Toner, its manufacturing method, developer containing the toner, and image forming apparatus using the developer

Abstract

To provide toner which has the low-temperature fixability and excellent heat-resistant storage stability, suppresses charge reduction of a developer due to development stress and can maintain the high image quality through a product life, a manufacturing method of the same, a developer including the same and an image formation apparatus using the same.SOLUTION: Toner includes: a toner base particle which at least includes a binder resin and a release agent; and an external additive which is externally added to a surface of the toner base particle. The binder resin includes a crystalline polyester-based resin. The toner base particle has 100,000-250,000 Pa s of the viscosity at 90°C. The external additive is a small-diameter silica particle subjected to hydrophobic treatment, and a barium titanate particle subjected to the hydrophobic treatment. The barium titanate particle has 20-40 nm of the average primary particle diameter and 2-7% of a covering rate with respect to the toner base particle.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a toner, a manufacturing method thereof, a developer containing the toner, and an image forming apparatus using the toner. More specifically, the present disclosure relates to a toner that has low-temperature fixability and excellent heat-resistant storage stability, suppresses a decrease in the charge of the developer due to development stress, and can maintain high image quality throughout the product life, a manufacturing method thereof, a developer containing the toner, and an image forming apparatus using the toner. [Background technology]

[0002] 2. Description of the Related Art In recent years, with the remarkable development of office automation equipment, image forming apparatuses (electrophotographic apparatuses) such as digital copying machines, printers, and facsimile machines that use electrophotography have become widespread. Furthermore, with the increase in contact charging methods using roller charging and the progress in image forming apparatuses with longer life, smaller size and higher speed, various functions are being demanded of image forming apparatuses and the toner used therein.

[0003] For example, if the low-temperature fixation of toner is promoted further than ever before, the toner base particles must be coated with many silica particles to ensure heat-resistant storage stability, and toner coated with many silica particles has a large environmental charge difference, and developers containing low-temperature fixation toner have the problem that external additives are easily embedded due to stress from the doctor blade. Therefore, if a charge control agent is used to suppress the environmental charge difference, the charge change when the agent itself is embedded in the toner becomes large, and in addition to the environmental charge difference, charge change due to development stress is added, resulting in problems such as ID reduction and fogging, which are image defects.

[0004] Therefore, conventionally, a ratio (allocation) of the amount of silica particles and the amount of charge control agent that reduces the environmental charge difference has been found and applied. Also, a method of suppressing embedding of the charge control agent in the toner by increasing the particle size of the charge control agent has been applied, but this reduces the specific surface area of ​​the charge control agent, which can result in a decrease in the charge control ability. Therefore, it has become more difficult to maintain the minimum amount of silica particles necessary to ensure the heat-resistant storage stability of low-temperature fixing toner, and to satisfy the environmental charging performance of the entire development life, including suppressing charging changes due to embedding of charge control agents.

[0005] Techniques have been proposed to improve these toner problems. For example, Japanese Patent Laid-Open No. 2017-076087 (Patent Document 1) describes a toner for developing electrostatic latent images, which contains a plurality of toner particles, and the toner particles have a toner core and a shell layer that covers the toner core, the shell layer contains a thermosetting resin and a thermoplastic resin, the toner core contains at least a polyester resin, and the melt viscosity of the toner particles at 80°C is 2.1 × 10 4 Pa·s or more 2.3×10 5 The melt viscosity of the toner particles at 90°C is 7.0×10 3 Pa·s or more 2.3×10 4 A toner for developing electrostatic latent images with a surface tension of Pa·s or less has been proposed, and barium titanate is exemplified as an external additive. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2017-076087 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, the present disclosure has been made based on the above circumstances, and its purpose is to provide a toner that has low-temperature fixing properties and excellent heat-resistant storage stability, suppresses a decrease in the charge of the developer due to development stress, and can maintain high image quality throughout the product life, a method for producing the toner, a developer containing the toner, and an image forming apparatus using the toner. [Means for solving the problem]

[0008] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, it was found that a toner comprising toner base particles containing at least a crystalline polyester resin and a release agent and having a specific viscosity, and an external additive externally added to the surfaces of the toner base particles, wherein the external additive is hydrophobically treated silica particles (small particle size silica particles) and hydrophobically treated barium titanate particles having a specific average primary particle diameter and a specific coverage rate relative to the toner base particles, can provide a toner and a developer containing the toner, which have low-temperature fixing properties and excellent heat-resistant storage stability, suppress a decrease in developer charge due to development stress, and can maintain high image quality throughout the product life (life), and this led to the completion of the present invention. The above-mentioned Patent Document 1 does not disclose a specific coverage rate of barium titanate and the effects resulting therefrom.

[0009] Thus, according to the present disclosure, a toner is provided which is composed of toner base particles containing at least a binder resin and a release agent, and an external additive which is externally added to the surface of the toner base particles, the binder resin contains a crystalline polyester resin, the toner base particles have a viscosity of 100,000 to 250,000 Pa·s at 90°C; the external additives are hydrophobized small-diameter silica particles and hydrophobized barium titanate particles, The barium titanate particles have an average primary particle diameter of 20 to 40 nm and a coverage of the toner base particles of 2 to 7%. A toner characterized by the above-mentioned is provided.

[0010] Further, according to the present disclosure, there is provided a method for producing the toner, a first external addition step of adding and mixing the barium titanate particles as an external additive to the toner base particles, thereby externally adding the external additive to the toner base particles; a second external addition step in which the external additive of the small-diameter silica particles is further added and mixed with the obtained toner base particles to externally add the external additive to the toner base particles; A method for producing a toner comprising the steps of:

[0011] According to the present disclosure, there is also provided a method for producing a toner, wherein the toner further contains large-diameter silica particles having an average primary particle diameter of 70 to 200 nm as an external additive, a first external addition step of adding and mixing the barium titanate particles as an external additive to the toner base particles, thereby externally adding the external additive to the toner base particles; a second external addition step of further adding and mixing the small-diameter silica particles as an external additive to the obtained toner base particles to externally add the external additive to the toner base particles; and a third external addition step in which the external additive of the large-diameter silica particles is further added and mixed with the obtained toner base particles to externally add the external additive to the toner base particles; A method for producing a toner comprising the steps of:

[0012] The present disclosure also provides a developer comprising the above toner and a carrier.

[0013] Furthermore, according to the present disclosure, there is provided an image forming apparatus that forms an image by forming an electrostatic latent image on the surface of an electrophotographic photosensitive member and transferring toner developed on the electrostatic latent image to a transfer material, wherein the toner is the toner described above. [Effects of the Invention]

[0014] According to the present disclosure, it is possible to provide a toner that has low-temperature fixing properties and excellent heat-resistant storage stability, suppresses a decrease in the charge of the developer due to development stress, and can maintain high image quality throughout the product life, a method for producing the toner, a developer containing the toner, and an image forming apparatus using the toner. In other words, the inventors believe that by using barium titanate particles, which have a high ability to suppress environmental charge differences per unit area covered by the charge control agent, the amount of coating can be reduced, and although this increases the environmental charge difference of the initial development, it is possible to keep the overall change in development life small, and by using them in combination with small-diameter silica particles, the barium titanate particles can be moved to the recesses on the toner surface, thereby reducing their embedding in the toner surface and preventing deterioration in life such as fogging. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 4 is a diagram showing the relationship between the temperature and melt viscosity of toner base particles. [Figure 2] 1 is a schematic side view illustrating an example of a configuration of a main part of an image forming apparatus according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0016] (1) Toner The toner of the present disclosure is composed of toner base particles containing at least a binder resin and a release agent, and an external additive that is externally added to the surface of the toner base particles, the binder resin contains a crystalline polyester resin, the toner base particles have a viscosity of 100,000 to 250,000 Pa·s at 90°C; the external additives are hydrophobized small-diameter silica particles and hydrophobized barium titanate particles, The barium titanate particles have an average primary particle diameter of 20 to 40 nm and a coverage of the toner base particles of 2 to 7%. It is characterized by: The mechanism by which the toner of the present disclosure exerts its effects, the toner base particles and external additives that are characteristic parts of the toner, the method for producing the toner, the developer containing the toner, and the image forming apparatus using the developer will be described below.

[0017] The present inventors believe that the mechanism by which the toner of the present disclosure exerts its effects and the guidelines for doing so are as follows. By increasing the amount of the crystalline polyester resin of the binder resin in the toner mother particles, while realizing low-temperature fixing of the toner, the external additive on the toner surface is embedded in the toner mother particles due to the physical stress in the developing tank of the image forming apparatus, and it cannot contribute to triboelectrification, and it will exhibit the same charging behavior as when the amount of the external additive is reduced. The degree of embedding of the external additive can be grasped by drawing a calibration curve with data obtained from measuring the charge amount of the toner with the amount of the external additive increased or decreased, and comparing it with the charge amount of the developer at the end of the product life. Also, the amount of embedding can be confirmed by observing and comparing the initial developer and the developer at the end of the product life with a scanning electron microscope.

[0018] The developer needs to maintain high image quality from the initial stage to the end of the product life even in a low-humidity environment or a high-humidity environment, and the charge control agent needs to remain in a certain amount without being embedded even at the end of the product life. If the charge control agent is widely distributed on the toner surface, the probability of receiving physical stress is high. There are many depressions on the surface of the toner mother particles prepared by the pulverization method, and if the charge control agent fits into them, it becomes difficult to receive physical stress. However, the area of the depressions and grooves is small and insufficient compared to the total area.

[0019] Conventionally, materials such as alumina and strontium titanate have been used as the charge control agent, and materials having a lower resistance value than the toner mother particles have been used. When charges are unevenly distributed on the toner surface by triboelectrification, it is considered that the charge control agent having a low resistance value functions to make the distribution of charges uniform to some extent, but it is also considered that the dielectric constant of the charge control agent affects other functions. The inventor externally added alumina (AL), strontium titanate (TS), and barium titanate (TB) having the same particle size and the same surface treatment to the toner mother particles, pelletized these externally added toners, and measured the capacitance. As a result, the dielectric constants were in the same order of AL < TS < TB. Also, externally added toners with the amount of these charge control agents increased or decreased were prepared, and the environmental charging performance was measured. As a result, the improvement of the environmental charging performance per coating area of the charge control agent was also in the order of AL < TS < TB. From the above results, the inventors of the present invention considered that TB has a strong ability to improve environmental charging performance per coating area, allows for a reduction in the amount of external additive, has a large specific gravity, and therefore the coating area calculated by the projection method is smaller than that of AL and TS at the same mass%, and that the amount that can be fitted into the depressions and grooves on the toner surface makes it possible to maintain environmental charging performance until the end of the product's lifespan.

