JP2016153817A - Toner for electrostatic latent image development and two-component developer for electrostatic latent image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner for electrostatic latent image development that maintains cleaning performance for the toner for electrostatic latent image development for a long period, and can suppress damage to the surface of a photoreceptor caused by passing of the toner for electrostatic latent image development and an external additive.SOLUTION: A toner for electrostatic latent image development of the present invention is a toner for electrostatic latent image development that contains at least toner particles comprising toner base particles and an external additive, and contains at least two types of spherical silica particles having a number average particle diameter within a range from 30 to 200 nm as the external additive. The number average particle diameter and the specific gravity of the two types of spherical silica particles are different from each other.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an electrostatic latent image developing toner and an electrostatic latent image developing two-component developer. More specifically, the present invention maintains the cleaning property of the electrostatic latent image developing toner for a long period of time, and suppresses scratches on the surface of the photoreceptor due to slipping of the electrostatic latent image developing toner and the external additive. The present invention relates to a toner for developing an electrostatic latent image.

In recent years, electrophotographic copying machines and printers have been used not only in the conventional office area but also in the production print market due to the increased printing speed.
In the production print market, high-definition and high-quality image quality equivalent to offset printing is required. For this reason, toners and carriers used there tend to have a smaller particle size.
In addition, with the growing awareness of reducing environmental impact, there is an increasing demand for low-temperature fixing from the viewpoint of energy saving.
Under such circumstances, the performance required for toner is becoming increasingly sophisticated.

  The performance required for an electrostatic latent image developing toner (hereinafter also simply referred to as “toner”) used for electrophotographic image formation includes charging performance, fluidity, transferability, and cleaning performance. .

  Conventionally, particles made of various organic compounds and inorganic compounds called external additives are added to the toner for the purpose of imparting and improving these characteristics. As typical external additives, inorganic particles such as silica and titanium oxide are known.

In particular, in order to ensure the cleaning properties of the toner, as shown in FIG. 1, a large-diameter external additive (for example, silica particles C) having a uniform shape and number average particle diameter is added to the toner to thereby add physical properties of the toner. The agglomerates of the large-sized external additive are closely packed in the nip portion 102 (hereinafter also referred to as “blade nip portion”) between the photoconductor 100 and the cleaning blade 101 while reducing the general adhesion force. A technique has been proposed in which the stationary layer 103 in a state is formed and the toner particles 104 are damped (see, for example, Patent Document 1).
However, such a large-diameter external additive has an effect of reducing the physical adhesion force of the toner itself, but is actively detached from the toner and actively attached to the tip of the cleaning blade 101. When an aggregate of the agent (static layer 103, see FIG. 1) is formed, the aggregated external additive having a large diameter collapses from the stationary layer 103 and scratches the surface of the photoreceptor 100 while passing through the cleaning blade 101. There is a problem of attaching.

JP 2007-264142 A

  The present invention has been made in view of the above-described problems and circumstances, and a solution to the problem is to maintain the cleaning property of the electrostatic latent image developing toner over a long period of time, and to improve the electrostatic latent image developing toner and external additives. It is an object to provide a toner for developing an electrostatic latent image that can prevent the photoconductor from being scratched by slipping.

In order to solve the above-mentioned problems, the present inventor, in the process of examining the cause of the above-mentioned problem, as an external additive, at least the number average particle diameter is within a specific range, and the number average particle diameter is true. By adopting two types of spherical silica particles with different specific gravity, it is possible to prevent charging of external additives and toner particles while preventing charging of external additives on the toner surface and ensuring charging stability over a long period of time. Therefore, the present inventors have found that it is possible to provide a toner for developing an electrostatic latent image that can maintain the cleaning property of the toner for developing an electrostatic latent image for a long period of time, and thus can suppress the occurrence of scratches on the photoreceptor.
That is, the said subject which concerns on this invention is solved by the following means.

1. An electrostatic latent image developing toner containing at least toner particles composed of toner base particles and an external additive,
As the external additive, at least the number average particle diameter contains two types of spherical silica particles in the range of 30 to 200 nm,
An electrostatic latent image developing toner, wherein the two types of spherical silica particles have different number average particle diameters and true specific gravity.

  2. 2. The electrostatic latent image according to claim 1, wherein a spherical silica particle having a larger number average particle diameter of the two types of spherical silica particles has a number average particle diameter in a range of 60 to 150 nm. Development toner.

  3. The toner for developing an electrostatic latent image according to item 1 or 2, wherein the toner base particles contain a crystalline polyester resin.

  4). An electrostatic latent image developing two-component developer comprising the electrostatic latent image developing toner according to any one of Items 1 to 3 and a carrier.

