JP2008304602A - Electrostatic latent image developing toner and developer using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic latent image developing toner which has high stress resistance and proper fluidity, ensures less performance variations due to environmental differences of temperature and humidity, even in long-time use under high stress, and is less likely to cause image defects, such as fogging and uneven halftone, while being a low glass transition temperature (Tg) toner having ultra-low temperature fixability. <P>SOLUTION: The electrostatic latent image developing toner has an external additive comprising inorganic particles surface-treated with a silicon compound surface treating agent, wherein at least one kind of the inorganic particles satisfies that (a) the silicon compound surface treating agent comprises, at least a short chain silicon compound where an alkyl group bonding to an Si atom has a maximum number of 1-5C and a long chain silicon compound where an alkyl group bonding to an Si atom has a maximum number of ≥6C, and that (b) the inorganic particles have a number average particle diameter of 60-200 nm. The toner has a glass transition temperature of 20-45°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a toner for developing an electrostatic latent image and a developer using the same.

  As a technical background of the present invention, energy saving at the time of thermal fixing is being promoted in an electrostatic latent image developing type image forming method. From the viewpoint of promoting energy saving, the toner is being fixed at a low temperature, and the glass transition point (Tg) of the electrostatic latent image developing toner (hereinafter sometimes simply referred to as toner) is set low. It has become to. However, there is a tendency that the hardness of the toner is lowered and the stress resistance is also lowered.

  For the above reasons, even if the inorganic fine particles added to the toner as an external additive are held on the toner as in the prior art, the inorganic fine particles are buried in the toner surface when stress is applied to the toner. Therefore, large particle size particles are added as an external additive for the toner, and a spacer function is provided so as not to change the existence state of the small particle size particles on the toner surface, thereby stabilizing the developability and transferability. A technique is known (for example, Patent Document 1).

  However, as full color progresses, it is necessary to cope with various printing ratios, and particularly when the printing ratio is low and the toner staying time in the developing device is long, it is a severe use condition for the toner. . Even when large particle size particles are used in combination, small particle size particles (ordinary external additives) are buried in the toner particles, and the chargeability and fluidity of the toner cannot be maintained, so that developability and fixability are stabilized. The tendency to become unable to hold was strong.

On the other hand, the inorganic particles used as the external additive also need to have roles of ensuring fluidity and adjusting the chargeability. However, generally used silica-based particles have a strong negative polarity, and tend to excessively increase the charge of negatively charged toner particularly in a low temperature and low humidity environment, while in a high temperature and high humidity environment. Has a problem in that it takes in moisture and decreases the chargeability, resulting in a large difference in chargeability between the two. As a result, density reproducibility, fogging, and internal contamination may be caused. In order to improve these, it has been proposed to use a surface-treated inorganic fine particle (for example, Patent Document 2). However, it is difficult to ensure charging stability with respect to the environment only by using these inorganic fine particles.
JP 2006-39023 A JP 2005-338880 A

  An object of the present invention is a low glass transition point (Tg) toner having ultra-low temperature fixability, yet having high stress resistance, good fluidity, and even when used for a long time under high stress. It is an object of the present invention to provide a toner for developing an electrostatic latent image that is less likely to cause image defects such as fogging and halftone unevenness with little performance fluctuation due to a difference in humidity environment.

  In order to solve the above problem, in the present invention, the surface treatment agent for large particle size particles is changed from the conventional one, and the dispersibility of the large particle size particles on the toner particle surface is improved. Spacer effect can work effectively to obtain a toner that has high stress resistance, and does not change its chargeability due to changes in the temperature and humidity environment used, and does not cause fogging or internal contamination. I was able to.

  That is, by performing a double treatment with a surface treatment agent for large particle size silica with a short chain having 1 to 5 carbon atoms in the alkyl group and a long chain having 6 or more carbon atoms, It was possible to improve the degree of hydrophobicity, to stabilize the chargeability against environmental differences, and to stabilize the chargeability and fluidity of the toner even under long-term stress.

  That is, the object of the present invention is achieved by adopting the following configuration.

(1)
In the electrostatic latent image developing toner having an external additive composed of inorganic particles surface-treated with a silicon compound surface treating agent,
At least one of the inorganic particles satisfies (a) and (b),
(A) The silicon compound surface treatment agent is at least one of a short chain having 1 to 5 maximum carbon atoms in the alkyl group bonded to the Si atom and a long chain having 6 or more maximum carbon atoms. A toner for developing an electrostatic latent image, wherein the number average particle diameter of two types of inorganic particles (b) is 60 to 200 nm, and the glass transition point of the toner is 20 to 45 ° C.

(2)
The toner for developing an electrostatic latent image according to (1), wherein the inorganic particles are silica particles.

(3)
After the external additive consisting of inorganic particles treated with at least two kinds of surface treatment agents is treated with a short-chain surface treatment agent having 1 to 5 carbon atoms in the alkyl group bonded to the Si atom, The toner for developing an electrostatic latent image according to (1), which is treated with a long-chain surface treatment agent having 6 or more carbon atoms.

(4)
The toner for developing an electrostatic latent image according to (1), wherein the short-chain alkyl group of the alkyl group has 1 or 2 carbon atoms.

(5)
(1)-(3) The electrostatic latent image developing toner and the carrier having a mass average particle diameter of 20-70 μm are used.

  According to the present invention, although it is a low glass transition point (Tg) toner having ultra-low temperature fixability, it has high stress resistance, good fluidity, and can be used for a long time under high stress. It is possible to provide a toner for developing an electrostatic latent image that has little performance fluctuation due to the difference and hardly causes image defects such as fogging and halftone unevenness.

  In recent years, color image formation has become popular, and in off-fishes, there is a demand for an image forming apparatus that can handle various printing rates. In particular, the printing rate is low and the residence time of the toner in the developing unit becomes long. A strong stress / deterioration effect based on toner agitation is applied. The present invention aims to improve toner stress resistance and prevent fluidity deterioration by adding large particle size inorganic particles with a specific treatment agent to the toner and making the dispersion of the external additive uniform on the toner. As a result, halftone image unevenness is prevented, the transfer rate is maintained over time, and the development / transfer process is stabilized. At the same time, the variation in environmental difference is improved by increasing the degree of hydrophobicity of the external additive.

  The toner residence time in the developing device varies greatly depending on the printing rate. In particular, when an image is formed under a low printing rate condition on a high-speed machine, the stress applied until each toner particle is used increases, and the external additive on the surface of the toner particle is buried in the toner particle. As a result, the transferability of toner and the stability of development are greatly reduced, and particularly when a full-color image is formed, there arises a problem that the image stability varies greatly depending on the printing rate. As a countermeasure against this, adding a large particle size particle gives a spacer function against excessive stress, prevents excessive stress from being applied to the small particle size particle, and prevents the presence state from fluctuating. Efforts are also made to maintain the stability of transfer and development. However, when external additives have been used so far, fluctuations in characteristics such as chargeability due to fluctuations in temperature and humidity are large, and when surface-treated large particle diameter particles are added, fluctuations due to environmental differences are further increased. Therefore, this time, the surface treatment agent for hydrophobizing the large particle size has a short chain of 1 to 5 carbon atoms and a relatively large carbon number of 6 or more. When the surface treatment was carried out with seeds, it was possible to reduce the difference in characteristic variation due to changes in the temperature and humidity environment and to improve the dispersibility on the toner particles, thereby improving the stress resistance. The reason for this is that the alkyl group bonded to the Si atom has 1 to 5 carbon atoms and a short-chain silicon compound surface treatment agent to improve fluidity and a relatively large number of carbon atoms having 6 or more carbon atoms. It is estimated that this is because it was possible to simultaneously reduce the difference in chargeability variation due to temperature and humidity fluctuations with the silicon compound surface treatment agent.

