JP6504132B2 - Toner for developing electrostatic latent image and method for producing the same - Google Patents

Description

  The present invention relates to a toner for electrostatic latent image development and a method for producing the same.

  A toner including a plurality of toner particles including a core and a shell layer covering the surface of the core is known (see, for example, Patent Document 1). In the toner particles described in Patent Document 1, the degree of circularity is sufficiently high, and the surface unevenness is small. Therefore, sufficient transportability of toner particles and sufficient resolution of an image can be realized.

JP 2004-294469 A

  When forming an image, first, the charging device and the exposure device of the image forming apparatus form an electrostatic latent image on the photosensitive member based on the image data. In the vicinity of the photosensitive member, a developing roller is disposed. The toner is supplied from the surface of the developing roller to the photosensitive member and adheres to the electrostatic latent image formed on the photosensitive member. Thus, a toner image is formed on the photoreceptor. The toner image is transferred to an intermediate transfer member and then transferred to a recording medium (for example, printing paper). Thus, an image is formed on the recording medium. Thereafter, a toner remaining on the photosensitive member is removed by a cleaning unit represented by a cleaning blade.

  Patent Document 1 describes toner particles having a high degree of circularity, but toner particles having a high degree of circularity easily slip through the cleaning portion. The toner particles that have slipped through the cleaning portion remain on the photosensitive member without being removed from the photosensitive member. Thus, if the toner particles have a high degree of circularity, the cleaning performance is reduced. Therefore, in order to improve the cleaning property, it is preferable that the circularity of the toner particles be low.

  On the other hand, when the circularity of the toner particles is lowered, the contact area between the toner particles and the object with which the toner particles are in contact increases. Therefore, the adhesion between the toner particles and the object in contact with the toner particles is increased. The objects with which the toner particles come in contact include, for example, a developing roller, a photoreceptor, an intermediate transfer member, and other toner particles. If the adhesion between the toner particles and the developing roller, the photosensitive member, and the intermediate transfer member is increased, the developability is lowered. In addition, if the adhesion between toner particles is increased, the heat resistant storage stability of the toner particles is lowered.

  Specifically, when the adhesion between the toner particles and the developing roller is increased, the adhesion state of the toner particles to the developing roller is maintained even when the toner is supplied from the surface of the developing roller to the photosensitive member. Therefore, toner particles are difficult to be supplied from the surface of the developing roller to the photosensitive member, and the formation of a toner image on the photosensitive member is inhibited. As a result, the developability is reduced.

  If the adhesion between the toner particles and the photosensitive member is increased, the adhesion of the toner particles to the photosensitive member is maintained even when the toner image is transferred from the photosensitive member onto the intermediate transfer member. Therefore, transfer to the intermediate transfer member is inhibited, resulting in a decrease in developability.

  When the adhesion between the toner particles and the intermediate transfer member is increased, the adhesion state of the toner particles to the intermediate transfer member is maintained even when the toner image is transferred from the intermediate transfer member to the recording medium. As a result, transfer to the recording medium is inhibited, leading to a decrease in developability.

  When the adhesion between toner particles is increased, aggregation of toner particles is likely to occur. Here, the aggregation of the toner particles is remarkable when the toner containing a plurality of toner particles or the developer containing a plurality of toner particles is stored at a temperature higher than room temperature. Therefore, if the adhesion between toner particles is increased, the heat resistant storage stability of the toner particles is reduced.

  As described above, the cleaning property and the developability are in a trade-off relationship. Also, the cleaning property and the heat resistant storage stability of toner particles are in a trade-off relationship. Therefore, it is difficult to simultaneously achieve the improvement of the cleaning property, the improvement of the developing property, and the improvement of the heat resistant storage stability of the toner particles. However, the realization is desired.

  The present invention has been made in view of such circumstances, and the object of the present invention is to maintain the cleaning property and the heat-resistant storage stability of toner particles high, and maintain the developability in an appropriate state. It is providing a toner for developing a latent image. Another object of the present invention is to provide a method for producing a toner for developing an electrostatic latent image, which can maintain high cleaning performance and heat-resistant storage stability of toner particles and maintain developability in an appropriate state. .

The toner for developing an electrostatic latent image according to the present invention includes a plurality of toner particles including a core and a shell layer covering the surface of the core. A plurality of first recesses are formed on the surface of the core. The shell layer is present in both the inner region of the first recess and the outer region of the first recess in the surface region of the core. A second recess corresponding to the first recess is formed on the surface of the toner particle. The circularity of the toner particles is 0.960 or more and 0.970 or less. The number of the second recesses present on the surface of the toner particle is 0.300 or more and 0.500 or less per 1 μm ² of the surface area of the toner particle. The opening area of the second recess is 1.0 μm ² or less.

  The method for producing a toner for developing an electrostatic latent image according to the present invention comprises the steps of preparing an aqueous medium containing a core and a shell material and having a pH of 3 or more and 6 or less, and the temperature of the prepared aqueous medium. And a step of maintaining the temperature of the aqueous medium at the target temperature after the end of the temperature raising step. The core contains a non-crystalline polyester resin having a softening point equal to or lower than the target temperature, and a non-crystalline polyester resin having a softening point higher than the target temperature. The temperature raising step further includes the step of changing the pH of the aqueous medium to 8 or more and 12 or less when the temperature of the aqueous medium reaches a pH change temperature. The pH change temperature is lower than the target temperature.

  According to the present invention, the cleaning property and the heat resistant storage stability of the toner particles can be maintained high, and the developability can be maintained in an appropriate state.

FIG. 3 is a view showing an example of the cross-sectional structure of toner particles contained in the electrostatic latent image developing toner according to the embodiment of the present invention. FIG. 2 is a plan view showing a partial region of the surface region of the toner particle shown in FIG. 1; It is the III-III sectional view in FIG.

  Embodiments of the present invention will be described. The evaluation results (values indicating the shape, physical properties, etc.) of the toner core, toner base particles, external additive, or toner are the number average of the values measured for a considerable number of particles unless otherwise specified.

The number average particle diameter of the powder is the number average value of the circle equivalent diameter of the primary particles (diameter of a circle having the same area as the projected area of the particles) measured using a microscope if nothing is specified. . In addition, if the measured value of the volume median diameter (D ₅₀ ) of the powder is not specified at all, the Coulter principle (pore electrical resistance method) using “Coulter Counter Multisizer 3” manufactured by Beckman Coulter, Inc. It is the value measured based on

  The measured value of each of an acid value and a hydroxyl value is a value measured according to "JIS (Japanese Industrial Standard) K0070-1992", if it does not prescribe at all. Moreover, each measured value of a number average molecular weight (Mn) and a mass average molecular weight (Mw) is a value measured using gel permeation chromatography, if it does not prescribe at all. Further, the glass transition point (Tg) and the melting point (Mp) are values measured using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) unless otherwise specified. Further, the softening point (Tm) is a value measured using a Koka-type flow tester ("CFT-500D" manufactured by Shimadzu Corporation) unless otherwise specified.

  Hereinafter, “system” may be added after the compound name to generically generically refer to the compound and its derivative. When a “system” is added after the compound name to represent a polymer name, it means that the repeating unit of the polymer is derived from the compound or its derivative. Moreover, acryl and methacryl may be generically called "(meth) acryl" generically.

[Configuration of electrostatic latent image developing toner according to the present embodiment]
The electrostatic latent image developing toner according to the present embodiment (hereinafter sometimes referred to as toner) contains a plurality of toner particles. Such toners can be used, for example, in forming an image in an electrophotographic apparatus. Hereinafter, the toner according to the exemplary embodiment will be further described after an example of an image forming method using an electrophotographic apparatus is described.

  First, a charging device and an exposure device of an electrophotographic apparatus form an electrostatic latent image on a photosensitive member based on image data. Next, the formed electrostatic latent image is developed using a developer containing toner.

  In the developing step, the developing sleeve of the developing roller disposed in the vicinity of the photosensitive member attracts the toner by the magnetic force of the magnet roll incorporated in the developing roller. Thus, the toner is carried on the surface of the developing roller. Then, the toner on the developing sleeve is supplied to the photosensitive member by the rotation of the developing sleeve. As a result, toner adheres to the electrostatic latent image formed on the photosensitive member, and a toner image is formed on the photosensitive member.

  In the subsequent transfer step, after the toner image on the photosensitive member is transferred to the intermediate transfer member, the toner image on the intermediate transfer member is further transferred to the recording medium. Thereafter, the fixing device heats and presses the toner to fix the toner on the recording medium. As a result, an image is formed on the recording medium. For example, a full color image can be formed by superposing four color toner images of black, yellow, magenta and cyan. After the image is formed, the toner remaining on the photosensitive member is removed by a cleaning unit represented by a cleaning blade.

The description will be returned to the toner according to the present embodiment. The toner according to the present embodiment includes a plurality of toner particles including a core and a shell layer covering the surface of the core. A plurality of first recesses are formed on the surface of the core. The shell layer is present in both the inner region of the first recess and the outer region of the first recess in the surface region of the core. A second recess corresponding to the first recess is formed on the surface of the toner particle. The circularity of the toner particles is 0.960 or more and 0.970 or less. The number of second recesses present on the surface of the toner particle is 0.300 or more and 0.500 or less per 1 μm ² of the surface area of the toner particle. The opening area of the second recess is 1.0 μm ² or less, preferably 0.8 μm ² or less.

In the present embodiment, a hole having a depth of 100 nm or more is referred to as a “recess”, in order to distinguish minute irregularities on the surface of the toner core that are naturally formed unintentionally from the first recess and the second recess. Further, “the opening area of the second recess is 1.0 μm ² or less” means that the opening area of each of the plurality of second recesses formed in the toner is 1.0 μm ² or less. Therefore, “the opening area of the second recess is 1.0 μm ² or less” can be put another way as “the maximum value of the opening area of the second recess is 1.0 μm ² ”. The same can be said for “the opening area of the second recess is 0.8 μm ² or less”. Moreover, below, a "1st recessed part" is described as a "base recessed part", and a "2nd recessed part" is described as a "surface recessed part." In the following, "core" may be described as "toner core".

  The toner according to the exemplary embodiment includes a plurality of toner particles having the above configuration. As described above, in the toner according to the exemplary embodiment, the circularity of the toner particles, the number of surface recesses per unit area of the surface area of the toner particles, and the opening area of the surface recesses are optimized. Thus, the cleaning property and the heat resistant storage stability of the toner particles can be maintained high, and the developability can be maintained in an appropriate state.

  Specifically, the circularity of the toner particles is 0.960 or more and 0.970 or less, which is relatively low. Thus, when cleaning the surface of the photosensitive member after image formation, it is possible to prevent the toner particles contained in the toner according to the exemplary embodiment from slipping through the cleaning unit. Thus, after the image formation, the toner remaining on the photosensitive member is removed by the cleaning unit. Therefore, the cleaning property can be maintained high.

