Toner, two-component developer, and method for manufacturing toner

Abstract

To provide a toner that has low temperature fixability and can curb the occurrence of fogging and a reduction in electrification when an image forming apparatus is operated for a long period, a two-component developer, and a method for manufacturing the toner.SOLUTION: A toner having an external additive attached to a surface of a toner particle has the following configuration. The toner particle includes a crystalline polyester resin and wax, and has an apparent viscosity at 90°C of 100000 Pa s or more and 200000 Pa s or less. The external additive includes a first external additive, and a second external additive having a larger average primary particle diameter than the first external additive. The aerated bulk density of the toner is 0.3 g / cm3 or more and 0.35 g / cm3 or less. When a pressure of 1.2 N / cm2 is applied at 50°C, the degree of compression of the toner is 50% or less, and the stress relaxation rate of the toner is 27% or more.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to a toner, a two-component developer, and a method for manufacturing a toner.

Background Art

[0002] An electrostatic latent image developing toner used in an image forming apparatus such as a copying machine, a multifunction peripheral, a printer, or a facsimile apparatus that uses an electrophotographic method generally has a configuration in which an external additive is adhered to the surface of toner particles (toner core).

[0003] In recent years, since further energy saving of image forming apparatuses has been desired, low-temperature fixability has been required for toners in order to achieve it. A low-temperature fixing toner with enhanced low-temperature fixability is composed of toner particles made of a resin capable of being fixed at a lower temperature than before.

[0004] For example, Patent Document 1 discloses a toner in which an external additive is adhered to the surface of toner particles having a softening point of 110°C or lower. In this toner, the toner particles contain a crystalline polyester resin and a wax, the external additive contains fine powder and silica particles, the fine powder is obtained by hydrophobizing the surface of a composition containing strontium titanate and silica with a silane compound, the number average circular equivalent diameter of the primary particles of the fine powder is 20 nm or more and 50 nm or less, and the number average circular equivalent diameter of the primary particles of the silica particles is 50 nm or more and 200 nm or less.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] When an image forming apparatus operates for a long time, the temperature inside the developing tank reaches approximately 40° C. to 50° C. In such a temperature environment, low-temperature fixing toner has a problem that, compared to conventional toner, the toner is subjected to the same level of stress (load), but the embedding of external additives into toner particles is more likely to progress than in a room temperature environment.

[0007] Possible methods to address this problem include increasing the amount of small particle external additives added to increase the coverage of the toner particle surface with the external additives, and increasing the amount of medium to large particle external additives of about 40 nm to 120 nm added to expect an increase in the spacer effect. However, these methods have the problem that the external additives in the toner retained in the developing tank are quickly embedded in the toner particles at the initial stage of operation of the image forming device, causing a decrease in charge, and there are problems that "roughness" and "fog" occur on the printed surface in a high humidity environment.

[0008] Note that "roughness" refers to a state in which image quality is uneven and rough, and "fogging" refers to the phenomenon in which low-charge toner is developed in non-image areas where toner is not normally developed (the phenomenon in which low-charge toner adheres to the photoconductor).

[0009] The contents of the present disclosure have been discovered in consideration of the above circumstances regarding low-temperature fixing toner, and the main object of the present disclosure is to provide a toner, a two-component developer, and a method for producing a toner that can suppress charge reduction and the occurrence of fogging when an image forming apparatus is operated for long periods of time. [Means for solving the problem]

[0010] The toner disclosed herein, which has been made to solve the above problems, is a toner having an external additive attached to the surface of the toner particles, and has the following configuration. The toner particles contain a crystalline polyester resin and a wax, and have an apparent viscosity at 90°C of 100,000 Pa·s or more and 200,000 Pa·s or less. The external additives include a first external additive and a second external additive having an average primary particle diameter larger than that of the first external additive. The loose bulk density of the toner is 0.3 g / cm. 3 More than 0.35g / cm3 Less than 1.2N / cm at 50℃ 2 When pressure is applied, the compression degree of the toner is 50% or less, and the stress relaxation rate of the toner is 27% or more.

[0011] In the toner described above, it is preferable that the first external additive is silica particles, titanium oxide particles, aluminum oxide particles, silica particles having aluminum hydroxide attached to their surfaces, or strontium titanate particles to which silica has been added, and that the first external additive has an average primary particle diameter of 10 nm or more and 35 nm or less.

[0012] In the toner, the second external additive is preferably silica particles and titanium oxide particles, and the silica particles and titanium oxide particles as the second external additive preferably have an average primary particle diameter of 38 nm or more and 120 nm or less.

[0013] In addition, in the above toner, it is preferable that the content of the first external additive is 0.1 parts by mass or more and 0.5 parts by mass or less per 100 parts by mass of the toner particles, and the content of the second external additive is 4.0 parts by mass or more and 6.0 parts by mass or less per 100 parts by mass of the toner particles.

[0014] In the toner, it is preferable that the adhesion strength of the first external additive to the toner particles is 90% or more and 100% or less, and the adhesion strength of the second external additive to the toner particles is 30% or more and 50% or less.

[0015] In the above toner, the toner particles are preferably pulverized toner particles.

[0016] The two-component developer disclosed herein, which has been made to solve the above problems, is characterized by including the toner and a carrier.

[0017] The toner manufacturing method of the present disclosure, which has been made to solve the above problems, includes a first external addition step of mixing the first external additive with the toner particles to cause the first external additive to adhere to the surfaces of the toner particles, and a second external addition step of mixing the second external additive with the toner particles to cause the second external additive to adhere to the surfaces of the toner particles, and is characterized in that the second external addition step is performed after the first external addition step. Effect of the Invention

[0018] The toner, two-component developer, and toner manufacturing method of the present disclosure exhibit excellent effects such as being able to provide low-temperature fixing properties and being able to suppress charge reduction and the occurrence of fogging when an image forming apparatus is operated for a long period of time. [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic diagram illustrating a state of gaps between toner particles when a container is filled with toner having a weak adhesive strength of a large particle external additive to the toner particles without a load. FIG. [Diagram 2] 1 is a schematic diagram illustrating a state of gaps between toner particles when a container is filled with toner in which a large particle external additive has strong adhesion strength to the toner particles without applying a load; FIG. [Diagram 3] 1 is a schematic diagram illustrating a state of gaps between toner particles when a container is filled with toner having many small particle diameter external additives attached thereto without a load. FIG. [Figure 4] 1 is a schematic diagram illustrating a state of gaps between toner particles when a container is filled with toner having a small particle diameter external additive with weak adhesion strength to the toner particles without load. FIG. [Diagram 5] 1 is a schematic diagram illustrating the movement of toner particles when a load is applied to a toner having a large particle diameter external additive attached thereto from a no load state; FIG. [Figure 6] 5A to 5C are schematic diagrams illustrating the movement of toner particles when a load is applied to the toner according to the present embodiment after a load is applied thereto from a no load state. [Figure 7]5A and 5B are schematic diagrams for explaining how stress applied to the toner particles according to the present embodiment is alleviated over time when a load is applied to the toner particles. [Figure 8] 4 is a graph showing the stress relaxation rate of the toner of Example 1. [Figure 9] 4 is a graph showing a stress relaxation rate of the toner of Comparative Example 1. [Figure 10] 13 is a graph showing a stress relaxation rate of the toner of Comparative Example 3. [Figure 11] 13 is a graph showing a stress relaxation rate of the toner of Comparative Example 4. [Figure 12] 13 is a graph showing a stress relaxation rate of the toner of Comparative Example 5. [Figure 13] 1 is a graph illustrating a method for measuring a stress relaxation rate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The toner and two-component developer of the present disclosure will be described in detail below. First, the characteristics of the toner as a whole will be described, and then the materials constituting the toner will be described.

[0021] 1. Toner The toner according to the present embodiment is a toner having an external additive attached to the surface of the toner particles, and satisfies the following requirements (A) to (D). (A) The toner particles contain a crystalline polyester resin and a wax, and have an apparent viscosity at 90°C of 100,000 Pa·s or more and 200,000 Pa·s or less. The (B) external additive includes a first external additive and a second external additive having an average primary particle diameter larger than that of the first external additive. (C) The loose bulk density of the toner is 0.3 g / cm 3 More than 0.35g / cm 3 The following is the result. (D) 1.2N / cm at 50℃ 2 When the toner is pressed, the compression degree of the toner is 50% or less, and the stress relaxation rate of the toner is 27% or more.

[0022] Regarding the above requirement (A), from the viewpoint of low-temperature fixability, the toner particles according to this embodiment more preferably have an apparent viscosity at 90° C. of 110,000 Pa·s or more and 150,000 Pa·s or less.

[0023] Regarding the above requirement (C), from the viewpoint of the mechanism described later, the loose bulk density of the toner is 0.3 g / cm 3 More than 0.34g / cm 3 More preferably, it is 0.3 g / cm or less. 3 More than 0.33g / cm 3 It is even more preferable that:

[0024] Regarding the degree of toner compression of the above requirement (D), if the degree of toner compression is high when the load is large, the mobility of the toner decreases in the mechanism described below. Therefore, it is more preferable that the degree of toner compression is 49% or less, and the lower limit of the degree of toner compression is preferably 45% or more, and more preferably 47% or more.

[0025] Regarding the stress relaxation rate of the toner in the above requirement (D), from the viewpoint of the mechanism described below, the stress relaxation rate of the toner is more preferably 30% or more.

[0026] The reason why the toner according to the present embodiment can solve the above problems is believed to be as follows.

[0027] When an image forming apparatus operates for a long time, the temperature inside the developing tank reaches approximately 40°C to 50°C. In such a temperature environment, low-temperature fixing toner is more likely to cause external additives to embed in toner particles than in a normal temperature environment, even if the stress (load) that the toner receives is the same as that of a conventional toner. The load is transmitted by contact between the toner and carrier, or by contact between toner particles.