[0020] The present inventors have also investigated the necessity of devising an external additive that allows the barium titanate particles to move to the depressions on the toner surface. Based on past experience, when the circularity of the charge control agent is high and the molecular weight of the hydrophobic surface treatment agent is small, the fluidity of the toner tends to increase. Therefore, we focused on the order of external addition and the difference in particle size of the external additives and conducted further investigations. Therefore, the inventors discovered that by externally adding barium titanate particles in the first external addition step and silica with a smaller particle size than the barium titanate particles in the second external addition step, the barium titanate particles are swept away by the smaller silica and become embedded in the depressions on the toner surface, thereby increasing adhesion strength, and that the behavior of the particles on the toner surface can be determined by EDX mapping using a scanning electron microscope, etc.; further, by externally adding silica with a larger particle size (for example, 70 to 200 nm) than the silica used in the second external addition step in the third external addition step, the larger silica covers the depressions into which the barium titanate particles have become embedded, making it possible to further avoid physical stress during development; and that a sufficient number of the externally added barium titanate particles need to fit into the depressions on the toner surface, and that this state can be confirmed by the mobility of the barium titanate particles. The mobility of barium titanate particles can be measured by measuring and comparing the adhesion strength of the barium titanate particles before and after stirring the toner containing the externally added barium titanate particles, as described below. The inventors have confirmed that if the barium titanate particles have already been moved by the external addition process and are sufficiently embedded in the recesses, additional stirring will not significantly increase the adhesion strength.

[0021] (1-1) External additives External additives generally have the function of improving the transportability and chargeability of the toner, as well as the agitation property with the carrier when the toner is used in a two-component developer. The toner of the present disclosure comprises hydrophobically treated small size silica particles and hydrophobically treated barium titanate particles.

[0022] (1-1-1) Barium titanate particles The hydrophobized barium titanate particles used in the present disclosure have an average primary particle size of 20 to 40 nm and a coverage of 2 to 7% with respect to the toner base particles. Furthermore, the barium titanate particles are preferably particulate, but may also be spherical, acicular, non-spherical, etc., and may have either a single particle structure or an aggregate structure of several particles.

[0023] As barium titanate particles, silica particles that have been hydrophobized by surface treatment commonly used in the art, such as hexamethyldisilazane (HMDS), dimethyldichlorosilane (DDS), octylsilane (OTAS), and polydimethylsiloxane (PDMS), can be used. If the particles have not been hydrophobized, they can be treated before use.

[0024] If the average primary particle diameter of barium titanate particles is less than 20 nm, a developer near the end of its product life may experience a decrease in ID in low-humidity environments and an increase in fog value in high-humidity environments.On the other hand, if the average primary particle diameter of barium titanate particles is more than 40 nm, a developer in its early stages may experience a decrease in ID in low-humidity environments and an increase in fog value in high-humidity environments. The average primary particle size of the barium titanate particles is preferably 25 to 35 nm.

[0025] If the coverage of barium titanate particles is less than 2% of the toner base particles, developers at the end of their product life may experience a decrease in ID in low-humidity environments and an increase in fog value in high-humidity environments.On the other hand, if the coverage of barium titanate particles is more than 7%, developers in their early stages may experience an increase in fog value in high-humidity environments. The preferred coverage of the barium titanate particles is 2 to 5%.

[0026] <Adhesion strength> 2.0 g of toner is added to 40 mL of a 0.2% by mass aqueous solution of polyoxyethylene octylphenyl ether and stirred for 1 minute. The resulting aqueous solution is irradiated with ultrasonic waves at an output of 40 μA for 4 minutes, and then left to stand for 3 hours to separate the toner and the liberated external additives. After removing the supernatant, approximately 50 mL of pure water is added to the precipitate and stirred for 5 minutes. The mixture is then suction filtered using a membrane filter with a pore size of 1 μm. The toner remaining on the membrane filter is vacuum dried overnight to perform an external additive removal treatment to obtain a toner after the external additive removal treatment. When the strength SA2 of the barium element in 1 g of the obtained toner after the external additive removal treatment and the strength SB2 of the barium element Ba in 1 g of the toner before the external additive removal treatment are measured by fluorescent X-ray analysis, it is preferable that the adhesion strength of the barium titanate particles (SA2 / SB2) x 100 is 80% or more. If the adhesion strength (SA2 / SB2) x 100 is less than 80%, a developer nearing the end of its product life may experience a decrease in ID in a low humidity environment or an increase in fogging value in a high humidity environment. The adhesive strength is preferably 95% or more, and more preferably 98% or more. The measurement of adhesive strength will be specifically described in the Examples.

[0027] <Mobility> The toner was placed in a 500 mL stainless steel container and stirred for 180 seconds at a rotation speed of the stirring blade tip of 40 m / s. When the adhesion strength FB of the barium titanate of the resulting contents and the adhesion strength FA of the barium titanate of the toner before stirring were measured, The mobility (FB / FA)×100 is preferably 1.1 or less. If the mobility (FB / FA)×100 exceeds 1.1, a developer nearing the end of its product life may experience a decrease in ID in a low-humidity environment or an increase in fogging value in a high-humidity environment. The mobility is preferably 0.7 or more. The measurement of mobility will be specifically described in the Examples.

[0028] <Distribution deviation value> For each toner particle 50 by a scanning electron microscope, qualitative and quantitative analysis was performed on 200 locations in total, including 2 locations at the recessed parts such as steps and grooves on the surface of each toner and 2 locations at the flat parts without recesses. When the average value BF of the ratio of barium element Ba in the flat part and the average value BH of the ratio of barium element Ba in the recessed part were measured, It is preferable that the distribution deviation value (BH / BF) of the barium titanate particles is 2.0 or more. When the distribution deviation value is less than 2.0, ID reduction in a low humidity environment and an increase in fog value in a high humidity environment may occur in the developer at the end of the product life. The distribution deviation value is preferably 2.1 or more. The measurement of the distribution deviation value will be specifically described in the examples.

[0029] (1-1-2) Small particle size silica particles The hydrophobically treated small particle size silica particles used in the present disclosure preferably have an average primary particle size smaller than that of the barium titanate particles, and it is preferable that the average primary particle size PS of the small particle size silica particles and the average primary particle size PB of the barium titanate particles satisfy the relationship of PS < PB. When the small particle size silica particles and the barium titanate particles do not satisfy the above relationship, that is, when the average primary particle size PS of the small particle size silica particles is equal to or greater than the average primary particle size PB of the barium titanate particles, ID reduction in a low humidity environment and an increase in fog value in a high humidity environment may occur in the developer at the end of the product life. The average primary particle size of the small particle size silica particles is not particularly limited, but is preferably 6 to 16 nm.

[0030] The small particle size silica particles preferably have a coating rate of 70 to 90% with respect to the toner mother particles. If the coverage rate of small silica particles is less than 70% of the toner base particles, toners using toner base particles with a viscosity of 100,000 to 250,000 Pa·s at 90°C will lack heat-resistant storage performance, and the product may not be able to be stored while maintaining its quality.On the other hand, if the coverage rate of small silica particles exceeds 90%, the adhesive strength of other types of external additives will decrease, and developers nearing the end of their product life may experience a decrease in ID in low-humidity environments and an increase in fogging value in high-humidity environments. A more preferable coverage rate of the small silica particles is 80 to 90%.

[0031] As small-diameter silica particles, silica particles that have been hydrophobized by surface treatment commonly used in the art, such as hexamethyldisilazane (HMDS), dimethyldichlorosilane (DDS), octylsilane (OTAS), and polydimethylsiloxane (PDMS), can be used. If the silica particles have not been hydrophobized, they can be treated before use. The origin of the small-diameter silica particles is not particularly limited, and for example, silica particles obtained by a flame hydrolysis method in which silicon tetrachloride is burned in an oxyhydrogen flame, a sol-gel method, or the like, and then subjected to a hydrophobic treatment can be used.

[0032] (1-1-3) Large silica particles The toner of the present disclosure preferably further contains, as an external additive, large-diameter silica particles having an average primary particle diameter of 70 to 200 nm, in addition to the small-diameter silica particles and barium titanate particles. If the average primary particle diameter of large silica particles is less than 70 nm, the effect of suppressing the decrease in ID in low-humidity environments and further suppressing the increase in fog value in high-humidity environments may not be realized in developers at the end of their product life.On the other hand, if the average primary particle diameter of large silica particles is more than 200 nm, the adhesion strength is weak and they may detach from the toner, causing image defects such as filming. The preferred average primary particle size of the large silica particles is 90 to 130 nm.

[0033] As for the large-diameter silica particles, similar to the small-diameter silica particles, silica particles that have been hydrophobized by a surface treatment commonly used in the art, such as hexamethyldisilazane (HMDS), dimethyldichlorosilane (DDS), octylsilane (OTAS), and polydimethylsiloxane (PDMS), can be used. If the large-diameter silica particles have not been hydrophobized, they can be subjected to a treatment before use. The origin of the large-diameter silica particles is not particularly limited, and for example, silica particles obtained by a flame hydrolysis method in which silicon tetrachloride is burned in an oxyhydrogen flame, a sol-gel method, or the like, and then subjecting the silica to a hydrophobic treatment can be used.

[0034] The coverage of the large silica particles with respect to the toner base particles is preferably 3 to 14%. If the coverage of the large silica particles is less than 3% of the toner base particles, the developer at the end of its product life may not be effective in suppressing the decrease in ID in low-humidity environments or in further suppressing the increase in fog value in high-humidity environments.On the other hand, if the coverage of the large silica particles exceeds 14%, image defects such as filming may occur. A more preferable coverage rate of the large silica particles is 3 to 11%.

[0035] (1-2) Toner base particles The toner base particles contained in the toner of the present disclosure contain at least a binder resin and a release agent, and may contain known additives such as a colorant and a charge control agent, as necessary, within a range that does not impair the effects of the present disclosure.

[0036] <Viscosity at 90℃> The toner base particles of the present disclosure have a viscosity at 90°C of 100,000 to 250,000 Pa·s. If the viscosity of the toner base particles at 90°C is less than 100,000 Pa·s, a developer at the end of its product life may experience a decrease in ID in a low-humidity environment or an increase in fog value in a high-humidity environment.On the other hand, if the viscosity of the toner base particles at 90°C exceeds 250,000 Pa·s, it becomes difficult to form toner base particles having the low-temperature fixability of the toner of the present invention. The viscosity of the preferred toner mother particles at 90 °C is 120,000 to 180,000 Pa·s. The measurement of the viscosity will be specifically described in the examples.