Further, the number of surface depressions present on the surface of the toner particle is 0.300 or more and 0.500 or less per 1 μm ² of the surface area of the toner particle, and the opening area of the surface depression is 1.0 μm ² or less . Here, in the portion of the surface of the toner particle where the surface concave portion is formed, the toner particle is hard to contact the object with which the toner particle contacts. Therefore, by forming the surface recesses on the surface of the toner particles, the contact area between the toner particles and the object with which the toner particles are in contact can be reduced. Therefore, the adhesion between the toner particles and the object in contact with the toner particles can be reduced. Here, examples of the object with which the toner particles come in contact include a developing roller, a photosensitive member, an intermediate transfer member, and other toner particles.

  If the adhesion between the toner particles and the developing roller is small, the toner particles detach from the developing roller and scatter to the photosensitive member when forming a toner image. Thereby, a toner image is formed on the photosensitive member. Therefore, in spite of the relatively low value of the circularity of the toner particles of 0.960 or more and 0.970 or less, the developability can be maintained in an appropriate state. That is, it is possible to maintain the developability in an appropriate state while maintaining high cleanability.

  If the adhesion between the toner particles and the photosensitive member is small, at the time of transferring the toner image to the intermediate transfer member, the toner particles contained in the toner image are detached from the photosensitive member and move to the intermediate transfer member. Thus, the toner image is transferred to the intermediate transfer member. Therefore, in spite of the relatively low value of the circularity of the toner particles of 0.960 or more and 0.970 or less, the developability can be maintained in an appropriate state. That is, it is possible to maintain the developability in an appropriate state while maintaining high cleanability.

  If the adhesion between the toner particles and the intermediate transfer member is small, at the time of transfer of the toner image to the recording medium, the toner particles contained in the toner image detach from the intermediate transfer member and move to the recording medium. Thus, the toner image is transferred to the recording medium. Therefore, in spite of the relatively low value of the circularity of the toner particles of 0.960 or more and 0.970 or less, the developability can be maintained in an appropriate state. That is, it is possible to maintain the developability in an appropriate state while maintaining high cleanability.

  When the adhesion between toner particles is small, the aggregation of toner particles can be prevented. Therefore, even when the toner containing a plurality of toner particles or the developer containing a plurality of toner particles is stored at a temperature higher than room temperature, the aggregation of the toner particles can be prevented. Therefore, despite the relatively low value of the circularity of the toner particles of 0.960 or more and 0.970 or less, the heat resistant storage stability of the toner particles can be maintained high. That is, the heat resistance storage stability of the toner particles can be maintained high while maintaining high cleaning performance. In the following, storing a toner containing a plurality of toner particles or a developer containing a plurality of toner particles at a temperature higher than room temperature is referred to as "storing a plurality of toner particles at a high temperature".

As described above, in the portion of the surface of the toner particle where the surface concave portion is formed, the toner particle is difficult to contact the object with which the toner particle contacts. Therefore, if the number of surface depressions present on the surface of the toner particle is less than 0.300 per 1 μm ² of the surface area of the toner particle, the contact area between the toner particle and the object contacting the toner particle is sufficiently small. It is difficult to do. As a result, the adhesion between the toner particles and the object in contact with the toner particles is increased. As a result, the developability is lowered. In addition, the heat resistant storage stability of toner particles is lowered.

In addition, when the number of surface depressions present on the surface of the toner particle is more than 0.500 per 1 μm ² of the surface area of the toner particle, it becomes difficult to maintain the heat-resistant storage stability of the toner particle high.

In addition, if the opening area of the surface concave portion exceeds 1.0 μm ² , it is difficult to reduce the adhesion between the toner particles and the object with which the toner particles are in contact. Therefore, it becomes difficult to maintain developability in an appropriate state. In addition, it becomes difficult to maintain the heat-resistant storage stability of the toner particles high.

  The circularity of the toner particles is measured using a flow type particle image analyzer (for example, "FPIA (registered trademark) -3000" manufactured by Sysmex Corporation).

  As an object to be measured, toner particles after the external addition treatment may be used, or toner base particles may be used. Here, the toner particles after the external addition treatment mean toner particles including toner base particles and an external additive attached to the surface of the toner base particles. Also, the toner base particles can be said to be toner particles before the external additive treatment.

  When the toner particles contain an external additive, the circularity of the toner particles means the circularity of the toner base particles. When toner particles after external addition processing are used as the measurement target, the degree of circularity of the toner particles may be measured while avoiding the external additive. When toner base particles are used as the measurement target, toner particles before the external addition treatment may be used, or toner particles after the external addition treatment may be subjected to pretreatment. As pretreatment for the toner particles after the external addition treatment, for example, an external additive is dissolved using an alkaline solution, and an external additive is detached from the surface of the toner base particles using an ultrasonic cleaner. It can be mentioned. These items regarding the object to be measured are when measuring the opening area of the surface recess, the number of surface recesses per unit area of the surface area of the toner particles, the overall shell coverage described later, and the recess shell coverage described later. Also applies.

In addition, the opening area of the surface concave portion is determined using a field emission scanning electron microscope (FE-SEM, for example, “JSM-7600F” manufactured by JEOL Ltd.). It is determined by observing. According to the same method, the number of surface recesses per unit area of the surface area of toner particles can be determined. When the opening area of the surface concave portion is measured according to such a method, the measurement lower limit value is 0.005 μm ² . Therefore, the lower limit of the opening area of the surface recess is 0.005 μm ² .

  Hereinafter, an example of the configuration of toner particles contained in the toner according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a view showing an example of the cross-sectional structure of toner base particles 10 contained in toner particles. FIG. 2 is a plan view showing a partial region of the surface region of toner mother particle 10 shown in FIG. FIG. 3 is a cross-sectional view taken along the line III-III in FIG.

  The toner base particle 10 shown in FIG. 1 includes a toner core 11 and a shell layer 12 covering the surface of the toner core 11. The shell layer 12 partially covers the surface of the toner core 11.

As shown in FIGS. 2 and 3, base recesses H 4 and H 11 to H 13 are formed on the surface of the toner core 11. The shell layer 12 is present in the outer region of the base recesses H4 and H11 to H13, the inner region of the base recess H12, and the inner region of the base recess H13 in the surface region of the toner core 11. However, the shell layer 12 is not present in the inner region of the base recess H4 and the inner region of the base recess H11. Therefore, on the surface of the toner base particle 10, a base recess H4, a base recess H11, a surface recess H22 corresponding to the base recess H12, and a surface recess H23 corresponding to the base recess H13 are formed. The circularity of the toner base particle 10 is 0.960 or more and 0.970 or less. Further, the number of surface depressions per unit area of the surface area of toner mother particle 10 is 0.300 / μm ² or more and 0.500 / μm ² or less, and the opening area of the surface depressions is 1.0 μm ² or less is there.

  FIG. 3 shows a state in which the resin particles contained in the shell layer 12 are connected to form a film. However, at a part of the shell layer 12, the resin particles contained in the shell layer 12 may remain spherical. In addition, when the resin particles contained in the shell layer 12 are connected to form a film, the resin particles may be flattened. The shell layer 12 may contain such flat resin particles.

  In FIG. 3, regarding the base recess H11, the range R1 indicates the range of the inner region of the base recess H11, and the depth D1 indicates the depth of the base recess H11. Further, regarding the base recess H13, the range R3 indicates the range of the inner region of the base recess H13, and the depth D3 indicates the depth of the surface recess H23 corresponding to the base recess H13. An example of the configuration of toner particles contained in the toner according to the exemplary embodiment has been described above with reference to FIGS. 1 to 3.

(Preferred Configuration of Toner According to the Embodiment)
Hereinafter, preferable configurations of the toner according to the exemplary embodiment will be shown.
Preferably, in the surface area of the toner core, the ratio of the area of the toner core covered by the shell layer (hereinafter referred to as the total shell coverage) is 30% or more and 80% or less. Here, the shell layer is more heat resistant than the toner core. Therefore, even if heat is applied to the toner at the time of image formation, melting of the shell layer in the surface area of the toner core can be prevented. This makes it possible to prevent the disappearance of the surface depression due to the melting of the shell layer in the surface area of the toner core. That is, it can prevent that the opening area of a surface recessed part becomes small. Therefore, the contact area between each of the developing roller, the photosensitive member, and the intermediate transfer member and the toner particles can be kept small, so that the adhesion of the toner particles to each of the developing roller, the photosensitive member, and the intermediate transfer member can be kept small. Therefore, even when heat is applied to the toner at the time of image formation, the developability can be maintained in an appropriate state.

  In addition, since it is possible to prevent the opening area of the surface concave portion from being reduced even when heat is applied to the toner, the contact area between toner particles can be maintained further smaller even when a plurality of toner particles are stored at high temperature. As a result, the adhesion between toner particles can be kept smaller, and therefore, the aggregation of toner particles can be further prevented. Thus, the heat resistant storage stability of the toner particles is improved.

  Preferably, the ratio of the area of the inner region covered by the shell layer in the inner region of the base recess (hereinafter, referred to as the recess shell coverage) is 30% or more and 80% or less. As described above, the shell layer is more heat resistant than the toner core. Therefore, even if heat is applied to the toner at the time of image formation, it is possible to prevent melting of the shell layer in the inner region of the base recess. Thereby, the disappearance of the surface recess due to the melting of the shell layer in the inner region of the base recess can be prevented. That is, it can prevent that the opening area of a surface recessed part becomes small. Therefore, the contact area between each of the developing roller, the photosensitive member, and the intermediate transfer member and the toner particles can be kept small, so that the adhesion of the toner particles to each of the developing roller, the photosensitive member, and the intermediate transfer member can be kept small. Therefore, even when heat is applied to the toner at the time of image formation, the developability can be maintained in an appropriate state.

  In addition, since it is possible to prevent the opening area of the surface concave portion from being reduced even when heat is applied to the toner, the contact area between toner particles can be maintained further smaller even when a plurality of toner particles are stored at high temperature. As a result, the adhesion between toner particles can be kept smaller, and therefore, the aggregation of toner particles can be further prevented. Thus, the heat resistant storage stability of the toner particles is improved.

More preferably, the area difference obtained by subtracting the overall shell coverage from the recessed shell coverage is −5% or more and 5% or less. In such a toner, the difference between the coverage of the shell layer in the inner region of the base recess and the coverage of the shell layer in the outer region of the base recess is small. Therefore, even when the toner is used for a long time, it is possible to prevent the deterioration of the toner from locally advancing in either the inner region of the surface recess or the outer region of the surface recess. Thus, the excellent characteristics of the toner can be maintained for a long time. More preferably, the area difference obtained by subtracting the overall shell coverage from the recessed shell coverage is -3% or more and 3% or less. Here, the area difference obtained by subtracting the overall shell coverage from the concave shell coverage is calculated by the following equation.
(Area difference) (unit:%) = (recessed shell coverage) (unit:%)-(total shell coverage) (unit:%)

  The total shell coverage (unit:%) is represented by the formula “total shell coverage = 100 × area of surface area of toner core covered by shell layer / area of entire surface of toner core”. An overall shell coverage of 100% means that the entire surface of the toner core is covered with a shell layer. The method of measuring the overall shell coverage is the same method as the embodiment described later or an alternative method thereof.