  Hereinafter, the present invention will be described in detail.

  The toner of the present invention is a toner having at least hydrophobized inorganic particles as an external additive and having a glass transition temperature of 20 to 45 ° C. If necessary, the toner contains a colorant, a release agent, and the like. be able to.

  First, the external additive will be described.

(External additive)
As an external additive, in addition to a large particle size external additive having a particle size of 60 to 200 nm, a commonly used external additive having a small particle size of less than 60 nm can be used. The difference in particle size between the large particle size external additive and the small particle size particle is preferably 30 nm or more. By setting the thickness to 30 nm or more, the spacer effect is remarkably exhibited, and the small particle size particles can be held on the toner particle surface for a long period of time. Thereby, even if the toner is stressed in the developing unit or the like, the influence can be reduced by the spacer effect.

(Large particle size external additive)
The number average primary particle size of the large particle size external additive is 60 to 200 nm, preferably 80 to 120 nm, in order to achieve both the fixation to the toner particle surface and the spacer effect.

  This is because when the number average primary particle size is 60 nm or less, the spacer effect is lowered, and the small particle size external additive is buried in the toner particle surface during long-term use.

  If the number average primary particle size exceeds 200 nm, the spacer effect can be expected. However, even if the number average primary particle size is initially fixed on the toner particle surface, it tends to be released from the toner particle surface due to its volume and weight. Therefore, liberation becomes significant in long-term use.

  Further, in order to obtain a uniform effect as a spacer, a spacer having a spherical shape and a narrow particle size distribution is preferable.

  Examples of inorganic particles that can be used as a large particle size external additive include inorganic particles having a conventionally known composition. Specifically, examples of inorganic particles include silica particles, titania particles, alumina particles, and composite oxides thereof. These inorganic particles need to be hydrophobized as described later.

  As the large particle size external additive, inorganic particles having higher hardness and higher specific gravity are easier to obtain the desired characteristics, and specifically, silica particles are preferable. When the hardness is high and the specific gravity is heavy, the toner particles are easily fixed, and the silica particles are particularly preferable because the toner particles can be expected to have a negative charging property.

  The toner of the present invention preferably contains 1.5 to 4.0 parts by mass of a large particle size external additive in 100 parts by mass of the toner. By adjusting to the above range, it is possible to maintain the suppression of the burying of the small particle size external additive, and it is possible to prevent the photoreceptor from being worn and the cleaning blade from being worn.

(Silicon compound for surface treatment of large particle size external additives)
Examples of the silicon compound of the present invention include a short-chain silicon compound having 1 to 5 carbon atoms in the alkyl group bonded to the Si atom shown below and a long-chain silicon compound having 6 or more carbon atoms. Can be mentioned.

1) Specific examples of short-chain silicon compounds in which the maximum number of carbon atoms n of the alkyl group bonded to the Si atom is 1 to 5 1-1; CH ₃ SiCl ₃ (n = 1)
1-2; (CH ₃ ) HSiCl ₂ (n = 1)
1-3; (CH ₃ ) ₂ SiCl ₂ (n = 1)
1-4; (CH ₃ ) ₃ SiCl (n = 1)
1-5; CH ₃ Si (OCH ₃ ) ₃ (n = 1)
1-6; (CH ₃ ) ₂ Si (OCH ₃ ) ₂ (n = 1)
1-7; (CH ₃ ) ₂ Si (OC ₂ H ₅ ) ₂ (n = 1)
1-8; (CH ₃ ) ₂ CHCH ₂ Si (OCH ₃ ) ₃ (n = 4)
1-9; tC ₄ H ₉ (CH ₃ ) ₂ SiCl (n = 4)
1-10; (CH ₃ ) ₃ SiNHSi (CH ₃ ) ₃ (n = 1)
1-11; C ₂ H ₅ SiCl ₃ (n = 2)
In the present invention, the short-chain hydrophobizing agent preferably has 1 or 2 carbon atoms. The short-chain silicon compound in which the maximum number of carbon atoms n of the alkyl group bonded to the Si atom is 1 to 5, is relatively easy to be uniformly treated on the surface of the inorganic particles because the molecular chain is relatively short. The fluidity of the particle surface can be improved.

2) Specific examples of long-chain silicon compounds having a maximum number of carbon atoms n of 6 or more bonded to Si atoms 2-1; C ₆ H ₅ SiCl ₃ (n = 6)
2-2; (C ₆ H ₅ ) ₂ SiCl ₂ (n = 6)
2-3; C ₆ H ₅ Si (OCH ₃ ) ₃ (n = 6)
2-4; (C ₆ H ₅ ) ₂ Si (OCH ₃ ) ₂ (n = 6)
2-5; C ₆ H ₅ Si (OC ₂ H ₅ ) ₃ (n = 6)
2-6; (C ₆ H ₅ ) ₂ Si (OC ₂ H ₅ ) ₂ (n = 6)
2-7; C ₈ H ₁₇ Si (OC ₂ H ₅ ) ₃ (n = 8)
2-8; n-C ₁₀ H ₂₁ Si (OCH ₃ ) ₃ (n = 10)
2-9; n-C ₁₈ H ₃₇ Si (OCH ₃ ) ₃ (n = 18)
In the present invention, the long-chain hydrophobizing agent preferably has 6 to 10 carbon atoms. The long-chain silicon compound having a maximum number of carbon atoms n of 6 or more bonded to the Si atom has a long molecular chain, and thus forms a three-dimensional surface layer on the surface of the inorganic particles. It is presumed that this three-dimensional layer formation makes it difficult for water molecules to be adsorbed on the surface of the inorganic particles, leading to stabilization of the chargeability of the toner.
(Silicon compound surface treatment method)
The hydrophobizing treatment can be performed by a method that is usually performed.

  As a method for surface treatment with a silicon compound on the surface of the inorganic particles, a dry method or a wet method can be used.

  For example, the dry processing method includes stirring or mixing inorganic particles and a silicon compound in a fluidized bed reactor. As an alternative method, the wet method includes dispersing inorganic particles in a solvent to form an inorganic particle slurry, and then adding a silicon compound to the slurry, thereby modifying the surface of the inorganic particles with the silicon compound. In addition, the inorganic particles can be prepared using a batch or continuous process in which the dry inorganic particles are contacted with a liquid silicon compound or silicon compound vapor with thorough mixing. In a preferred embodiment, the mixture is then kept at a temperature sufficient for a sufficient time to modify the surface properties of the inorganic particles. Typically, temperatures ranging from 25 ° C to 200 ° C are suitable for times between 30 minutes and 16 hours. In a preferred embodiment, temperatures ranging from 80 ° C. to 100 ° C. for times between 30 minutes and 2 hours can effectively modify the properties of the inorganic particles.