[0028] Toner with a low loose bulk density has many gaps (spaces) between toner particles, so when a load is applied, the toner particles move into the gaps, reducing the internal pressure. This reduction in internal pressure can be observed as a relaxation of the stress on the toner due to the applied load. By utilizing this phenomenon and reducing the contact force between toner particles, a toner that is resistant to stress can be created.

[0029] Furthermore, when a large load is applied to the toner, depending on the state of external additives to the toner particles (the type of external additive and its adhesion state), the movement of the toner particles is restricted, the stress is not alleviated, and the problem of the external additives becoming embedded occurs. Therefore, it is preferable for the toner to be one that can alleviate the stress by causing slippage on the contact surface of the toner particles even under a large load, and allowing the toner particles to move into the gaps.

[0030] However, if the contact surfaces of toner particles are slippery even before a load is applied to the toner, the toner particles will move to fill the gaps without a load, resulting in a state in which there are insufficient gaps between the toner particles, resulting in a toner with a high loose bulk density.

[0031] From the above viewpoints, by producing a toner having a small bulk density (loose bulk density) when no load is applied, and having an external additive state in which the surface of the toner particles exhibits an appropriate degree of slipperiness and stress is relieved when a load is applied, it is possible to suppress embedding of the external additive into the toner particles when the image forming apparatus is operated for an extended period of time, and ultimately to suppress charge reduction and the occurrence of fogging.

[0032] Next, the external additive state in which the bulk density (loose bulk density) is small when there is no load, and when a load is applied, the toner particle surface exhibits an appropriate degree of slipperiness and stress is relaxed will be explained using Figures 1 to 6. Note that the explanation using Figures 1 to 6 is based on a model in which a load is applied to the toner contained in a container by a piston, but in reality, the external additive becomes embedded in the toner particles due to the stress (load) and temperature environment that the developer receives while being transported in the developer tank.

[0033] Figs. 1 to 4 are schematic diagrams exemplifying the state of the gaps between toner particles when the toner is filled in a container without load, and toners with different external addition states with respect to the toner particles are exemplified for each figure.

[0034] Fig. 1 shows a case of a toner in which the adhesion strength of the large particle diameter external additive 2' to the toner particles 1' is weak. In this case, the loose bulk density of the toner is small and the gaps between the toner particles are many. On the other hand, Fig. 2 shows a case of a toner in which the adhesion strength of the large particle diameter external additive 2' to the toner particles 1' is strong. In this case, the spacer effect by the large particle diameter external additive is weakened, the loose bulk density of the toner is large, and the gaps between the toner particles are few. When the loose bulk density of the toner is lower, there are more places (the moving destinations of the toner particles) for the force to escape when a load is applied to the toner. Therefore, by weakly adhering the large particle diameter external additive to the toner particles, it is possible to design so that the loose bulk density of the toner becomes low. Thus, in the toner according to the present embodiment, it is preferable that the adhesion strength of the second external additive is within the range described later.

[0035] Fig. 3 shows a case of a toner in which many small particle diameter external additives 3' are adhered to the toner particles 1'. Since many small particle diameter external additives are present, the mobility between the toner particles is high, and before a load is applied, the toner particles move so as to fill the gaps, so the loose bulk density is large and the gaps between the toner particles are few. Fig. 4 shows a case of a toner in which the adhesion strength of the small particle diameter external additive 3' to the toner particles 1' is weak. Since the small particle diameter external additive is weakly adhered to the toner particles, the mobility between the toner particles is high, and before a load is applied, the toner particles move so as to fill the gaps, so the loose bulk density is large and the gaps between the toner particles are few. Therefore, by strongly adhering a small amount of the small particle diameter external additive to the toner particles, it is possible to design so that the loose bulk density of the toner becomes low. Thus, in the toner according to the present embodiment, it is preferable that the adhesion strength and the content of the first external additive are within the ranges described later.

[0036] 5 and 6 are schematic diagrams illustrating the movement of toner particles when a load is applied from an unloaded state. When no load is applied, the piston and toner particles are located at the position indicated by the dashed line, and when a load is applied by lowering the piston, they move to the position indicated by the solid line. The arrows indicate the direction of movement of the toner particles.

[0037] Figure 5 shows the case of toner in which large particle external additive 2' has adhered to toner particles 1', and because this is an external additive state in which the loose bulk density is small, there are many gaps between the toner particles when no load is applied. When a load is applied, the toner particles try to move into the gaps to disperse the force, but because the toner particle surfaces have no slipperiness, they stop after only a short movement. Although there are gaps between the toner particles, the toner particles do not move, so force is applied to the contact points and the external additive becomes embedded. In this way, the toner in the container does not distribute pressure well, and when viewed from the piston side, the stress on the toner in response to the applied load is not alleviated.

[0038] In contrast, Figure 6 shows the case of the toner according to this embodiment, where when a load is applied, the toner particles move into the gaps to disperse the force. Even when the load increases, the movement of the toner particles is not hindered because the toner particle surfaces are slippery. As a result, the movement of the toner particles into the gaps continues more than in the case shown in Figure 5, so that no large force is applied to the contact points, and the embedding of the external additives is suppressed. In this way, the pressure of the toner in the container is dispersed, and the stress of the toner against the applied load is alleviated when viewed from the piston side.

[0039] FIG. 7 is a schematic diagram for explaining that the stress of the toner under a load relaxes over time in the toner according to the present embodiment. FIG. 7(a) shows the state before applying a load to the toner in the container. Next, as shown in FIG. 7(b), when the toner in the container is compressed with a piston and the height of the piston, that is, the volume of the toner, is kept constant, the internal pressure of the container increases. Immediately after compression, the stress of the toner on the piston is the same value as the load. As described with reference to FIG. 6, in the toner according to the present embodiment, since the toner particles have mobility to move into the gaps, the force between the toner particles is dispersed, and as shown in FIG. 7(c), the internal pressure of the container decreases. That is, the stress of the toner on the piston relaxes over time.

[0040] Due to such a mechanism, in the case where the image forming apparatus is operated for a long time, the toner according to the present embodiment can suppress the external additive from being embedded in the toner particles, and thus can suppress the occurrence of charge reduction and fogging.

[0041] 2. Toner Particles (Toner Core) The toner particles according to the present embodiment are composed of an internal additive such as a colorant and a binder resin, and the internal additive is dispersed in the binder resin. An external additive adheres to the surface of the toner particles. Further, if necessary, optional components may be contained as long as the effects according to the present disclosure are not impaired. The average primary particle diameter of the toner particles can be appropriately selected according to the purpose, and for example, it is 4.5 μm or more and 8 μm or less.

[0042] 2-1. Binder Resin The toner particles according to the present embodiment contain at least an amorphous polyester resin as a binder resin and a crystalline polyester resin. By adding the crystalline polyester resin, the softening temperature and the melt viscosity of the toner can be decreased. In other words, by using toner particles in which an amorphous polyester resin and a crystalline polyester resin are used in combination, a low-temperature fixing toner with improved low-temperature fixing property can be obtained.

[0043] In the present disclosure, amorphous resins and crystalline resins are distinguished by their crystallinity index, with a resin having a crystallinity index of 0.6 or more and 1.5 or less being crystalline resins, and a resin having a crystallinity index of less than 0.6 or more than 1.5 being amorphous resins. Resins having a crystallinity index of more than 1.5 are amorphous, and resins having a crystallinity index of less than 0.6 have low crystallinity and many amorphous portions.

[0044] The crystallinity index is a physical property that is an index of the degree of crystallization of a resin, and is defined as the ratio of the softening temperature to the highest endothermic peak temperature (softening temperature / highest endothermic peak temperature). Here, the highest endothermic peak temperature refers to the temperature of the highest endothermic peak observed. In a crystalline polyester resin, the highest peak temperature is the melting point, and in an amorphous polyester resin, the highest endothermic peak is the glass transition temperature.

[0045] The degree of crystallization of the resin can be controlled by adjusting the types and ratio of the monomers used as materials, as well as the production conditions (for example, reaction temperature, reaction time, cooling rate), and the like.

[0046] <Amorphous polyester resin> The amorphous polyester resin contained in the toner particles according to this embodiment is obtained, for example, by a polycondensation reaction between a carboxylic acid monomer containing terephthalic acid or isophthalic acid as a main component and a polyhydric alcohol containing ethylene glycol as a main component.

[0047] The dicarboxylic acid monomer used in the synthesis of the amorphous polyester resin contains terephthalic acid or isophthalic acid as a main component, and the molar content of terephthalic acid or isophthalic acid in the dicarboxylic acid monomer is preferably 70% or more and 100% or less, and more preferably 80% or more and 100% or less.

[0048] The dicarboxylic acid monomer may contain an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid other than terephthalic acid and isophthalic acid. Examples of aromatic dicarboxylic acids other than terephthalic acid and isophthalic acid include fumaric acid, and examples of aliphatic dicarboxylic acids include adipic acid, sebacic acid, and succinic acid. The dicarboxylic acid monomer may contain an ester-forming derivative of terephthalic acid or isophthalic acid, an ester-forming derivative of an aromatic dicarboxylic acid other than terephthalic acid and isophthalic acid, or an ester-forming derivative of an aliphatic dicarboxylic acid. In the present disclosure, the ester-forming derivative includes an acid anhydride, an alkyl ester, or the like of a carboxylic acid. Note that these dicarboxylic acid monomers may be used alone or in combination of two or more.

[0049] In the synthesis of the amorphous polyester resin, a polycarboxylic acid monomer having three or more valences may be used together with the dicarboxylic acid monomer. As the polycarboxylic acid monomer having three or more valences, a polycarboxylic acid having three or more valences, such as trimellitic acid and pyromellitic acid, and an ester-forming derivative thereof may be used. These polycarboxylic acid monomers having three or more valences may be used alone or in combination of two or more kinds.

[0050] The diol monomer used in the synthesis of the amorphous polyester resin contains ethylene glycol as a main component, and the molar content of ethylene glycol in the diol monomer is preferably 70% or more and 100% or less, and more preferably 80% or more and 100% or less.