  The concave shell coverage (unit:%) is expressed by the formula “concave shell coverage = 100 × area of inner region of base recess covered by shell layer / area of entire inner region of base recess”. The concave shell coverage of 100% means that the entire inner region of the base concave portion is covered with the shell layer. The method of measuring the recess shell coverage is the same method as the embodiment described later or an alternative method thereof.

  Preferably, the thickness of the shell layer is 1 nm or more and 50 nm or less. Here, the depth of the base recess is 100 nm or more. Therefore, if the thickness of the shell layer is 1 nm or more and 50 nm or less, the thickness of the shell layer is sufficiently smaller than the depth of the base recess. Thus, the surface recesses are easily formed. Therefore, the effect obtained by the formation of the surface concave portion can be easily obtained. That is, the developability can be easily maintained in an appropriate state, and the heat resistant storage stability of the toner particles is further improved.

  If the thickness of the shell layer is sufficiently smaller than the depth of the base recess, it is considered that the depth of the surface recess is approximately the same as the depth of the base recess. Therefore, when the depth of the base recess is 100 nm or more and the thickness of the shell layer is 1 nm or more and 50 nm or less, the depth of the surface recess is 100 nm or more. Moreover, in order to ensure sufficient formation easiness of the surface recess, the depth of the base recess is preferably 3 μm or less.

  The thickness of the shell layer means the size of the shell layer in the radial direction of the toner particles, and is measured according to the following method. First, a cross-sectional TEM photograph of toner particles is taken using a transmission electron microscope (TEM, for example, “H-7100 FA” manufactured by Hitachi High-Technologies Corporation). Next, a cross-sectional TEM photograph of the obtained toner particles is analyzed using image analysis software (for example, "WinROOF" manufactured by Mitani Corporation). Specifically, two orthogonal straight lines are drawn at the approximate center of the cross section of the toner particles. In each of the two straight lines, the length from the interface between the toner core and the shell layer (corresponding to the surface of the toner core) to the surface of the shell layer is measured. The average value of the four lengths measured in this manner is taken as the thickness of the shell layer included in one toner particle. Such thickness measurement of the shell layer is performed on a plurality of toner particles, and an average value of the thickness of the shell layer included in the plurality of toner particles (measurement target) is obtained. The average value of the thickness of the shell layer determined in this manner is taken as "the thickness of the shell layer".

  When the boundary between the toner core and the shell layer is unclear in the cross-sectional TEM photograph of the toner particle, the cross-sectional TEM photograph of the toner particle is used as an electron energy loss spectroscopy (EELS) detector (for example, "GIF TRIDIEM" manufactured by Gatan Co., Ltd.). It is preferable to analyze using (registered trademark) "and image analysis software (for example," WinROOF "manufactured by Mitani Corporation). As a result, the boundary between the toner core and the shell layer becomes clear in the cross-sectional TEM photograph of the toner particles, so that the thickness of the shell layer can be determined.

  The configuration of the toner according to the present embodiment and the preferable configuration of the toner according to the present embodiment have been described above. The toner particles contained in the toner according to the exemplary embodiment may be toner particles after the external addition treatment, or may be toner base particles. In addition, the toner according to the exemplary embodiment may include both the toner particles after the external addition treatment and the toner base particles. Further, the toner according to the present embodiment may include toner particles not having a shell layer. Hereinafter, preferable materials of the resin contained in the toner core and preferable materials of the resin contained in the shell layer are shown in order.

(Preferred Material of Resin Contained in Toner Core)
Preferably, the toner core contains a non-crystalline polyester resin having a softening point of 80 ° C. or less and a non-crystalline polyester resin having a softening point of 100 ° C. or more. Here, a non-crystalline polyester resin having a softening point of 80 ° C. or less hydrolyzes at a low temperature as compared to a non-crystalline polyester resin having a softening point of 100 ° C. or more. Therefore, when the toner core contains the non-crystalline polyester resin having a softening point of 80 ° C. or less, the formation of the base concave portion is promoted. Thus, the toner according to the present embodiment can be easily manufactured. For example, of the resin contained in the toner core, the proportion occupied by the non-crystalline polyester resin having a softening point of 80 ° C. or less is preferably 20% by mass or more. This will be described in detail in (Temperature raising step: pH change step) of the following [Production of toner according to the present embodiment].

  Further, when the toner core contains a non-crystalline polyester resin having a softening point of 100 ° C. or more, the heat resistance of the toner core is enhanced. Therefore, even when a plurality of toner particles are stored at high temperature, melting of the toner core can be further prevented. Thus, the heat resistant storage stability of the toner particles is further improved. For example, in the resin contained in the toner core, the proportion of the non-crystalline polyester resin having a softening point of 100 ° C. or more is preferably 5% by mass or more.

  The proportion of the non-crystalline polyester resin having a softening point of 100 ° C. or more in the resin contained in the toner core is preferably 50% by mass or less. Thus, when the resin contained in the toner core is composed of the non-crystalline polyester resin having a softening point of 80 ° C. or less and the non-crystalline polyester resin having a softening point of 100 ° C. or more, among the resins contained in the toner core The proportion of the non-crystalline polyester resin having a softening point of 80 ° C. or less is 50% by mass or more. Therefore, fixation at low temperature can be realized.

  In summary, among the resins contained in the toner core, the proportion occupied by the non-crystalline polyester resin having a softening point of 80 ° C. or less is preferably 20% by mass or more, and more preferably 20% by mass to 95% by mass More preferably, they are 20 mass% or more and 50 mass% or less. The proportion of the non-crystalline polyester resin having a softening point of 100 ° C. or more in the resin contained in the toner core is preferably 5% by mass or more, more preferably 5% by mass to 80% by mass. More preferably, it is 5% by mass or more and 50% by mass or less.

  When the toner core contains a non-crystalline polyester resin, the non-crystalline polyester resin preferably has a number average molecular weight (Mn) of 1,000 or more and 2,000 or less. This improves the strength of the toner core and the fixability of the toner. The molecular weight distribution of the non-crystalline polyester resin is preferably 9 or more and 21 or less. Here, the molecular weight distribution of the non-crystalline polyester resin means the ratio (Mw / Mn) of mass average molecular weight (Mw) to number average molecular weight (Mn).

  More preferably, the toner core contains a crystalline polyester resin in addition to the non-crystalline polyester resin. Here, crystalline polyester resins are more susceptible to hydrolysis than non-crystalline polyester resins. Therefore, when the toner core contains the crystalline polyester resin in addition to the non-crystalline polyester resin, the hydrolysis of the polyester resin contained in the toner core is promoted. Thus, the formation of the base recess is further promoted. For example, the toner core preferably further comprises 1 to 20 parts by mass of a crystalline polyester resin, more preferably 3 to 10 parts by mass, per 100 parts by mass of the non-crystalline polyester resin. Further contains a water-soluble polyester resin.

  More preferably, the toner core contains a crystalline polyester resin having a crystallinity index of 0.98 or more and 1.20 or less. This further accelerates the hydrolysis of the polyester resin contained in the toner core. Thus, the formation of the base recess is further promoted. Here, the crystallinity index corresponds to the ratio of the softening point (Tm) to the melting point (Mp) (= Tm / Mp). The crystallinity index of the polyester resin can be adjusted by changing the type or amount of material for synthesizing the polyester resin. For example, the crystallinity index of the polyester resin can be adjusted by changing the type or amount of at least one of alcohol and carboxylic acid. In addition, about non-crystalline polyester resin, clear Mp can not often be measured.

  Specific examples of the polyester resin contained in the toner core will be described in (Binder resin: polyester resin) in the following [Examples of materials of toner core, shell layer, and external additive]. In addition, the toner core may further contain the thermoplastic resin described in (Binder resin: thermoplastic resin) of the following [examples of materials of toner core, shell layer, and external additive].

(Preferred material of resin contained in shell layer)
Preferably, the shell layer contains a thermoplastic resin. This further improves the heat resistant storage stability of the toner particles. More preferably, the shell layer further contains a thermosetting resin in addition to the thermoplastic resin. Specific examples of the resin contained in the shell layer include (shell layer: thermoplastic resin) and (shell layer: thermosetting resin) of the following [examples of materials of toner core, shell layer, and external additive] Describe.

[Production of Toner According to the Present Embodiment]
The production of the toner according to the present embodiment is not particularly limited. For example, a method is conceivable in which after forming the base recess on the surface of the toner core, a shell layer is formed on the surface of the toner core on which the base recess is formed. However, in this method, it is difficult to manufacture the toner according to the present embodiment. Specifically, it is difficult for the shell layer to be formed in the inner region of the base recess. In addition, when the thickness of the shell layer is increased in order to ensure sufficient adhesive strength between the inner region of the base recess and the shell layer, the recess is difficult to be formed on the surface of the toner particles after the formation of the shell layer. That is, it is difficult to form the surface recess.

  Another possible method is to form a shell layer on the surface of the toner core and then form a base recess on the surface of the toner core. However, even with this method, it is difficult to form the shell layer in the inner region of the base recess. Therefore, it is difficult to manufacture the toner according to the present embodiment.

  The inventor diligently studied a method capable of easily producing the toner according to the present embodiment, and reached the following conclusion. The pH of the liquid is adjusted while raising the temperature of the liquid containing the toner core and the material of the shell layer (hereinafter referred to as the shell material) to a predetermined target temperature. Thereby, the formation of the base recess on the toner core and the formation of the shell layer proceed simultaneously. As a result, the toner according to the present embodiment is obtained.

  That is, the electrostatic latent image developing toner according to the exemplary embodiment includes the preparation process of the aqueous medium, the temperature raising process, and the heat retention process. In the aqueous medium preparation step, an aqueous medium containing a core and a shell material and having a pH of 3 or more and 6 or less is prepared. In the temperature raising step, the temperature of the prepared aqueous medium is raised to a predetermined target temperature. In the heat retention step, the temperature of the aqueous medium is maintained at the target temperature after completion of the temperature raising step. The core is a non-crystalline polyester resin (hereinafter referred to as LTm-non-crystalline polyester resin) having a softening point equal to or lower than a target temperature, and a non-crystalline polyester resin (hereinafter referred to as HTm) having a softening point higher than the target temperature. -Described as a non-crystalline polyester resin). The temperature raising step includes a pH change step. In the pH change step, when the temperature of the aqueous medium reaches the pH change temperature, the pH of the aqueous medium is changed to 8 or more and 12 or less. The pH change temperature is lower than the target temperature.