[0037] <BET specific surface area> The toner mother particles of the present disclosure preferably have a BET specific surface area of 0.5 to 2.5 m 2 / g as defined in JIS Z8830:2013. When the BET specific surface area of the toner mother particles is less than 0.5 m 2 / g, there may be a decrease in ID in a low-humidity environment and an increase in fog value in a high-humidity environment with the developer at the end of the product life. On the other hand, when the BET specific surface area of the toner mother particles exceeds 2.5 m 2 / g, there may be an increase in fog value in a high-humidity environment with the initial developer. A more preferred BET specific surface area of the toner mother particles is 0.6 to 2.4 m 2 / g, and more preferably 1.8 to 2.4 m 2 / g.

[0038] <Average primary particle diameter> The toner mother particles preferably have an average primary particle diameter of 5 to 7 μm. If the average primary particle diameter of the toner mother particles is within the above range, the purpose of high-definition image and reduction of toner consumption at the initial design stage can be achieved. The measurement of the average primary particle diameter will be specifically described in the examples.

[0039] (1-2-1)Binder resin The binder resin contained in the toner mother particles of the present disclosure includes a crystalline polyester resin. Examples of binder resins include polyester resins, polystyrene resins such as styrene-acrylic resins, (meth)acrylic ester resins, polyolefin resins, polyurethane resins, and epoxy resins, and these resins can be used alone or in combination of two or more. Among these, polyester resins are preferred because the resin properties can be easily controlled by setting the conditions for the polycondensation reaction as described below, and binder resins with desired properties can be produced. Therefore, the binder resin may contain other resins as long as it contains a crystalline polyester resin, but it is preferable to combine it with an amorphous polyester resin.

[0040] The polyester resin used as the binder resin is usually obtained by polycondensation reaction of one or more selected from dihydric alcohol components and trihydric or higher polyhydric alcohol components with one or more selected from dicarboxylic acids and trihydric or higher polycarboxylic acids by a known method via an esterification reaction or an ester exchange reaction. The conditions for the polycondensation reaction may be appropriately set depending on the reactivity of the monomer components, and the reaction may be terminated when the polymer has reached suitable physical properties. For example, the reaction temperature is about 170 to 250°C, and the reaction pressure is about 5 mmHg to atmospheric pressure.

[0041] Examples of the dihydric alcohol component include alkylene oxide adducts of bisphenol A such as polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(3.3)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(2.0)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(2.0)-polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane, and polyoxypropylene(6)-2,2-bis(4-hydroxyphenyl)propane; ethylene glycol; Examples of suitable olefin copolymers include diols such as ethanol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; bisphenol A; propylene adducts of bisphenol A; ethylene adducts of bisphenol A; and hydrogenated bisphenol A.

[0042] Examples of trihydric or higher polyhydric alcohol components include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose (cane sugar), 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

[0043] In the present disclosure, one of the above dihydric alcohol components and trihydric or higher polyhydric alcohol components may be used alone, or two or more of them may be used in combination. Examples of dicarboxylic acids include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n-dodecenylsuccinic acid, n-dodecylsuccinic acid, n-octylsuccinic acid, isooctenylsuccinic acid, isooctylsuccinic acid, and acid anhydrides and lower alkyl esters thereof. Examples of trivalent or higher polyvalent carboxylic acids include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empol trimer acid, and acid anhydrides and lower alkyl esters thereof. In the present disclosure, one of the above dicarboxylic acids and tricarboxylic or higher polycarboxylic acids may be used alone, or two or more of them may be used in combination.

[0044] The binder resin of the toner base particles of the toner of the present disclosure contains a crystalline polyester-based resin, and preferably contains an amorphous polyester-based resin. In the present disclosure, crystalline resins and amorphous resins are distinguished by their crystallinity index, with resins having a crystallinity index in the range of 0.6 to 1.5 being crystalline resins and resins 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 a large amount of amorphous portions. The crystallinity index is a physical property that indicates 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. For crystalline polyester resins, the highest peak temperature is the melting point, and for amorphous polyester resins, the highest peak temperature is the glass transition point.

[0045] The degree of crystallization can be controlled by adjusting the types and ratios of raw material monomers, as well as production conditions (for example, reaction temperature, reaction time, cooling rate). The crystalline polyester resin is a polyester resin having a crystallinity index of 0.6 to 1.5, preferably a polyester resin having a crystallinity index of 0.8 to 1.2. The crystalline polyester resin can be obtained, for example, by polycondensing a polybasic acid and a polyhydric alcohol. For example, it can be produced by a known method such as that described in JP-A-2006-113473.

[0046] The acid value of the crystalline polyester resin is preferably 5 to 20 mgKOH / g, and the hydroxyl value of the crystalline polyester resin is preferably 5 to 20 mgKOH / g. The molecular weight of the crystalline polyester resin is preferably such that the weight average molecular weight (Mw) is 5,000 to 100,000 and the number average molecular weight (Mn) is 3,000 to 20,000. In the present disclosure, the weight average molecular weight and number average molecular weight are values ​​measured by gel permeation chromatography (GPC), using chloroform as the mobile phase and polystyrene as the standard. The softening temperature of the crystalline polyester resin is preferably 60 to 105°C.

[0047] In the toner according to the present disclosure, the content of the crystalline polyester resin is not particularly limited, but is preferably 1% by mass or more and 20% by mass or less, and more preferably 2 to 20% by mass, of the toner particles. When the content of the crystalline polyester resin is equal to or more than the lower limit, it is possible to easily improve the low-temperature fixability. When the content of the crystalline polyester resin is equal to or less than the upper limit, it is possible to easily improve the heat-resistant storage stability of the toner.

[0048] The amorphous polyester resin is a polyester resin having a crystallinity index of less than 0.6 or more than 1.5, with polyester resins having a crystallinity index of more than 1.5 being preferred. The amorphous polyester resin can be obtained, for example, by polycondensation of a polybasic acid and a polyhydric alcohol.

[0049] As the polybasic acid, known monomers for polyester synthesis can be used, and examples thereof include aromatic carboxylic acids such as terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, and naphthalenedicarboxylic acid, aliphatic carboxylic acids such as maleic anhydride, fumaric acid, succinic acid, alkenylsuccinic anhydride, and adipic acid, and methyl esters of these polybasic acids. These polybasic acids may be used alone or in combination of two or more.

[0050] As the polyhydric alcohol, known monomers for polyester synthesis can be used, and examples thereof include aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, and glycerin, alicyclic polyhydric alcohols such as cyclohexanediol, cyclohexanedimethanol, and hydrogenated bisphenol A, and aromatic diols such as ethylene oxide adducts of bisphenol A and propylene oxide adducts of bisphenol A. These polyhydric alcohols may be used alone or in combination of two or more.

[0051] The polycondensation reaction of a polybasic acid and a polyhydric alcohol can be carried out according to conventional methods. For example, the polybasic acid and the polyhydric alcohol are contacted in the presence or absence of an organic solvent and in the presence of a polycondensation catalyst (e.g., tin octoate). The reaction is terminated when the acid value and softening temperature of the resulting polyester reach the desired values. This results in an amorphous polyester resin. If a methyl ester of a polybasic acid is used as part of the polybasic acid, a demethanolization polycondensation reaction is carried out. In this polycondensation reaction, the content of carboxyl groups at the terminals of the polyester can be adjusted by appropriately changing the blending ratio and reaction rate of the polybasic acid and the polyhydric alcohol, for example, and thus the properties of the resulting amorphous polyester resin can be modified. Furthermore, using trimellitic anhydride as the polybasic acid allows for easy introduction of carboxyl groups into the polyester main chain.

[0052] The polycondensation reaction between a polybasic acid and a polyhydric alcohol is usually carried out at a temperature of about 150 to 300° C., preferably about 170 to 280° C. The polycondensation reaction can be carried out under normal pressure, reduced pressure, or increased pressure, and it is desirable to appropriately adjust the pressure in the system while monitoring the progress of the polycondensation reaction by monitoring physical property values ​​(e.g., acid value, melting point, etc.) and the stirring torque or power value of the reactor.

[0053] The acid value of the amorphous polyester resin is preferably from 10 to 30 KOHmg / g, more preferably from 15 to 25 KOHmg / g. The weight average molecular weight (Mw) of the amorphous polyester resin is preferably 5,000 to 50,000, and the number average molecular weight (Mn) is preferably 1,000 to 10,000. In the present disclosure, the weight average molecular weight and number average molecular weight are values ​​measured by gel permeation chromatography (GPC), using tetrahydrofuran (THF) as the mobile phase and polystyrene as the standard. The glass transition temperature (Tg) of the amorphous polyester resin is preferably 55 to 70°C. In the toner according to the present disclosure, the content of the amorphous polyester resin is not particularly limited, but is preferably 67 to 89% by mass in the toner base particles.

[0054] (1-2-2) Release agent As the release agent contained in the toner base particles of the present disclosure, any release agent commonly used in the technical field can be used. Examples include petroleum-based waxes such as paraffin wax and microcrystalline wax and their derivatives; hydrocarbon-based synthetic waxes such as Fischer-Tropsch wax, polyolefin wax (polyethylene wax, polypropylene wax, etc.), low-molecular-weight polypropylene wax and polyolefin-based polymer wax (low-molecular-weight polyethylene wax, etc.) and their derivatives; plant-based waxes such as carnauba wax, rice wax, candelilla wax and their derivatives, and Japan wax; animal-based waxes such as beeswax and spermaceti; oil-based synthetic waxes such as fatty acid amides and phenol fatty acid esters; long-chain carboxylic acids and derivatives thereof; long-chain alcohols and derivatives thereof; silicone-based polymers; and higher fatty acids, and among these, hydrocarbon-based waxes are preferred. The derivatives include oxides, block copolymers of vinyl monomers and wax, and graft modified products of vinyl monomers and wax. In the present disclosure, the above-mentioned release agents can be used alone or in combination of two or more.

[0055] The release agent preferably has a melting point of 70° C. or less in order to achieve both low-temperature fixability and hot offset resistance of the toner in a belt fixing device, particularly in terms of low-temperature fixability. The lower limit of the melting point is about 60° C.

