixed at a temperature lower than that of the prior art, and environmentally friendly image formation with reduced power consumption can be realized.

The softening point of the toner can be controlled by, for example, the following methods alone or in combination. That is,
(1) The type and composition ratio of monomers used for resin formation are adjusted.
(2) The molecular weight of the resin is adjusted according to the type and amount of chain transfer agent.
(3) Adjust the type and amount of wax.

Further, the method for measuring the softening point temperature of the toner is specifically “Flow Tester CFT-500 (manufactured by Shimadzu Corporation)”, molded into a columnar shape with a height of 10 mm, and at a heating rate of 6 ° C./min. While being heated, a pressure of 1.96 × 10 ⁶ Pa is applied from the plunger, and the pressure is pushed out from a nozzle having a diameter of 1 mm and a length of 1 mm. Thereby, a curve between the plunger drop amount and temperature of the flow tester (softening flow curve) ), And the temperature at the first outflow is the melting start temperature, and the temperature for the drop of 5 mm is the softening point temperature.

  Next, the developer using the toner according to the present invention will be described. The toner according to the present invention is used as a dry toner, and a developer form used as a dry toner, that is, as a two-component developer composed of a carrier and a toner, or a non-magnetic one component composed only of toner It can be used as a developer.

  When the toner according to the present invention is used as a two-component developer, for example, a full-color print can be produced at high speed by using a tandem image forming apparatus described later. Carriers that are magnetic particles used when used as a two-component developer include conventionally known materials such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead. It is possible to use. Among these, ferrite particles are preferable.

  The volume-based particle diameter of the carrier is preferably 15 to 100 μm, more preferably 25 to 80 μm. The saturation magnetization value is preferably 20 to 80 emu / g. By using a carrier having such a particle size and saturation magnetization value, a soft magnetic brush is formed on the developing sleeve during image formation, and a toner image having excellent sharpness can be formed. The volume average particle diameter and the saturation magnetization value can be measured with a known measuring device. Specifically, the volume reference particle size is measured by a laser diffraction particle size analyzer “HELOS (manufactured by Sympatec Co., Ltd.)” equipped with a wet disperser, and the saturation magnetization is “DC magnetization characteristic automatic recording device 3257-35 (horizontal It is possible to measure by “Kawaden Co., Ltd.”).

  The two-component developer can be obtained by mixing the toner and the carrier by a known method. The mixing amount of the toner with respect to the carrier is preferably 2 to 10% by mass. Further, the mixing device is not particularly limited, and for example, a Nauter mixer, a W cone, a V-type mixer, or the like can be used.

  When the toner is used as a non-magnetic one-component developer that forms an image without using a carrier, the toner is slid and pressed against the charging member and the developing roller surface during image formation. Image formation by the non-magnetic one-component development method can simplify the structure of the developing device, and thus has an advantage that the entire image forming device can be made compact. Therefore, by using the above-mentioned toner as a non-magnetic one-component developer, it is possible to create full-color prints with a compact color printer, making it possible to create full-color prints with excellent color reproducibility in space-constrained work environments. To do.

Next, an image forming method in which the toner according to the present invention can be used will be described. In the image forming method in which the toner according to the present invention can be used, a toner image is formed on a transfer paper through at least the following steps to produce a print.
(1) A latent image forming step for forming a latent image on the surface of the electrophotographic photosensitive member (2) A toner obtained by developing the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer carried on a developer carrying member Developing step for forming an image (3) Transfer step for transferring the toner image to the surface of the transfer member (4) Fixing step for thermally fixing the toner image transferred to the surface of the transfer member.

  FIG. 2 is an example of a monochrome type image forming apparatus that performs printing using the toner according to the present invention. An image forming apparatus 1 shown in FIG. 1 is a digital image forming apparatus and includes an image reading unit A, an image processing unit B, an image forming unit C, and a transfer paper transport unit D.

  On the upper part of the image reading unit A, automatic document feeding means for automatically conveying the document is provided. In the automatic document feeder, the document is placed on the document placing table 11, and the placed document is separated and conveyed one by one by the conveying roller 12, and the image is read at the reading position 13a. The document that has been read is discharged onto the document discharge tray 14 by the transport roller 12.

  On the other hand, when reading an original placed on the platen glass 13, the original image is read by a plurality of mirror units 15 and 16 including an illumination lamp constituting a scanning optical system and a plurality of mirrors.

  The image read by the image reading unit A is formed on the light receiving surface of the image sensor CCD through the projection lens 17. The optical image formed on the image sensor CCD is sequentially converted into an electric signal (luminance signal), A / D converted, and subjected to processing such as density conversion and filter processing in the image processing unit B as image data. Once stored in memory.