  In the toner manufacturing method according to the present embodiment, the formation of the base concave portion and the formation of the shell layer, which are caused by the hydrolysis of the polyester resin, proceed simultaneously. Therefore, the shell layer is formed not only in the outer region of the base recess but also in the inner region of the base recess. Thus, the toner according to the present embodiment can be easily manufactured. Hereinafter, the method of manufacturing the toner according to the exemplary embodiment will be further described based on more specific examples.

(Preferred Method of Manufacturing Toner According to the Embodiment)
A preferred method of manufacturing the toner according to the present embodiment includes a preparation step of the toner core and a formation step of the shell layer. A preferred method of producing a toner according to the present embodiment may further include at least one of a filtration step, a washing step, a drying step, and an external addition step.

(Toner core preparation process)
It is preferable to produce the toner core by the aggregation method or the pulverization method. Thereby, the toner core can be easily obtained.

  Hereinafter, an example of the pulverization method will be described. First, the binder resin and the internal additive are mixed. As the internal additive, for example, at least one of a colorant, a release agent, a charge control agent, and a magnetic powder can be used. Subsequently, the obtained mixture is melt-kneaded. Subsequently, the obtained melt-kneaded product is crushed and classified. As a result, a toner core having a desired particle size is obtained.

  Hereinafter, an example of the aggregation method will be described. First, these particles are coagulated to a desired particle size in an aqueous medium containing fine particles of each of a binder resin, a release agent, and a colorant. Thereby, aggregated particles including the binder resin, the release agent, and the colorant are formed. Subsequently, the obtained aggregated particles are heated to unite the components contained in the aggregated particles. As a result, a dispersion of the toner core is obtained. Thereafter, unnecessary substances are removed from the dispersion of the toner core. Unwanted substances include surfactants. In this way, a toner core having a desired particle size is obtained.

  Regardless of the method of producing the toner core, the binder resin used contains an LTm-noncrystalline polyester resin and an HTm-noncrystalline polyester resin. Thereby, a toner core containing the LTm-noncrystalline polyester resin and the HTm-noncrystalline polyester resin is manufactured. The binder resin preferably contains 20% by mass or more of LTm-noncrystalline polyester resin, more preferably 20% by mass to 95% by mass of LTm-noncrystalline polyester resin, and still more preferably 20% by mass. It contains not less than 50% by mass of LTm-noncrystalline polyester resin. The binder resin preferably contains 5% by mass or more of HTm-noncrystalline polyester resin, more preferably 5% by mass to 80% by mass of HTm-noncrystalline polyester resin, and more preferably Contains 5% by weight or more and 50% by weight or less of HTm-noncrystalline polyester resin. The binder resin preferably further contains a crystalline polyester resin. In addition, as LTm-non-crystalline polyester resin, the non-crystalline polyester resin of 80 degrees C or less of softening points can be used, for example. Moreover, as HTm-polyester resin, the non-crystalline polyester resin of 100 degreeC or more of softening points can be used, for example.

(Step of forming shell layer)
The step of forming the shell layer includes the step of preparing the aqueous medium, the step of raising the temperature, and the step of keeping the temperature. The temperature raising step includes a pH change step.

(Formation process of shell layer: Preparation process of aqueous medium)
In the aqueous medium preparation step, first, an aqueous medium is prepared.
The aqueous medium is a medium containing water as a main component, and is, for example, pure water or a mixed solution of water and a polar medium. The aqueous medium may function as a solvent. The solute may be dissolved in the aqueous medium. The aqueous medium may function as a dispersion medium. The dispersoid may be dispersed in the aqueous medium. For example, an alcohol can be used as the polar medium in the aqueous medium, and methanol or ethanol can be used as the alcohol. The boiling point of the aqueous medium is preferably about 100.degree. More preferably, ion exchange water is prepared as an aqueous medium.

  Subsequently, the pH of the aqueous medium is adjusted to a predetermined pH using an acidic substance. For example, the pH of the aqueous medium is adjusted to 3 or more and 6 or less using hydrochloric acid. Subsequently, the toner core obtained according to the method described above and the shell material are added to an aqueous medium adjusted to a pH of 3 or more and 6 or less. As the amount of addition of the shell material is increased, the thickness of the formed shell layer tends to be thicker.

  It is believed that adding the toner core and shell material to the aqueous medium causes the particles of the shell material to adhere to the surface of the toner core in the aqueous medium. When a suspension containing particles made of a non-water-soluble thermoplastic resin is used as a shell material, it is considered that particles made of a non-water-soluble thermoplastic resin adhere to the surface of the toner core.

  Further, by forming the shell layer in an aqueous medium, it is possible to suppress the dissolution or elution of the toner core component at the time of forming the shell layer. Specifically, by forming the shell layer in an aqueous medium, it is possible to suppress the dissolution or elution of the binder resin and the release agent at the time of forming the shell layer.

  In order to adhere the shell material uniformly to the surface of the toner core, it is preferable to highly disperse the toner core in a liquid containing the shell material. In order to highly disperse the toner core in the liquid, a surfactant may be contained in the liquid, or the liquid may be stirred using a strong stirring device (for example, "Hi-bis-Disper Mix" manufactured by Primix Corporation). May be When the toner core has an anionic property, aggregation of the toner core can be suppressed by using an anionic surfactant having the same polarity. As an anionic surfactant, for example, a sulfate, a sulfonate, a phosphate, or a soap can be used. In this way, an aqueous medium comprising a core and a shell material and having a pH of 3 or more and 6 or less is prepared.

(Formation process of shell layer: heating process)
In the temperature raising step, the temperature of the aqueous medium prepared according to the above method is raised to a predetermined target temperature. Specifically, while stirring the prepared aqueous medium, the temperature of the aqueous medium is raised at a predetermined rate to a predetermined target temperature. The temperature of the aqueous medium at the start of heating is, for example, a temperature selected from 20 ° C. or more and 35 ° C. or less. The pH of the aqueous medium at the start of the temperature rise is, for example, a pH selected from 3 or more and 6 or less. The rate of temperature rise is, for example, a rate selected from 0.1 ° C./min to 3.0 ° C./min. The target temperature for temperature rise is a temperature at which the temperature rise is stopped, and is a temperature selected from, for example, 60 ° C. or more and 70 ° C. or less.

(Heating process: pH change process)
When the temperature of the aqueous medium reaches the pH change temperature during the temperature rise, a pH change step is performed. In the pH change step, when the temperature of the aqueous medium reaches the pH change temperature, the pH of the aqueous medium is changed to 8 or more and 12 or less. For example, by adding a basic substance to the aqueous medium, the pH of the aqueous medium can be changed from an acid value to an alkaline value. As a basic substance, for example, sodium hydroxide can be used. Moreover, it is preferable to change the pH of the aqueous medium in a short time, for example, it is preferable to change the pH of the aqueous medium within 10 seconds.

  It is considered that the base concave portion is formed by performing the pH change step during the temperature rise of the aqueous medium. In order to obtain such an effect, the toner core preferably contains a polyester resin, and more preferably contains an LTm non-crystalline polyester resin.

  In detail, the pH change step is performed during the temperature rise of the aqueous medium. Therefore, after the temperature of the aqueous medium rises to some extent, the pH of the aqueous medium changes from an acid value to an alkaline value. Thereby, it is considered that the hydrolysis of the polyester resin contained in the toner core proceeds. As a result, a base recess is formed in the toner core.

  When the toner core contains an LTm-noncrystalline polyester resin, the LTm-noncrystalline polyester resin is softened when the temperature of the aqueous medium approaches the softening point of the LTm-noncrystalline polyester resin. Here, the softening point of the LTm-noncrystalline polyester resin is equal to or lower than the target temperature for temperature increase. Further, it is considered that the LTm-noncrystalline polyester resin is easily hydrolyzed by softening. From these facts, LTm-non-crystalline polyester resin changes the pH of the aqueous medium during heating (specifically, the pH of the aqueous medium changes from an acid value to an alkaline value during heating) In addition to softening, it is easy to hydrolyze not only by temperature increase but also by softening. Therefore, if the toner core contains an LTm-noncrystalline polyester resin, the resin contained in the toner core is likely to be hydrolyzed during the temperature rise. Therefore, the formation of the base recess is promoted. Preferably, 20% by mass or more of the resins contained in the toner core is an LTm-non-crystalline polyester resin.

  More preferably, the toner core further contains a crystalline polyester resin. As described above, crystalline polyester resins are more susceptible to hydrolysis than non-crystalline polyester resins. Therefore, when the toner core further contains the crystalline polyester resin, the hydrolysis of the resin contained in the toner core is further promoted. Thus, the formation of the base recess is further promoted.

  In addition, the toner core further contains an HTm-polyester resin. Here, the softening point of the HTm-noncrystalline polyester resin is higher than the target temperature for raising the temperature. Therefore, even if the temperature of the aqueous medium approaches the target temperature for temperature increase, it is possible to prevent the entire toner core from being softened. Thus, the aggregation of toner cores can be prevented. Preferably, 5% by mass or more of resins contained in the toner core is an HTm-polyester resin.

  As described above, by performing the pH change step while raising the temperature of the aqueous medium, the base concave portion is formed. Hereinafter, the pH change temperature and the pH of the aqueous medium after the pH change step (hereinafter, referred to as pH after change) will be further described.

(PH change process: pH change temperature)
The pH change temperature is preferably higher than the temperature of the aqueous medium at the start of the temperature rise. As a result, the resin contained in the toner core is easily softened, and thus easily hydrolyzed. Thus, the formation of the base recess is promoted. The pH change temperature is preferably (softening point of LTm-non-crystalline polyester resin) ± 10 ° C., more preferably a temperature selected from 30 ° C. or more and 60 ° C. or less, still more preferably 35 ° C. or more and 55 ° C. or less It is a temperature selected from

(PH change process: pH after change)
The pH after change is 8 or more and 12 or less. If the pH after change is 8 or more, hydrolysis of the resin contained in the toner core proceeds. Thereby, the base recess is formed. If the pH after change is more than 12, hydrolysis of the resin contained in the toner core proceeds excessively. Therefore, the base concave portions are formed excessively, and the number (surface / μm ² ) of the surface concaves per unit area of the surface area of the toner particle may exceed 0.500. In addition, the opening area of the surface recess may be more than 1.0 μm ² .

(Heating process: after pH change process)
Even after the end of the pH change step, the temperature of the aqueous medium is raised to a predetermined target temperature without stopping the temperature rise of the aqueous medium. As a result, the surface of the toner core in which the base recess is formed is covered with the shell material. Therefore, if the temperature rising time after the pH change step is short, the adhesion amount of the shell material on the surface of the toner core decreases. As a result, the formation of the shell layer becomes difficult, and hence the formation of the surface recess becomes difficult. Based on this, it is preferable to set the temperature rising time after the pH change step. The temperature rising time after the pH changing step is changed by changing at least one of the temperature rising speed, the pH change temperature, and the temperature rising target temperature. Therefore, it is preferable to set the rate of temperature rise, the pH change temperature, and the target temperature for temperature rise so that the temperature rise time after the pH change step becomes a desired time. The pH change temperature is preferably lower than the target temperature for temperature increase, and for example, the difference between the pH change temperature and the target temperature for temperature increase is preferably 10 ° C. or more.