[0056] The content of the release agent in the toner base particles of the present disclosure is not particularly limited, but is preferably 0.2 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, and particularly preferably 1.0 to 8.0 parts by mass, relative to 100 parts by mass of the binder resin. If the content of the release agent is within the above range, it is possible to form an image having a high image density and excellent image quality without impairing various physical properties of the toner. In terms of the amount of the releasing agent contained in the toner base particles, the amount is preferably 2.0 to 7.0% by mass, and more preferably 3.0 to 5.0% by mass.

[0057] (1-2-3) Coloring agents As the colorant contained in the toner base particles of the present disclosure, various types and colors of organic and inorganic pigments and dyes commonly used in the art can be used, and examples thereof include black, white, yellow, orange, red, purple, blue, and green colorants.

[0058] Examples of black colorants include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, non-magnetic ferrite, magnetic ferrite, and magnetite. Examples of white colorants include zinc oxide, titanium oxide, antimony white, and zinc sulfide.

[0059] Examples of yellow colorants include yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, tartrazine lake, CI pigment yellow 12, CI pigment yellow 13, CI pigment yellow 14, CI pigment yellow 15, CI pigment yellow 17, CI pigment yellow 93, CI pigment yellow 94, and CI pigment yellow 138.

[0060] Examples of orange colorants include red lead yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, induthrene brilliant orange RK, benzidine orange G, induthrene brilliant orange GK, CI pigment orange 31, and CI pigment orange 43.

[0061] Examples of red colorants include red iron oxide, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, lithol red, pyrazolone red, watching red, calcium salt, lake red C, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B, CI pigment red 2, CI pigment red 3, CI pigment red 5, CI pigment red 6, CI pigment red 7, CI pigment red 8, CI pigment red 9, CI pigment red 10, CI pigment red 11, CI pigment red 12, CI pigment red 13, CI pigment red 14, CI pigment red 15, CI pigment red 16, CI pigment red 17, CI pigment red 18, CI pigment red 19, CI pigment red 20, CI pigment red 21, CI pigment red 22, CI pigment red 23, CI pigment red 24, CI pigment red 25, CI pigment red 26, CI pigment red 27, CI pigment red 28, CI pigment red 29 ... Examples of pigments that can be used include CI Pigment Red 7, CI Pigment Red 15, CI Pigment Red 16, 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.

[0062] Examples of purple colorants include manganese violet, fast violet B, and methyl violet lake. Examples of blue colorants include Prussian blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, fast sky blue, indanthrene blue BC, CI pigment blue 15, CI pigment blue 15:2, CI pigment blue 15:3, CI pigment blue 16, and CI pigment blue 60. Examples of green colorants include chrome green, chromium oxide, pigment green B, mica light green lake, final yellow green G, and CI pigment green 7.

[0063] In the toner of the present disclosure, the above colorants can be used alone or in combination of two kinds, and the combinations can be of different colors or the same color. Two or more colorants may be used in the form of composite particles. The composite particles can be produced, for example, by adding an appropriate amount of water, a lower alcohol, etc. to two or more colorants, granulating the mixture using a general granulator such as a high-speed mill, and drying the mixture. Furthermore, in order to uniformly disperse the colorant in the binder resin, the colorant may be used in the form of a masterbatch. The composite particles and masterbatch are mixed into the toner composition during dry mixing.

[0064] The content of the colorant in the toner base particles of the present disclosure is not particularly limited, but is preferably 0.1 to 20 parts by mass, and more preferably 0.2 to 10 parts by mass, relative to 100 parts by mass of the binder resin. If the content of the colorant is within the above range, it is possible to form an image having a high image density and excellent image quality without impairing various physical properties of the toner. In terms of the total mass, the content of the colorant in the toner base particles is preferably 2.5 to 7.5% by mass, and more preferably 3.0 to 6.5% by mass.

[0065] (1-2-4) Charge control agent As the charge control agent contained in the toner of the present disclosure, a charge control agent for negative charge control commonly used in the technical field can be used. Examples of charge control agents for negative charge control include oil-soluble dyes such as oil black and Spiron black, metal-containing azo compounds, azo complex dyes, metal naphthenate salts, metal complexes and metal salts of salicylic acid and its derivatives (metals include chromium, zinc, zirconium, etc.), boron compounds, fatty acid soaps, long-chain alkyl carboxylate salts, and resin acid soaps. In the toner of the present disclosure, the above charge control agents can be used alone or in combination of two or more.

[0066] The content of the charge control agent in the toner base particles of the present disclosure is not particularly limited, but is preferably 0.5 to 3 parts by mass, and more preferably 1 to 2 parts by mass, per 100 parts by mass of the binder resin. If the content of the charge control agent is within the above range, it is possible to form an image having a high image density and very good image quality without impairing various physical properties of the toner. In terms of conversion, the content of the charge control agent in the toner base particles is preferably 0.5 to 2.0% by mass, and more preferably 0.7 to 1.5% by mass.

[0067] (2) Toner manufacturing method The method for producing a toner according to the present disclosure includes: a first external addition step of adding and mixing an external additive of barium titanate particles to the toner base particles to externally add the external additive to the toner base particles; a second external addition step in which small-diameter silica particles are further added and mixed with the obtained toner base particles to externally add the external additive to the toner base particles; The present invention is characterized by comprising:

[0068] In addition, a method for producing a toner in which the toner further contains large-diameter silica particles having an average primary particle diameter of 70 to 200 nm as an external additive is as follows: a first external addition step of adding and mixing the barium titanate particles as an external additive to the toner base particles to externally add the external additive to the toner base particles; a second external addition step of further adding and mixing small-diameter silica particles as an external additive to the obtained toner base particles to externally add the external additive to the toner base particles; and a third external addition step in which an external additive of large-diameter silica particles is further added and mixed with the obtained toner base particles to externally add the external additive to the toner base particles; The present invention is characterized by comprising:

[0069] (2-1) First external addition process In the first external addition step, an external additive of barium titanate particles is added to the toner base particles and mixed. The adding and mixing operations can be carried out using known devices commonly used in the relevant technical field, and the process conditions may be appropriately set depending on the target materials and the desired physical properties.

[0070] (2-2) Second external addition process In the second external addition step, small-diameter silica particles as an external additive are further added to the obtained toner base particles and mixed. As in the first external addition step, the addition and mixing operation can be carried out using a known apparatus commonly used in the technical field, and the conditions in the step may be appropriately set depending on the target material and the desired physical properties.

[0071] (2-3) Third external addition process In the second external addition step, external additives of large particle diameter silica particles are further added to the obtained toner base particles and mixed. As in the first external addition step, the addition and mixing operation can be carried out using a known apparatus commonly used in the technical field, and the conditions in the step may be appropriately set depending on the target material and the desired physical properties.

[0072] (2-4) Method for producing toner base particles The toner base particles used in the present disclosure can be produced by a known method using a known device commonly used in the technical field, for example, by a mixing step of mixing a filler with a coarsely pulverized molten kneaded material containing at least a binder resin and a release agent, a fine pulverization step of finely pulverizing the mixture obtained in the mixing step, a classification step of classifying the finely pulverized material obtained in the fine pulverization step, and a spheronization treatment step of spheronizing the classified material obtained in the classification step with hot air. Dry methods are preferred in that they require fewer steps and require less equipment cost than wet methods, and among these, pulverization is particularly preferred. The conditions for each of the following steps may be appropriately set depending on the target material and the desired physical properties.

[0073] (3) Developer (two-component developer) The developer of the present disclosure includes the toner of the present disclosure and a carrier. (Career) The toner of the present disclosure can be used in the form of either a one-component developer or a two-component developer, and when used as a two-component developer, a carrier is further blended in addition to the external additive. As the carrier, carriers commonly used in the art can be used, such as simple or composite ferrites made of iron, copper, zinc, nickel, cobalt, manganese, chromium, etc., and carrier core particles surface-coated with known coating materials. The average particle size of the carrier is preferably 10 to 100 μm, more preferably 20 to 50 μm. The amount of the carrier to be added is not particularly limited, but is preferably 4 to 15 parts by mass, and more preferably 5 to 10 parts by mass, per 100 parts by mass of the toner base particles.

[0074] (4) Image forming device The image forming apparatus of the present disclosure is an image forming apparatus that forms an electrostatic latent image on the surface of an electrophotographic photosensitive member and transfers the toner developed on the electrostatic latent image to a transfer material to form an image, wherein the toner is the toner described above.

[0075] The image forming apparatus of the present disclosure is not particularly limited as long as it has the above-mentioned configuration requirements, but examples include an image forming apparatus that includes at least a photosensitive member, a charging means for charging the photosensitive member, an exposure means for exposing the charged photosensitive member to light to form an electrostatic latent image, a developing means for developing the electrostatic latent image formed by exposure to form a toner image, a transfer means for transferring the toner image formed by development onto a recording medium, a fixing means for fixing the transferred toner image on the recording medium to form an image, a cleaning means for removing and recovering toner remaining on the photosensitive member, and a discharging means for discharging surface charges remaining on the photosensitive member. An example of an image forming apparatus and its operation will be described below with reference to the drawings, but the present invention is not limited to this.

[0076] FIG. 2 is a schematic side view showing the configuration of the main part of the image forming apparatus 100 of the present disclosure. 2 includes a photoreceptor 1, an exposure means (semiconductor laser) 31, a charging means (charger) 32, a developing means (developer) 33, a transfer means (transfer charger) 34, a conveyor belt (not shown), a fixing means (fixer) 35, and a cleaning means (cleaner) 36. Reference numeral 51 denotes a recording medium (recording paper or transfer paper).

[0077] The photoreceptor 1 is not particularly limited as long as it is one that is used as a photoreceptor for an image forming device in the relevant technical field, and examples thereof include a laminated photoreceptor in which a charge generation layer containing a charge generation substance and a charge transport layer containing a charge transport substance are laminated in this order on a substrate, or a photoreceptor that includes at least a single-layer photoreceptor containing a charge generation substance and a charge transport substance.

[0078] Photoreceptor 1 is rotatably supported on the main body of image forming apparatus 100 and is driven to rotate around rotation axis 44 in the direction of arrow 41 by driving means (not shown). The driving means includes, for example, an electric motor and a reduction gear, and transmits its driving force to a conductive support constituting the core of photoreceptor 1, thereby driving photoreceptor 1 to rotate at a predetermined peripheral speed. Charging means (charger) 32, exposure means 31, developing means (developer) 33, transfer means (transfer charger) 34, and cleaning means (cleaner) 36 are provided in this order along the outer circumferential surface of photoreceptor 1 from upstream to downstream in the direction of rotation of photoreceptor 1, as indicated by arrow 41.