  In addition, as a procedure of the surface treatment method using the two kinds of surface treatment agents of the present invention, first, the surface is formed by a short-chain silicon compound in which the maximum carbon atom number n of the alkyl group bonded to the Si atom is 1 to 5. A method of treating the surface of a long-chain silicon compound having a maximum number of carbon atoms n of 6 or more bonded to Si atoms after the treatment is preferred. From the viewpoint of imparting the fluidity of the large-diameter external additive, it is more effective to treat the silicon compound with a short chain structure that is easy to uniformly treat the surface first, and also in terms of the steric hindrance effect on the inorganic particle resurface, This is because the effect is enhanced when a long-chain silicon compound having a maximum number of carbon atoms n bonded to Si atoms of 6 or more is finally treated.

  The amount of the surface treatment agent is preferably 1 to 50 parts by mass and more preferably 3 to 40 parts by mass with respect to 100 parts by mass of the inorganic particles.

(Small particle size external additive)
The number average primary particle size of the small particle size external additive is 5 to 40 nm, preferably 10 to 30 nm, and is usually widely used in order to roll the toner particle surface and obtain good fluidity and a stable charge amount. It may be of the same particle size as the above.

  Examples of those that can be used as a small particle size external additive include conventionally known inorganic particles and organic particles, but inorganic particles are preferred. Specifically, silica fine particles, titania fine particles, alumina fine particles, and complex oxides thereof can be preferably used as the inorganic particles. These inorganic particles are preferably hydrophobic in order to prevent water absorption and to reduce characteristic fluctuations caused by fluctuations in the temperature and humidity environment.

  The toner of the present invention preferably contains 0.5 to 2.0 parts by mass of a small particle size external additive in 100 parts by mass of the toner. By setting the content in the above range, the fluidity and chargeability of the toner can be maintained well.

  Next, a method for measuring the particle diameter of the external additive will be described.

(Measurement method of external additive particle size)
The number average primary particle size of the external additive is specifically measured by the following method.

  A 30,000 times photograph of the toner is taken with a scanning electron microscope, and the photograph image is captured by a scanner. In the image processing analysis apparatus “LUZEX AP (manufactured by Nireco)”, the external additive present on the surface of the toner particles of the photographic image is binarized, and the horizontal ferret diameter for 100 external additives is determined. The calculated average value is defined as the number average particle diameter.

  In addition, if you are uncertain whether to specify a small particle size external additive or a large particle size external additive, perform elemental analysis on the particles observed in the photograph, and clarify the external additive elements. . When the large particle size external additive and the small particle size external additive are composed of the same element, out of 100 measured particles, those having a particle size of less than 60 nm are used as the small particle size external additive. One having the above particle size is used as a large particle size external additive.

  The external additive used in the present invention has two peaks as a particle size distribution. The peak on the small particle size side is the small particle size external additive, and the peak on the large particle size side is the large particle size external additive. This is because the effect of the present invention cannot be obtained even when particles having a different particle size are present when the particle size distribution is wide such that there is only one peak.

  Although the small particle size external additive used in the present invention is in a state of adhering to the toner particle surface, the spacer effect of the large particle size external additive fixed on the toner particle surface makes the toner particle surface long-term. It is presumed that, since the toner is not buried in the toner and the chargeability of the toner is stabilized, the toner becomes difficult to be released and the occurrence of release and scattering by the small particle size external additive can be suppressed.

(Toner of the present invention)
The toner of the present invention has a glass transition point of 20 to 45 ° C. and contains the aforementioned external additive. The glass transition point is more preferably 20 to 40 ° C. from the viewpoint of fluidity stability and chargeability stability. Further, when the toner particles have a core-shell structure, those having a shell Tg higher by 10 ° C. or more than the core Tg are preferably used.

  The median diameter (D50) of the toner particles on the volume basis is preferably 3 to 8 μm.

(Method for measuring glass transition point of toner)
The glass transition point of the toner of the present invention can be determined using a DSC-7 differential scanning calorimeter (manufactured by PerkinElmer) or a TAC7 / DX thermal analyzer controller (manufactured by PerkinElmer).

  As a measurement procedure, 4.5 to 5.0 mg of toner is precisely weighed to two decimal places, enclosed in an aluminum pan (KITNO.0219-0041), and set in a DSC-7 sample holder. The reference used an empty aluminum pan. The measurement conditions were a measurement temperature of 0 to 200 ° C., a temperature increase rate of 10 ° C./min, a temperature decrease rate of 10 ° C./min, and heat-cool-heat temperature control. Analysis was performed based on the data in Heat. The glass transition point draws an extension of the baseline before the rise of the first endothermic peak and a tangent line indicating the maximum slope between the rise portion of the first peak and the peak apex, and the intersection is taken as the glass transition point. Show.

  Next, a toner manufacturing method will be described.

(Toner preparation method)
The method for producing the toner is not particularly limited, but a method using an emulsion association method is preferably used. Particularly preferred is a production method in which resin particles having a multi-stage polymerization structure formed by emulsion polymerization of miniemulsion polymerized particles are associated (aggregated / fused).

Hereinafter, an example of a method for producing a toner by the miniemulsion polymerization association method will be described in detail. In this toner manufacturing method, the toner is manufactured through the following steps.
(1) Dissolution / dispersion step of dissolving or dispersing the release agent in the radical polymerizable monomer (2) The polymerizable monomer solution in which the release agent is dissolved / dispersed is formed into droplets in a solution medium, and the mini Polymerization step for preparing a dispersion of resin particles by emulsion polymerization (3) Colorant dispersion step for dispersing a colorant in the contained solution medium (4) Associating the resin particles with the colorant particles in the solution medium Aggregation / fusion step for obtaining particles (5) Aging step for adjusting the shape by aging the associated particles with heat energy to form toner particles (6) Cooling step for cooling the dispersion of toner particles (7) Cooling The toner particles are solid-liquid separated from the toner particle dispersion, and the surfactant is removed from the toner base. (8) The washed toner particles are dried. (9) The toner particles are dried. Add external additives to toner particles That process steps will be described below.

(1) Dissolution / dispersion step This step is a step of preparing a radical polymerizable monomer solution of the release agent by dissolving or dispersing the release agent in the radical polymerizable monomer.

(2) Polymerization step In a preferred example of this polymerization step, a radical polymerizable monomer solution in which the release agent is dissolved or dispersed is added to a solution medium containing a surfactant, and mechanical energy is increased. In addition, droplets are formed, and then the polymerization reaction proceeds in the droplets by radicals from the water-soluble radical polymerization initiator. Note that resin particles may be added as core particles to the solution medium.