[0051] The diol monomer may include 1,3-propylene glycol, 1,4-butanediol, etc. These diol monomers may be used alone or in combination of two or more.

[0052] The amorphous polyester resin used in the toner according to the present embodiment can be produced in the same manner as in the ordinary polyester production method. For example, the amorphous polyester resin can be synthesized by carrying out a polycondensation reaction at 190°C to 240°C in a nitrogen gas atmosphere using a dicarboxylic acid monomer and a polyhydric alcohol, and optionally a trivalent or higher polycarboxylic acid monomer. In the polycondensation reaction, the reaction ratio of the diol monomer and the carboxylic acid monomer (including a dicarboxylic acid monomer and optionally a trivalent or higher polycarboxylic acid monomer) is preferably 1.3:1 to 1:1.2 in terms of the equivalent ratio [OH]:[COOH] of the hydroxyl group to the carboxyl group. In the polycondensation reaction, the molar content of the dicarboxylic acid monomer in the carboxylic acid monomer is preferably 80% to 100%. Furthermore, in the polycondensation reaction, an esterification catalyst such as dibutyltin oxide or titanium alkoxide (e.g., tetrabutoxytitanate) may be used as necessary.

[0053] The content of the amorphous polyester resin in the toner particles according to this embodiment is preferably from 40% by mass to 95% by mass, and more preferably from 50% by mass to 80% by mass.

[0054] <Crystalline polyester resin> In the toner particles according to the present embodiment, the crystalline polyester resin is dispersed in the amorphous polyester resin. The crystalline polyester resin is preferably composed of a linear saturated aliphatic polyester unit obtained by polycondensing a carboxylic acid monomer containing an aliphatic dicarboxylic acid having 9 to 22 carbon atoms as a main component and a polyhydric alcohol containing an aliphatic diol having 2 to 10 carbon atoms as a main component. By being composed of the linear saturated aliphatic polyester unit, the crystalline polyester resin and the amorphous polyester resin are less likely to be compatible with each other.

[0055] The dicarboxylic acid monomer used in the synthesis of the crystalline polyester resin contains, as a main component, an aliphatic dicarboxylic acid having 9 to 22 carbon atoms. Here, the molar content of the aliphatic dicarboxylic acid having 9 to 22 carbon atoms in the dicarboxylic acid monomer is preferably 80% or more and 100% or less.

[0056] Examples of the aliphatic dicarboxylic acid having 9 to 22 carbon atoms include azelaic acid, sebacic acid, 1,10-decanedicarboxylic acid, and 1,18-octadecanedicarboxylic acid. The dicarboxylic acid monomer may also contain an ester-forming derivative of these aliphatic dicarboxylic acids. These dicarboxylic acid monomers may be used alone or in combination of two or more.

[0057] In the synthesis of the crystalline polyester resin, a polycarboxylic acid monomer having three or more valences may be used together with the dicarboxylic acid monomer. As the polycarboxylic acid monomer having three or more valences, a polycarboxylic acid having three or more valences, such as trimellitic acid and pyromellitic acid, and an ester-forming derivative thereof may be used. These polycarboxylic acid monomers having three or more valences may be used alone or in combination of two or more kinds.

[0058] The diol monomer used in the synthesis of the crystalline polyester resin contains, as a main component, an aliphatic diol having 2 to 10 carbon atoms. Here, the molar content of the aliphatic diol having 2 to 10 carbon atoms in the diol monomer is preferably 80% or more and 100% or less.

[0059] Examples of the aliphatic diol having 2 to 10 carbon atoms include ethylene glycol, 1,4-butanediol, 1,6-hexanediol, etc. These diol monomers may be used alone or in combination of two or more.

[0060] In the synthesis of the crystalline polyester resin, a polyol monomer having three or more valences may be used together with the diol monomer. As the polyol monomer having three or more valences, glycerin, trimethylolpropane, etc. can be used. These polyol monomers having three or more valences may be used alone or in combination of two or more.

[0061] The crystalline polyester resin used in the toner according to the present embodiment can be produced in the same manner as in the ordinary polyester production method. For example, the crystalline polyester resin can be synthesized by carrying out a polycondensation reaction at a temperature of 190°C to 240°C in a nitrogen gas atmosphere using a dicarboxylic acid monomer, a diol monomer, and optionally a trivalent or higher polycarboxylic acid monomer or a trivalent or higher polyol monomer.

[0062] In the above polycondensation reaction, the equivalent ratio (OH group / COOH group) of the hydroxyl group of the polyol monomer (including a diol monomer and, in some cases, a trivalent or higher polyol monomer) to the carboxyl group of the carboxylic acid monomer (including a dicarboxylic acid monomer and, in some cases, a trivalent or higher polycarboxylic acid monomer) is preferably 0.83 to 1.3 from the viewpoint of storage stability, etc.

[0063] In the polycondensation reaction, the molar content of the dicarboxylic acid monomer in the carboxylic acid monomer is preferably 90% to 100%. The smaller the molar content of the dicarboxylic acid monomer, the lower the crystallization rate and speed, and the toner aggregation resistance (resistance to toner aggregation) may become insufficient.

[0064] Furthermore, in the polycondensation reaction, the molar content of the diol monomer in the polyol monomer is preferably 80% to 100%. In the polycondensation reaction, an esterification catalyst such as dibutyltin oxide or titanium alkoxide (e.g., tetrabutoxytitanate) may be used as necessary.

[0065] The content of the crystalline polyester resin in the toner particles according to this embodiment is preferably from 5% by mass to 50% by mass, and more preferably from 10% by mass to 30% by mass.

[0066] 2-2. Release agent The toner particles according to the present embodiment contain a wax as a release agent. The wax used is preferably an ester wax, and when the endothermic peak temperature during heating measured using a differential scanning calorimeter is T1 and the exothermic peak temperature during cooling measured using the ester wax is T2, T1-T2 is preferably 15°C or more and 30°C or less. A more preferred range is 17°C or more and 23°C or less. An ester wax whose T1-T2 satisfies the above condition has a high internal lubrication effect (the effect of increasing material compatibility during melt kneading).

[0067] By blending wax into toner particles, localized charge-up can be suppressed even in low humidity environments, and external additives can be suppressed from being embedded in toner particles throughout the product's life. In other words, a toner with excellent charge stability against environmental changes and throughout its life can be realized.

[0068] Examples of ester waxes include WE-14, WE-15, and WEP-5, both of which are products of NOF Corporation.

[0069] The wax content in the toner particles according to this embodiment is preferably from 0.5% by mass to 8% by mass, and more preferably from 2% by mass to 7% by mass.

[0070] 2-3.Coloring agents The toner particles according to the present embodiment may contain a colorant. The colorant is not particularly limited, and may be an organic dye, an organic pigment, an inorganic dye, an inorganic pigment, or the like used in the field of electrophotography.

[0071] Black colorants include, for example, carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, non-magnetic ferrite, magnetic ferrite, and magnetite.

[0072] Examples of yellow colorants include CI Pigment Yellow 12, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 15, CI Pigment Yellow 17, CI Pigment Yellow 74, CI Pigment Yellow 93, CI Pigment Yellow 94, CI Pigment Yellow 138, CI Pigment Yellow 180, and CI Pigment Yellow 185.

[0073] Magenta colorants include, for example, CI Pigment Red 48:1, CI Pigment Red 53:1, CI Pigment Red 57:1, CI Pigment Red 122, CI Pigment Red 123, CI Pigment Red 139, CI Pigment Red 144, CI Pigment Red 149, CI Pigment Red 166, CI Pigment Red 177, CI Pigment Red 178, and CI Pigment Red 222.

[0074] Cyan colorants include, for example, CI Pigment Blue 15, CI Pigment Blue 15:2, CI Pigment Blue 15:3, CI Pigment Blue 16, and CI Pigment Blue 60.

[0075] In the toner according to the present embodiment, the content of the colorant is not particularly limited, but is preferably 4% by mass or more and 10% by mass or less in the toner particles. The colorant may be used alone or in combination of two or more kinds. The colorant may be used in the form of a master batch in order to disperse it uniformly in the binder resin.

[0076] 2-4.Charge control agent The toner particles according to the present embodiment may contain a charge control agent. The charge control agent is added to impart a preferred chargeability to the toner. The charge control agent is not particularly limited, and charge control agents for positive charge control and negative charge control used in the electrophotographic field can be used. Examples of charge control agents for positive charge control include quaternary ammonium salts, pyrimidine compounds, triphenylmethane derivatives, guanidine salts, and amidine salts.

[0077] Examples of charge control agents for negative charge control include metal-containing azo compounds, azo complex dyes, metal complexes and metal salts of salicylic acid and its derivatives (metals include chromium, zinc, zirconium, etc.), organic bentonite compounds, and boron compounds.

[0078] The content of the charge control agent in the toner particles according to the present embodiment is not particularly limited, but is preferably 0.5% by mass or more and 5% by mass or less. The charge control agent may be used alone or in combination of two or more kinds.

[0079] 3.External additives External additives generally have the function of improving the transportability and chargeability of the toner, as well as the stirring property with the carrier when the toner is made into a two-component developer.

[0080] The toner according to the present embodiment contains two or more types of external additives having different average primary particle diameters, that is, a first external additive and a second external additive having a larger average primary particle diameter than the first external additive.

[0081] The average primary particle diameter of the particles used as the first external additive is preferably 10 nm or more and 35 nm or less, more preferably 10 nm or more and 20 nm or less, and even more preferably 10 nm or more and 15 nm or less. By having the average primary particle diameter of the particles used as the first external additive within the above range, it is possible to impart appropriate slipperiness to the contact surface of the toner particles. In addition, it is possible to achieve both the function of maintaining the gap between the toner particles before a load is applied to the toner and the function of alleviating the stress when a load is applied to the toner.

[0082] The average primary particle diameter of the particles used as the second external additive is preferably 38 nm or more and 120 nm or less, more preferably 40 nm or more and 115 nm or less. By having the average primary particle diameter of the particles used as the second external additive within the above range, it is possible to provide an appropriate gap between the toner particles in the filled toner. In turn, it is possible to relieve the stress when a load is applied to the toner.