  The image forming unit C includes a drum-shaped electrophotographic photosensitive member 1 which is an image carrier. A charging unit 2 for charging the outer periphery of the photosensitive member 1, a potential detecting unit 220 for detecting the surface potential of the charged photosensitive member, a developing unit 4, a transfer unit 5, a cleaning unit 6, and a PCL (light-eliminating unit) Precharge lamps 8 are arranged in the order of operation. Further, density detecting means 222 for measuring the reflection density of the patch image formed on the photoreceptor 1 is provided downstream of the developing means 4. The photoreceptor 1 is driven to rotate in the clockwise direction shown in the figure.

  The photoreceptor 1 is uniformly charged by the charging unit 2 and then image-exposed by the image exposure unit 3 based on the image signal from the memory of the image processing unit B. The image exposure unit 3 performs image exposure on the photoconductor 1 at the position Ao, whereby an electrostatic latent image is formed on the surface of the photoconductor 1.

  Next, the electrostatic latent image formed on the photoconductor 1 is developed by the developing unit 4 to form a toner image on the surface of the photoconductor 1.

  The transfer paper transport unit D includes paper feed units 41 (A), 41 (B), and 41 (C) that store transfer papers P of different sizes, and also provides manual paper feed for performing manual paper feed. A paper unit 42 is provided on the side, and an appropriate transfer paper P is selected from these paper feeding units. The transfer paper P is transported along the transport path 40 by the guide roller 43, and the inclination and bias are corrected by the registration roller 44. The transfer paper P corrected by the registration roller 44 is conveyed again along the conveyance path 40 and guided to the pre-transfer roller 43 a, the paper feed path 46, and the entry guide plate 47. The toner image on the photoconductor 1 is transferred to the transfer paper P by the transfer pole 24 and the separation pole 25 at the transfer position Bo, and the transfer paper P is separated from the surface of the photoconductor 21 and conveyed from the transfer means 5 to the fixing means 50. The

  The fixing unit 50 includes a fixing roller 51 and a pressure roller 52. The transfer sheet P is passed between the fixing roller 51 and the pressure roller 52, and is heated and pressed to fix the toner image. After the toner image has been fixed, the transfer paper P is discharged onto the paper discharge tray 64.

  The above is an explanation of image formation on one side of the transfer paper P. When image formation is performed on both sides, the transfer paper P is conveyed in the direction of the broken line arrow by the operation of the paper discharge switching member 170 and the transfer paper guide section 177. Is done. Further, the transfer paper P is transported downward and switched back by the transport mechanism 178, and the double-sided printing paper feeding unit 130 is transported with the rear end portion of the transfer paper P being the leading end. Then, the transfer paper P is transported again through the transport path 40 by the operation of the transport guide 131 and the paper feed roller 132 of the duplex printing paper supply unit 130, and a toner image is also formed on the back surface of the transfer paper P by the above-described procedure. Can do.

  In the image forming apparatus, components such as the photosensitive member, the developing unit, and the cleaning unit may be unitized as a process cartridge, and may be configured to be freely detachable from the apparatus main body in units. The charging unit, the image exposure unit, the developing unit, the transfer or separation unit, and the cleaning unit may be a process cartridge integrated with the photosensitive member, and may be a single unit that can be freely attached to and detached from the apparatus main body.

  FIG. 3 is a schematic view showing an example of an image forming apparatus capable of forming a color image using the toner according to the present invention.

  In FIG. 3, 1Y, 1M, 1C and 1Bk are photoreceptors, 4Y, 4M, 4C and 4Bk are developing devices, 5Y, 5M, 5C and 5Bk are primary transfer rolls as primary transfer means, and 5A is a secondary transfer. Secondary transfer rolls as means, 6Y, 6M, 6C, and 6Bk are cleaning devices, 7 is an intermediate transfer member unit, 50 is a heat roll type fixing device, and 70 is an intermediate transfer member.

  This image forming apparatus is called a tandem color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10Bk, an endless belt-shaped intermediate transfer body unit 7 as a transfer unit, and a recording member P. An endless belt-shaped paper feeding and conveying means 21 and a heat roll type fixing device 50 as a fixing means. A document image reading device SC is arranged on the upper part of the main body A of the image forming apparatus.

  As one of the different color toner images formed on each photoconductor, an image forming unit 10Y that forms a yellow image includes a drum-shaped photoconductor 1Y as a first photoconductor, and a periphery of the photoconductor 1Y. A charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a primary transfer roll 5Y as a primary transfer unit, and a cleaning unit 6Y.

  An image forming unit 10M that forms a magenta image as another different color toner image is disposed around a drum-shaped photoconductor 1M as a first photoconductor, and the photoconductor 1M. A charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roll 5M as a primary transfer unit, and a cleaning unit 6M. In addition, an image forming unit 10C that forms a cyan image as one of other different color toner images is disposed around the photoconductor 1C as a drum-type photoconductor 1C as a first photoconductor. The charging unit 2C, the exposure unit 3C, the developing unit 4C, the primary transfer roll 5C as the primary transfer unit, and the cleaning unit 6C are provided.