  By this polymerization step, resin particles containing a release agent and a binder resin are obtained. The resin particles to be applied may be colored particles or non-colored particles. The colored resin particles can be obtained by polymerizing a monomer composition containing a colorant. In addition, when using uncolored resin particles, in the aggregation step described later, the dispersion of the colorant particles is added to the dispersion of the resin particles to aggregate the resin particles and the colorant particles. It can be a particle.

(3) Dispersing Step of Colorant Particles This step is a step of adding colorant particles to a solution medium containing a surfactant and dispersing the colorant particles in the solution medium using a dispersing device.

  The dispersing device used in the step of dispersing the colorant particles is not particularly limited, and a known device can be used. Preferred dispersing devices include pressure dispersers such as an ultrasonic disperser, a mechanical homogenizer, a manton gourin, and a pressure homogenizer, and medium dispersers such as a sand grinder, a Getzman mill, and a diamond fine mill.

  The colorant may be surface-modified. In the surface modification method of the colorant, the colorant particles are dispersed in a solvent, the surface modifier is added to the dispersion, and the system is reacted by raising the temperature. After completion of the reaction, the colorant particles are filtered off, washed and filtered with the same solvent, and then dried to obtain a colorant treated with the surface modifier.

  As the black colorant used in the present invention, the above colorants can be used.

  From the viewpoint of more preferably obtaining the effect described in the present invention, the average dispersion diameter of the black colorant dispersed in the solution medium during the toner production process is preferably 2 to 300 nm, more preferably 2 to 200 nm. preferable. The average dispersion diameter of the black colorant can be controlled by the type and amount of the compound represented by the general formula (1), the amount of the surfactant, the rotational speed of the dispersion apparatus, the dispersion time, and the like.

(4) Aggregation / fusion process The aggregation process is a process of forming colored particles using the resin particles and the colorant particles obtained by the polymerization process. In the aggregation step, resin particles and colorant particles can be aggregated together with release agent particles, internal additive particles such as charge control agents, and the like.

  A preferred aggregating method is to add a salting-out agent composed of an alkali metal salt, an alkaline earth metal salt, or the like as an aggregating agent having a critical aggregation concentration or more in water in which resin particles and colorant particles are present, In this method, the particles are aggregated by heating to a temperature not lower than the glass transition temperature of the resin particles and not lower than the melting peak temperature (° C.) of the release agent.

(5) Aging process Aging is preferably performed by thermal energy (heating).

  Specifically, the liquid containing the associated particles is heated and stirred to adjust the shape of the associated particles to the desired circularity by adjusting the heating temperature, stirring speed, and heating time to obtain toner particles. .

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

(7) Washing Step In this solid-liquid separation / washing step, the solid-liquid separation process for solid-liquid separation of the toner particles from the dispersion liquid of the toner particles cooled to a predetermined temperature in the above step, and the solid-liquid separated toner A cleaning process is performed to remove deposits such as surfactants and salting-out agents and the alkali agent used in the aging step from the cake (aggregation obtained by agglomerating toner particles in a wet state).

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

(8) Drying Step This step is a step of drying the washed toner cake to obtain dried toner particles. Examples of dryers used in this process include spray dryers, vacuum freeze dryers, vacuum dryers, etc., stationary shelf dryers, mobile shelf dryers, fluidized bed dryers, rotary dryers It is preferable to use a stirring dryer or the like. The water content of the dried colored particles is preferably 5% by mass or less, more preferably 2% by mass or less. In addition, when the toner particles subjected to the drying treatment are aggregated due to weak interparticle attraction, the aggregate may be crushed. Here, as the crushing treatment device, a mechanical crushing device such as a jet mill, a Henschel mixer, a coffee mill, a food processor, or the like can be used.

(9) Step of mixing external additive with toner particles This step is a step of preparing toner by mixing two or more kinds of external additives according to the present invention with toner particles. As an external additive mixing device, a mechanical mixing device such as a Henschel mixer or a coffee mill can be used.

  The two or more types of external additives according to the present invention may be mixed by adding two or more types of external additives to the toner particles at the same time, or may be added and mixed separately. In order to obtain a spacer effect by the external additive, a method in which only the large particle size external additive is first mixed with the toner particles and then the small particle size particles are mixed and processed is preferable.

  The external additive is mixed by first adding the large particle size external additive into the toner particles (immobilization first step), immobilizing the large particle size external additive on the toner particle surface, and then reducing the small particle size. A method in which an external additive is added (fixation second step) and the small particle size external additive is adhered to the toner particle surface is preferable.

  First fixing step: After adding the large particle size external additive to the toner particles, the mixing time is lengthened or the mixing speed (stirring speed) is increased to fix the large particle size external additive on the toner particle surface. .

  Second fixing step: The small particle size external additive is mixed by slowing the mixing speed (stirring speed) to adhere the small particle size external additive to the toner particle surface.

  Moreover, as conditions for the mixing apparatus, the peripheral speed is preferably 20 to 50 m / sec, and the peripheral speed of the large particle size external additive treatment is preferably faster than the peripheral speed of the small particle size external additive treatment. The treatment time is preferably 3 to 40 minutes, but the treatment time is preferably set longer because the smaller the external additive, the easier it is for the external additive particles to aggregate.

The median diameter (D ₅₀ ) on the volume basis of the toner is obtained by measuring with the following measuring method.

  Measurement and calculation are performed using a device in which a computer system (manufactured by Coulter) equipped with data processing software “Software V3.51” is connected to Coulter Multisizer 3 (manufactured by Coulter).

  As a measurement procedure, 0.02 g of toner is blended with 20 ml of a surfactant solution (for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant component 10 times with pure water for the purpose of dispersing the toner). After that, ultrasonic dispersion is performed for 1 minute to prepare a toner dispersion. This toner dispersion is injected into a beaker containing ISOTON II (manufactured by Coulter) in a sample stand with a pipette until the display density of the measuring instrument becomes 5% to 10%. By setting this concentration range, a reproducible measurement value can be obtained. In the measuring machine, the measurement particle count is 25000, the aperture diameter is 50 μm, and the frequency value is calculated by dividing the measurement range of 1 to 30 μm into 256 parts. The particle diameter of 50% from the larger volume integrated fraction is defined as the volume-based median diameter.

  Next, materials constituting the toner particles will be described.

(Binder resin)
As the polymerizable monomer constituting the binder resin, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichloro are used. Styrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn -Styrene or styrene derivatives such as decylstyrene, pn-dodecylstyrene, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-methacrylate Octyl, 2-ethylhexyl methacrylate, stearyl methacrylate Methacrylic acid ester derivatives such as lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, acrylic Acrylates such as isobutyl acid, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, olefins such as ethylene, propylene, isobutylene, vinyl chloride, vinylidene chloride, Halogenated vinyls such as vinyl bromide, vinyl fluoride and vinylidene fluoride, vinyl esters such as vinyl propionate, vinyl acetate and vinyl benzoate, vinyl methyl ether, vinyl ethyl ether Vinyl ethers such as ether, vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, vinyl hexyl ketone, N-vinyl compounds such as N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone, vinyl naphthalene, vinyl pyridine, etc. There are acrylic acid or methacrylic acid derivatives such as vinyl compounds, acrylonitrile, methacrylonitrile, acrylamide and the like. These vinyl monomers can be used alone or in combination.