[0083] The first external additive is preferably silica particles, titanium oxide particles, aluminum oxide particles, silica particles with aluminum hydroxide attached to the surface, or strontium titanate particles with silica added (hereinafter, also simply referred to as "silica-added strontium titanate particles"). In addition, it is preferable to use fumed silica as the silica particles of the first external additive. Note that, although silica particles, titanium oxide particles, aluminum oxide particles, or silica-added strontium titanate particles are actually used as the first external additive in the examples described below, silica particles with aluminum hydroxide attached to the surface can also be used as the first external additive because they have the effect of suppressing the charge reduction and the occurrence of fogging in addition to the effect of stress relaxation.

[0084] The second external additive preferably contains both silica particles and titanium oxide particles. Although fumed silica can be used as the silica particles as the second external additive, it is more preferable to use colloidal silica having a narrow particle size distribution.

[0085] Furthermore, it is preferable to use two kinds of silica particles with different average primary particle diameters as the silica particles of the second external additive. In other words, it is preferable that the silica particles as the first external additive are small particle diameter silica particles, and the second external additive contains medium particle diameter silica particles and large particle diameter silica particles. In this case, the average primary particle diameter of the medium particle diameter silica particles is preferably 38 nm or more and 60 nm or less, and more preferably 40 nm or more and 50 nm or less. In addition, the average primary particle diameter of the large particle diameter silica particles is preferably 90 nm or more and 120 nm or less, and more preferably 100 nm or more and 115 nm or less.

[0086] The average primary particle size of the titanium oxide particles as the second external additive is preferably 40 nm or more and 70 nm or less, and more preferably 45 nm or more and 60 nm or less.

[0087] The content of the first external additive in the toner according to the present embodiment is preferably 0.1 parts by mass or more and 0.5 parts by mass or less, more preferably 0.2 parts by mass or more and 0.4 parts by mass or less, relative to 100 parts by mass of the toner particles. The content of the second external additive in the toner according to the present embodiment is preferably 4.0 parts by mass or more and 6.0 parts by mass or less, more preferably 4.2 parts by mass or more and 5.0 parts by mass or less, relative to 100 parts by mass of the toner particles. By having the contents of the first external additive and the second external additive within the above range, it is possible to achieve both a function of maintaining the gap between the toner particles before a load is applied to the toner and a function of alleviating the stress when a load is applied to the toner.

[0088] When the second external additive contains medium particle diameter silica particles, large particle diameter silica particles, and titanium oxide particles, the content of each particle in the toner according to this embodiment is preferably such that, relative to 100 parts by mass of toner particles, the content of medium particle diameter silica particles is preferably 0.5 parts by mass or more and 1.5 parts by mass or less, the content of large particle diameter silica particles is preferably 2 parts by mass or more and 3 parts by mass or less, and the content of titanium oxide particles is preferably 0.5 parts by mass or more and 1.5 parts by mass or less.

[0089] In the toner according to the present embodiment, the adhesion strength of the first external additive to the toner particles is preferably 90% or more and 100% or less, more preferably 95% or more and 100% or less. The adhesion strength of the second external additive to the toner particles is preferably 30% or more and 50% or less, more preferably 35% or more and 45% or less. As described above, the adhesion strength of the external additive affects the function of maintaining the gap between the toner particles before a load is applied to the toner and the function of relaxing the stress when a load is applied to the toner. Therefore, by having the adhesion strength of the first external additive and the second external additive within the above range, both functions can be achieved, and thus the occurrence of charge reduction and fogging when the image forming apparatus is operated for a long time can be suppressed.

[0090] The particles used as the external additive preferably have a hydrophobic surface, and the hydrophobic surface is preferably silane-treated. Silane-treatment means surface modification using a silane coupling agent, and examples of the silane coupling agent include hexamethyldisilazane (HMDS), dimethyl-dichlorosilane (DDS), octylsilane (OTAS), polydimethylsiloxane (PDMS), etc.

[0091] Examples of silica particles as external additives include silica particles commonly used in the technical field, for example, dry process silica particles such as fumed silica obtained by burning silicon tetrachloride and arc process silica in which silica is microparticulated in the gas phase by high energy such as plasma; wet process silica particles such as precipitation process silica synthesized under alkaline conditions using an aqueous sodium silicate solution as a raw material and gel process silica synthesized under acidic conditions; colloidal silica particles obtained by making acidic silicic acid alkaline and polymerizing it; and sol-gel process silica particles obtained by hydrolysis of an organic silane compound, and the like. In order to improve the electrical properties of the photoconductor, these may be surface-treated with a surface treatment agent such as the above-mentioned silane coupling agent.

[0092] As the silica particles as an external additive, commercially available hydrophobically treated silica particles may be used, or silica particles that have not been hydrophobically treated may be used after being subjected to a treatment.

[0093] An example of the "silica particles with aluminum hydroxide attached to the surface" as an external additive is a fine powder in which the surface of a core, which is a composition of aluminum hydroxide and silica, is silane-treated. The main component of the composition constituting the fine powder is silica, and aluminum hydroxide is attached to the surface of the silica. The content of aluminum hydroxide is 5% by mass or more and 15% by mass or less, and preferably about 10% by mass. The average primary particle size of the fine powder is preferably 10 nm or more and 35 nm or less, and more preferably 13 nm or more and 20 nm or less.

[0094] The above fine powder as "silica particles having aluminum hydroxide attached to the surface" can be produced, for example, by the following procedures (1) to (4). (1) Ion-exchanged water and hydrophilic fumed silica are mixed to obtain a silica dispersion. (2) After heating the resulting dispersion to 45°C, Al(OH) was added to the dispersion to adjust the pH to 6.0. 3 A sodium aluminate solution with a concentration of 50 g / L and a 5N aqueous sodium hydroxide solution are dropped. Next, 0.5N dilute hydrochloric acid is added so that the pH of the dispersion becomes 3 to 4, and then γ-aminopropyltriethoxysilane is added. Next, a 2N aqueous sodium hydroxide solution is added so that the pH of the dispersion becomes 6.5, and the resulting dispersion is filtered to obtain a wet cake. The resulting wet cake is washed with water and then dried to obtain a dried product 1. (3) The dried product 1 is pulverized in a collision plate type jet pulverizer to obtain a pulverized product. The pulverized product is added to a surface treatment solution obtained by adding and mixing n-hexane and amino-modified silicone oil, and the mixture is stirred to obtain a mixed liquid. The resulting mixed liquid is heated to 70°C, stirred, and dried in a reduced pressure dryer until the mass of the contents stops decreasing, to obtain a dried product 2. (4) The dried product 2 is heated in an electric furnace at 200°C for 3 hours and then cooled to obtain an aggregate of a composition of silica and aluminum hydroxide. The obtained aggregate is pulverized in a collision plate type jet pulverizer to obtain the target fine powder.

[0095] As an external additive, "strontium titanate particles with added silica" (strontium titanate particles with added silica) may be mentioned fine powder in which the surface of a core of strontium titanate with added silica is hydrophobized with a silane compound. The average primary particle size of the fine powder is preferably 10 nm or more and 35 nm or less, more preferably 20 nm or more and 30 nm or less.

[0096] In the fine powder as "silica-added strontium titanate particles", the molar ratio Si / Ti of silicon to titanium is preferably 0.03 or more and less than 1.0, more preferably 0.04 or more and 0.06 or less. Si / Ti represents the content ratio of silica in the fine powder. If Si / Ti is less than the lower limit, the negative chargeability is weakened, and the fogging value may increase due to a decrease in charge in a high humidity environment. If Si / Ti exceeds the upper limit, the negative chargeability is strengthened, and the adhesion force between the toner and the carrier increases due to an increase in charge in a low humidity environment, so that the toner supplied later becomes difficult to mix and is not sufficiently charged when developed, which results in an increase in toner scattering and a high fogging value.

[0097] The above-mentioned fine powder as "silica-added strontium titanate particles" can be produced, for example, by the following procedures (1) to (5). (1) Metatitanic acid obtained by the sulfuric acid method is desulfurized and bleached, then desulfurized by adding an aqueous solution of sodium hydroxide, and then neutralized with hydrochloric acid, filtered, and washed with water to obtain a washed cake. (2) Water is added to the washed cake to make a slurry, and then hydrochloric acid is added to perform a peptization treatment. This is solution 1, and is mixed with solution 2, an aqueous solution of strontium chloride, and solution 3, an aqueous solution of sodium silicate. The mixing ratio of solutions 1, 2, and 3 is set so that the molar ratio of (Sr+Si) / Ti is within the range of 1.18 to 2.10. (3) The mixed solution is heated to 90°C under a nitrogen gas atmosphere, stirred for 2 hours while adding an aqueous sodium hydroxide solution, and then reacted at 90°C for 1 hour with stirring. (4) After the reaction, the slurry is cooled to 50°C, hydrochloric acid is added and stirred for 1 hour. The resulting precipitate is washed, separated by filtration, and then dried. (5) The obtained dried material is pulverized in a blender for 1 minute, and the coarse powder is removed by sieving. The fine powder substrate obtained is then surface-coated with a silane coupling agent. Examples of methods for surface-coating with a silane coupling agent include surface treatments commonly used in the art using hexamethyldisilazane (HMDS), dimethyl-dichlorosilane (DDS), octylsilane (OTAS), polydimethylsiloxane (PDMS), etc.

[0098] 4. Toner manufacturing method According to the present disclosure, in a toner using pulverized toner particles, it is possible to effectively suppress embedding of an external additive in the toner particles. Therefore, the toner particles according to the present embodiment are preferably pulverized toner particles. In the present disclosure, pulverized toner particles refer to toner particles produced by a pulverization method.