  As described above, in the shell layer forming step, the pH change step is performed during the temperature rise of the aqueous medium, and the temperature rise of the aqueous medium is continued even after the pH change step. Thereby, the shell layer is formed on the surface of the toner core including the inner region of the base recess while forming the base recess.

  For example, a suspension containing particles made of a styrene-acrylic acid resin as a shell material is used, the temperature of the aqueous medium at the start of heating in the heating step is 30 ° C., and the heating rate in the heating step is 1 ° C. Take the case of / minute as an example. In this case, it is considered that the surface area of the toner core is sufficiently covered with the shell material when the temperature of the aqueous medium reaches 40.degree. In addition, it is believed that by the time the temperature of the aqueous medium reaches 60 ° C., the shell material starts to be immobilized on the surface of the toner core.

(Heating process)
In the heat retention step, after the temperature raising step is completed, the temperature of the aqueous medium is maintained at the target temperature for raising for a predetermined time. The predetermined time is, for example, a time selected from 30 minutes to 4 hours. By keeping the temperature of the aqueous medium at the target temperature for raising the temperature, it is considered that the reaction proceeds between the shell material adhering to the surface of the toner core and the toner core. The shell material is combined with the toner core to form a shell layer. Specifically, it is considered that a particle-like film (shell layer) is formed by two-dimensionally connecting particles of the shell material on the surface of the toner core. In this way, a dispersion of toner mother particles is obtained.

(Filtration process)
First, cold water is added to the obtained dispersion of toner mother particles, and the contents of the flask are cooled to normal temperature (about 25 ° C.). Subsequently, the dispersion of toner mother particles is filtered using, for example, a Buchner funnel. Thereby, the toner base particles are separated from the liquid, and wet cake-like toner base particles are obtained.

(Washing process, drying process)
The obtained wet cake toner base particles are washed. Subsequently, the washed toner base particles are dried.

(External addition process)
The dried toner base particles and the external additive are mixed using a mixer (for example, an FM mixer manufactured by Nippon Coke Industry Co., Ltd.). This physically bonds the external additive to the surface of the toner base particles. Thus, a toner containing a large number of toner particles is obtained.

  When the washed toner base particles are dried using a spray dryer, it is preferable to spray the dispersion liquid of the external additive on the toner base particles. Thus, the drying of the washed toner base particles and the external additive treatment can be performed simultaneously.

  The contents and order of the above-described toner manufacturing method can be arbitrarily changed in accordance with the required configuration or characteristics of the toner. For example, the shell material may be added to the aqueous medium at one time or may be added to the aqueous medium in multiple portions. After the external addition step, the toner may be sieved. Also, unnecessary steps may be omitted. For example, when a commercially available product can be used as a material as it is, the step of preparing the material can be omitted by using the commercially available product.

  Further, the material of the toner core and the shell material are not limited to the materials described in the following [examples of materials of the toner core, the shell layer, and the external additive], respectively. For example, derivatives of the materials described in the following [exemplification of materials of toner core, shell layer, and external additive] may be used as the material or shell material of the toner core. A prepolymer may be used instead of the monomer. In addition, in order to obtain the materials described in the following [exemplification of materials for each of toner core, shell layer, and external additive], salts, esters, hydrates, or anhydrides of the compounds are used as raw materials. It is also good.

  In addition, in order to produce toner efficiently, it is preferable to simultaneously form a large number of toner particles. The toner particles produced simultaneously are considered to have substantially the same configuration.

[Example of materials of toner core, shell layer, and external additive]
Hereinafter, specific examples of materials of the toner core, the shell layer, and the external additive will be sequentially described.

(Toner core)
The toner core contains a binder resin. The toner core may further contain at least one of a colorant, a release agent, a charge control agent, and a magnetic powder.

(Toner core: Binder resin)
In the toner core, generally, the binder resin occupies most (for example, 85% by mass or more) of the components. Therefore, it is considered that the properties of the binder resin greatly affect the properties of the entire toner core.

  Further, by combining and using plural kinds of resins as the binder resin, the properties of the binder resin (more specifically, the hydroxyl value, the acid value, the Tg, the Tm, etc.) can be adjusted. For example, when the binder resin has an ester group, a hydroxyl group, an ether group, an acid group, or a methyl group, the toner core tends to be anionic. When the binder resin has an amino group or an amide group, the toner core tends to be cationic. In order for the binder resin to have strong anionic property, it is preferable that at least one of the acid value and the hydroxyl value of the binder resin is 10 mg KOH / g or more.

(Binder resin: polyester resin)
The toner core preferably contains the polyester resin shown below.
The polyester resin is obtained by condensation polymerization of one or more alcohols and one or more carboxylic acids. As an alcohol for synthesizing a polyester resin, for example, a dihydric alcohol or a trivalent or higher alcohol shown below can be suitably used. As the dihydric alcohol, for example, diols or bisphenols can be used. As a carboxylic acid for synthesize | combining polyester resin, the bivalent carboxylic acid or trivalent or more carboxylic acid shown below can be used conveniently, for example. If at least one of the alcohol and the carboxylic acid has an aromatic ring in the molecule, the synthesized polyester resin tends to exhibit crystallinity.

  Preferred examples of the diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-butene-1,4 Diol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol or polytetramethylene glycol.

  Preferable examples of bisphenols include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, or bisphenol A propylene oxide adduct.

  Preferred examples of trihydric or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, and 1,2,4-butane. Triol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane or 1,3,5- Trihydroxymethylbenzene is mentioned.

  Preferred examples of the divalent carboxylic acid include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, malonic acid , Succinic acid, alkylsuccinic acid (more specifically, n-butylsuccinic acid, isobutylsuccinic acid, n-octylsuccinic acid, n-dodecylsuccinic acid, or isododecylsuccinic acid, etc.), or alkenylsuccinic acid (more specifically Examples thereof include n-butenylsuccinic acid, isobutenylsuccinic acid, n-octenylsuccinic acid, n-dodecenylsuccinic acid, and isododecenylsuccinic acid).

  Preferred examples of trivalent or higher carboxylic acids include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylene carboxyl) Methane, 1,2,7,8-octane tetracarboxylic acid, pyromellitic acid, or Empol trimer acid can be mentioned.

(Binder resin: Thermoplastic resin)
The toner core may further contain a thermoplastic resin shown below, in addition to the above-mentioned polyester resin.

  As a thermoplastic resin, a styrene resin, acrylic acid resin, an olefin resin, a vinyl resin, a polyamide resin, or a urethane resin can be used suitably, for example. Further, a copolymer of each of these resins, that is, a copolymer in which an arbitrary repeating unit is introduced into the above-mentioned resin can also be suitably used as a thermoplastic resin constituting toner particles. For example, a styrene-acrylic acid resin or a styrene-butadiene resin can also be suitably used as a thermoplastic resin constituting a toner core.

  As acrylic resin, acrylic acid ester polymer or methacrylic acid ester polymer can be used, for example. As an olefin resin, a polyethylene resin or a polypropylene resin can be used, for example. As a vinyl resin, a vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, or N-vinyl resin can be used, for example.

  The styrene-acrylic acid resin is a copolymer of one or more styrene monomers and one or more acrylic monomers. In order to synthesize a styrene-acrylic acid-based resin, for example, styrene-based monomers and acrylic acid-based monomers shown below can be suitably used. By using an acrylic acid type monomer, a carboxyl group can be introduced into a styrene-acrylic acid type resin. Moreover, a hydroxyl group can be introduce | transduced into styrene- acrylic acid type resin by using the monomer which has a hydroxyl group. As the monomer having a hydroxyl group, for example, p-hydroxystyrene, m-hydroxystyrene, or (meth) acrylic acid hydroxyalkyl ester can be used.

  Preferred examples of styrenic monomers include styrene, alkylstyrene, p-hydroxystyrene, m-hydroxystyrene, vinyl toluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene or p-chlorostyrene Be Examples of the alkylstyrene include α-methylstyrene, p-ethylstyrene, and 4-tert-butylstyrene.

  Preferred examples of the acrylic acid-based monomer include (meth) acrylic acid, (meth) acrylic acid alkyl ester, or (meth) acrylic acid hydroxyalkyl ester. Preferred examples of (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, (meth) acrylic Examples include n-butyl acid, iso-butyl (meth) acrylate, or 2-ethylhexyl (meth) acrylate. Preferred examples of (meth) acrylic acid hydroxyalkyl ester include 2-hydroxyethyl (meth) acrylic acid, 3-hydroxypropyl (meth) acrylic acid, 2-hydroxypropyl (meth) acrylic acid, or (meth) acrylic The acid 4-hydroxybutyl is mentioned.

(Toner Core: Colorant)
As the colorant, known pigments or dyes may be used in accordance with the color of the toner. In order to form a high quality image using toner, the amount of the colorant is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The toner core may contain a black colorant. Examples of black colorants include carbon black. The black colorant may be a colorant toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

  The toner core may contain color colorants such as yellow colorants, magenta colorants, or cyan colorants.

  As the yellow colorant, for example, one or more compounds selected from the group consisting of condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and arylamide compounds can be used. Examples of yellow colorants include C.I. I. Pigment yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155 168, 174, 175, 176, 180, 181, 191 or 194), Naphthol Yellow S, Hansa Yellow G or C.I. I. Bat yellow can be suitably used.

  The magenta colorant is selected, for example, from the group consisting of condensation azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. One or more compounds can be used. Examples of magenta colorants include C.I. I. Pigment red (2, 3, 5, 6, 7, 19, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177 184, 185, 202, 206, 220, 221 or 254) can be suitably used.

  As the cyan colorant, for example, one or more compounds selected from the group consisting of a copper phthalocyanine compound, an anthraquinone compound, and a basic dye lake compound can be used. Examples of cyan colorants include C.I. I. Pigment blue (1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62 or 66), phthalocyanine blue, C.I. I. Bat blue or C.I. I. Acid blue can be suitably used.

(Toner core: mold release agent)
The release agent is used, for example, for the purpose of improving the fixing property or the offset resistance of the toner. In order to enhance the anionic property of the toner core, it is preferable to produce the toner core using an anionic wax. In order to improve the fixing property or the offset resistance of the toner, the amount of the releasing agent is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin.