  Further, it is more preferable to use a combination of monomers having an ionic dissociation group as the polymerizable monomer constituting the resin. For example, it has a substituent such as a carboxyl group, a sulfonic acid group, a phosphoric acid group as a constituent group of the monomer, specifically, acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumar Acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-methylpropane sulfonic acid, acid phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxy And propyl methacrylate.

  Furthermore, polyfunctionality such as divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, etc. It is also possible to use a crosslinkable resin by using a functional vinyl.

  These polymerizable monomers can be polymerized using a radical polymerization initiator. In this case, an oil-soluble polymerization initiator can be used in the suspension polymerization method. Examples of the oil-soluble polymerization initiator include 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carboxyl). Nitriles), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azo- or diazo-based polymerization initiators such as azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate , Cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis- (4,4- t-butylperoxycyclohexyl) propane, tris- Peroxide polymerization initiator or a peroxide such as t- butylperoxy) triazine and the like polymeric initiator having a side chain.

  Moreover, when using an emulsion polymerization method, a water-soluble radical polymerization initiator can be used. Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, hydrogen peroxide and the like.

(Chain transfer agent)
In order to adjust the molecular weight of the resin, a commonly used chain transfer agent can be used. The chain transfer agent used is not particularly limited. For example, mercaptans such as n-octyl mercaptan, n-decyl mercaptan, tert-dodecyl mercaptan, and mercaptopropionate esters such as n-octyl-3-mercaptopropionate. , Terpinolene, carbon tetrabromide and α-methylstyrene dimer are used.

(Coloring agent)
As the colorant used in the present invention, the above-described black colorant can be used.

  These colorants may be used alone or in combination of two or more as required. The addition amount of the colorant is set in the range of 1 to 30% by mass, preferably 2 to 20% by mass with respect to the whole toner.

(Release agent)
A known compound can be used as the release agent used in the present invention.

  As such, for example, polyolefin wax such as polyethylene wax and polypropylene wax, long chain hydrocarbon wax such as paraffin wax and sazol wax, dialkyl ketone wax such as distearyl ketone, carnauba wax, montan wax, Trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitic acid, distearyl maleate, etc. And amide waxes such as ethylenediamine behenyl amide and trimellitic acid tristearyl amide.

  The amount of the release agent contained in the toner is preferably 1 to 20% by mass and more preferably 3 to 15% by mass with respect to the whole toner.

(Charge control agent)
A charge control agent can be added to the toner according to the present invention as necessary. A known compound can be used as the charge control agent.

(Developer / Photoreceptor)
The toner of the present invention can be used as a one-component developer or a two-component developer.

  When used as a one-component developer, a non-magnetic one-component developer, or a magnetic one-component developer containing about 0.1 μm to 0.5 μm of magnetic particles in the toner can be used. be able to.

  Further, it can be mixed with a carrier and used as a two-component developer. As the carrier, conventionally known magnetic particles such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead can be used. Ferrite particles are particularly preferable. The particle diameter of the carrier is preferably 20 to 100 μm, more preferably 20 to 70 μm in terms of mass average particle diameter.

  The particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

  The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The coating resin is not particularly limited, and for example, an olefin resin, a styrene resin, a styrene-acrylic resin, a silicon resin, an ester resin, a fluorine-containing polymer resin, or the like is used. The resin for constituting the resin-dispersed carrier is not particularly limited, and known resins can be used. For example, styrene-acrylic resin, polyester resin, fluorine resin, phenol resin, etc. are used. be able to. Among these, a coat carrier coated with a styrene-acrylic resin is more preferable because it can prevent the external additive from being detached and ensure durability.

  The photoreceptor used in the present invention is obtained by forming a coating film containing a photosensitive layer on a substrate. As these photoreceptors, those conventionally used widely can be used.

(Image forming method and image forming apparatus used in the present invention)
Next, an image forming method and an image forming apparatus for forming a toner image using the toner of the present invention will be described.

  FIG. 1 is a schematic view showing an example of an image forming apparatus in which the toner of the present invention can be used.

  In FIG. 1, 1Y, 1M, 1C and 1K are photosensitive members, 4Y, 4M, 4C and 4K are developing means, 5Y, 5M, 5C and 5K are primary transfer rolls as primary transfer means, and 5A is a secondary transfer. Secondary transfer rolls as means, 6Y, 6M, 6C and 6K are cleaning means, 7 is an intermediate transfer member unit, 24 is a heat roll type fixing device, and 70 is an intermediate transfer member.

  This image forming apparatus is called a tandem color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an endless belt-shaped intermediate transfer body unit 7 as a transfer unit, and a recording member P. An endless belt-shaped sheet feeding / conveying means 21 and a heat roll type fixing device 24 as a fixing means. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.

  As one of the different color toner images formed on each photoconductor, an image forming unit 10Y that forms a yellow image includes a drum-shaped photoconductor 1Y as a first photoconductor, and a periphery of the photoconductor 1Y. A charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a primary transfer roll 5Y as a primary transfer unit, and a cleaning unit 6Y. An image forming unit 10M that forms a magenta image as another different color toner image is disposed around a drum-shaped photoconductor 1M as a first photoconductor, and the photoconductor 1M. A charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roll 5M as a primary transfer unit, and a cleaning unit 6M. In addition, an image forming unit 10C that forms a cyan image as another different color toner image is disposed around the photoconductor 1C as a drum-type photoconductor 1C as a first photoconductor. The charging unit 2C, the exposure unit 3C, the developing unit 4C, the primary transfer roll 5C as the primary transfer unit, and the cleaning unit 6C are provided. Further, an image forming unit 10K that forms a black image as one of other different color toner images is disposed around a drum-shaped photosensitive member 1K as a first photosensitive member, and the photosensitive member 1K. It has a charging means 2K, an exposure means 3K, a developing means 4K, a primary transfer roll 5K as a primary transfer means, and a cleaning means 6K.

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

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred onto the rotating endless belt-shaped intermediate transfer body 70 by the primary transfer rolls 5Y, 5M, 5C, and 5K, and is combined. A colored image is formed. A recording member P such as a sheet as a transfer material accommodated in the sheet feeding cassette 20 is fed by the sheet feeding / conveying means 21, passes through a plurality of intermediate rolls 22 A, 22 B, 22 C, 22 D, and a registration roll 23, and is secondary. A color image is transferred onto the recording member P at a time by being conveyed to a secondary transfer roll 5A as a transfer means. The recording member P to which the color image has been transferred is fixed by the heat roll type fixing device 24, is sandwiched by the paper discharge roll 25, and is placed on the paper discharge tray 26 outside the apparatus.

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

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

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

  Further, the housing 8 can be pulled out from the apparatus main body A through the support rails 82L and 82R.

  The housing 8 includes image forming units 10Y, 10M, 10C, and 10K, and an endless belt-shaped intermediate transfer body unit 7.