[0079] The charger 32 is a charging means for uniformly charging the outer peripheral surface of the photosensitive member 1 to a predetermined potential. Examples of the charging means include a non-contact charging method such as a corona charging method using a charger, and a contact charging method using a charging roller or a charging brush. The exposure means 31 has a semiconductor laser as a light source, and irradiates the surface of the photoreceptor 1 between the charger 32 and the developer 33 with a laser beam light output from the light source, thereby exposing the charged outer peripheral surface of the photoreceptor 1 in accordance with image information. The light is repeatedly scanned in the main scanning direction, that is, the direction of extension of the rotation axis 44 of the photoreceptor 1, and these are focused to sequentially form electrostatic latent images on the surface of the photoreceptor 1. In other words, the amount of charge on the photoreceptor 1, which has been uniformly charged by the charger 32, differs depending on whether or not it is irradiated with the laser beam, thereby forming an electrostatic latent image.

[0080] The developing device 33 is a developing means that develops the electrostatic latent image formed on the surface of the photosensitive member 1 by exposure with a developer (toner), and is provided facing the photosensitive member 1 and includes a developing roller 33a that supplies toner to the outer peripheral surface of the photosensitive member 1, and a casing 33b that supports the developing roller 33a rotatably around a rotation axis parallel to the rotation axis 44 of the photosensitive member 1 and contains a developer containing toner in its internal space.

[0081] The transfer charger 34 is a transfer means that transfers a toner image, which is a visible image formed on the outer peripheral surface of the photosensitive member 1 by development, onto transfer paper 51, which is a recording medium that is supplied between the photosensitive member 1 and the transfer charger 34 from the direction of arrow 42 by a transport means (not shown). The transfer charger 34 is, for example, a contact-type transfer means that includes a charging means and transfers the toner image onto the transfer paper 51 by applying a charge of the opposite polarity to that of the toner to the transfer paper 51.

[0082] The cleaner 36 is a cleaning means that removes and collects toner remaining on the outer peripheral surface of the photoreceptor 1 after the transfer operation by the transfer charger 34, and includes a cleaning blade 36a that separates the toner remaining on the outer peripheral surface of the photoreceptor 1, and a collection casing 36b that contains the toner separated by the cleaning blade 36a. The cleaner 36 is also provided together with a static elimination lamp (not shown).

[0083] The image forming apparatus 100 is also provided with a fixing device 35, which is a fixing means for fixing the transferred image, downstream of the transport of the transfer paper 51 that has passed between the photoreceptor 1 and the transfer charger 34. The fixing device 35 is provided with a heating roller 35a having a heating means (not shown), and a pressure roller 35b that is provided opposite the heating roller 35a and is pressed against the heating roller 35a to form a contact portion. Reference numeral 37 denotes a separating means for separating the transfer paper from the photosensitive member, and reference numeral 38 denotes a housing for accommodating the above-mentioned means of the image forming apparatus.

[0084] The image forming operation by this image forming apparatus 100 is performed as follows. First, when the photosensitive member 1 is rotated in the direction of arrow 41 by the driving means, the surface of the photosensitive member 1 is uniformly charged to a predetermined positive potential by the charger 32, which is located upstream of the image-forming point of the light by the exposure means 31 in the direction of rotation of the photosensitive member 1.

[0085] Next, light corresponding to image information is irradiated from exposure means 32 onto the surface of photoreceptor 1. This exposure removes surface charge from the areas of photoreceptor 1 that have been irradiated with light, creating a difference in surface potential between the areas that have been irradiated with light and the areas that have not been irradiated with light, forming an electrostatic latent image. Toner is supplied from a developing device 33, which is located downstream in the rotational direction of the photosensitive member 1 from the point where light is focused by the exposure means 33, to the surface of the photosensitive member 1 on which the electrostatic latent image is formed, thereby developing the electrostatic latent image and forming a toner image.

[0086] In synchronization with the exposure of the photoreceptor 1, transfer paper 51 is supplied between the photoreceptor 1 and transfer charger 34. The transfer charger 34 imparts a charge of opposite polarity to that of the toner to the supplied transfer paper 51, and the toner image formed on the surface of the photoreceptor 1 is transferred onto the transfer paper 51. The transfer paper 51 onto which the toner image has been transferred is transported by the transport means to the fixing device 35, and is heated and pressurized as it passes through the contact area between the heating roller 35a and the pressure roller 35b of the fixing device 35, and the toner image is fixed onto the transfer paper 51 to form a solid image. The transfer paper 51 on which the image has been formed in this way is ejected to the outside of the image forming apparatus 100 by the transport means.

[0087] Meanwhile, any toner remaining on the surface of photoreceptor 1 after the transfer of the toner image by transfer charger 34 is peeled off and collected from the surface of photoreceptor 1 by cleaner 36. The charge on the surface of photoreceptor 1 from which the toner has been removed in this way is removed by light from the discharging lamp, and the electrostatic latent image on the surface of photoreceptor 1 disappears. Thereafter, photoreceptor 1 is rotated again, and the series of operations starting with charging are repeated again to form images continuously.

[0088] The image forming apparatus 100 described above is a monochrome image forming apparatus (printer), but it may also be, for example, an intermediate transfer type color image forming apparatus capable of forming color images. Specifically, it may be a so-called tandem type full-color image forming apparatus having a configuration in which multiple photoconductors on which toner images are respectively formed are arranged side by side in a predetermined direction (for example, horizontal direction H or approximately horizontal direction H). Furthermore, the image forming apparatus 100 may also be another color image forming apparatus, a copier, a multifunction machine, or a facsimile machine. [Example]

[0089] The present disclosure will be specifically explained below with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited to the following Examples as long as it does not depart from the gist of the present invention. In the Production Examples, Examples and Comparative Examples, the physical properties were measured by the methods shown below.

[0090] [Average primary particle diameter of toner base particles (μm)] 20 mg of sample and 1 ml of sodium alkyl ether sulfate were added to 50 ml of electrolyte (ISOTON-II, manufactured by Beckman Coulter, Inc.), and the mixture was dispersed at 20 kHz for 3 minutes using an ultrasonic disperser (VS-D100, tabletop dual-frequency ultrasonic cleaner, manufactured by AS ONE Corporation) to obtain a measurement sample. The resulting measurement sample was measured using a particle size distribution analyzer (Multisizer 3, manufactured by Beckman Coulter, Inc.) with an aperture diameter of 100 μm and a particle count of 50,000 counts, and the average primary particle size (μm) was determined from the volumetric particle size distribution of the sample particles.

[0091] [Average primary particle size of each external additive (nm)] The particles of the external additive are photographed using a scanning electron microscope (SEM) (Hitachi High-Technologies Corporation, model: S-4800), and the particle sizes (major diameters) of 100 particles of the external additive are measured from the obtained image. The average value of these values ​​is calculated, and this is taken as the average primary particle size.

[0092] [Viscosity of toner base particles at 90°C] A flow tester (Shimadzu Corporation, model: CFT-100C) was used to apply a load of 10 kgf / cm 2 The pressure is set to (0.98 MPa) so that 1 g of toner is extruded from a die (nozzle diameter 1.0 mm, length 1.0 mm), and the toner is heated from 80 to 120°C at a temperature increase rate of 6°C / min, and the melt viscosity (apparent viscosity Pa·s) is measured.

[0093] [External additive coverage] The toner with external additives is photographed with a scanning electron microscope (SEM) (Hitachi High-Technologies Corporation, model: S-4800). A model calculation is performed using the average particle diameter D and specific gravity ρt of the toner base particles and the average particle diameter d and specific gravity ρi of each external additive to determine the coverage F of each external additive using the following formula. C is the number of parts of external additive added.

number

[0094] [Distribution bias value of barium titanate] Using a scanning electron microscope (Hitachi, Model: S-4800+EDX), qualitative and quantitative analysis was performed on 50 particles of externally added toner at 200 locations, including two locations on the toner surface where there were steps or grooves or other depressions, and two locations on flat areas without depressions.The average value BF of the proportion of barium element Ba in the flat areas and the average value BH of the proportion of barium element Ba in the depressed areas were measured, and the distribution bias value (BH / BF) of barium titanate particles was calculated.

[0095] [Adhesion strength of barium titanate] The toner is subjected to an external adhesion strength test according to the following procedure to obtain a toner after the external additive removal treatment. (1) 2.0 g of toner is added to 40 ml of a 0.2% by mass aqueous solution of polyoxyethylene octylphenyl ether (Rohm and Haas (now Dow Chemical Company), product name: Triton (registered trademark)), and the mixture is stirred for 1 minute. (2) Using an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd., model: US-300T), the resulting aqueous solution is irradiated with ultrasonic waves at an output of 40 μA for 4 minutes. (3) After that, the mixture is left for 3 hours, and the toner and the free external additives are separated. (4) After removing the supernatant, add approximately 50 ml of purified water to the precipitate and stir for 5 minutes. (5) The solution is subjected to suction filtration using a membrane filter (manufactured by Advantec) with a pore size of 1 μm. (6) The toner remaining on the membrane filter is vacuum dried overnight to obtain the toner after the external additive removal treatment.

[0096] The strength of the barium element Ba in the external additives in 1 g of toner was analyzed using a fluorescent X-ray analyzer (Rigaku Corporation, model: ZSX Primus II) for the obtained toner after the external additive removal process and the toner before the external additive removal process, and the adhesion strength of barium titanate was calculated as the ratio SA2 / SB2 × 100 (%) of the strength SA2 after the external additive adhesion strength test to the strength SB2 before the external additive adhesion strength test.

[0097] [Mobility of barium titanate] 50g of toner is placed in a 500mL stainless steel container and stirred for 180 seconds at a rotation speed of 1700rpm (rotational speed of the stirring blade tip: 40m / s) using a blender (Yamato Scientific Co., Ltd., model: small blender MODEL 31BL42). The adhesion strength FB of the barium titanate in the resulting contents and the adhesion strength FA of the barium titanate in the toner before stirring are measured, and the mobility of the barium titanate particles (FB / FA) x 100 (%) is calculated.