  As a mold release agent, for example, low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, or aliphatic hydrocarbon wax such as Fischer-Tropsch wax; oxidized polyethylene wax or block thereof Oxides of aliphatic hydrocarbon waxes such as copolymers; vegetable waxes such as candelilla wax, carnauba wax, wax wax, jojoba wax, or rice wax; animal nature such as bees wax, lanolin or wax wax Waxes; mineral waxes such as ozokerite, ceresin, or petrolatum; waxes based on fatty acid esters such as montanic acid ester wax or castor wax; fatty acids such as deacidified carnauba wax The wax portion of the ester or the whole was deoxygenated can be suitably used. One type of release agent may be used alone, or two or more types of release agents may be used in combination.

  A compatibilizer may be added to the toner core in order to improve the compatibility between the binder resin and the release agent.

(Toner core: charge control agent)
The charge control agent is used, for example, for the purpose of improving the charge stability or charge rise characteristics of the toner. The charge rising characteristic of the toner is an indicator of whether or not the toner can be charged to a predetermined charge level in a short time.

  By including a negatively chargeable charge control agent in the toner core, the anionic property of the toner core can be enhanced. In addition, the cationic property of the toner core can be enhanced by containing a positively chargeable charge control agent in the toner core. However, in the case where sufficient chargeability is ensured in the toner, it is not necessary to contain the charge control agent in the toner core.

(Toner core: Magnetic powder)
As the material of the magnetic powder, for example, a ferromagnetic metal or an alloy thereof, a ferromagnetic metal oxide, or a material subjected to a ferromagnetic treatment can be suitably used. As a ferromagnetic metal, iron, cobalt or nickel can be used, for example. As the ferromagnetic metal oxide, for example, ferrite, magnetite or chromium dioxide can be used. As a ferromagnetization process, a heat treatment is mentioned, for example. One type of magnetic powder may be used alone, or two or more types of magnetic powder may be used in combination.

  In order to suppress the elution of metal ions (for example, iron ions) from the magnetic powder, it is preferable to surface-treat the magnetic powder. In the case where a shell layer is formed on the surface of the toner core under acidic conditions, when metal ions are eluted on the surface of the toner core, the toner cores are easily fixed to each other. By suppressing the elution of metal ions from the magnetic powder, it is considered that the adhesion between toner cores can be suppressed.

(Shell layer)
The shell layer may be a film having no graininess or may be a film having a graininess. When resin particles are used as a material for forming the shell layer, it is considered that if the resin particles are completely dissolved and cured in the form of a film, a film without a granular feeling is formed as the shell layer. On the other hand, if the resin particles are not completely dissolved and cured in a film-like form, it is considered that a film (a film having a granular feeling) having a form in which resin particles are two-dimensionally connected is formed as a shell layer. .

(Shell layer: thermoplastic resin)
The shell layer preferably contains at least one of the polyester resin described in (Binder resin: polyester resin), and the thermoplastic resin described in (Binder resin: thermoplastic resin).

(Shell layer: thermosetting resin)
The shell layer preferably further contains a thermosetting resin described below, in addition to the above-mentioned thermoplastic resin.

  As a suitable example of a thermosetting resin, an amino aldehyde resin, a polyimide resin, or a xylene resin is mentioned. An aminoaldehyde resin is a resin produced by condensation polymerization of a compound having an amino group and an aldehyde. Here, for example, formaldehyde can be used as the aldehyde. Examples of the aminoaldehyde resin include melamine resins, urea resins, sulfonamide resins, glyoxal resins, guanamine resins, or aniline resins. As the polyimide resin, for example, a maleimide polymer or a bismaleimide polymer can be used.

  In order to improve the film quality of the shell layer, the resin contained in the shell layer is derived from 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate. One or more alcoholic hydroxyl groups may be introduced.

  In order to improve the charging stability of the toner, it is particularly preferable that the shell layer contains a copolymer of one or more styrenic monomers and one or more acrylic acid monomers. For example, styrene can be used as the styrene-based monomer. As an acrylic acid type monomer, acrylic acid ester can be used, for example.

  The charge stability of the toner may be improved by incorporating a charge control agent in the shell layer. In order to incorporate the charge control agent in the shell layer, repeating units derived from the charge control agent (for example, quaternary ammonium salt) may be incorporated in the resin constituting the shell layer, or in the resin constituting the shell layer The charged particles may be dispersed in the In order to positively charge the toner particles, the shell layer preferably contains resin particles having positively chargeability.

(External additive)
The external additive is used, for example, to improve the flowability of toner particles or the handleability of toner. For example, the amount of the external additive is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner base particles. The particle diameter of the external additive is preferably 0.01 μm or more and 1.0 μm or less.

  As the external additive, silica particles or metal oxide particles can be suitably used. The metal oxide is preferably, for example, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or barium titanate. One type of external additive may be used alone, or a plurality of external additives may be used in combination.

[Example of application of toner according to this embodiment]
The toner according to the present embodiment can be suitably used, for example, as a positively chargeable toner for developing an electrostatic latent image. The toner of the present embodiment may be used as a one-component developer or may be used as a toner contained in a two-component developer.

(Example of Use of Toner According to the Embodiment: Two-Component Developer)
When the toner of the present embodiment is used as a toner contained in a two-component developer, a two-component developer can be prepared by mixing the toner and a carrier using a mixing device. As a mixing apparatus, for example, a ball mill can be used.

  It is preferable to use a ferrite carrier as the carrier. Thereby, a high quality image can be formed. As the carrier, it is more preferable to use magnetic carrier particles comprising a carrier core and a resin layer covering the carrier core. This makes it possible to form a high quality image over a long period of time. In order to impart magnetism to the carrier particles, the carrier particles may be formed of a magnetic material, or the carrier particles may be formed of a resin in which the magnetic particles are dispersed. In addition, magnetic particles may be dispersed in a resin layer that covers the carrier core. In order to form a high quality image, the amount of toner in the two-component developer is preferably 5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the carrier. The positively chargeable toner contained in the two-component developer is positively charged by the friction with the carrier.

  An embodiment of the present invention will be described. However, the present invention is not at all limited to the following examples.

  Toners T-1 to T-18 shown in Table 1 were manufactured according to the method described below.

  Hereinafter, a method of manufacturing the toners T-1 to T-18, an evaluation method, and an evaluation result will be described in order. In addition, in the evaluation which an error produces, the measurement value of a considerable number which an error becomes small enough was obtained, and the arithmetic mean of the obtained measurement value was made into the evaluation value. Further, the number average particle diameter of the powder is a number average value of equivalent circular diameters of primary particles measured using a transmission electron microscope (TEM), unless specified. Moreover, Tg (glass transition point) and Tm (softening point) were measured by the method shown below, respectively.

<Method of measuring Tg>
An endothermic curve (vertical axis: heat flow (DSC signal), horizontal axis: temperature) of a sample (for example, resin) was determined using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.). Subsequently, the Tg (glass transition point) of the sample was read from the obtained endothermic curve. The temperature of the change point of specific heat in the obtained endothermic curve (the intersection of the extrapolation line of the baseline and the extrapolation line of the falling line) corresponds to the Tg (glass transition point) of the sample.

<Method of measuring Tm>
A sample (for example, resin) is set in a high-rise type flow tester ("CFT-500D" manufactured by Shimadzu Corporation), and the conditions of the die pore diameter 1 mm, plunger load 20 kg / cm ² , heating rate 6 ° C./min Then, 1 cm ³ of the sample was melted and flowed out to obtain an S-shaped curve (horizontal axis: temperature, vertical axis: stroke) of the sample. Subsequently, the Tm (softening point) of the sample was read from the obtained S-shaped curve. In the obtained S-curve, assuming that the maximum value of the stroke is S ₁ and the stroke value of the baseline on the low temperature side is S ₂ , the value of the stroke in the S-curve is “(S ₁ + S ₂ ) / 2” The corresponding temperature is equivalent to the Tm (softening point) of the sample.

[Production of Toner T-1]
(Preparation of toner core)
66 parts by mass of low viscosity non-crystalline polyester resin (Tg = 38 ° C., Tm = 65 ° C.), 9 parts by mass of medium viscosity non-crystalline polyester resin (Tg = 53 ° C., Tm = 84 ° C.), 12 parts Parts of high viscosity non-crystalline polyester resin (Tg = 71 ° C., Tm = 120 ° C.), 5 parts by mass of carnauba wax ("Carnauba wax No. 1" manufactured by Kato Yoko Co., Ltd.), and 8 parts by mass of colorant ("KET BLUE 111" manufactured by DIC Corporation, phthalocyanine blue) was mixed at a rotational speed of 2400 rpm using an FM mixer (manufactured by Japan Coke Industry Co., Ltd.).

Subsequently, the obtained mixture is fed using a twin-screw extruder ("PCM-30" manufactured by Ikegai Co., Ltd.) at a material supply rate of 5 kg / hour, a shaft rotational speed of 160 rpm, a set temperature range (cylinder temperature) of 80 ° C or more It melt-kneaded on the conditions of 130 degrees C or less. Subsequently, the obtained melt-kneaded product was cooled, and the cooled melt-kneaded product was roughly pulverized using a grinder ("ROTPLEX (registered trademark)" manufactured by Hosokawa Micron Corporation). Subsequently, the obtained coarsely pulverized material was finely pulverized using a jet mill ("Ultrasonic jet mill I type" manufactured by Nippon Pneumatic Mfg. Co., Ltd.). Subsequently, the obtained pulverized material was classified using a classifier ("Elbow Jet EJ-LABO type" manufactured by Nittetsu Mining Co., Ltd.). As a result, a toner core having a volume median diameter (D ₅₀ ) of 6 μm was obtained.

(Preparation of shell material)
A 1 L 3-neck flask equipped with a thermometer and a stirrer was set in the water bath. Subsequently, in a flask, 875 g of ion-exchanged water (temperature: 30 ° C.) and 75 g of an anionic surfactant (Latem® WX, manufactured by Kao Corporation), component: sodium polyoxyethylene alkyl ether sulfate, Solid content concentration: 26% by mass) was added. Then, the temperature in the flask was raised to 80 ° C. using a water bath while stirring the contents of the flask. Subsequently, while stirring the contents of the flask at 80 ° C., the two liquids (the first liquid and the second liquid) were dropped into the flask over 5 hours respectively. The first solution was a mixture of 17 grams of styrene and 3 grams of butyl acrylate. The second solution was a solution of 0.5 g of potassium persulfate in 30 g of deionized water.

  Subsequently, while maintaining the temperature in the flask at 80 ° C., the contents of the flask were further stirred for 2 hours to sufficiently advance the polymerization reaction of the contents of the flask. As a result, a suspension (solid content concentration: 3.6% by mass) containing particles made of a hydrophobic thermoplastic resin was obtained. The number average particle diameter of the resin particles contained in the obtained suspension was 32 nm, and the Tg was 71 ° C.