  The image forming units 10Y, 10M, 10C, and 10K are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer body unit 7 is arranged on the left side of the photoreceptors 1Y, 1M, 1C, and 1K in the figure. The endless belt-shaped intermediate transfer body unit 7 includes an endless belt-shaped intermediate transfer body 70 that can be rotated by winding rolls 71, 72, 73, 74, and 76, primary transfer rolls 5Y, 5M, 5C, and 5K, and a cleaning unit. 6A.

  The image forming units 10Y, 10M, 10C, and 10K and the endless belt-shaped intermediate transfer body unit 7 are integrally pulled out from the main body A by the drawer operation of the housing 8.

  In this way, toner images are formed on the photoreceptors 1Y, 1M, 1C, and 1K by charging, exposure, and development, and the toner images of the respective colors are superimposed on the endless belt-shaped intermediate transfer body 70, and are collectively applied to the recording member P. The image is transferred, and fixed by pressing and heating with a heat roll type fixing device 24 and fixed. The photoreceptors 1Y, 1M, 1C, and 1K after transferring the toner image to the recording member P are cleaned with the cleaning device 6A to remove the toner remaining on the photoreceptor, and then the above-described charging, exposure, and development cycle. The next image formation is performed.

(Transfer material)
The transfer material used in the present invention is a support for holding a toner image, and is usually called an image support, a recording material, or transfer paper. Specifically, various transfer materials such as plain paper and fine paper from thin paper to thick paper, coated printing paper such as art paper and coated paper, commercially available Japanese paper and postcard paper, plastic film for OHP, cloth, etc. However, it is not limited to these.

  The present invention will be specifically described below with reference to examples, but the embodiments of the present invention are not limited to these examples.

Preparation of External Additives As inorganic particles, silica particles not subjected to surface treatment (number average particle diameter 60, 80, 90, 100, 120, 200 nm), titania (number average particle diameter 100 nm), alumina (number average particle diameter) 100 nm), the surface treatment shown in Table 1 was performed, and the external additive was adjusted.

(Preparation of external additive 1)
A cylindrical metal pressure vessel was charged with 160 g of untreated surface silica particles (number average particle size 80 nm), and the vessel was slightly pressurized and replaced with dry nitrogen.

  Next, using a 50 mm airtight syringe equipped with a syringe pump and a Teflon (trademark) resin needle, 12 g of compound number (1-10) which is a short-chain silicon compound is placed in a stirred closed container under a dry nitrogen atmosphere. Was added continuously over 10 minutes. Stirring was continued for an additional 20 minutes after the addition was complete. The vessel was sealed under nitrogen and allowed to stand at room temperature for 16 hours, then heated at 90 ° C. for 16 hours.

  Furthermore, 12 g of the compound number (2-6) which is a long-chain silicon compound was continuously added over 10 minutes in the same manner as the compound number (1-10). Stirring was continued for an additional 20 minutes after the addition was complete.

  The container was sealed under nitrogen, allowed to stand at room temperature for 16 hours, then heated at 90 ° C. for 16 hours, and then cooled to room temperature to obtain external additive particles 1.

(Preparation of external additives 2 to 10, 14, and 15)
External additives 2 to 10, 14, and 15 were prepared in the same manner as in the preparation of the external additive 1, except that the types of inorganic particles and the types of the two silicon compounds were changed to those shown in Table 1.

(Preparation of external additive 11) Example of different processing order External additive 11 was prepared in the same manner except that the processing order of the short-chain silicon compound and the long-chain silicon compound was changed.

(Preparation of external additive 12)
A cylindrical metal pressure vessel was charged with 160 g of untreated surface silica particles (number average particle size 100 nm), and the vessel was slightly pressurized and replaced with dry nitrogen.

  Next, using a 50 mm airtight syringe equipped with a syringe pump and a Teflon (trademark) resin needle, 24 g of compound number (1-10), which is a short-chain silicon compound, is placed in a stirred closed container under a dry nitrogen atmosphere. Was added continuously over 10 minutes. Stirring was continued for an additional 20 minutes after the addition was complete. The vessel was sealed under nitrogen and allowed to stand at room temperature for 16 hours, then heated at 90 ° C. for 16 hours.

(Preparation of external additive 13)
External additive 13 was prepared in the same manner as in the preparation of external additive 12, except that compound number (2-6), which is a long chain compound, was changed to 24 g instead of the short chain compound.

2. Preparation of toner base A toner was prepared by the following method.

[Preparation of resin particles for core]
<< Preparation of core resin particle 1 >>
(1) First-stage polymerization In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introducing device, 90.8 parts by mass of styrene, 72.7 parts by mass of n-butyl acrylate, 12.3 parts by mass of methacrylic acid 93.8 parts by mass of paraffin wax “HNP-57” (manufactured by Nippon Seiki Co., Ltd.) was added as a mold release agent to the mixed solution, and heated to 80 ° C. to dissolve.

  On the other hand, a surfactant solution was prepared by dissolving 2.9 parts by mass of sodium polyoxyethylene (2) dodecyl ether sulfate in 1340 parts by mass of ion-exchanged water.

  After heating this surfactant solution to 80 ° C., the polymerizable monomer solution was mixed and dispersed for 2 hours with a mechanical dispersion “CLEARMIX” (manufactured by M Technique Co., Ltd.) having a circulation path, and dispersed particles (245 nm An emulsified liquid containing emulsified particles having) was prepared.

  Next, after adding 1460 parts by mass of ion-exchanged water, an initiator solution in which 6 parts by mass of a polymerization initiator (potassium persulfate) is dissolved in 142 parts by mass of ion-exchanged water, 1.5 parts by mass of n-octyl mercaptan, Then, the temperature was set to 80 ° C., and the system was heated and stirred at 80 ° C. for 3 hours to perform polymerization (first stage polymerization) to prepare resin particles. This is designated as “resin particle C1”.

(2) Second stage polymerization (formation of outer layer)
An initiator solution in which 5.1 parts by mass of potassium persulfate is dissolved in 197 parts by mass of ion-exchanged water is added to the “resin particles C1” obtained as described above, and styrene 274 is subjected to a temperature condition of 80 ° C. A monomer mixture composed of 0.1 part by mass, 168.6 parts by mass of n-butyl acrylate, 5.2 parts by mass of methacrylic acid, and 6.6 parts by mass of n-octyl mercaptan was added dropwise over 1 hour. After completion of the dropwise addition, the second-stage polymerization (formation of the outer layer) was performed by heating and stirring for 2 hours, and then cooled to 28 ° C. to obtain “core resin particles 1”.

  The core resin particles 1 had a weight average molecular weight of 21,300. The mass average particle diameter of the composite resin particles constituting “core resin particle 1” was 180 nm. Moreover, Tg of this resin particle was 20.1 degreeC.

<< Preparation of Resin Particle 2 for Core >>
In the preparation of the core resin particle 1, the monomer amount in the first stage polymerization is changed to 110.9 parts by mass of styrene, 52.8 parts by mass of n-butyl acrylate, 12.3 parts by mass of methacrylic acid, and the monomer in the second stage polymerization. “Core resin particle 2” was obtained in the same manner except that the amount was changed to 282.2 parts by mass of styrene, 134.4 parts by mass of n-butyl acrylate, and 31.4 parts by mass of methacrylic acid. The weight average molecular weight of the resin particles was 21,500, the mass average particle diameter was 180 nm, and Tg was 39.6 ° C.