[0098] (Production Example 1: Preparation of amorphous polyester resin) A 5-liter reaction vessel was charged with 440 g (2.7 mol) of terephthalic acid, 235 g (1.4 mol) of isophthalic acid, 7 g (0.05 mol) of adipic acid, 554 g (8.9 mol) of ethylene glycol, and 0.5 g of tetrabutoxy titanate as a polymerization catalyst, and the mixture was reacted at 210°C under a nitrogen stream for 5 hours while distilling off the resulting water and ethylene glycol. The mixture was then reacted under a reduced pressure of 5 to 20 mmHg for 1 hour. Next, 103 g (0.54 mol) of trimellitic anhydride was added, and the mixture was allowed to react under normal pressure for 1 hour. After that, the mixture was allowed to react under reduced pressure of 20 to 40 mmHg, and the resin was extracted at a predetermined softening point. 219 g (3.5 mol) of ethylene glycol was recovered. The obtained resin was cooled to room temperature and then pulverized to form particles, which were designated as amorphous polyester resin A. The amorphous polyester resin had a Tg of 56° C., a Tm of 135° C., a peak top molecular weight Mp of 5,000, an SP value of 11.0, an acid value of 37 mgKOH / g, and a hydroxyl value of 50 mgKOH / g.

[0099] (Production Example 2: Preparation of crystalline polyester resin) A 5-liter reaction vessel was charged with 132 g (1.12 mol) of 1,6-hexanediol, 230 g (1.0 mol) of 1,10-decanedicarboxylic acid, and 3 g of tetrabutoxy titanate as a polymerization catalyst. The reaction was carried out at 210°C under atmospheric pressure for 5 hours, while the resulting water was distilled off. The reaction was then continued under a reduced pressure of 5 to 20 mmHg, and the resin was removed when the acid value reached 2 mg KOH / g or less. The resulting resin was cooled to room temperature and then pulverized to form particles. This was designated crystalline polyester resin C. The crystalline polyester resin had a Tmp of 80°C, a Tm of 88°C, a Tm / Tmp of 1.1, a peak top molecular weight Mp of 30,000, an SP value of 9.5, an acid value of 1 mgKOH / g, and a hydroxyl value of 10 mgKOH / g.

[0100] (Production Example 3: Production of Toner Base Particles C) Toner base particles C used in the examples were prepared as follows. Binder resin: amorphous polyester resin (Production Example 1) 62% by mass : Crystalline polyester resin (Production Example 2) 25% by mass Colorant: CI Pigmant Blue 15:3 (DIC) 7% by mass Release agent: monoester wax (NOF Corporation, product name: WEP-3) 5% by mass Charge control agent: salicylic acid compound (Orient Chemical Industry Co., Ltd., product name: Bontron E-84) 1% by mass

[0101] The above materials were premixed for 5 minutes using an airflow mixer (Henschel mixer, manufactured by Mitsui Mining Co., Ltd. (now Nippon Coke & Engineering Co., Ltd.), model FM20C) [mixing process], and then melt-kneaded using an open-roll continuous kneader (manufactured by Mitsui Mining Co., Ltd. (now Nippon Coke & Engineering Co., Ltd.), model MOS320-1800) to obtain a molten mixture [kneading process]. The open roll conditions were: heating roll supply side temperature 130°C, discharge side temperature 100°C, cooling roll supply side temperature 40°C, discharge side temperature 25°C. The heating roll and cooling roll had a diameter of 320 mm and an effective length of 1550 mm, and the inter-roll gap on both the supply side and discharge side was 0.3 mm. The heating roll rotation speed was 75 rpm, the cooling roll rotation speed was 65 rpm, and the toner raw material supply rate was 5.0 kg / h.

[0102] The resulting melt-kneaded product was cooled on a cooling belt and then coarsely pulverized using a speed mill equipped with a φ2 mm screen to obtain a coarsely pulverized product [coarse pulverization step]. 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]. 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 base particles A having an average primary particle diameter of 6.0 μm [classification step].

[0103] (Production Example 4: Production of Toner Base Particles A) Toner base particles A used in a comparative example (reference example) were prepared in the same manner as in Production Example 3, except that no crystalline polyester resin was used and 87% by mass of an amorphous polyester resin was used.

[0104] (Production Example 5: Production of Toner Base Particles B) Toner base particles B used in the comparative example (reference example) were prepared in the same manner as in Production Example 3, except that the crystalline polyester resin was changed from 25% by mass to 20% by mass and the amorphous polyester resin was changed from 62% by mass to 67% by mass.

[0105] (Production Example 6: Production of Toner Base Particles D) Toner base particles D used in the examples were prepared in the same manner as in Production Example 3, except that the crystalline polyester resin was changed from 25% by mass to 27% by mass and the amorphous polyester resin was changed from 62% by mass to 60% by mass.

[0106] (Production Example 7: Production of Toner Base Particles E) Toner base particles E used in the comparative example were prepared in the same manner as in Production Example 3, except that the crystalline polyester resin was changed from 25% by mass to 30% by mass and the amorphous polyester resin was changed from 62% by mass to 57% by mass.

[0107] (Production Examples 8 to 13: Preparation of barium titanate particles A to F) Barium titanate powder (manufactured by Toda Kogyo Co., Ltd., product grade: T-BTO-030RF (average primary particle diameter 43 nm), product grade: T-BTO-050RF (average primary particle diameter 54 nm)) was used. 50 g of barium titanate powder was stirred and mixed in 250 g of isopropyl alcohol to disperse the powder, thereby obtaining a slurry. The resulting slurry was mixed with 540 g of 0.3 mm diameter zirconia beads and ground in a bead mill for 1 hour. The zirconia beads were separated from the ground product, and the resulting slurry was dried at 150°C for 4 hours. The dried product was passed through an impact mill to break down agglomerates, yielding barium titanate powder with a smaller average primary particle size than before grinding.

[0108] The barium titanate powder after pulverization was observed under SEM to observe the decrease in the average primary particle size. The decrease in the average primary particle size was calculated by measuring the long axis of the barium titanate particles and averaging the size of 100 particles. The above grinding process was repeated twice, and the powder was combined with the original powder before grinding to create three types of barium titanate powder with different average primary particle sizes. The raw barium titanate powders T-BTO-030RF and T-BTO-050RF were each subjected to the above-mentioned grinding process, yielding a total of six barium titanate powders with different average primary particle sizes.

[0109] Two types of barium titanate powder with different average primary particle diameters were selected from the six obtained, and the mixing ratio was adjusted to homogenize the powders, thereby obtaining barium titanate A to F substrates with average primary particle diameters of 15 to 45 nm for use in the examples and comparative examples. The barium titanate powder substrates were surface-treated by known methods with trifluoropropyltrimethoxysilane for barium titanate powders A to E and dimethylsiloxane for barium titanate powder F. <Average particle size> Barium titanate A: 15 nm Barium titanate B: 20nm Barium titanate C: 30nm Barium titanate D: 40nm Barium titanate E: 45nm Barium titanate F: 30 nm

[0110] (Production Example 14: Preparation of Carrier) A resin liquid was prepared by adding 10 parts by mass of PTFE (manufactured by Daikin Industries, Ltd., product name: LDE-410) as fluororesin microparticles to 100 parts by mass of silicone resin, and a carrier core material was immersed in this resin liquid to obtain carrier "SC-1."

[0111] Example 1 <External additive treatment> 100 parts by mass of the obtained toner base particles C and 0.84 parts by mass of barium titanate particles C (average primary particle diameter 30 nm) (corresponding to a 7% coverage rate with respect to the toner base particles) were added to an FM mixer (manufactured by Nippon Coke Co., Ltd., model: FM-20) and mixed at a rotation speed of 3500 rpm for 90 seconds (first external addition step). Next, 1.4 parts by mass (corresponding to a coverage rate of 88% relative to the toner base particles) of silica particles (average primary particle diameter 12 nm, hydrophobized with hexamethyldisilazane, manufactured by WACKER, product name: H2000T) were added as hydrophobized small-diameter silica particles, and mixed at a rotation speed of 3500 rpm for 90 seconds (second external addition step). The resulting mixture was sieved using a 270 mesh sieve to obtain an externally added toner.

[0112] <Adjustment of developer> The obtained externally added toner and the carrier obtained in Production Example 9 were put into a V-type mixer (manufactured by Tokuju Kogyosho Co., Ltd., product name: V-5) so that the toner concentration was 7% by mass, and mixed for 20 minutes to obtain the two-component developer of Example 1.

[0113] Example 2 The two-component developer of Example 2 was obtained in the same manner as Example 1, except that in the first external addition step, the amount of barium titanate particles C (average primary particle diameter 30 nm) was changed from 0.84 parts by mass (equivalent to a 7% coverage rate on the toner base particles) to 0.24 parts by mass (equivalent to a 2% coverage rate on the toner base particles).

[0114] Example 3 The two-component developer of Example 3 was obtained in the same manner as Example 1, except that in the first external addition step, 0.84 parts by mass (corresponding to a 7% coverage rate with respect to the toner base particles) of barium titanate particles C (average primary particle diameter 30 nm) was changed to 0.16 parts by mass (corresponding to a 2% coverage rate with respect to the toner base particles) of barium titanate particles B (average primary particle diameter 20 nm).

[0115] Example 4 The two-component developer of Example 4 was obtained in the same manner as Example 1, except that in the first external addition step, 0.84 parts by mass (corresponding to a 7% coverage rate with respect to the toner base particles) of barium titanate particles C (average primary particle diameter 30 nm) was replaced with 0.31 parts by mass (corresponding to a 2% coverage rate with respect to the toner base particles) of barium titanate particles D (average primary particle diameter 40 nm).

[0116] Example 5 The two-component developer of Example 5 was obtained in the same manner as Example 1, except that in the first external addition step, 0.84 parts by mass (corresponding to a 7% coverage rate with respect to the toner base particles) of barium titanate particles C (average primary particle diameter 30 nm) was changed to 0.24 parts by mass (corresponding to a 2% coverage rate with respect to the toner base particles) of barium titanate particles F (average primary particle diameter 30 nm).

[0117] Example 6 A two-component developer of Example 6 was obtained in the same manner as in Example 1, except that in the first external addition step, the amount of barium titanate particles C (average primary particle diameter 30 nm) was changed from 0.84 parts by mass (corresponding to a 7% coverage rate with respect to the toner base particles) to 0.24 parts by mass (corresponding to a 2% coverage rate with respect to the toner base particles), and after the second external addition step, 1.0 part by mass (corresponding to an 8% coverage rate with respect to the toner base particles) of silica particles (average primary particle diameter 110 nm, manufactured by Shin-Etsu Chemical Co., Ltd., product name: X-24-9163A) was added as hydrophobically treated large-diameter silica particles, and the mixture was mixed at a rotation speed of 3500 rpm for 60 seconds (third external addition step).