  Further, as one of the other different color toner images, the image forming unit 10Bk that forms a black image includes a drum-shaped photosensitive member 1Bk as a first photosensitive member, and a charge disposed around the photosensitive member 1Bk. Means 2Bk, exposure means 3Bk, developing means 4Bk, primary transfer roll 5Bk as primary transfer means, and cleaning means 6Bk.

  The endless belt-like intermediate transfer body unit 7 has an endless belt-like intermediate transfer body 70 as an intermediate transfer endless belt-like second image carrier that is wound around a plurality of rolls and is rotatably supported.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10Bk is sequentially transferred onto the rotating endless belt-shaped intermediate transfer body 70 by the primary transfer rolls 5Y, 5M, 5C, and 5Bk to be combined. A colored image is formed. A recording member P such as a sheet as a transfer material accommodated in the sheet feeding cassette 20 is fed by the sheet feeding / conveying means 21, passes through a plurality of intermediate rolls 22 A, 22 B, 22 C, 22 D, and a registration roll 23, and is secondary. A color image is transferred onto the recording member P at a time by being conveyed to a secondary transfer roll 5A as a transfer means. The recording member P to which the color image has been transferred is fixed by the heat roll type fixing device 50, is sandwiched by the paper discharge roll 25, and is placed on the paper discharge tray 26 outside the apparatus.

  On the other hand, after the color image is transferred to the recording member P by the secondary transfer roll 5A, the residual toner is removed by the cleaning unit 6A from the endless belt-shaped intermediate transfer body 70 in which the recording member P is separated by curvature.

  During the image forming process, the primary transfer roll 5Bk is always in pressure contact with the photoreceptor 1Bk. The other primary transfer rolls 5Y, 5M, and 5C are in pressure contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roll 5A comes into pressure contact with the endless belt-shaped intermediate transfer body 70 only when the recording member P passes through the secondary transfer roll 5A and secondary transfer is performed.

  In this manner, toner images are formed on the photoreceptors 1Y, 1M, 1C, and 1Bk by charging, exposure, and development, and the toner images of the respective colors are superimposed on the endless belt-shaped intermediate transfer body 70, and are collectively applied to the recording member P. The image is transferred and fixed by the fixing device 50 by pressure and heating. The photoreceptors 1Y, 1M, 1C, and 1Bk after transferring the toner image to the recording member P clean the toner remaining on the photoreceptor during transfer with the cleaning device 6A, and then perform the above charging, exposure, and development cycle. The next image formation is performed.

  Next, FIG. 4 is also a cross-sectional view of the color image forming apparatus as in FIG. 3, but has a different form from the image forming apparatus of FIG. The image forming apparatus shown in FIG. 4 has a charging unit, an exposure unit, a plurality of developing units, a transfer unit, a cleaning unit, and an intermediate transfer member around the organic photoreceptor. The belt-shaped intermediate transfer body 70 uses an elastic body having a medium resistance.

  Reference numeral 1 denotes a rotary drum type photoreceptor that is repeatedly used as an image forming body, and is driven to rotate at a predetermined peripheral speed in a counterclockwise direction indicated by an arrow. While rotating, the photosensitive member 1 is uniformly charged to a predetermined polarity / potential by the charging unit 2 and then subjected to image exposure by an image exposure unit 3 (not shown), whereby yellow (Y) of the target color image is obtained. An electrostatic latent image corresponding to the color component image (color information) is formed.

  Next, the electrostatic latent image is developed with yellow toner, which is the first color, by yellow (Y) developing means 4Y. At this time, the magenta, cyan, and black developing means 4M, 4C, and 4Bk, which are the second to fourth developing means, are not activated and do not act on the photoreceptor 1, and the yellow toner image of the first color is No influence from the second to fourth developing means.

  The intermediate transfer member 70 is stretched by rollers 79a, 79b, 79c, 79d, and 79e, and is driven to rotate in the clockwise direction at the same peripheral speed as the photosensitive member 1.

  The yellow toner image of the first color formed and supported on the photosensitive member 1 is applied to the intermediate transfer member 70 from the primary transfer roller 5a in the process of passing through the nip portion between the photosensitive member 1 and the intermediate transfer member 70. The intermediate transfer (primary transfer) is sequentially performed on the outer peripheral surface of the intermediate transfer body 70 by the electric field formed by the primary transfer bias.

  The surface of the photoreceptor 1 after the transfer of the first color yellow toner image corresponding to the intermediate transfer body 70 is cleaned by the cleaning device 6a.

  Similarly, the second color magenta toner image, the third color cyan toner image, and the fourth color black (black) toner image are sequentially superimposed and transferred onto the intermediate transfer body 70 to correspond to the target color image. A superimposed color toner image is formed.

  The secondary transfer roller 5b is supported in parallel with the secondary transfer counter roller 79b so as to be separated from the lower surface of the intermediate transfer body 70.

  The primary transfer bias for sequentially superimposing and transferring the first to fourth color toner images from the photosensitive member 1 to the intermediate transfer member 70 has a polarity opposite to that of the toner and is applied from a bias power source. The applied voltage is, for example, in the range of +100 V to +2 kV.