[0099] The production of toner particles by the pulverization method can be carried out, for example, by carrying out a mixing step of dry-mixing materials including an internal additive such as a colorant and a binder resin in a mixer, a melting and kneading step of melting and kneading the resulting mixture in a kneader, a grinding step of cooling and solidifying the resulting molten and kneaded mixture, and grinding the resulting solidified mixture in a grinder to obtain a finely pulverized product, and a classification step of adjusting the particle size of the resulting finely pulverized product using a classifier or the like as necessary.

[0100] The toner manufacturing method according to the present embodiment includes a first external addition step of adhering the first external additive to the surface of the toner particles by mixing the first external additive with the toner particles, and a second external addition step of adhering the second external additive to the surface of the toner particles by mixing the second external additive with the toner particles, and it is preferable to carry out the second external addition step after carrying out the first external addition step. This allows the adhesion strength of the first external additive to the toner particles to be adjusted to be greater than the adhesion strength of the second external additive to the toner particles, and thus makes it possible to manufacture a toner that can simultaneously maintain the gaps between the toner particles before a load is applied to the toner and relieve the stress when a load is applied to the toner.

[0101] As a method for mixing the toner particles and the external additive, there is a method in which the toner particles and the external additive are mixed by an air flow mixer such as a Henschel mixer.

[0102] 5. Two-component developer The developer according to the present embodiment is a two-component developer containing a toner and a carrier. The two-component developer can be produced by mixing the toner and the carrier using a known mixer. The mass ratio of the toner and the carrier is not particularly limited, and may be, for example, 3:97 to 12:88.

[0103] The carrier is stirred and mixed with the toner in the developing tank, giving the toner the desired charge. The carrier also acts as an electrode between the developing device and the photoconductor, carrying the charged toner to the electrostatic latent image on the photoconductor and forming a toner image. The carrier is held on the magnetic roller (developing roller) of the developing device by magnetic force, and after acting in development, it returns to the developing tank, where it is stirred and mixed again with new toner and used repeatedly until the end of its life.

[0104] The carrier is composed of a carrier core material and a resin coating layer that coats the surface of the carrier core material. The resin coating layer formed of the carrier resin may be treated with a coupling agent.

[0105] <Carrier core material> As the carrier core material, those commonly used in the art can be used, for example, magnetic metals such as iron, copper, nickel, cobalt, etc., and magnetic metal oxides such as ferrite, magnetite, etc. If these carrier core materials are used, a carrier suitable for a developer used in a magnetic brush development method can be obtained.

[0106] Among these, particles containing a ferrite component are preferred as the carrier core material. Ferrite has high saturation magnetization and can produce a coated carrier with low density, so that when used in a developer, the coated carrier is less likely to adhere to the photoreceptor, and a soft magnetic brush is formed, resulting in an image with high dot reproduction.

[0107] Examples of ferrites include zinc-based ferrite, nickel-based ferrite, copper-based ferrite, barium ferrite, strontium ferrite, nickel-zinc-based ferrite, manganese-magnesium-based ferrite, copper-magnesium-based ferrite, manganese-zinc-based ferrite, manganese-copper-zinc-based ferrite, and manganese-magnesium-strontium-based ferrite.

[0108] Ferrite can be prepared by a known method. For example, 2 O 3 , Mg(OH) 2 The ferrite raw materials are mixed, and the mixed powder is heated in a heating furnace and calcined. The calcined product is cooled and then pulverized in a vibration mill to particles of about 1 μm. A dispersant and water are added to the pulverized powder to produce a slurry. This slurry is wet-pulverized in a wet ball mill, and the resulting suspension is granulated and dried in a spray dryer to obtain ferrite particles.

[0109] The average primary particle diameter of the carrier core material is preferably 25 μm or more and 50 μm or less, more preferably 30 μm or more and 50 μm or less. If the average primary particle diameter of the carrier core material is in the above range, the toner can be stably transported to the electrostatic latent image formed on the photoreceptor, and a high-definition image can be formed for a long period of time. If the average primary particle diameter of the carrier core material is less than the above lower limit, it may be difficult to control carrier adhesion. On the other hand, if the average primary particle diameter of the carrier core material exceeds the above upper limit, it may be difficult to form a high-definition image.

[0110] <Carrier resin> The resin for forming the resin coating layer is not particularly limited, and may be any resin commonly used in the art, such as polyester resin, acrylic resin, acrylic modified resin, silicone resin, and fluororesin. These resins may be used alone or in combination of two or more.

[0111] Examples of the acrylic resin include polyacrylate, polymethyl methacrylate, polyethyl methacrylate, poly-n-butyl methacrylate, polyglycidyl methacrylate, fluorine-containing polyacrylate, styrene-methacrylate copolymer, styrene-butyl methacrylate copolymer, and styrene-ethyl acrylate copolymer.

[0112] Examples of commercially available acrylic resins include those manufactured by Mitsubishi Rayon Co., Ltd. under the trade name DIANAL SE-5437, those manufactured by Sekisui Chemical Co., Ltd. under the trade name S-LEC PSE-0020, those manufactured by Sanyo Chemical Industries, Ltd. under the trade name HYMER ST95, and those manufactured by Mitsui Chemicals, Inc. under the trade name FM601.

[0113] Silicone resins can suppress toner spent and improve the adhesion between the carrier core material and the resin coating layer, and among these, crosslinked silicone resins are preferred.

[0114] Examples of commercially available crosslinked silicone resins include those manufactured by Dow Corning Toray Co., Ltd. under the trade names SR2400, SR2410, SR2411, SR2510, SR2405, 840RESIN, and 804RESIN, and those manufactured by Shin-Etsu Chemical Co., Ltd. under the trade names KR350, KR271, KR272, KR274, KR216, KR280, KR282, KR261, KR260, KR255, KR266, KR251, KR155, KR152, KR214, KR220, X-4040-171, KR201, KR5202, and KR3093.

[0115] The resin forming the resin coating layer is preferably a silicone resin, particularly a crosslinked silicone resin, and may contain other resins within a range that does not impair its preferred properties. Examples of other resins include epoxy resins, urethane resins, phenolic resins, acrylic resins, styrene resins, polyamides, polyesters, acetal resins, polycarbonates, vinyl chloride resins, vinyl acetate resins, cellulose resins, polyolefins, fluororesins, and copolymer resins and blended resins thereof. Among these, acrylic resins are preferred because of their high charging ability. For example, bifunctional silicone oil may be contained in order to further improve the moisture resistance, releasability, etc. of the resin coating layer formed of silicone resins (particularly crosslinked silicone resins).

[0116] <Conductive particles> The resin coating layer preferably contains conductive fine particles, which can stably increase the carrier's ability to impart charge to the toner, i.e., can suppress charge-up of the carrier.

[0117] There are no particular limitations on the conductive fine particles, and conductive fine particles commonly used in the art can be used, such as conductive carbon black, and oxides such as conductive titanium oxide and tin oxide.

[0118] Carbon black is suitable for black toners because it can provide electrical conductivity even in small amounts, whereas antimony-doped conductive titanium oxide is suitable for color toners because of concerns about the detachment of carbon black from the resin coating layer.

[0119] The amount of conductive fine particles is not particularly limited, but is preferably 1 part by mass or more and 25 parts by mass or less, and more preferably 1 part by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the resin forming the resin coating layer. If the amount of conductive fine particles is less than the lower limit, the effect of the conductive fine particles may not be obtained. On the other hand, if the amount of conductive fine particles is more than the upper limit, the resin coating layer may not be formed uniformly.

[0120] <Coupling Agent> The resin coating layer may further contain a coupling agent such as a silane coupling agent for the purpose of adjusting the toner charge amount. Among the silane coupling agents, a silane coupling agent having an electron-donating functional group is preferred, and for example, an amino group-containing silane coupling agent represented by the following formula can be mentioned. (Y) n Si(R) m (Wherein, R may be the same or different and represent C 1 ~C 4 Alkyl group, C 1 ~C 4 represents an alkoxy group or a chlorine atom, and Y is the same or different, and each represents a C 1 ~C 10 represents a saturated hydrocarbon and / or aromatic hydrocarbon group, m and n each represent an integer of 1 to 3, and m+n=4.

[0121] In the above formula, examples of the alkyl group represented by R include linear or branched alkyl groups having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and a tert-butyl group. Of these, a methyl group is preferred.

[0122] In the above formula, examples of the alkoxy group represented by R include linear or branched alkoxy groups having 1 to 4 carbon atoms, such as a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, and a tert-butoxy group. Of these, a methoxy group and an ethoxy group are preferred.

[0123] In the above formula, examples of the saturated hydrocarbon and / or aromatic hydrocarbon group containing an amino group represented by Y include -(CH 2 ) a Examples of the alkyl group include -X (wherein X is an amino group, an aminocarbonylamino group, an aminoalkylamino group, a phenylamino group or a dialkylamino group, and a is an integer of 1 to 4), -Ph-X (wherein X is the same as above, and -Ph- is a phenylene group), and the like.

[0124] Specific examples of the amino group-containing silane coupling agent include the following: H 2 N(H 2 C) 3 Si(OCH 3 ) 3 H 2 N(H 2 C) 3 Si(OC 2 H 5 ) 3 H 2 N(H 3 C) 3 Si(CH 3 )(OCH 3 ) 2 H 2 N(H 2 C) 2 HN(H 2 C) 3 Si(CH 3 )(OCH 3 ) 2 H 2 NOCHN(H 2 C) 3 Si(OC 2 H 5 )3 H 2 N(H 2 C) 2 HN(H 2 C) 3 Si(OCH 3 ) 3 H 2 N-Ph-Si(OCH 3 ) 3 (In the formula, -Ph- represents a p-phenylene group.) Ph-HN(H 2 C) 3 Si(OCH 3 ) 3 (In the formula, Ph- represents a phenyl group.) (H 9 C 4 ) 3 N(H 2 C) 3 Si(OCH 3 ) 3

[0125] The above coupling agents may be used alone or in combination of two or more. The amount of the coupling agent is not particularly limited, but is preferably 1 to 15 parts by mass, more preferably 5 to 15 parts by mass, per 100 parts by mass of the carrier resin. If the amount of the coupling agent is within the above range, the toner can be given a sufficient charge, and the mechanical strength of the resin coating layer is not significantly reduced. EXAMPLES

[0126] The toner and two-component developer of the present disclosure will be specifically described below based on examples and comparative examples. First, various measurement methods and evaluation methods will be described.