(Formation of shell layer)
A 1 L three-necked flask equipped with a thermometer and a stirring blade was set in a water bath, and 300 g of deionized water was placed in the flask. Thereafter, the temperature in the flask was maintained at 30 ° C. using a water bath. Subsequently, dilute hydrochloric acid was added to the flask to adjust the pH of the contents of the flask to 4. Subsequently, in the flask, 30 g of shell material (suspension of hydrophobic thermoplastic resin particles prepared by the above-mentioned procedure) was added to obtain a dispersion of shell material.

(Formation of shell layer: elevated temperature)
Subsequently, 300 g of a toner core (the toner core prepared in the above-mentioned procedure) was added to the obtained dispersion of shell material, and the contents of the flask were stirred at a rotational speed of 200 rpm for 1 hour. Thereafter, 300 g of deionized water was further added to the flask. Subsequently, the contents of the flask were heated while stirring the contents of the flask at a rotational speed of 100 rpm. At the start of the temperature rise, the temperature of the contents of the flask (described as initial temperature in Table 1) was 30 ° C., and the pH of the contents of the flask (described as initial pH in Table 1) was 4. Moreover, regarding temperature rising conditions, the target temperature was 70 ° C., and the speed (described as the temperature rising speed in Table 1) was 1.0 ° C./min.

  During the temperature rise, when the temperature of the contents of the flask reached 35 ° C., an aqueous solution of sodium hydroxide was added to the flask to change the pH of the contents of the flask to 9. That is, when the toner T-1 was manufactured, the pH change temperature was 35.degree. The temperature rise was continued to the target temperature (70 ° C.) without stopping the temperature rise both at pH change and after pH change.

  When the temperature of the contents of the flask reaches 70 ° C. by the above temperature increase, the temperature of the contents of the flask is kept at that temperature (70 ° C.), and the contents of the flask are stirred for another hour under the conditions of 70 ° C. temperature and 100 rpm. did. Thereafter, cold water was put into the flask, and the contents of the flask were quenched to normal temperature (about 25 ° C.). As a result, a dispersion containing toner base particles was obtained.

(Washing)
The dispersion of toner base particles obtained as described above was filtered (solid-liquid separation) using a Buchner funnel. As a result, wet cake-like toner mother particles were obtained. Thereafter, the obtained wet cake toner base particles were re-dispersed in ion exchange water. Further, dispersion and filtration were repeated five times to wash the toner base particles.

(Dried)
Subsequently, the obtained toner base particles were dispersed in an aqueous ethanol solution having a concentration of 50% by mass. Thereby, a slurry of toner base particles was obtained. Subsequently, the toner base particles in the slurry were subjected to a hot air temperature of 45 ° C. and a blower air volume of 2 m ³ / min using a continuous surface reforming apparatus (“Coatmizer (registered trademark)” manufactured by Freund Corporation). It was allowed to dry. As a result, dried toner base particles (powder) were obtained.

(External attachment)
100 parts by mass of toner base particles (toner base particles obtained as described above), 1.5 parts by mass of dry silica particles ("AEROSIL (registered trademark) REA 90" manufactured by Nippon Aerosil Co., Ltd.), 1.5 Conductive part of conductive titanium oxide particles (manufactured by Titanium Kogyo Co., Ltd. “EC-100”, base: TiO ₂ particles, covering layer: Sb-doped SnO ₂ film, number average primary particle diameter: about 0.35 μm), The mixture was mixed for 5 minutes using a 10 L FM mixer (manufactured by Japan Coke Industry Co., Ltd.). Thus, the external additive (silica particles and titanium oxide particles) was attached to the surface of the toner base particles. Thereafter, the obtained toner was sieved using a 200 mesh (75 μm mesh) sieve. As a result, a toner (toner T-1) containing a large number of toner particles was obtained.

[Production of Toners T-2 to T-17]
According to the method for producing toner T-1, except that the temperature rise rate (° C./min), the pH change temperature (° C.), the target temperature (° C.), and the target pH were changed as shown in Table 1, −2 to T-17 were produced.

  In the toner T-12, the aqueous sodium hydroxide solution was not added to the flask in the temperature raising step at the time of formation of the shell layer. In the toner T-13, when the temperature of the contents of the flask reaches 35 ° C. in the temperature raising step at the time of formation of the shell layer, an aqueous solution of sodium hydroxide is added to the flask to set the pH of the contents of the flask to 4 Adjusted to

[Manufacture of Toner T-18]
Toner T-18 was manufactured according to the method of manufacturing toner T-15 except that the material of the low viscosity non-crystalline polyester resin was changed to the following materials to manufacture a toner core. Specifically, instead of 66 parts by mass of low viscosity non-crystalline polyester resin (Tg = 38 ° C., Tm = 65 ° C.), 33 parts by mass of low viscosity non-crystalline polyester resin (Tg = 38 ° C., Tm = 65 ° C.) And 33 parts by weight of a low viscosity non-crystalline polyester resin (Tg = 40.degree. C., Tm = 69.degree. C.) to prepare a toner core.

[Method for measuring the degree of circularity of toner particles]
With respect to the toners T-1 to T-18 obtained as described above, the circularity of the toner particles was measured. The measurement target was toner base particles contained in each of the toners T-1 to T-18. That is, the degree of circularity of the toner particles was measured before the toner base particles were externally added. Specifically, the circularity of each of the toner base particles dispersed in water was measured using a flow type particle image analyzer (“FPIA (registered trademark) -3000” manufactured by Sysmex Corporation). At this time, the maximum value of the particle size to be analyzed was set to 20 μm. The number average value of the measured circularity was taken as the circularity of the toner particles. The results are shown in Table 2.

[Method of measuring the maximum opening area of the recess and the number of recesses per unit area of the surface area of toner particles]
Regarding the toners T-1 to T-18 obtained as described above, the maximum opening area of the recesses formed on the surface of the toner particles and the number of recesses per unit area of the surface area of the toner particles were measured. . The measurement target was toner base particles contained in each of the toners T-1 to T-18. That is, before the toner base particles were subjected to the external additive treatment, the maximum opening area of the recesses was measured, and the number of recesses per unit area of the surface area of the toner particles was measured. Specifically, the entire surface of the toner base particles was observed using a field emission scanning electron microscope (FE-SEM) ("JSM-7600F" manufactured by JEOL Ltd.). Twenty toner mother particles were observed for one sample. Then, the maximum opening area (maximum value) of the concave portions and the number of concave portions per unit area (number average value) were determined. The results are shown in Table 2.

[How to measure shell coverage]
The overall shell coverage (unit:%) was measured for the toners T-1 to T-18 obtained as described above. The measurement target was toner base particles contained in each of the toners T-1 to T-18. That is, the shell coverage was measured before the toner base particles were externally added. Specifically, the toner mother particles are Ru-dyed by exposing the toner mother particles (powder) in a vapor of 2 mL of a 0.5% by mass aqueous RuO ₄ solution for 5 minutes in an air atmosphere at normal temperature (25 ° C.) did. Then, the dyed toner mother particles are observed at a magnification of 50000 times using a field emission scanning electron microscope (FE-SEM) ("JSM-7600F" manufactured by Nippon Denshi Co., Ltd.), and reflected electron of the toner mother particles I got an image. Of the surface area of the toner core, the area covered with the shell layer was easily stained with ruthenium.

Of the obtained backscattered electron images, the luminance value was divided into 256 parts, with the value of the brightest part being 255 and the value of the darkest part being 0. Then, using the image analysis software ("WinROOF" manufactured by Mitani Corporation), a binarization process based on the luminance value 144 was performed on the backscattered electron image. After the binarization process, the area S _{A1 of the} entire backscattered electron image of the toner base particle (corresponding to the total number of pixels in the backscattered electron image) and the area S _B1 of the area having a luminance value of 144 or more in the backscattered electron image The total shell coverage (unit:%) was calculated according to the following equation.
Overall shell coverage = 100 × area S _B1 / area S _A1

The concave shell coverage (unit:%) was measured in the same manner as the measurement of the overall shell coverage, except that the observation magnification was changed from 50000 times to 100,000 times. Area S _A2 of the inner area of the base recess (corresponding to the total number of pixels in the inner area of the base recess) and area S _B2 of the area where the brightness value is 144 or more in the inner area of the base recess (in the inner area of the base recess (Corresponding to the number of pixels having a luminance value of 144 or more) of (1), and the concave shell coverage (unit:%) was calculated according to the following equation.
Recessed shell coverage = 100 × area S _B2 / area S _A2

As shown in the following formula, the measurement value of the entire shell coverage was subtracted from the measurement value of the recess shell coverage, and the area difference (unit:%) was calculated. The results are shown in Table 2.
Area difference = recessed shell coverage-overall shell coverage

[Evaluation method]
(Developability)
The developability of the toners T-1 to T-18 obtained as described above was evaluated using a color multifunction peripheral ("FS-C 5300 DN" manufactured by KYOCERA Document Solutions Inc.). Specifically, 100 parts by weight of a developer carrier (carrier for FS-C 5300 DN) and 10 parts by weight of toner (the toner obtained as described above) are mixed for 30 minutes using a ball mill, and 2 A component developer was prepared.

The obtained two-component developer was set in the developing device of the color multifunction machine. The bias (voltage) applied at the time of development was set to 250 V, and an image pattern (toner image) to be a solid image with a printing rate of 5% was formed on the photosensitive member. Image formation was stopped before this image pattern was transferred to the intermediate transfer member, and the photosensitive member was taken out of the color multifunction peripheral. The toner image formed on the photoreceptor was applied to a tape of known area and mass. The mass of the tape to which the toner image was attached was measured, and the toner development amount (g / m ² ) was determined using the following equation.
Toner development amount (g / m ² ) = [(mass of the tape on which the toner image is attached (g)) − (mass of the tape before the toner image is attached (g)) / (of the surface of the tape Area of the surface on which the toner image is attached (m ² ))

According to the above method, the bias (voltage) applied at the time of development was changed to 350 V and 450 V, respectively, and the toner development amount (g / m ² ) was determined. Then, the obtained result is plotted in a graph in which the bias (voltage) applied at the time of development is shown on the horizontal axis, and the obtained toner development amount (g / m ² ) is shown on the vertical axis. The plotted data were approximated by a linear function by the least squares method. The slope (developability index) of the linear function was determined. The results are shown in Table 2.

  If the developability index is 0.022 or more, it was evaluated as good. If the developability index is less than 0.022, it was evaluated as not good.

(Cleanability)
The cleaning properties of the toners T-1 to T-18 obtained as described above were evaluated using a color multifunction peripheral ("FS-C 5300 DN" manufactured by Kyocera Document Solutions Inc.). Specifically, 100 parts by weight of a developer carrier (carrier for FS-C 5300 DN) and 10 parts by weight of toner (the toner obtained as described above) are mixed for 30 minutes using a ball mill, and 2 A component developer was prepared.