  In the primary transfer process of the first to third color toner images from the photosensitive member 1 to the intermediate transfer member 70, the secondary transfer roller 5b and the intermediate transfer member cleaning means 6b can be separated from the intermediate transfer member 70. is there.

  When the superimposed color toner image transferred onto the belt-shaped intermediate transfer member 70 is transferred onto the transfer paper P as the second image carrier, the secondary transfer roller 5b is brought into contact with the belt of the intermediate transfer member 70. At the same time, the transfer paper P is fed from the pair of paper feed registration rollers 23 through the transfer paper guide to the belt of the intermediate transfer body 70 to the contact nip with the secondary transfer roller 5b at a predetermined timing. A secondary transfer bias is applied to the secondary transfer roller 5b from a bias power source. By this secondary transfer bias, the superimposed color toner image is transferred (secondary transfer) from the intermediate transfer body 70 to the transfer paper P as the second image carrier. The transfer paper P that has received the transfer of the toner image is introduced into the fixing means 24 and fixed by heating.

  The transfer material capable of forming an image with the toner according to the present invention is generally called a transfer paper or an image support, and forms an image using a known method typified by the above-described image forming method. . Examples of the transfer material that can be used in the present invention include known materials such as plain paper from thin paper to thick paper, high-quality paper, art paper, coated printing paper such as coated paper, and commercially available Japanese paper. There are postcard paper, plastic films for OHP, cloth, and the like.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to the following. In the following text, “part” represents “part by mass”.

1. Preparation of “Toners 1 to 15” (1) Preparation of “Core Forming Resin Fine Particles A” (a) First Stage Polymerization A surfactant is installed in a reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introducing device. A surfactant solution was prepared by adding 4.0 parts by mass of polyoxyethylene (2) dodecyl ether sulfate sodium salt and 3000 parts by mass of ion-exchanged water. The surfactant solution was heated to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.

  Next, the “monomer mixed solution 1” containing the following compound was heated to 80 ° C. and then added to the surfactant solution, and the mechanical dispersion device “Claremix (M (Distributed by Technic Co., Ltd.) ”for 30 minutes to prepare an emulsified particle (oil droplet) dispersion.

Styrene 660 parts by mass n-butyl acrylate 265 parts by mass Methacrylic acid 46 parts by mass n-octyl mercaptan 18 parts by mass Paraffin wax “HNP-57 (manufactured by Nippon Wax Co., Ltd.)” 140 parts by mass By adding an aqueous initiator solution in which 15 parts by mass of potassium persulfate (KPS) is dissolved in 400 parts by mass of ion-exchanged water, the reaction system is treated at a stirring speed of 230 rpm at 80 ° C. for 1 hour. Polymerization (first stage polymerization) was performed. In this way, “resin fine particle dispersion a1” was produced.

(B) Second-stage polymerization After the first-stage polymerization, an initiator aqueous solution prepared by dissolving 5.45 parts by mass of potassium persulfate (KPS) in 220 parts by mass of ion-exchanged water is added, and the reaction system is added. At 80 ° C., and a mixture of the following compounds was added dropwise over 1 hour.

Styrene 306 parts by weight n-butyl acrylate 123 parts by weight Methacrylic acid 21 parts by weight n-octyl mercaptan 7.1 parts by weight After completion of the dropping, the mixture is heated for 2 hours and stirred at a stirring speed of 230 rpm for polymerization (second) Stepwise polymerization) was performed, and then the reaction system was cooled to 28 ° C. to prepare a dispersion containing resin fine particles for core formation. The obtained resin fine particles are referred to as “core-forming resin fine particles A”. The particle diameter of the “core forming resin fine particles A” was measured using an electrophoretic light scattering photometer “ELS-800 (manufactured by Otsuka Electronics Co., Ltd.)” and found to be 120 nm. Further, the ratio of the polymerizable monomer having a carboxyl group used in producing the “core-forming resin particles A” to the total polymerizable monomers was 4.7%.

1-2. Preparation of “shell forming resin fine particles 1 to 8” (1) Preparation of “shell forming resin fine particles 1” In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing device, the above “core forming resin” is prepared. The same surfactant solution used in the first stage polymerization for producing “fine particles A” was prepared. While this surfactant solution was stirred at a stirring speed of 230 rpm under a nitrogen stream, the internal temperature was raised to 80 ° C. Thereafter, an initiator solution prepared by dissolving 10 parts by mass of potassium persulfate (KPS) in 400 parts by mass of ion-exchanged water is added to the surfactant solution, and the liquid temperature is set to 80 ° C. The body mixed solution "was added dropwise over 2 hours.

Styrene 340 parts by weight n-butyl acrylate 113 parts by weight Methacrylic acid 47 parts by weight n-octyl mercaptan 22 parts by weight The above “monomer mixed solution” was added dropwise, followed by stirring at 270 rpm while stirring at 80 ° C. A “shell forming resin fine particle 1” was prepared by performing a polymerization reaction for 1.5 hours under cooling and cooling to room temperature.