[0127] 1. Measurement and evaluation methods <Method for measuring apparent viscosity of toner particles> A flow tester (Shimadzu Corporation, product name: CFT-100C) was used with a load of 10 kgf / cm 2(0.98 MPa) was applied, and the setting was such that 1 g of toner particles was extruded from a die (nozzle diameter 1.0 mm, length 1.0 mm). Heating was carried out from 80 °C to 120 °C at a heating rate of 6 °C / min, and the melt viscosity (apparent viscosity [Pa·s]) was determined.

[0128] <Method for Measuring the Adhesion Strength of Externally Added Agents to Toner Particles> The externally added agent adhesion strength test was carried out on the toner according to the following procedure. (1) 2.0 g of toner was added to 40 mL of an aqueous solution of polyoxyethylene octylphenyl ether with a concentration of 0.2 mass% (manufactured by Dow Chemical Company, trade name: Triton (registered trademark)) and stirred for 1 minute. (2) Using an ultrasonic homogenizer (manufactured by Nippon Seiki Co., Ltd., model: US-300T), the aqueous solution obtained in (1) above was irradiated with ultrasonic waves of an output of 40 μA for 4 minutes. (3) Then, it was left standing for 3 hours to separate the toner and the externally added agent released from the toner. (4) After removing the supernatant, about 50 mL of pure water was added to the precipitate and stirred for 5 minutes. (5) Suction filtration was carried out using a membrane filter with a pore size of 1 μm (manufactured by Advantec). (6) The toner remaining on the membrane filter was vacuum dried overnight to obtain the toner after the externally added agent removal treatment. (7) Regarding the obtained toner after the externally added agent removal treatment and the toner before the externally added agent removal treatment, using a fluorescent X-ray analyzer (manufactured by Rigaku Corporation, model: ZSXPrimus II), the X-ray intensity of the specific elements in 1 g of the externally added agent of the toner was measured.

[0129] The adhesion strength A of each element of the second externally added agent in Table 2 shown below is calculated as follows. Adhesion strength A = (X-ray intensity of specific elements after the externally added agent removal treatment by irradiating ultrasonic waves for 4 minutes) / (X-ray intensity of specific elements before the externally added agent removal treatment) × 100

[0130] Next, the externally added agent adhesion strength test was carried out in the same manner as (1) to (7) above, except that the ultrasonic irradiation time in (2) above was changed to 8 minutes. The adhesion strength Y of each element of this second externally added agent is calculated as follows. Adhesion strength Y = (X-ray intensity of specific elements after external additive removal treatment with 8 minutes of ultrasonic irradiation) / (X-ray intensity of specific elements before external additive removal treatment) x 100

[0131] The adhesive strength B of each element of the first external additive in Table 2 shown later is calculated by the following formula. Adhesive strength B = 1-(adhesive strength A-adhesive strength Y) The reason for calculating the adhesion strength B of each element of the first external additive in this manner is that it coincides well when the first external additive and the second external additive are composed of different elements, and that when the toner after measuring the adhesion strength A is observed under SEM, it is found that external additives of 40 nm to 120 nm have mainly been removed by ultrasound.

[0132] In this embodiment, since multiple types of external additives were used as the second external additive, the total adhesive strength A was calculated based on the mass ratio of each added element as follows: In the following formula, specific elements 1 and 2 indicate two specific elements in the multiple types of external additives. Adhesion strength A = (adhesion strength A of the second external additive containing characteristic element 1) x {(mass of the second external additive containing characteristic element 1) / (mass of the second external additive containing characteristic element 1 + mass of the second external additive containing characteristic element 2)} + (adhesion strength A of the second external additive containing characteristic element 2) x {(mass of the second external additive containing characteristic element 2) / (mass of the second external additive containing characteristic element 1 + mass of the second external additive containing characteristic element 2)}

[0133] <Method for measuring loose bulk density of toner> The mass of 30 mL of the toner that had been left to stand for 180 seconds was measured using a bulk density measuring device (manufactured by Ito Seisakusho Co., Ltd., JIS-K-5101), thereby measuring the loose bulk density of the toner.

[0134] <Method for measuring the stress relaxation rate of toner> The stress relaxation rate of the toner was measured using a powder flow analyzer (manufactured by Freeman Technology, Model: FT4) according to the following procedure. (1) 30 g of the toner to be measured is placed in a cylinder having a capacity of 200 mL and an inner diameter of 50 mm. (2) A silicon rubber heater is wrapped around the cylinder, and the toner is heated to 50° C. by the heater. The toner temperature is measured with a K thermocouple. (3) A 48 mm diameter blade is rotated and moved up and down once every three minutes to agitate the toner inside the cylinder and eliminate temperature unevenness. (4) The blade is removed and a piston with a diameter of 48 mm is attached. The piston is lowered at a speed of 0.5 mm / sec. When a load of 2 N is applied, the piston is stopped and the volume of the compressed toner is kept constant for 30 seconds. Stress relaxation occurs inside the compressed toner, and the load applied by the powder fluidity analyzer decreases over time, reaching a stable value after 30 seconds. This is recorded as the "stress 30 seconds after application of 2 N." (5) The piston is again lowered at a speed of 0.5 mm / sec. This time, the descent is stopped when a load of 3 N is applied, and the volume of the compressed toner is kept constant for 30 seconds. This is recorded as the "stress 30 seconds after application of 3 N." (6) This measurement is continued up to a load of 40 N, and the stress after 30 seconds is recorded.

[0135] The stress relaxation rate of the toner is calculated by the following formula. Stress relaxation rate [%] = (stress at the beginning of loading - stress after relaxation) / (stress at the beginning of loading) x 100

[0136] Fig. 13 is a graph illustrating the relationship between the stress on the toner and the passage of time when a load of 20 N is applied. Taking this case as an example, if the piston is stopped descending after a load of 20 N is applied and the toner volume is kept constant and allowed to stand for 30 seconds, the stress on the toner is relaxed as shown in the graph in Fig. 13. In this case, the stress is relaxed to 16 N, so the stress relaxation rate of the toner is calculated as follows: Stress relaxation rate [%] = (20N-16N) / 20N x 100 = 20 [%]

[0137] The pressure applied to the toner is calculated from the cross-sectional area of ​​the piston with a diameter of 48 mm. The stress relaxation rate shown in Table 3 below is calculated based on the stress applied to the toner of 1.2 N / cm 2The stress relaxation rate of the toner was measured when the toner was pressed with a pressure of 100 MPa.

[0138] <Method of measuring the degree of compression of toner> The degree of compression of the toner was calculated from the values ​​of the loose bulk density and the hardened bulk density according to the following formula. The method for measuring the loose bulk density is as described above. The hardened bulk density is calculated by applying a stress of 1.2 N / cm to the toner in the measurement of the stress relaxation rate of the toner. 2 The toner density was determined when the toner was pressed with a pressure of 100 MPa. Compressibility [%] = (hard bulk density - loose bulk density) / (hard bulk density) x 100

[0139] <Method for measuring the average primary particle size of external additives> The average primary particle diameter of the external additive was determined by photographing the toner particles using a scanning electron microscope (SEM) (manufactured by Hitachi High-Technologies Corporation, model: S-4800), measuring the particle diameters (longer diameter) of 100 external additive particles on the toner surface from the obtained image, and calculating the average value of the particle diameters of the 100 particles, which was defined as the average primary particle diameter.

[0140] <Method for evaluating durability of developer> - Evaluation method based on cover value - A color multifunction printer (model: BP-20C25, manufactured by Sharp Corporation) was used as the evaluation machine. The evaluation machine was operated in an environmental test room at a temperature of 30°C and a humidity of 85% RH, and 90,000 sheets of an image were printed in which 1% of the printable area of ​​A4 paper was filled with cyan toner. A color difference meter (model: ZE6000, manufactured by Nippon Denshoku Industries Co., Ltd.) was used to measure the brightness of a specific area of ​​the image that was not filled. The difference between this brightness and the brightness measured before printing was used as the fog value. The specified value of the fog value refers to a specified value determined by the evaluation machine and the evaluation content. In addition, the "fogging degree" in Table 3 shown below refers to the ratio [%] of the measured value to the specified value of the fog value.

[0141] The evaluation criteria based on the fog value are as follows: ◎ (Excellent): The measured value is 80% or less of the specified fogging value. ◯ (Good): The measured value is more than 80% and 90% or less of the specified fogging value. △ (Fair): The measured value is more than 90% and 100% or less of the specified fogging value. × (Fail): The measured value is more than 100% of the specified fogging value.

[0142] - Evaluation method based on charge reduction rate - The toner charge amount of the developer after printing 90,000 sheets in the "evaluation method based on fog value" above was measured using a suction type charge amount measuring device (Trek, model: 210HS-2A) and compared with the toner charge amount of the developer before printing 90,000 sheets. Because the toner concentration in the developer differs before and after printing, the charge amount was converted to the amount when the toner concentration was combined and then compared.

[0143] The evaluation criteria based on the charge reduction rate are as follows: ◎ (Excellent): The charge amount after printing 90,000 sheets is more than 80% of the charge amount of the initial developer. ◯ (Good): The charge amount after printing 90,000 sheets is more than 75% and less than 80% of the charge amount of the initial developer. △ (Fair): The charge amount after printing 90,000 sheets is more than 70% and 75% or less of the charge amount of the initial developer. × (Not acceptable): The charge amount after printing 90,000 sheets is 70% or less of the charge amount of the initial developer.