  The obtained two-component developer was set in the developing device of the above-described color multifunction peripheral to form a solid image on A4 size printing paper. The solid image had a strip shape (width: 30 mm) extending parallel to the longitudinal direction of the printing paper, and was formed at the center in the width direction of the printing paper. After the toner remaining on the photosensitive member was removed by the cleaning blade, the image formation was stopped, and the photosensitive member was removed from the color multifunction peripheral. Then, a cellophane tape was attached to a portion of the surface of the photosensitive member through which the cleaning blade passed, and the toner remaining on the photosensitive member was peeled off with the cellophane tape. The cellophane tape was attached to a blank sheet of paper. Using a Macbeth reflection densitometer ("RD 914" manufactured by X-Rite Co., Ltd.), the reflection density (ID: image density) of the portion to which the toner is attached on the white paper was measured. Thus, the amount of toner remaining on the photosensitive member (hereinafter referred to as the amount of remaining toner) was estimated.

  When the measured image density (ID) was 0.01 or less, it was judged that the residual amount of toner was small, and was evaluated as good (o). When the measured image density (ID) was more than 0.01, it was judged that the residual amount of toner was large, and was evaluated as bad (x).

(Heat resistant storage stability)
The heat resistant storage stability of the toners T-1 to T-18 obtained as described above was evaluated. Specifically, 2 g of the toner was put in a 20 mL polyethylene container and sealed, and the sealed container was allowed to stand for 3 hours in a thermostat set at 60 ° C. Thereafter, the toner removed from the thermostat was cooled to room temperature (about 25 ° C.) to obtain a toner for evaluation.

Subsequently, the obtained evaluation toner was placed on a sieve of 100 mesh (opening 150 μm) of known weight. Then, the mass of the sieve containing the evaluation toner was measured, and the mass of the toner before sifting was determined. Subsequently, the above sieve was set in a powder tester (manufactured by Hosokawa Micron Corporation), and the sieve was vibrated for 30 seconds under the condition of the rheostat graduation 5 according to the manual of the powder tester to sift the evaluation toner. After sieving, the mass of the toner not passing through the sieve was measured. Then, based on the mass of the toner before screening and the mass of the toner after screening, the toner aggregation degree (unit: mass%) was determined according to the following equation. The results are shown in Table 2. The “mass of toner after sieving” in the following formula is the mass of the toner not passing through the sieve, and is the mass of the toner remaining on the sieve after sieving.
Toner cohesion degree = 100 × mass of toner after sieving / mass of toner before sieving

  When the toner aggregation degree was 50% by mass or less, it was evaluated as good. If the toner aggregation degree exceeds 50% by mass, it is evaluated as not good.

In Table 2, in the "opening area", the maximum opening area (μm ² ) is described. The maximum opening area of 0 μm ² means that a recess having a depth of 100 nm or more is not formed on the surface of the toner particle. The “numerical aperture” describes the number of recesses per unit area of the surface area of the toner particles (number / μm ² ). In “area difference”, the area difference (%) determined by the following equation is described.
Area difference = recessed shell coverage-overall shell coverage

The toners T-1 to T-11 (toners according to Examples 1 to 11) had the above-described basic configuration. Specifically, the toner according to Examples 1 to 11 contained a plurality of toner particles each having a core and a shell layer covering the surface of the core. A plurality of first recesses were formed on the surface of the core. The shell layer was present in both the inner region of the first recess and the outer region of the first recess in the surface region of the core. A second recess corresponding to the first recess was formed on the surface of the toner particle. The circularity of the toner particles was 0.960 or more and 0.970 or less. The number of second recesses present on the surface of the toner particle was 0.300 or more and 0.500 or less per 1 μm ² of the surface area of the toner particle. The opening area of the second recess was 1.0 μm ² or less.

  As shown in Table 2, the toners T-1 to T-11 had excellent developability and cleanability, respectively, and the toner aggregation degree was suppressed to a low level. That is, in the toners T-1 to T-11, the cleaning performance and the heat-resistant storage stability of the toner particles can be maintained high, and the developability can be maintained in an appropriate state.

  The toners T-12 to T-13 (toners according to Comparative Examples 1 and 2) were inferior in the evaluation of developability as compared with the toners T-1 to T-11. The reason why such a result is obtained is considered that in the toners T-12 to T-13, a concave portion having a depth of 100 nm or more is not formed on the surface of the toner particles. Specifically, in the toner T-12, the aqueous sodium hydroxide solution was not added in the temperature raising step at the time of formation of the shell layer. Therefore, it is considered that no recess was formed on the surface of the toner particle. Further, in the toner T-13, the pH of the contents of the flask was kept acidic in the temperature raising step at the time of formation of the shell layer. Therefore, it is considered that it was difficult to form a recess on the surface of the toner particle.

  The toners T-14 and T-17 (toners according to Comparative Examples 3 and 6) were inferior in evaluation of developability as compared with the toners T-1 to T-11. The reason why such a result is obtained is considered that in the toners T-14 and T-17, the number of recesses per unit area of the surface area of the toner particles is less than 0.300. Specifically, in the toner T-14, the pH change temperature and the target temperature were the same temperature in the temperature raising step at the time of formation of the shell layer. Therefore, it is considered that the time from the time of pH change of the contents of the flask to the time of the end of the temperature raising process can not be secured, and therefore, a concave portion is difficult to be formed on the surface of the toner particles. As a result, it is considered that the number of recesses per unit area of the surface area of the toner particles is less than 0.300. In the toner T-17, in the temperature raising step at the time of formation of the shell layer, the pH change temperature was 35 ° C., the target temperature was 60 ° C., and the temperature rise rate was 1.0 ° C./min. Therefore, it is difficult to secure the time from the time of pH change of the contents of the flask to the end of the temperature raising process, and it is considered that a concave portion is difficult to be formed on the surface of the toner particles. As a result, it is considered that the number of recesses per unit area of the surface area of the toner particles is less than 0.300.

The toner T-15 (the toner according to Comparative Example 4) was inferior in the evaluation of developability as compared with the toners T-1 to T-11. The reason why such a result was obtained is that, in the toner T-15, although the concave portion is formed on the surface of the toner particle, it is considered that the maximum opening area of the concave portion is 3.5 μm ² . Specifically, with toner T-15, an aqueous solution of sodium hydroxide was added to the flask so that the pH of the contents of the flask changed to 13 when the shell layer was formed. Therefore, it is considered that a concave portion is excessively formed on the surface of the toner particle. Therefore, it is considered that the maximum opening area of the recess is 3.5 μm ² .

  The toner T-16 (the toner according to Comparative Example 5) was inferior in the evaluation of the cleaning property as compared with the toners T-1 to T-11. The reason why such a result is obtained is considered that the toner T-16 has a high degree of circularity of toner particles. Specifically, in the toner T-16, in the temperature raising step at the time of formation of the shell layer, the pH change temperature was 35 ° C., the target temperature was 75 ° C., and the temperature rise rate was 1.0 ° C./min. . Therefore, it is considered that the target temperature was high, and the time from the change time of the pH of the contents of the flask to the end time of the heating process tended to be long. Therefore, it is considered that toner particles having a high degree of circularity were produced.

  The toner T-18 (the toner according to Comparative Example 7) was inferior in the evaluation of heat resistant storage stability as compared with the toners T-1 to T-11. The reason why such a result is obtained is considered that in the toner T-18, the number of concave portions per unit area of the surface area of the toner particles is more than 0.500. Specifically, with toner T-18, an aqueous sodium hydroxide solution was added to the flask so that the pH of the contents of the flask changed to 13 when forming the shell layer. Therefore, it is considered that a concave portion is excessively formed on the surface of the toner particle. Therefore, it is considered that the number of concave portions per unit area of the surface area of the toner particles is more than 0.500.

  The electrostatic latent image developing toner according to the present invention can be used, for example, to form an image in a copying machine, a printer, or a multifunction machine.

DESCRIPTION OF SYMBOLS 10 Toner mother particle 11 Toner core 12 Shell layer H4, H11-H13 Base recessed part H22, H23 Surface recessed part

Claims (8)

An electrostatic latent image developing toner comprising a plurality of toner particles comprising a core and a shell layer covering the surface of the core,
A plurality of first recesses are formed on the surface of the core,
The shell layer is present in both the inner region of the first recess and the outer region of the first recess in the surface region of the core,
A second recess corresponding to the first recess is formed on the surface of the toner particle,
The circularity of the toner particles is 0.960 or more and 0.970 or less,
The number of the second recesses present on the surface of the toner particle is 0.300 or more and 0.500 or less per 1 μm ² of the surface area of the toner particle,
The toner for developing an electrostatic latent image, wherein an opening area of the second concave portion is 1.0 μm ² or less.   The electrostatic latent image developing toner according to claim 1, wherein a ratio of an area of the core covered by the shell layer in a surface area of the core is 30% or more and 80% or less.   The electrostatic latent image developing toner according to claim 1, wherein a ratio of an area of the inner area covered by the shell layer in the inner area of the first concave portion is 30% or more and 80% or less.   The area difference obtained by subtracting the ratio of the area of the core covered by the shell layer in the surface area of the core from the ratio of the area of the inner area covered by the shell layer in the inner area of the first recess is − The toner for electrostatic latent image development according to any one of claims 1 to 3, which is 5% or more and 5% or less. The core contains a non-crystalline polyester resin having a softening point of 80 ° C. or less and a non-crystalline polyester resin having a softening point of 100 ° C. or more,
The proportion of the non-crystalline polyester resin having a softening point of 80 ° C. or less among the resins contained in the core is 20% by mass or more and 95% by mass or less,
The ratio which the non-crystalline polyester resin of the said softening point of 100 degreeC or more occupies among the resin contained in the said core is 5 mass% or more and 80 mass% or less, It is described in any one of Claims 1-4. Toner for electrostatic latent image development.   The toner for electrostatic latent image development according to any one of claims 1 to 5, wherein a thickness of the shell layer is 1 nm or more and 50 nm or less. A method for producing the electrostatic latent image developing toner according to any one of claims 1 to 6, wherein
Preparing an aqueous medium comprising a core and a shell material and having a pH of 3 to 6;
Raising the temperature of the prepared aqueous medium to a predetermined target temperature;
Maintaining the temperature of the aqueous medium at the target temperature after completion of the temperature raising step;
Including
The core contains a non-crystalline polyester resin having a softening point equal to or lower than the target temperature, and a non-crystalline polyester resin having a softening point higher than the target temperature,
The temperature raising step further includes the step of changing the pH of the aqueous medium to 8 or more and 12 or less when the temperature of the aqueous medium reaches a pH change temperature,
The method for producing a toner for developing an electrostatic latent image, wherein the pH change temperature is lower than the target temperature. The heating rate is 0.1 ° C./min or more and 3.0 ° C./min or less,
The method for producing a toner for electrostatic latent image development according to claim 7, wherein the target temperature is 60 ° C. or more and 70 ° C. or less, and the pH change temperature is 30 ° C. or more and 60 ° C. or less.

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