  The particle diameter of the “shell forming resin fine particles 1” was 80 nm when measured using an electrophoretic light scattering photometer “ELS-800 (manufactured by Otsuka Electronics Co., Ltd.)”. In addition, the ratio of the polymerizable monomer having a carboxyl group used in producing the resin particles to the total polymerizable monomer was 9.4%.

(2) Production of “shell-forming resin fine particles 2 to 5” In the production of “shell-forming resin fine particles 1”, the stirring speed after dropping “monomer mixed solution” was 300 rpm, 240 rpm, 200 rpm, and 330 rpm, respectively. “Shell-forming resin fine particles 2 to 5” were prepared by taking the same procedure except that the change was made. The particle diameters of “shell forming resin fine particles 2 to 5” were measured using an electrophoretic light scattering photometer “ELS-800 (manufactured by Otsuka Electronics Co., Ltd.)” and found to be 60 nm, 110 nm, 140 nm, and 40 nm, respectively. .

(3) Preparation of “shell forming resin fine particles 6 to 8” In the preparation of “shell forming resin fine particles 2”, the addition amount of each polymerizable monomer constituting “monomer mixed solution” is as follows. The “shell forming resin fine particles 6” were prepared in the same manner except that the above procedure was changed. In addition, the addition amount of the polymerizable monomer is
Styrene 360 parts by mass n-butyl acrylate 106 parts by mass Methacrylic acid 35 parts by mass n-octyl mercaptan 22 parts by mass The particle size of the above-mentioned “resin particle 6 for shell formation” was measured using the above-mentioned electrophoresis light scattering photometer. The ratio of the polymerizable monomer having a carboxyl group used for producing the resin particles to 60 nm to the total polymerizable monomer was 6.9%.

Further, “shell forming resin fine particles 7” were prepared in the same manner except that the addition amount of each polymerizable monomer constituting the “monomer mixed solution” was changed as follows. That is,
Styrene 375 parts by weight n-butyl acrylate 102 parts by weight Methacrylic acid 23 parts by weight n-octyl mercaptan 22 parts by weight Further, the addition amount of each polymerizable monomer constituting the “monomer mixed solution” was changed as follows: Then, “Shell-forming resin fine particles 8” were produced in the same manner as others. That is,
Styrene 325 parts by weight n-butyl acrylate 116 parts by weight Methacrylic acid 60 parts by weight n-octyl mercaptan 22 parts by weight The particle size of the above-mentioned “resin particles 7 and 8 for shell formation” was measured using the aforementioned electrophoretic light scattering photometer. As a result, both were 60 nm. Further, the ratio of the polymerizable monomer having a carboxyl group used in producing the resin particles to the total polymerizable monomers was 4.6% and 11.8%, respectively.

1-3. Preparation of “Cyan Colorant Particle Dispersion 1” 11.5 parts by mass of sodium n-dodecyl sulfate was added to 160 parts by mass of ion-exchanged water, and dissolved and stirred to prepare an aqueous surfactant solution. 25 parts by mass of “CI Pigment Blue 15: 3” is gradually added to this aqueous surfactant solution, and dispersion treatment is performed using “Clear Mix W Motion CLM-0.8 (M Technique Co., Ltd.)”. In this way, “Cyan Colorant Particle Dispersion 1” was prepared. The “cyan colorant particles 1” in the obtained “cyan colorant particle dispersion 1” had an average particle size of 98 nm.

1-4. Production of “Toners 1-15” “Toners 1-15” having a core-shell structure were produced by the following procedure.

(1) Preparation of “Toner 1” In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing device,
Core forming resin fine particles A 1430 parts by mass (solid content conversion)
820 parts by mass of pure water 70 parts by mass of cyan colorant particles 1 (in terms of solid content)
Was added and stirred. After adjusting the temperature in the reaction vessel to 30 ° C., a 5 mol / liter aqueous sodium hydroxide solution was added to adjust the pH to 10.

  Next, an aqueous solution in which 200 parts by mass of magnesium chloride hexahydrate was dissolved in 1000 parts by mass of pure water was added dropwise at 30 ° C. for 10 minutes with stirring. After completion of the dropping, the temperature was raised while stirring, and the temperature was raised until the temperature of the system reached 75 ° C. to perform aggregation and fusion. At this time, the particle size of the aggregated particles is measured by “Multisizer 3 (manufactured by Beckman Coulter)” and the average circularity of the particles is measured by using “FPIA-2100 (manufactured by Sysmex)”. Depositing was performed to form core particles. When the volume-based median diameter of the aggregated particles (core particles) becomes 6.3 μm, an aqueous solution in which 40 parts by mass of sodium chloride is dissolved in 500 parts by mass of pure water is added to stop the aggregation, and then the system is continued. The aging treatment was carried out while maintaining the temperature at 75 ° C.