[0144] 2. Toner and two-component developer manufacturing examples <Toner particle production process> -Preparation of toner particles (I)- The following toner materials were used to prepare the toner particles (toner cores). ·Binding resin Amorphous polyester resin 62% by mass Crystalline polyester resin 25% by mass Coloring agents CIPigmant Blue 15:3 (manufactured by DIC Corporation) 7% by mass Release agent Ester wax (NOF Corporation, product name: WEP-5) 5% by mass Charge control agent Salicylic acid compound (manufactured by Orient Chemical Industry Co., Ltd., product name: Bontron E-84) 1% by mass

[0145] The above materials were premixed for 5 minutes using a Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd., model: FM20C), and then melt-kneaded using an open-roll type continuous kneader (manufactured by Nippon Coke and Engineering Co., Ltd., model: MOS320-1800) to obtain a melt-kneaded product [mixing and kneading process]. The open roll setting conditions were: heating roll supply side temperature 130°C, discharge side temperature 100°C, cooling roll supply side temperature 40°C, and discharge side temperature 25°C. The heating roll and cooling roll were rolls with a diameter of 320 mm and an effective length of 1550 mm, and the gap between the rolls on the supply side and discharge side was both 0.3 mm. The rotation speed of the heating roll was 75 rpm, the rotation speed of the cooling roll was 65 rpm, and the supply amount of the toner material was 5.0 kg / h.

[0146] The resulting molten kneaded product was cooled with a cooling belt and then coarsely pulverized using a speed mill having a φ2 mm screen to obtain a coarsely pulverized product [coarse pulverization step].

[0147] The obtained coarsely pulverized product was finely pulverized using a jet pulverizer (manufactured by Nippon Pneumatic Mfg. Co., Ltd., model: IDS-2) to obtain a finely pulverized product [fine pulverization step].

[0148] Next, the obtained finely pulverized product was classified using an elbow jet classifier (manufactured by Nittetsu Mining Co., Ltd., model: EJ-LABO) to obtain toner particles (I) having an average primary particle diameter of 6.0 μm [classification step].

[0149] - Preparation of toner particles (II) - Toner particles (II) were obtained in the same manner as in the above "Preparation of toner particles (I)" except that the blending ratio of the binder resin was changed as follows. ·Binding resin Amorphous polyester resin 47% by mass Crystalline polyester resin 40% by mass

[0150] -Preparation of toner particles (III)- Toner particles (III) were obtained in the same manner as in the above "Preparation of toner particles (I)" except that the blending ratio of the binder resin was changed as follows. ·Binding resin Amorphous polyester resin 87% by mass

[0151] <External addition process (toner production process)> [Example 1] The external addition process for attaching the external additive to the toner particle surface was divided into a first external addition process and a second external addition process. In the first external addition process, 100 parts by mass of the toner particles (I) and 0.3 parts by mass of silica particles (average primary particle diameter 12 nm, manufactured by Teika Corporation, product name: MSN-002) were charged into a container, and the contents of the container were mixed at a rotation speed of 3500 rpm for 120 seconds using a Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd., model: FM20C).

[0152] Next, in the second external addition step, 0.95 parts by mass of silica particles (average primary particle diameter 40 nm, manufactured by Nippon Aerosil Co., Ltd., product name: RY50), 0.95 parts by mass of titanium oxide particles (average primary particle diameter 50 nm, manufactured by Fuji Titanium Co., Ltd., product name: TAF-500MSA), and 2.5 parts by mass of silica particles (average primary particle diameter 110 nm, manufactured by Shin-Etsu Chemical Co., Ltd., product name: X-24-9163A) were added to the above container and mixed for 180 seconds at a rotation speed of 3500 rpm. The resulting mixture was sieved using a 270 mesh sieve to obtain the toner of Example 1.

[0153] [Example 2] The toner of Example 2 was obtained in the same manner as in Example 1, except that among the external additives added in the first external addition process, silica particles having an average primary particle diameter of 12 nm (manufactured by Teika Corporation, product name: MSN-002) were changed to silica particles having an average primary particle diameter of 7 nm (manufactured by Nippon Aerosil Co., Ltd., product name: R976S).

[0154] [Example 3] The toner of Example 3 was obtained in the same manner as in Example 1, except that among the external additives added in the first external addition step, silica particles having an average primary particle diameter of 12 nm (manufactured by Teika Corporation, product name: MSN-002) were changed to silica particles having an average primary particle diameter of 37 nm (manufactured by Cabot Corporation, product name: TG-5180).

[0155] [Example 4] The toner of Example 4 was obtained in the same manner as in Example 1, except that among the external additives added in the second external addition step, silica particles having an average primary particle diameter of 110 nm (manufactured by Shin-Etsu Chemical Co., Ltd., product name: X-24-9163A) were changed to silica particles having an average primary particle diameter of 37 nm (manufactured by Cabot Corporation, product name: TG-5180).

[0156] [Example 5] The toner of Example 5 was obtained in the same manner as in Example 1, except that among the external additives added in the second external addition step, silica particles having an average primary particle diameter of 110 nm (manufactured by Shin-Etsu Chemical Co., Ltd., product name: X-24-9163A) were changed to silica particles having an average primary particle diameter of 200 nm (manufactured by Cabot Corporation, product name: TG-C6020).

[0157] [Example 6] The toner of Example 6 was obtained in the same manner as in Example 1, except that the amount of silica particles (manufactured by Shin-Etsu Chemical Co., Ltd., product name: X-24-9163A) having an average primary particle diameter of 110 nm added in the second external addition step was changed from 2.5 parts by mass to 2.0 parts by mass.

[0158] [Example 7] The toner of Example 7 was obtained in the same manner as in Example 1, except that the amount of silica particles (manufactured by Shin-Etsu Chemical Co., Ltd., product name: X-24-9163A) having an average primary particle diameter of 110 nm added in the second external addition step was changed from 2.5 parts by mass to 4.2 parts by mass.

[0159] [Example 8] A toner of Example 8 was obtained in the same manner as in Example 1, except that the mixing time in the first external addition step (first external addition time) was changed from 120 seconds to 60 seconds.

[0160] [Example 9] The toner of Example 9 was obtained in the same manner as in Example 1, except that the mixing time in the second external addition step (second external addition time) was changed from 180 seconds to 150 seconds.

[0161] [Example 10] The toner of Example 10 was obtained in the same manner as in Example 1, except that the mixing time in the second external addition step (second external addition time) was changed from 180 seconds to 240 seconds.

[0162] [Example 11] The toner of Example 11 was obtained in the same manner as in Example 1, except that among the external additives added in the first external addition step, silica particles having an average primary particle diameter of 12 nm (manufactured by Teika Corporation, product name: MSN-002) were changed to titanium oxide particles having an average primary particle diameter of 15 nm (manufactured by Teika Corporation, product name: MTX150AO).

[0163] [Example 12] The toner of Example 12 was obtained in the same manner as in Example 1, except that among the external additives added in the first external addition step, silica particles having an average primary particle diameter of 12 nm (manufactured by Teika Corporation, product name: MSN-002) were changed to aluminum oxide particles having an average primary particle diameter of 13 nm (manufactured by Nippon Aerosil Co., Ltd., product name: C805).

[0164] [Example 13] A toner of Example 13 was obtained in the same manner as in Example 1, except that among the external additives added in the first external addition step, silica particles (manufactured by Teika Corporation, product name: MSN-002) having an average primary particle diameter of 12 nm were changed to silica-added strontium titanate particles having an average primary particle diameter of 25 nm. The silica-added strontium titanate particles used were prepared according to the following procedure. (1) Metatitanic acid obtained by the sulfuric acid method was deironized and bleached, then desulfurized by adding an aqueous solution of sodium hydroxide, and then neutralized with hydrochloric acid. After filtration and washing with water, a washed cake was obtained. (2) Water was added to the washed cake to make a slurry, and then hydrochloric acid was added to perform a peptization treatment. This was solution 1, and was mixed with solution 2, an aqueous solution of strontium chloride, and solution 3, an aqueous solution of sodium silicate. The mixing ratio of solutions 1, 2, and 3 was set so that the molar ratio of (Sr+Si) / Ti was 1.2. (3) The mixed solution was heated to 90°C under a nitrogen gas atmosphere, and the reaction was carried out by stirring for 2 hours while adding an aqueous sodium hydroxide solution. (4) After the reaction, the slurry was cooled to 50°C, hydrochloric acid was added, and the mixture was stirred for 2 hours. The resulting precipitate was washed, separated by filtration, and then dried. (5) The dried material was ground in a blender for 1 minute, and the coarse powder was removed using a sieve. The fine powder substrate obtained was then surface-coated with a silane coupling agent, DDS (dimethyl-dichlorosilane).

[0165] [Example 14] The toner of Example 14 was obtained in the same manner as in Example 1, except that in the second external addition step, a combination of silica particles having an average primary particle diameter of 40 nm and silica particles having an average primary particle diameter of 110 nm was used instead of 3.45 parts by mass of silica particles having an average primary particle diameter of 110 nm (manufactured by Shin-Etsu Chemical Co., Ltd., product name: X-24-9163A).

[0166] [Comparative Example 1] A toner of Comparative Example 1 was obtained in the same manner as in Example 1, except that the toner particles used were changed from toner particles (I) to toner particles (II).

[0167] [Comparative Example 2] A toner of Comparative Example 2 was obtained in the same manner as in Example 1, except that the toner particles used were changed from toner particles (I) to toner particles (III).

[0168] [Comparative Example 3] The toner of Comparative Example 3 was obtained in the same manner as in Example 1, except that the amount of silica particles (manufactured by Teika Corporation, product name: MSN-002) having an average primary particle diameter of 12 nm added in the first external addition step was changed from 0.3 parts by mass to 0.6 parts by mass.

[0169] [Comparative Example 4] Comparative Example 4 is an example in which the first external addition step in Example 1 was not carried out, and only the second external addition step was carried out, with the mixing time being changed to 290 seconds (300 seconds minus 10 seconds, the rotation start-up time of the Henschel mixer).