<< Preparation of resin particle 3 for core >>
In the preparation of the core resin particle 1, the monomer amount in the first stage polymerization is changed to 115.3 parts by mass of styrene, 48.4 parts by mass of n-butyl acrylate, 12.3 parts by mass of methacrylic acid, and the monomer in the second stage polymerization. “Core resin particles 3” were obtained in the same manner except that the amount was changed to 293.4 parts by mass of styrene, 123.2 parts by mass of n-butyl acrylate, and 31.4 parts by mass of methacrylic acid. The weight average molecular weight of the resin particles was 22,000, the mass average particle diameter was 180 nm, and Tg was 44.0 ° C.

<< Preparation of Resin Particle 4 for Core >>
In the preparation of the core resin particle 1, the monomer amount in the first stage polymerization is changed to 119.7 parts by mass of styrene, 44.0 parts by mass of n-butyl acrylate, 12.3 parts by mass of methacrylic acid, and the monomer in the second stage polymerization. “Core resin particles 4” were obtained in the same manner except that the amount was changed to 304.6 parts by mass of styrene, 112.0 parts by mass of n-butyl acrylate, and 31.4 parts by mass of methacrylic acid. The weight average molecular weight of the resin particles was 22,500, the mass average particle diameter was 180 nm, and Tg was 49.0 ° C.

<< Preparation of core resin particles 5 >>
In the preparation of the resin particles 1 for the core, the monomer amount in the first stage polymerization is changed to 103.5 parts by mass of styrene, 70.4 parts by mass of n-butyl acrylate, and 2.1 parts by mass of methacrylic acid. The “core resin particles 5” were obtained in the same manner except that the amount was changed to 263.4 parts by mass of styrene, 179.2 parts by mass of n-butyl acrylate, and 5.4 parts by mass of methacrylic acid. The weight average molecular weight of the resin particles was 21,000, the mass average particle diameter was 180 nm, and Tg was 18.8 ° C.

(Preparation of resin particles for shell)
A surfactant solution in which 2.0 parts by mass of polyoxyethylene (2) sodium dodecyl ether sulfate was dissolved in 3000 parts by mass of ion-exchanged water was charged into a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction device. The internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.

  An initiator solution in which 10 parts by mass of a polymerization initiator (potassium persulfate: KPS) is dissolved in 200 parts by mass of ion-exchanged water is added to this surfactant solution, and 528 parts by mass of styrene and 176 of n-butyl acrylate are added. Polymerization is carried out by adding dropwise a monomer mixture comprising 3 parts by mass, 120 parts by mass of methacrylic acid and 22 parts by mass of n-octyl mercaptan over 3 hours, and heating and stirring the system at 80 ° C. for 1 hour. To prepare resin particles. This is referred to as “shell resin particles”.

  The weight average molecular weight of the resin particles for shell was 12,000, the mass average particle diameter was 120 nm, and Tg was 53 ° C.

<Preparation of colorant dispersion>
(Preparation of colorant dispersion C1)
While stirring 900 parts by weight of an aqueous solution of 10% by weight of sodium dodecyl sulfate, 210 parts by weight of “CI Pigment Blue 15: 3” was gradually added, and then the stirring device “Clearmix” (M Technique Co., Ltd.) A dispersion of colorant particles was prepared by carrying out a dispersion treatment using This is designated as “colorant dispersion Bk1”. The average dispersion diameter of the colorant particles in the colorant dispersion was measured using a dynamic light scattering particle size analyzer “Microtrack UPA150” (manufactured by Nikkiso Co., Ltd.), and found to be 150 nm.

<Preparation of toner base particles 1>
(Salting out / fusion (association / fusion) process) (core formation)
420.7 parts by mass (solid content conversion) of “core resin particles 1”, 900 parts by mass of ion-exchanged water, and 200 parts by mass of “colorant particle dispersion C1”, a temperature sensor, a cooling pipe, a nitrogen introducing device, The mixture was stirred in a reaction vessel equipped with a stirrer. After adjusting the temperature in the container to 30 ° C., 5 mol / L sodium hydroxide aqueous solution was added to this solution to adjust the pH to 9.

  Next, an aqueous solution obtained by dissolving 2 parts by mass of magnesium chloride hexahydrate in 1000 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After standing for 3 minutes, the temperature was raised and the system was heated to 65 ° C. over 60 minutes. In this state, the particle size of the associated particles was measured with “Coulter Multisizer 3” (manufactured by Coulter Co.), and when the median diameter (D50) on the volume basis of the particles became 5.5 μm, sodium chloride 40.2 An aqueous solution in which 1000 parts by mass of ion-exchanged water is dissolved is added to stop the growth of particle size, and further, the fusion is continued by heating and stirring at a liquid temperature of 70 ° C. for 1 hour as an aging treatment. Part 1 "was formed.

  The circularity of the “core part 1” was measured by “FPIA2100” (manufactured by Systex) and found to be 0.930.

(Formation of shell layer (shelling operation))
Next, at 65 ° C., 50 parts by mass (in terms of solid content) of “resin particles for shell” is added, and an aqueous solution in which 2 parts by mass of magnesium chloride hexahydrate is dissolved in 1000 parts by mass of ion-exchanged water is added over 10 minutes. Then, the temperature is raised to 70 ° C. (shelling temperature), stirring is continued for 1 hour, and the particles of “resin particles for shell” are fused to the surface of “core part 1”, and then 75 ° C. And a aging treatment was performed for 20 minutes to form a shell layer.

  Here, 40.2 parts by mass of sodium chloride was added and cooled to 30 ° C. under the condition of 8 ° C./min to obtain “an aqueous solution containing toner base particles”.

(Washing and drying process)
The aqueous solution containing the toner base particles was subjected to solid-liquid separation with a basket-type centrifuge “MARK III model number 60 × 40” (manufactured by Matsumoto Kikai Co., Ltd.) to form a wet cake of toner base particles. The wet cake was washed with water using the basket-type centrifuge until the electric conductivity of the filtrate reached 5 μS / cm, and then transferred to a “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.). % To dryness to produce “toner base particle Bk1”. The obtained toner base particles Bk1 were particles having a core-shell structure and a volume-based median diameter (D50) of 6.0 μm and Tg of 20.5 ° C.

<Preparation of toner base particles 2>
In the production of the toner base particles 1, the “toner base particles 2” were prepared in the same manner except that the core resin particles used in the core forming step were changed to the “core resin particles 2”. The volume-based median diameter (D50) of the particles was 6.0 μm, and Tg was 40.0 ° C.

<Preparation of toner base particles 3>
In the production of the toner base particles 1, the “toner base particles 3” were prepared in the same manner except that the core resin particles used in the core forming step were changed to the “core resin particles 3”. The volume-based median diameter (D50) of this particle was 6.1 μm, and Tg was 44.5 ° C.

<Preparation of toner base particles 4>
In the production of the toner base particles 1, the “toner base particles 4” were prepared in the same manner except that the core resin particles used in the core forming step were changed to the “core resin particles 4”. The volume-based median diameter (D50) of this particle was 6.1 μm, and Tg was 49.3 ° C.