  The maturation process was continued while measuring the average circularity of the core particles, and when the average circularity of the core particles reached 0.87, 180 parts by mass of the above-mentioned “shell forming resin fine particles 1” (in terms of solid content) ) Was added, and aggregation and fusion were continued. Here, the process from the addition of the aqueous sodium chloride solution to the addition of the “shell forming resin fine particles 1” is defined as a first aging treatment process.

  The agglomeration and fusion were continued, a small amount of solution was taken out from the reaction system, and this was centrifuged with a centrifugal separator to confirm that the supernatant became transparent, and then ripening was continued. The reaction system was cooled to room temperature when the average circularity of the core-shell structured particles reached 0.95. After cooling, the produced particles were washed with pure water and repeatedly filtered and washed, and then dried with hot air at 35 ° C. to produce “colored particles 1” having a core-shell structure as base toner particles. .

  The following external additive was added to the “colored particles 1” produced by the above procedure, and the external additive treatment was performed with “Henschel mixer (manufactured by Mitsui Miike Mining Co., Ltd.)” to produce “Toner 1”.

Silica treated with hexamethylsilazane (average primary particle size 12 nm)
0.6 part by mass n-octylsilane-treated titanium dioxide (average primary particle size 24 nm)
0.8 parts by mass The external additive treatment by the Henschel mixer was performed under conditions of a peripheral speed of the stirring blade of 35 m / second, a treatment temperature of 35 ° C., and a treatment time of 15 minutes.

  In order to confirm the structure of the “toner 1” produced through the above procedure, a transmission electron microscope observation was performed according to the above-described procedure. As a result, a shell having a thickness of 70 nm completely and uniformly covered the core particles. It was confirmed that it has a structure.

(2) Preparation of “Toner 2” “Toner 2” was prepared in the same manner as in the preparation of “Toner 1” except that the amount of the “shell-forming resin fine particles 1” was changed to 80 parts by mass (in terms of solid content). 2 "was produced. Observation of the produced “Toner 2” using a transmission electron microscope in the procedure of the previous operation confirmed that the shell having a thickness of 45 nm completely and uniformly covered the core particles. .

(3) Production of “Toner 3” In the production of “Toner 1”, “Shell-forming resin fine particles 2” were used instead of “Shell-forming resin fine particles 1”. In addition, when the time of the first aging treatment step was extended and the average circularity of the core particles became 0.93, 180 parts by mass (in terms of solid content) of the “shell forming resin fine particles 2” was added. . Other than that, “Toner 3” was prepared in the same procedure as that of “Toner 1”.

  When the “Toner 3” produced was observed with a transmission electron microscope in the above-described procedure, it was confirmed that the shell having a thickness of 45 nm completely and uniformly covered the core particles.

(4) Preparation of “Toner 4” “Toner 4” was prepared in the same manner as in the preparation of “Toner 3” except that the addition amount of “shell forming resin fine particles 2” was changed to 80 parts by mass (in terms of solid content). Was made. When the “Toner 4” produced was observed with a transmission electron microscope in the above-described procedure, it was confirmed that the shell having a thickness of 30 nm had a structure in which the core particles were completely and uniformly covered.

(5) Preparation of “Toner 5 and 6” In the preparation of “Toner 1”, 150 parts by mass (in terms of solid content) of “shell forming resin fine particles 3” was used instead of “shell forming resin fine particles 1”. Other than that, “Toner 5” was prepared in the same procedure. “Toner 6” was prepared in the same procedure except that the amount of “shell forming resin fine particles 3” was changed to 80 parts by mass (in terms of solid content). When the "Toner 5, 6" was observed with a transmission electron microscope in the above-described procedure, the "Toner 5" had a structure in which the core particles were completely and uniformly covered by the 80 nm thick shell. It was confirmed that In addition, it was confirmed that “Toner 6” has a structure in which a shell having a thickness of 65 nm completely and uniformly covers the core particles.

(6) Preparation of “Toner 7 and 8” In the preparation of “Toner 1”, 70 parts by mass (converted to solid content) of “shell forming resin fine particles 4” was used instead of “shell forming resin fine particles 1”. Other than that, “Toner 7” was prepared in the same procedure. Further, “Toner 8” was prepared in the same procedure except that the addition amount of “shell forming resin fine particles 4” was changed to 150 parts by mass (in terms of solid content). When the “Toners 7 and 8” thus prepared were observed with a transmission electron microscope according to the procedure described above, a shell with a thickness of 90 nm was formed in “Toner 7”, but the core particles were not completely covered. It was of structure. In addition, it was confirmed that “Toner 8” has a structure in which a shell having a thickness of 135 nm completely and uniformly covers the core particles.