[0170] Specifically, 100 parts by mass of toner particles (I), 0.95 parts by mass of silica particles (average primary particle diameter 40 nm, manufactured by Nippon Aerosil Co., Ltd., product name: RY50), 0.95 parts by mass of titanium oxide particles (average primary particle diameter 50 nm, manufactured by Fuji Titanium Industrial Co., Ltd., product name: TAF-500MSA), and 2.5 parts by mass of silica particles (average primary particle diameter 110 nm, manufactured by Shin-Etsu Chemical Co., Ltd., product name: X-24-9163A) were charged into a container, and the contents of the container were mixed at a rotation speed of 3500 rpm for 290 seconds using a Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd., model: FM20C). The resulting mixture was sieved using a 270 mesh sieve to obtain a toner of Comparative Example 4.

[0171] [Comparative Example 5] The toner of Comparative Example 5 was obtained in the same manner as in Example 1, except that in the first external addition step, the amount of silica particles (manufactured by Teika Corporation, product name: MSN-002) added having an average primary particle diameter of 12 nm was changed from 0.3 parts by mass to 1.2 parts by mass, and the mixing time (first external addition time) was changed from 120 seconds to 40 seconds.

[0172] <Carrier manufacturing process> 0.375 parts by mass of silicone resin 1 (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR240) and 0.375 parts by mass of silicone resin 2 (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR251) were dissolved in 12 parts by mass of toluene, and 0.0375 parts by mass of conductive fine particles (manufactured by Cabot Corporation, product name: VULCAN XC-72) and 0.0225 parts by mass of coupling agent (manufactured by Toray Dow Corning Co., Ltd., product name: AY43-059) were dispersed therein to prepare a coating resin liquid. 12.8 parts by mass of the coating resin liquid was used per 100 parts by mass of the carrier core material. The surface of the carrier core material was coated with the coating resin liquid by the immersion method. After a curing process at a curing temperature of 200°C and a curing time of 1 hour, the carrier was produced by sieving through a sieve with a mesh size of 150 μm.

[0173] <Production process of two-component developer> The toners of Examples 1 to 14 and Comparative Examples 1 to 5 were combined with the prepared carrier to prepare the two-component developers of Examples 1 to 14 and Comparative Examples 1 to 5. These two-component developers were prepared by mixing for 20 minutes in a V-type mixer (manufactured by Tokuju Machinery Co., Ltd., product name: V-5) so that the toner concentration became 7% by mass.

[0174] [Table 1]

[0175] [Table 2]

[0176] [Table 3]

[0177] Table 1 shows a summary of the types of additives used in the preparation of the toners of the examples and comparative examples, the amounts added, and the mixing time (addition time) in the addition step.

[0178] Table 2 shows the calculation results of the adhesion strength of the external additive to the toner particles in the examples and comparative examples. The values ​​shown in the "Adhesion Strength A (total)" column in Table 2 correspond to the "adhesion strength of the second external additive," and the values ​​shown in the "Adhesion Strength B" column correspond to the "adhesion strength of the first external additive."

[0179] Table 3 shows the physical properties and evaluation results of the examples and comparative examples. Also, Figures 8 to 12 are graphs showing the measurement results of the stress relaxation rates of Example 1 and Comparative Examples 1 and 3 to 5. The gray areas in the graphs indicate stresses of 1.2 N / cm 2 This is described to make it easier to visually check whether the stress relaxation rate of the toner is 27% or more when pressed with pressure, and in Example 1 of FIG. 8, it can be visually confirmed that the stress relaxation rate is 27% or more.

[0180] As is clear from the evaluation results in Table 3, the toners of Examples 1 to 14, which satisfy the following requirements (A) to (D), have low-temperature fixing properties and can suppress the decrease in charge and the occurrence of fogging when the image forming apparatus is operated for a long period of time. (A) The toner particles contain a crystalline polyester resin and a wax, and have an apparent viscosity at 90°C of 100,000 Pa·s or more and 200,000 Pa·s or less. The (B) external additive includes a first external additive and a second external additive having an average primary particle diameter larger than that of the first external additive. (C) The loose bulk density of the toner is 0.3 g / cm 3 More than 0.35g / cm 3 The following is the result. (D) 1.2N / cm at 50℃ 2 When the toner is pressed, the compression degree of the toner is 50% or less, and the stress relaxation rate of the toner is 27% or more.

[0181] In contrast, among Comparative Examples 1 to 5 which do not satisfy these requirements, Comparative Examples 2 to 5 were inferior to the Examples in at least one of the evaluations based on the fog value and the evaluation based on the charge reduction rate. Also, Comparative Example 1 is an example which does not correspond to a low-temperature fixing toner (an example with poor low-temperature fixing properties). Therefore, the evaluations based on the fog value and the charge reduction rate for Comparative Example 1 in Table 3 are indicated as "◎ (low-temperature fixing ×)".

[0182] Comparing Example 1 with Examples 2 and 3, it is found that Example 1, in which the average primary particle diameter of the first external additive is 10 nm or more and 35 nm or less, is superior in the evaluations based on the fogging value and the charge reduction rate to Example 2, in which the average primary particle diameter of the first external additive is less than the above-mentioned lower limit, and Example 3, in which the average primary particle diameter exceeds the above-mentioned upper limit.

[0183] Comparing Example 1 with Examples 4 and 5, it can be seen that Example 1, in which the average primary particle diameter of the silica particles and titanium oxide particles as the second external additive is 38 nm or more and 120 nm or less, is superior in the evaluations based on the fogging value and the charge reduction rate to Example 4, in which the average primary particle diameter of the silica particles as the second external additive is less than the above-mentioned lower limit, and Example 5, in which the average primary particle diameter exceeds the above-mentioned upper limit.

[0184] Comparing Example 1 with Examples 6 and 7, it can be seen that Example 1, in which the content of the second external additive is 4.0 parts by mass or more and 6.0 parts by mass or less, is superior in the evaluations based on the fogging value and the charge reduction rate to Example 6, in which the content of the second external additive is less than the above lower limit, and Example 7, in which the content of the second external additive exceeds the above upper limit.

[0185] Comparing Example 1 and Example 8, it can be seen that Example 1, in which the adhesion strength of the first external additive is 90% or more and 100% or less, is superior in the evaluations based on the fogging value and the charge reduction rate to Example 8, in which the adhesion strength of the first external additive is less than the above lower limit.

[0186] Comparing Example 1 with Examples 9 and 10, it can be seen that Example 1, in which the adhesion strength of the second external additive is 30% or more and 50% or less, is superior in the evaluations based on the fog value and the charge reduction rate to Example 9, in which the adhesion strength of the second external additive is less than the lower limit, and Example 10, in which the adhesion strength exceeds the upper limit.

[0187] Examples 1 and the like are examples in which silica particles are used as the first external additive, whereas Example 11 is an example in which titanium oxide particles are used as the first external additive, Example 12 is an example in which aluminum oxide is used as the first external additive, and Example 13 is an example in which strontium titanate particles added with silica are used as the first external additive. According to the evaluation results of Examples 11 to 13, it can be seen that even when titanium oxide particles, aluminum oxide particles, or strontium titanate particles added with silica are used as the first external additive, the charge reduction and fogging during long-term operation of the image forming apparatus can be suppressed.

[0188] Also, Examples 1 and the like are examples in which medium particle size silica particles (average primary particle size: 40 nm), large particle size silica particles (average primary particle size: 110 nm), and titanium oxide particles are used as the second external additive, whereas Example 14 is an example in which large particle size silica particles and titanium oxide particles are used. Also in the case of Example 14, it can be seen that the charge reduction and fogging during long-term operation of the image forming apparatus can be suppressed.

[0189] The embodiments disclosed this time are illustrative in all respects and are not a basis for limiting interpretation. Therefore, the technical scope of the present disclosure is not construed only by the above-described embodiments, but is defined based on the description of the claims. Also, all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Signs

[0190] 1 Toner particle 2 Large particle size external additive 3 Small particle size external additive T Toner

Claims

1. A toner having an external additive attached to the surface of a toner particle, the toner particles contain a crystalline polyester resin and a wax, and have an apparent viscosity at 90° C. of 100,000 Pa·s or more and 200,000 Pa·s or less; the external additive includes a first external additive and a second external additive having an average primary particle diameter larger than that of the first external additive, The loose bulk density of the toner is 0.3 g / cm ３ 0.35g / cm or more ３ is as follows: 1.2 N / cm at 50°C ２ a compression ratio of the toner is 50% or less and a stress relaxation ratio of the toner is 27% or more when the toner is pressed with a pressure of 1000 MPa.

2. 2. The toner according to claim 1, the first external additive is a silica particle, a titanium oxide particle, an aluminum oxide particle, a silica particle having aluminum hydroxide attached to its surface, or a strontium titanate particle having silica added thereto; The toner, wherein the first external additive has an average primary particle diameter of 10 nm or more and 35 nm or less.

3. The toner according to claim 1 or 2, the second external additive is silica particles and titanium oxide particles; The toner, wherein the silica particles and titanium oxide particles as the second external additive have an average primary particle diameter of 38 nm or more and 120 nm or less.

4. The toner according to claim 1 or 2, The content of the first external additive is 0.1 parts by mass or more and 0.5 parts by mass or less with respect to 100 parts by mass of the toner particles, The toner, wherein the content of the second external additive is 4.0 parts by mass or more and 6.0 parts by mass or less with respect to 100 parts by mass of the toner particles.

5. The toner according to claim 1 or 2, an adhesion strength of the first external additive to the toner particles is 90% or more and 100% or less; The toner, wherein the adhesion strength of the second external additive to the toner particles is 30% or more and 50% or less.

6. The toner according to claim 1 or 2, The toner particles are pulverized toner particles.

7. A two-component developer comprising the toner according to claim 1 or 2 and a carrier.

8. A method for producing the toner according to claim 1 or 2, comprising the steps of: a first external addition step of mixing the first external additive with the toner particles to cause the first external additive to adhere to surfaces of the toner particles; a second external addition step of mixing the second external additive with the toner particles to cause the second external additive to adhere to surfaces of the toner particles; A method for producing a toner, comprising the steps of: performing the first external addition step and then performing the second external addition step.

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