[0118] Example 7 The two-component developer of Example 7 was obtained in the same manner as in Example 1, except that in the first external addition step, toner base particles C were changed to toner base particles D and 0.24 parts by mass (corresponding to a coverage rate of 2% relative to the toner base particles) of barium titanate particles C (average primary particle diameter 30 nm) were used.

[0119] Example 8 A two-component developer of Example 8 was obtained in the same manner as in Example 1, except that in the second external addition step, 4.7 parts by mass (equivalent to a coverage rate of 88% with respect to the toner base particles) of silica particles (average primary particle diameter 40 nm, hydrophobized with hexamethyldisilazane, manufactured by Aerosil, product name: RX50) were used instead of 1.4 parts by mass (equivalent to a coverage rate of 88% with respect to the toner base particles) of silica particles (average primary particle diameter 12 nm, hydrophobized with hexamethyldisilazane, manufactured by WACKER, product name: H2000T) as the hydrophobized small-diameter silica particles.

[0120] Example 9 The two-component developer of Example 9 was obtained in the same manner as in Example 1, except that in the external addition treatment, the order of the first external addition step and the second external addition step was changed so that small-diameter silica particles were added in the first external addition step and barium titanate particles were added in the second external addition step.

[0121] (Comparative Example 1: Reference Example) A two-component developer of Comparative Example 1 was obtained in the same manner as in Example 1, except that in the first external addition step, toner base particles A were used instead of toner base particles C, and 1.52 parts by mass of aluminum oxide particles (average primary particle diameter 30 nm) were used instead of barium titanate particles C per 100 parts by mass of toner base particles (equivalent to a 20% coverage rate with respect to the toner base particles), and in the second external addition step, 1.1 parts by mass of silica particles (average primary particle diameter 12 nm, hydrophobized with hexamethyldisilazane, manufactured by WACKER, product name: H2000T) were used (equivalent to a 70% coverage rate with respect to the toner base particles).

[0122] (Comparative Example 2: Reference Example) A two-component developer of Comparative Example 2 was obtained in the same manner as in Example 1, except that in the first external addition step, toner base particles B were used instead of toner base particles C, and 1.53 parts by mass (corresponding to a 15% coverage rate with respect to the toner base particles) of strontium titanate particles (average primary particle diameter 30 nm) were used instead of barium titanate particles C per 100 parts by mass of toner base particles, and in the second external addition step, 1.1 parts by mass (corresponding to a 70% coverage rate with respect to the toner base particles) of silica particles (average primary particle diameter 12 nm, hydrophobized with hexamethyldisilazane, manufactured by WACKER, product name: H2000T) were used.

[0123] (Comparative Examples 3 to 5) The two-component developers of Comparative Examples 3 to 5 were obtained in the same manner as in Example 1, except that in the first external addition step, 1.90 parts by mass, 1.52 parts by mass, and 1.14 parts by mass of aluminum oxide particles (alumina, average primary particle diameter 30 nm) were used instead of barium titanate particles C, relative to 100 parts by mass of toner base particles (corresponding to a coverage of 25%, 20%, and 15%, respectively, relative to the toner base particles), and in the second external addition step, 1.1 parts by mass of silica particles (average primary particle diameter 12 nm, hydrophobized with hexamethyldisilazane, manufactured by WACKER, product name: H2000T) were used (corresponding to a coverage of 70% relative to the toner base particles).

[0124] (Comparative Examples 6 to 8) The two-component developers of Comparative Examples 6 to 8 were obtained in the same manner as in Example 1, except that in the first external addition step, strontium titanate particles (average primary particle diameter 30 nm) were used in place of barium titanate particles C in amounts of 1.84 parts by mass, 1.53 parts by mass, and 1.22 parts by mass (corresponding to a coverage of 18%, 15%, and 12%, respectively, relative to 100 parts by mass of toner base particles), and in the second external addition step, 1.1 parts by mass (corresponding to a coverage of 70% relative to toner base particles) of silica particles (average primary particle diameter 12 nm, hydrophobized with hexamethyldisilazane, manufactured by WACKER, product name: H2000T) was used.

[0125] (Comparative Examples 9 and 10) Two-component developers of Comparative Examples 9 and 10 were obtained in the same manner as in Example 1, except that in the first external addition step, the amount of barium titanate particles C (average primary particle diameter 30 nm) was changed from 1.2 parts by mass (equivalent to a 7% coverage rate on the toner base particles) to 1.37 parts by mass and 0.17 parts by mass (equivalent to 8% and 1% coverage rate on the toner base particles, respectively).

[0126] (Comparative Examples 11 and 12) Two-component developers of Comparative Examples 11 and 12 were obtained in the same manner as in Example 1, except that in the first external addition step, 0.84 parts by mass of barium titanate particles C (average primary particle diameter 30 nm) (corresponding to a coverage rate of 7% relative to the toner base particles) were replaced with 0.12 parts by mass of barium titanate particles A (average primary particle diameter 15 nm) (corresponding to a coverage rate of 2% relative to the toner base particles) and 0.36 parts by mass of barium titanate particles E (average primary particle diameter 45 nm) (corresponding to a coverage rate of 2% relative to the toner base particles).

[0127] (Comparative Example 13) A two-component developer of Comparative Example 13 was obtained in the same manner as in Example 1, except that the toner base particles C were changed to the toner base particles E in the external addition treatment.

[0128] [evaluation] Using an evaluation machine modified from a digital copier (manufactured by Sharp Corporation, model: BP-20C25), printing tests were carried out on the two-component developers prepared in Examples 1 to 9 and Comparative Examples 1 to 13, and the remaining amount of charge control agent (barium titanate) after the test was measured, and the ID value and fogging value were measured and evaluated before and after the test. The printing test was carried out in an environmental testing room, where the evaluation machine was operated under three different environments: temperature 25°C, humidity 5% RH, temperature 25°C, humidity 50% RH, and temperature 25°C, humidity 80% RH. 90,000 images were printed, with 10% of the printable area of ​​A4 paper filled in with cyan toner.

[0129] [Remaining amount of charge control agent] A calibration curve for determining the remaining amount of charge control agent was created in the following procedure, and the remaining amount of charge control agent (the proportion of external additives embedded in the developer at the end of the product life) was determined. (1) When the amount of external additive in the toner (externally-added base toner) of the example and comparative example is set to 1, four formulations of externally-added toner are prepared so that the amount of external additive is 1, 0.75, 0.5, and 0.25. (2) Each of the four formulations of externally added toner obtained and the carrier "SC-1" obtained in Production Example 9 were placed in a V-type mixer (manufactured by Tokuju Kogyosho Co., Ltd., product name: V-5) in the same manner as in <Preparation of Developer> in Example 1 so that the toner concentration was 7% by mass, and mixed for 20 minutes to obtain a two-component developer.

[0130] (3) 10 g of developer is placed in a 25 ml glass container with a lid, and left for 12 hours with the lid open in an environment of 25°C temperature and 50% humidity. After that, the lid of the glass container is closed, and the developer is stirred using a shaker (Retsch, model: Mixer Mill MM200) at a shaking frequency of 25.4 Hz for 60 seconds. The charge amount is then measured using a suction-type charge amount measuring device (Trek, model: 210HS-2A). (4) The measured values ​​of the charge amount of the four formulations of externally added toner are graphed, and the line connecting the values ​​is used as the calibration curve. (5) In the same manner as in the above operation (3), the charge amount of the developer after the printing test is measured, and the remaining amount of charge control agent (the proportion of external additives embedded in the developer at the end of its product life) is calculated in accordance with the calibration curve.

[0131] [ID value] Using the evaluation machine, we printed an image in which 10% of the printable area of ​​A4 paper was filled with cyan toner in a low-humidity environment (temperature 25°C, relative humidity 5%), a standard environment (temperature 25°C, relative humidity 50%), and a high-humidity environment (temperature 25°C, relative humidity 85%). Using a densitometer (Videojet X-Rite, model: spectrophotometer / densitometer X-Rite eXact), we measured the density of a specific area of ​​the filled area (a band approximately 2 cm wide filled in along the length of the A4 paper, the average of five points in the center). The result was judged according to the following criteria based on the relationship between the measured value and the specified ID value (specified by the evaluation machine and the evaluation content). ◎: The measured value is 100% or more of the specified ID value. ○: The measured value is 90% or more but less than 100% of the specified ID value. △: The measured value is 80% or more but less than 90% of the specified ID value ×: The measured value is less than 80% of the specified ID value.

[0132] [Covers] Using the evaluation machine, images were printed in which 10% of the printable area of ​​A4 paper was filled with cyan toner in a low-humidity environment (temperature 25°C, relative humidity 5%), a standard environment (temperature 25°C, relative humidity 50%), and a high-humidity environment (temperature 25°C, relative humidity 85%).The brightness of specific areas that were not filled in was measured using a colorimeter (manufactured by Nippon Denshoku Industries Co., Ltd., model: ZE6000). The difference between the brightness measured before printing and the measured value was taken as the fogging value, and the fogging was judged according to the following criteria. ◎: The measured value is 80% or less of the specified fogging value. ○: The measured value is more than 80% but less than 90% of the specified value of the fogging value. △: The measured value is more than 90% and less than 100% of the specified fogging value. ×: The measured value with respect to the specified value of the overlapping value exceeds 100%

[0133] [Judgment combining ID value and overlapping value] Based on the measurement results of the ID value and the measurement results of the overlapping value in a low-humidity environment and a high-humidity environment, the judgment was made according to the following criteria. ◎: Both the ID value and the overlapping value in the low-humidity environment and the high-humidity environment are judged as ◎ ○: Either the ID value or the overlapping value in the low-humidity environment and the high-humidity environment is judged as ○ or higher △: Either the ID value or the overlapping value in the low-humidity environment and the high-humidity environment is judged as △ or higher. ×: Either the ID value or the overlapping value in the low-humidity environment and the high-humidity environment is judged as × or higher

[0134] [Overall judgment of image quality] Based on the judgment results of the ID value and the overlapping value of the developer in the initial state (Tables 1 and 2) and the judgment results of the ID value and the overlapping value of the developer in the worn and deteriorated state (end of life), the overall judgment was made according to the following criteria. ◎: The judgment results of the ID value and the overlapping value from the initial state to the worn and deteriorated state are ◎ ○: The judgment result of combining either the ID value or the overlapping value in either the initial state or the worn and deteriorated state is ○ △: The judgment result of combining either the ID value or the overlapping value in either the initial state or the worn and deteriorated state is △ ×: The judgment result of combining either the ID value or the overlapping value in either the initial state or the worn and deteriorated state is ×

[0135] Table 1 shows the constituent materials of the toner of the example and their physical properties, Table 2 shows the constituent materials of the toner of the comparative example and their physical properties, and Table 3 shows the evaluation results. In Tables 1 and 2, A to E of the material types of the toner mother particles mean toner mother particles A to E, TB-A to TB-F of the charge control agent mean barium titanate particles A to F, AL means alumina particles, and TS means strontium titanate particles. Also, in Tables 1 and 2, "○" where PS < PB means that the average primary particle diameter PS of the small particle size silica particles and the average primary particle diameter PB of the barium titanate particles satisfy the relational expression.