(7) Preparation of “Toner 9, 10” In the preparation of “Toner 2”, the same procedure was followed except that “Shell-forming resin fine particles 5” were used instead of “Shell-forming resin fine particles 1”. “Toner 9” was produced. In addition, “Toner 10” was prepared in the same manner as in “Toner 3” except that “Shell-forming resin fine particles 2” was used instead of “Shell-forming resin fine particles 2”. When the “Toner 9 and 10” thus prepared were observed with a transmission electron microscope in the above-described procedure, the “Toner 9” was formed with a shell having a thickness of 30 nm, but the core particles were not completely covered and the core was exposed. Of the structure. Further, it was confirmed that “toner 10” has a structure in which the shell completely and uniformly covers the core particles, but the thickness is 20 nm.

(8) Preparation of “Toners 11 to 13” In the preparation of “Toner 1”, the same procedure was used except that “Shell-forming resin fine particles 6” were used instead of “Shell-forming resin fine particles 1”. “Toner 11” was produced. Further, “Toner 12” was prepared by taking the same procedure except that “Shell-forming resin fine particles 7” were used. Further, “Toner 13” was prepared in the same manner as in “Toner 3” except that “Shell-forming resin fine particles 8” were used instead of “Shell-forming resin fine particles 2”.

  The manufactured “Toners 11 to 13” were observed with a transmission electron microscope in accordance with the above-described procedure. In “Toner 11” and “Toner 12”, the 55 nm-thick shell completely and uniformly covered the core particles. It was confirmed that the structure has Further, it was confirmed that the “toner 13” has a structure in which the core particle is completely and uniformly covered with the shell having a thickness of 45 nm, similarly to the “toner 3” described above.

(9) Preparation of “Toners 14 and 15” In the preparation of “Toner 1”, when the time of the first aging treatment step was shortened and the average circularity of the core particles became 0.83, 180 parts by mass (converted to solid content) of “shell forming resin fine particles 1” was added and continued, and “Toner 14” was produced through the same procedure as that of “Toner 1”. When the manufactured “Toner 14” was observed with a transmission electron microscope according to the above-described procedure, a shell with a thickness of 60 nm was formed, but the core particles were not completely covered, and there were portions where the core was exposed. The structure was confirmed.

  In addition, “Toner 15” was prepared in the same manner as in “Toner 14” except that the addition amount of “Shell-forming resin fine particles 1” was 250 parts by mass (in terms of solid content). When the manufactured “Toner 15” was observed with a transmission electron microscope according to the procedure described above, it was confirmed that the shell had a thickness of 100 nm and the core particles were not completely covered.

  Table 1 below shows the performance of “toners 1 to 15” having a core-shell structure manufactured by the above procedure. In the table, “Covering status” in the “Shell performance” section is indicated by “O and X”, but “O” is a structure in which the shell completely covers the core particles, while “X” "Is a structure in which the shell cannot completely cover the core particles and the core portion is exposed in some places.

2. Evaluation Experiment (1) Preparation of “Developers 1 to 15” Carriers having an average particle diameter of 35 μm formed by coating ferrite particles with styrene-acrylic resin and the above “toners 1 to 15” were mixed and toner concentration was determined. Produced 8% of “Developers 1 to 15”.

(2) Evaluation Experiment The above-mentioned “Developers 1 to 15” are mounted on an evaluation machine obtained by modifying a fixing device of a commercially available digital copying machine “bizhub PRO C500” (manufactured by Konica Minolta Business Technologies Co., Ltd.). Performance and fixing performance were evaluated. Here, "Examples 1-9" using "Developers 1-6, 11-13" and "Comparative Examples 1-6" using "Developers 7-10, 14, 15" As described above, the fixing offset performance, the fixing performance, and the heat-resistant storage property of the toner were evaluated. The fixing device is modified so that the surface temperature of the fixing heat roller can be changed in the range of 105 ° C to 210 ° C.

<Evaluation of fixing offset performance>
The temperature was changed in increments of 5 ° C. in the range of 105 ° C. to 210 ° C., and A4 images having a solid band image were conveyed and fixed by vertical feeding at each temperature to evaluate the occurrence of image smear due to fixing offset. The sample was an A4 image having a solid band image of 5 mm width and a halftone image of 20 mm width perpendicular to the transport direction, which was transported and fixed by vertical feeding, and image contamination occurred on the low temperature side and the high temperature side. The fixing temperature was evaluated. The high temperature side was 200 ° C. or higher and no image stain was generated, and the low temperature side was 150 ° C. or lower and no image stain was generated.

<Evaluation of fixing performance>
In the same manner as in “Evaluation of fixing offset performance”, the temperature of the fixing heat roller was changed in increments of 5 ° C. in the range of 105 ° C. to 210 ° C. to evaluate the fixed image. In the evaluation, development was performed under the condition that the toner adhesion amount on the transfer paper was 11 mg / cm ^2, and the transfer paper on which the toner image was formed was fixed in an environment of a temperature of 10 ° C. and a humidity of 10% RH.