By the above-mentioned means of the present invention, it is possible to maintain the cleaning property of the electrostatic latent image developing toner for a long period of time, and to prevent the surface of the photoreceptor from being scratched due to slipping of the electrostatic latent image developing toner and the external additive. An electrostatic latent image developing toner can be provided.
The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

  Conventionally, there is a means for adding a large-diameter external additive from the viewpoint of maintaining developability, transferability, and charging stability over a long period of time. Such a large-diameter external additive exhibits a spacer effect (which can reduce the contact area between the toner and the photoreceptor) and can suppress the burying of the external additive particles, thereby stabilizing the developer charging property. Can do. The external additive having a large diameter in this case is a monodispersed spherical silica particle having a uniform shape and number average particle diameter from the viewpoint of imparting charging uniformity to the toner particle surface and reducing the adhesion force of the toner particle itself. Some are preferred.

However, the large-sized external additive tends to be detached from the surface of the toner particles and easily transferred (attached) to the carrier. In addition, when particles having a high specific gravity such as titania are used as an external additive, they are easily detached from the toner, so that they are easily transferred to a carrier and cause a decrease in charge.
For this reason, as the external additive having a large diameter, spherical silica particles are preferable among the inorganic particles because it is difficult to impart charge to the toner particles themselves and to prevent the external additive from being detached.

  Furthermore, the present inventors consider that the following matters (a) to (c) are important in terms of cleaning properties in order to suppress the slipping of the toner particles themselves and to prevent the surface of the photoreceptor from being scratched. I guessed.

(A) The van der Waals force between the toner and a member in the copying machine, such as an electrostatic latent image carrier or an intermediate transfer member, is reduced by attaching spherical silica particles to the surface of the toner base particles. b) The agglomerate forming the stationary layer forms a loosely aggregated state and collapses and is replaced. (c) A stationary layer is formed by the aggregate of the external additive in the blade nip portion, and the external additive gradually To reduce the torque between the cleaning blade and the member constituting the toner.

When one type of spherical silica particle C is used as the large-sized external additive particle, it is possible to form a stationary layer 103 having a strong aggregation state with the same spherical silica particle C (see FIG. 2).
However, in the state where the wear of the cleaning blade has progressed, such as after long-term printing, particles in a strongly aggregated state may fall out as a lump and damage the surface of the photoreceptor. Moreover, the same thing may occur even when close packing is performed with a single spherical silica particle having a wide particle size distribution as in the technique described in JP-A-2007-264142.

In addition, hard particles such as cerium oxide are used to break up the agglomerated state and promote the rearrangement of silica particles. When these particles pass through, there are factors that cause scratches on the surface of the photoreceptor. It becomes.
In addition, spherical silica particles having a wide particle size distribution are biased in the distribution of the external additive on the surface of the toner particles, which is disadvantageous for long-term charging stability.

Therefore, the present inventors considered a method of adding two types of monodispersed spherical silica particles having different number average particle diameters.
By using spherical silica particles A and B having different number average particle diameters and true specific gravity, as shown in FIG. 3, voids 105 are provided in an aggregate (static layer 103) of particles such as external additives and toner particles. It is inferred that the above (a) can be realized (in FIG. 3, for the sake of simplicity, the stationary layer 103 is described as consisting of only spherical silica particles A and B).
Further, since the two types of spherical silica particles are spherical silica particles A and B having different true specific gravities, the particles having different specific gravities are easily moved and replaced by vibrations at the tip of the cleaning blade. Infer that b) can be realized. Furthermore, it is possible to prevent the aggregates of spherical silica particles from slipping through, and as a result, it is possible to suppress deep scratches that can become image defects on the surface of the photoreceptor.
Moreover, since the two types of spherical silica particles of the present invention gradually slip through the blade nip portion, the torque at the blade nip portion can be reduced and the above (c) can be realized. Further, since the photoconductor can be uniformly cut, it is assumed that as a result, the roughness of the photoconductor can also be suppressed.
Further, by using monodispersed silica particles having a uniform particle size as the spherical silica particles, it is possible to prevent the surface state of the toner particles from being biased.

Schematic diagram explaining an example of cleaning Schematic diagram explaining an example of conventional cleaning Schematic diagram of cleaning when the electrostatic latent image developing toner according to the present invention is used. Schematic diagram showing an example of the configuration of toner particles according to the present invention

  The electrostatic latent image developing toner of the present invention is an electrostatic latent image developing toner containing at least toner particles composed of toner base particles and an external additive, and the external additive includes at least number average particles. Two types of spherical silica particles having a diameter in the range of 30 to 200 nm are contained, and the number average particle size and true specific gravity of the two types of spherical silica particles are different. This feature is a technical feature common to the inventions according to claims 1 to 4.