<Preparation of toner base particles 5>
In the production of the toner base particles 1, the “toner base particles 5” were prepared in the same manner except that the core resin particles used in the core forming step were changed to the “core resin particles 5”. The volume-based median diameter (D50) of this particle was 6.1 μm, and Tg was 19.2 ° C.

<Preparation of Toner 1>
First, 3.0% by mass of the external additive 1 shown in “Table 3” was added to 100 parts by mass of the “toner base particle 2” produced above, and a “Henschel mixer” (manufactured by Mitsui Miike Chemical Co., Ltd.) was added. After mixing for 5 minutes at a peripheral speed of 40 m / sec, 0.6 mass% of hydrophobic silica fine particles (number average primary particle diameter = 10 nm) were added as a small-diameter external additive, and the peripheral speed was 35 m / sec. “Toner 1” was prepared by mixing for 25 minutes.

(Preparation of toners 2 to 19)
Toners 1 to 19 were prepared in the same manner as in Preparation Example of Toner 1 except that the toner base particles and external additive 1 were changed to those shown in Table 3.

<Production of developer>
Each of the above toners was mixed with a ferrite carrier having a volume average median diameter (D50) of 40 μm coated with a silicone resin to prepare “Developers 1 to 19” having a toner concentration of 5 mass%.

<Evaluation>
As an image forming apparatus for evaluation, “bizhub PRO C500 (manufactured by Konica Minolta Business Technologies)” was prepared. The evaluation was performed by loading each developer prepared above on the image forming apparatus in a cyan developing machine and performing printing.

As for the printing environment, 5000 sheets of printing were evaluated at high temperature and high humidity (30 ° C., 80% RH). The transfer paper was A4 size fine paper (64 g / m ² ). As a printed document, a black character image having a printing rate of 5% and a blue character image having a printing rate of 0.1% were used.

(Environmental difference)
Place 20g of cyan developer after printing 5000 sheets into a 20ml glass container, shake it 200 times per minute, swing angle 45 degrees, arm 50cm for 20 minutes in the following two environments (low temperature and low humidity environment, high temperature and high humidity environment). Thereafter, the charge amount was measured by a blow-off method.

Low-temperature and low-humidity environment: 10 ° C, set to 10% RH atmosphere High-temperature and high-humidity environment: Set to 30 ° C, 85% RH atmosphere Depending on the charge amount in the low-temperature and low-humidity environment and the charge amount in the high-temperature and high-humidity environment, The rank was evaluated.

Evaluation criteria A: Less than 5 μC / g (excellent)
○: 5 μC / g to less than 15 μC / g (good)
Δ: 15 μC / g to less than 20 μC / g (practical)
×: 20 μC / g or more (not practical)
(Toner fluidity)
The bulk density was determined by a Kawakita type bulk density measuring machine (IH2000 type) as an index of fluidity.
The specific method for measuring the bulk density is as follows.

Using the toner before image evaluation, put the toner on a 120 mesh sieve and drop it for 90 seconds at a vibration strength of 6, then stop the vibration and let stand for 30 seconds to determine the dry bulk density (toner mass / volume). Ask.
The larger the (bulk density) / (true density), the better the fluidity, leading to improved handling and transferability even in the copying machine. The rank was evaluated as follows.

Evaluation criteria ○: 0.370 or more (good)
Δ: 0.340 to less than 0.370 (practical)
X: Less than 0.340 (unusable) Transfer defect occurs under high temperature and high humidity.

<Fog>
The fog density was measured by using a reflection densitometer “RD-918” manufactured by Macbeth Co., Ltd. for the blank paper that was not printed at first, and the average value was defined as the blank paper density.

  Subsequently, the density of 20 places was measured in the same manner on the 5000th white background portion continuously printed, and the above-mentioned white paper density was determined as the fog density from this average value, and the anti-fogging property was evaluated according to the following criteria. . Note that ◎ to Δ are acceptable levels.

Evaluation criteria A: Fog density is less than 0.003 B: Fog density is less than 0.003 to less than 0.006 B: Fog density is less than 0.006 to less than 0.010 X: Fog density Is 0.010 or more.

<Transfer rate>
At the initial stage and after the completion of printing 5000 sheets, a cyan image (20 mm × 50 mm) having a pixel density of 1.30 was formed, and the transfer rate was determined by the following formula and evaluated.

Transfer rate (%) = (mass of toner transferred onto transfer material / mass of toner developed on photoreceptor) × 100
Note that a transfer rate of 90% or more is acceptable.

(Halftone unevenness)
Density unevenness of the halftone image is the difference between the maximum density and the minimum density when printing a halftone image of cyan near 0.2 density after the printing of 5000 sheets at the initial stage and measuring the absolute image density at 20 locations. (ΔHD) was evaluated as density unevenness. The image density was measured using “RD-918 (Macbeth reflection densitometer)”.

Evaluation Criteria A: Concentration unevenness is 0.05 or less, good ○: Concentration unevenness is greater than 0.05 and less than 0.1, but there is no practical problem ×: Concentration unevenness is 0.1 or more There are practical problems.

  As is clear from Table 4, Examples 1 to 13 in the present invention are in practical use, but Comparative Examples 1 to 6 outside the present invention have problems in at least any of the characteristics. .

FIG. 3 is a schematic diagram illustrating an example of an image forming apparatus in which the toner of the present invention can be used.

Explanation of symbols

1Y, 1M, 1C, 1K Photoconductors 4Y, 4M, 4C, 4K Developing means 5Y, 5M, 5C, 5K Primary transfer roller as primary transfer means 5A Secondary transfer roller as secondary transfer means 6Y, 6M, 6C, 6K Cleaning means 7 Endless belt-shaped intermediate transfer body unit

Claims (5)

In the electrostatic latent image developing toner having an external additive composed of inorganic particles surface-treated with a silicon compound surface treating agent,
At least one of the inorganic particles satisfies (a) and (b),
(A) The silicon compound surface treatment agent is at least one of a short chain having 1 to 5 maximum carbon atoms in the alkyl group bonded to the Si atom and a long chain having 6 or more maximum carbon atoms. A toner for developing an electrostatic latent image, wherein the number average particle diameter of the two types of (b) inorganic particles is 60 to 200 nm, and the glass transition point of the toner is 20 to 45 ° C. The electrostatic latent image developing toner according to claim 1, wherein the inorganic particles are silica particles. After the external additive consisting of inorganic particles treated with at least two kinds of surface treatment agents is treated with a short-chain surface treatment agent having 1 to 5 carbon atoms in the alkyl group bonded to the Si atom, 2. The electrostatic latent image developing toner according to claim 1, wherein the toner is processed with a long-chain surface treatment agent having 6 or more carbon atoms. 2. The electrostatic latent image developing toner according to claim 1, wherein the short-chain alkyl group of the alkyl group has 1 or 2 carbon atoms. A developer comprising the electrostatic latent image developing toner according to claim 1 and a carrier having a mass average particle diameter of 20 to 70 μm.

Images