The image portion of the transfer paper subjected to the fixing process was folded using a folding machine, and air of 0.35 MPa was blown onto the folded portion, and the state of the image of the folded portion was evaluated based on the following evaluation criteria. Evaluation was made in five ranks as shown in the following evaluation criteria. The fixing temperature at rank 3 was defined as the lower limit fixing temperature, and the lower limit fixing temperature was determined to be 150 ° C. or lower. That is,
(Evaluation criteria)
Rank 5: No folds Rank 4: Some peeling is observed according to some folds Rank 3: Thin linear peeling is observed according to the folds, but there is no practical problem Rank 2: Thick according to the folds Peeling was observed and there was a problem in practical use. Rank 1: Large peeling occurred on the image.

<Evaluation of heat-resistant storage stability of toner>
Further, the heat resistant storage property of the toner was evaluated by the following procedure. First, 0.5 g of each toner is put in a 10 ml glass bottle having an inner diameter of 21 mm, the lid is closed, and the mixture is shaken 600 times with a tap denser “KYT-2000 (manufactured by Seishin Enterprise Co., Ltd.)”. And left in an environment with a humidity of 35% RH for 2 hours. Next, the toner was placed on a 48 mesh (aperture 350 μm) sieve so as not to disintegrate, set in a “powder tester (manufactured by Hosokawa Micron)”, and fixed with a press bar and a knob nut.

  The “powder tester” was adjusted to a vibration intensity of a feed width of 1 mm, and vibration was applied for 10 seconds. Thereafter, the amount of toner remaining on the sieve was measured, and the ratio of the remaining toner was calculated to determine the toner aggregation rate (mass%). This was evaluated as heat resistant storage stability.

The toner aggregation rate is calculated by the following formula:
Toner aggregation rate (mass%) = [(residual toner mass on sieve (g)) / 0.5 (g)] × 100
Evaluation of heat-resistant storage property was performed based on the following criteria. That is,
A: Toner yield is less than 10% by mass (very good heat-resistant storage)
○: The toner aggregation rate is 10% by mass or more and 20% by mass or less (good heat storage stability)
X: The toner aggregation rate exceeds 20% by mass (the toner has poor heat storage stability and cannot be used)
Among the above criteria, ◎ and ○ were accepted.

  The results are shown in Table 2.

  As shown in Table 2, all of “Examples 1 to 9” using the toner produced through the configuration of the toner production method according to the present invention have good low-temperature fixing performance and wide fixing. It was confirmed that the toner has excellent offset resistance and does not cause image contamination in the temperature range. That is, a step of forming a shell by adding resin particles having a volume-based median diameter of 60 nm to 110 nm in the core particle dispersion when the average circularity of the core particles is 0.87 to 0.93. After that, it was found that a toner having the above effects can be obtained by preparing a toner. On the other hand, “Comparative Examples 1 to 6” using a toner that does not have the configuration of the toner manufacturing method according to the present invention cannot achieve both offset resistance and low-temperature fixability, or completely cover the core surface with a shell. The obtained toner could not be obtained and had problems with heat-resistant storage, and problems with low-temperature fixability and offset resistance.

1 (1Y, 1M, 1C, 1Bk) Photoconductor 2 (2Y, 2M, 2C, 2Bk) Charging unit 3 (3Y, 3M, 3C, 3Bk) Image exposure unit 4 (4Y, 4M, 4C, 4Bk) Developing unit 5 Transfer unit 5Y, 5M, 5C, 5Bk Primary transfer roll 6 (6Y, 6M, 6C, 6Bk) Cleaning unit 7 Intermediate transfer unit 70 Intermediate transfer belt 10 (10Y, 10M, 10C, 10Bk) Image forming unit 50 Fixing unit (Thermal roll type fixing device)
A Image reading unit B Image processing unit C Image forming unit D Transfer paper transport unit P Transfer paper (recording member)
T toner TA core particle TB shell C1 colorant particle R1
R2

Claims (3)

A toner manufacturing method for producing a core-shell toner through a step of forming core particles containing at least a resin and a colorant, and a step of forming a shell by adding resin particles around the core particles. And
In the step of forming the core particles, when the average circularity of the core particles is 0.87 or more, the formation of the core particles is terminated,
In the step of forming the shell, the shell is formed by adding the resin particles having a volume-based median diameter of 60 nm to 110 nm in the dispersion of the core particles. The resin contained in the core particles constituting the toner and the resin particles forming the shell are formed using a polymerizable monomer having at least a carboxyl group,
The ratio of the content of the polymerizable monomer having a carboxyl group of the resin particle forming the shell to the content of the polymerizable monomer having a carboxyl group of the resin contained in the core particle is 1.5 or more and 3 The toner production method according to claim 1, wherein the toner production method is 0.0 or less. A core-shell toner having a shell formed by adding resin particles around core particles containing at least a resin and a colorant,
The toner is obtained by adding a resin particle having a volume-based median diameter of 60 nm or more and 110 nm or less to form a shell when the average circularity of the core particles is 0.87 or more.
A toner characterized in that a thickness of the shell constituting the toner is 30 nm or more and 80 nm or less.

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