[0136] The relationship between the temperature and melt viscosity of the toner base particles is shown in Figure 1. According to Figure 1, toner base particles C and D satisfy the requirements of the present disclosure.

[0137] [Table 1]

[0138] [Table 2]

[0139] [Table 3]

[0140] The following can be seen from Tables 1 to 3. (1) A developer containing the toner of the present disclosure maintains high image quality from the beginning to the end of the product life in both low-humidity and high-humidity environments, has low-temperature fixability and excellent heat-resistant storage stability, suppresses developer charge loss due to development stress, and maintains high image quality throughout the product life (Examples 1 to 9). (2) When the average primary particle diameter of barium titanate particles is reduced from 30 nm to 20 nm, they are less likely to flow into the depressions on the toner surface, and at the end of the product life, they are filled to the same extent as the remaining required amount, but this does not affect image quality (Example 3).

[0141] (3) When the average primary particle diameter of barium titanate particles increases from 30 nm to 40 nm, the surface area of ​​barium titanate relative to the coating area becomes slightly smaller, and the ability to improve environmental charging performance becomes slightly weaker, but there is no effect on image quality (Example 4). (4) By changing the surface treatment agent for hydrophobic treatment of barium titanate particles from trifluoropropyltrimethoxysilane to dimethylsiloxane, the toner particles are less likely to flow into the depressions on the surface of the toner, and at the end of the product life, they are filled to the same extent as the remaining required amount, and there is no impact on image quality (Example 5).

[0142] (5) In the third external addition step, large silica particles with an average primary particle diameter of 110 nm are externally added. This allows high image quality to be maintained from the beginning to the end of the product life in both low-humidity and high-humidity environments. The particles remain sufficiently present even at the end of the product life, maintaining environmental charging performance (Example 6). (6) Even in the case of toner base particles with low viscosity at 90°C, the remaining amount of barium titanate exceeds the required lower limit, and high image quality is maintained from the beginning to the end of the product life in both low-humidity and high-humidity environments (Example 7).

[0143] (7) When the silica particles in the second external addition process are 40 nm, which is larger than the average primary particle diameter of the barium titanate particles of 30 nm, they are embedded to the same extent as the remaining required amount at the end of the product life, and although a slight decrease in ID is observed, there is almost no effect on image quality (Example 8). (8) When small silica particles are added in the first external addition process and barium titanate particles are added in the second external addition process, the particles are not sufficiently introduced into the depressions on the toner surface, and at the end of the product life, the particles are embedded to the same extent as the remaining required amount, resulting in a slight decrease in ID, but there is almost no effect on image quality (Example 9).

[0144] (9) In the case of conventional toners using toner base particles with a viscosity of more than 250,000 Pa·s at 90°C, the environmental charging performance is maintained from the beginning to the end of the product life by externally adding alumina particles with a coverage rate of 20% and strontium titanate particles with a coverage rate of 15% (Comparative Examples 1 and 2: Reference Examples). (10) In the case of conventional toners using toner base particles with a viscosity of 250,000 Pa·s or less at 90°C, the amount of remaining alumina decreases significantly toward the end of the product life, and if the amount of externally added alumina particles is excessive, fogging occurs in an initial high-humidity environment (Comparative Example 3). Also, toward the end of the product life, the amount of remaining alumina falls below the lower limit, causing a decrease in ID in a low-humidity environment (Comparative Example 4), and a decrease in ID and white spots occur in a low-humidity environment (Comparative Example 5).

[0145] (11) In the case of conventional toners using toner base particles with a viscosity of 250,000 Pa·s or less at 90°C, the amount of strontium titanate remaining at the end of the product life is significantly reduced by adding strontium titanate particles as an external additive at coverage rates of 18%, 15%, and 12%. At the end of the product life, the amount of strontium titanate remaining falls below the lower limit, causing a decrease in ID in a low-humidity environment (Comparative Examples 6 to 8). (12) When the amount of barium titanate particles added is large, fogging occurs in a high-humidity environment at the beginning (Comparative Example 9), and when the amount of added is small, the required remaining amount of barium titanate is not met at the end of the product life, causing a decrease in ID in a low-humidity environment (Comparative Example 10).

[0146] (13) When the average primary particle diameter of barium titanate particles is reduced from 30 nm to 15 nm, they are less likely to flow into the depressions on the toner surface, and the remaining amount falls below the required amount at the end of the product life, causing a decrease in ID (Comparative Example 11). (14) When the average primary particle diameter of barium titanate particles increases from 30 nm to 45 nm, the surface area of ​​barium titanate relative to the coating area decreases, the ability to improve environmental charging performance weakens, and ID decreases in low-humidity environments (Comparative Example 12). (15) When toner base particles having a viscosity of less than 100,000 Pa·s at 90°C are used, the remaining amount of barium titanate at the end of the product life falls below the required lower limit, resulting in a decrease in ID (Comparative Example 15). [Explanation of symbols]

[0147] 1. Electrophotographic photoreceptor 31 Exposure means (semiconductor laser) 32 Charging means (charger) 33 Developing means (developer) 33a Developing roller 33b casing 34 Transfer means (transfer charger) 35 Fixing means (fixing device) 35a Heating roller 35b Pressure roller 36 Cleaning means (cleaner) 36a cleaning blade 36b Recovery casing 37 Separation means 38 Housing 41, 42 arrow mark 44 Rotation axis 51 Recording media (recording paper or transfer paper) 100 Image forming device (laser printer)

Claims

1. The toner is composed of toner base particles containing at least a binder resin and a release agent, and an external additive that is externally added to the surface of the toner base particles, the binder resin contains a crystalline polyester resin, the toner base particles have a viscosity at 90°C of 100,000 to 250,000 Pa·s; the external additives are hydrophobized small-diameter silica particles and hydrophobized barium titanate particles, the barium titanate particles have an average primary particle diameter of 20 to 40 nm and a coverage of 2 to 7% with respect to the toner base particles, The average primary particle diameter PS of the small-particle silica particles and the average primary particle diameter PB of the barium titanate particles satisfy the relationship PS<PB. A toner characterized by:

2. The toner base particles have a particle size of 0.5 to 2.5 m as defined in JIS Z8830:2013. 2 2. The toner according to claim 1, having a BET specific surface area of ​​1 / g.

3. 2.0 g of the toner was added to 40 mL of a 0.2% by mass aqueous solution of polyoxyethylene octylphenyl ether, and the mixture was stirred for 1 minute. The resulting aqueous solution was irradiated with ultrasonic waves at an output of 40 μA for 4 minutes, and then the mixture was left for 3 hours to separate the toner and the liberated external additives. After the supernatant was removed, approximately 50 mL of pure water was added to the precipitate, and the mixture was stirred for 5 minutes. The mixture was then suction filtered using a membrane filter with a pore size of 1 μm, and the toner remaining on the membrane filter was vacuum dried overnight to perform an external additive removal treatment to obtain a toner after the external additive removal treatment.

3. The toner according to claim 1, wherein when the intensity SA2 of the barium element in 1 g of the obtained toner after the external additive removal treatment and the intensity SB2 of the barium element Ba in 1 g of the obtained toner before the external additive removal treatment are measured by fluorescent X-ray analysis, the adhesion strength of the barium titanate particles (SA2 / SB2) x 100 is 80% or more.

4. 50 g of the toner was placed in a 500 mL stainless steel container, and stirred for 180 seconds at a rotation speed of the stirring blade tip of 40 m / s. When the adhesion strength FB of the barium titanate of the resulting contents and the adhesion strength FA of the barium titanate of the toner before stirring were measured, 3. The toner according to claim 1, wherein the mobility of the barium titanate particles (FB / FA) x 100 is 1.1 or less.

5. 50 particles of the toner were subjected to qualitative and quantitative analysis using a scanning electron microscope at two locations on the toner surface where there were depressions such as steps or grooves, and two locations on flat areas without depressions, for a total of 200 locations. When the average value BF of the proportion of barium element Ba in the flat areas and the average value BH of the proportion of barium element Ba in the depressed areas were measured, 3. The toner according to claim 1, wherein the distribution bias value (BH / BF) of the barium titanate particles is 2.0 or more.

6. 3. The toner according to claim 1, wherein the toner base particles have an average primary particle diameter of 5 to 7 μm, and the small-diameter silica particles have a coverage of 70 to 90% of the toner base particles.

7. 3. The method for producing the toner according to claim 1 or 2, a first external addition step of adding and mixing the barium titanate particles as an external additive to the toner base particles, thereby externally adding the external additive to the toner base particles; and a second external addition step in which the external additive of the small-diameter silica particles is further added and mixed with the obtained toner base particles to externally add the external additive to the toner base particles; A method for producing a toner, comprising:

8. 3. The toner according to claim 1, further comprising large silica particles having an average primary particle size of 70 to 200 nm as an external additive.

9. The method for producing the toner according to claim 8, a first external addition step of adding and mixing the barium titanate particles as an external additive to the toner base particles, thereby externally adding the external additive to the toner base particles; a second external addition step of further adding and mixing the external additive of the small-diameter silica particles to the obtained toner base particles to externally add the external additive to the toner base particles; and a third external addition step in which the external additive of the large-diameter silica particles is further added and mixed with the obtained toner base particles to externally add the external additive to the toner base particles; A method for producing a toner, comprising:

10. A developer comprising the toner according to claim 1 or 2 and a carrier.

11. 3. An image forming apparatus which forms an image by forming an electrostatic latent image on the surface of an electrophotographic photosensitive member and transferring toner developed on the electrostatic latent image to a transfer material, wherein the toner is the toner according to claim 1 or 2.

Images