  In an embodiment of the present invention, the surface of the photoreceptor is such that the number average particle size of the spherical silica particles having the larger number average particle size of the two types of spherical silica particles is in the range of 60 to 150 nm. It is preferable because scratches can be further suppressed.

  In the present invention, it is preferable that the toner base particles contain a crystalline polyester resin, because the flexibility of the toner base particles is improved and the spherical silica particles are easily retained, and from the viewpoint of low-temperature fixability. Is also preferable.

  The toner for developing an electrostatic latent image of the present invention can be suitably used as a two-component developer for developing an electrostatic latent image containing a carrier. As a result, the electrostatic latent image developing toner can be maintained over a long period of time, and can be prevented from being scratched on the surface of the photoreceptor due to slipping of the electrostatic latent image developing toner and the external additive. A two-component developer for development can be provided.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

<Overview of electrostatic latent image developing toner>
The electrostatic latent image developing toner of the present invention (hereinafter also simply referred to as “toner”) is an electrostatic latent image developing toner containing at least toner particles composed of toner base particles and an external additive. The external additive contains at least two types of spherical silica particles having a number average particle size in the range of 30 to 200 nm, and the number average particle size and true specific gravity of the two types of spherical silica particles are different. It is characterized by that.

[Toner particles]
The toner particles according to the present invention include at least toner base particles and an external additive.
FIG. 4 shows an example of the configuration of the toner particles according to the present invention. In the example shown in FIG. 4, spherical silica particles A having a large number average particle size and spherical silica particles B having a number average particle size smaller than the spherical silica particles A adhere to the toner base particles 10, and toner particles 1 is configured.

[External additive]
The external additive according to the present invention contains at least two types of spherical silica particles having a number average particle diameter in the range of 30 to 200 nm.

<Two types of spherical silica particles>
The two types of spherical silica particles according to the present invention have different number average particle diameter and true specific gravity.

Of the two types of spherical silica particles, the larger number average particle size of the spherical silica particles is preferably in the range of 60 to 150 nm.
From the viewpoint of reducing the adhesion of toner particles, it is preferable to contain spherical silica particles of 60 nm or more for the transferability and cleaning properties of the toner. On the other hand, it is preferably 150 nm or less from the viewpoint of suppressing the migration of spherical silica particles to the carrier and charging stability of the developer.
The difference in number average particle size between the two types of spherical silica particles is preferably 30 nm or more. With such a difference in number average particle diameter, a gap is formed between two types of true specific gravity and spherical silica particles having different number average particle diameters in the nip portion between the image carrier such as the photosensitive drum and the cleaning blade. A gently agglomerated stationary layer can be formed.
Moreover, when the number average particle diameter of the spherical silica particles is less than 30 nm, it is difficult to produce the spherical silica particles by a sol-gel method.

(Measurement of number average particle diameter)
The number average particle diameter (median diameter on a number basis) is measured by the following method.
Using a scanning electron microscope (SEM) “JEM-7401F” (manufactured by JEOL Ltd.), an SEM photograph of the toner magnified 30,000 times was taken, and the SEM photograph was observed to observe primary particles of spherical silica particles. The particle size (Ferret diameter) is measured. The two types of spherical silica particles can be easily distinguished from the shape and size, and by measuring the particle size, it can be confirmed that there are two peaks in the particle size. That is, it can be determined that the particles are present. The particle size is measured by selecting a region where the total number of particles is about 100 to 200 in the SEM image.

  The two types of spherical silica particles according to the present invention are each monodispersed and are preferably spherical silica particles produced by a sol-gel method. The spherical silica particles produced by the sol-gel method are preferable because they have a uniform particle size (narrow particle size distribution, that is, monodisperse) as compared with fumed silica which is a general production method.

In the spherical silica particles according to the present invention, the term “spherical” means that the degree of spheroidization is 0.6 or more.
In the present invention, the sphericity is Wadell's true sphericity.
That is, the degree of spheroidization is represented by the following formula (1).

Formula (1) Degree of spheroidization = (surface area of sphere having the same volume as actual particle) / (surface area of actual particle)
Here, the “surface area of a sphere having the same volume as an actual particle” can be obtained by arithmetic calculation from the number average particle diameter obtained by the above method.
The “surface area of the actual particles” can be substituted with the BET specific surface area determined using “Powder Specific Surface Area Measuring Device SS-100” (manufactured by Shimadzu Corporation).

In the present invention, as described above, the sphericity of the spherical silica particles is 0.6 or more, preferably 0.8 or more. If the sphericity is less than 0.6, the effect of improving development and transfer is significantly reduced.
In addition, since the spherical silica particles of the present invention are monodispersed and spherical, they are uniformly dispersed on the surface of the toner base particles, and can stably exhibit a spacer effect (which can reduce the contact area between the toner and the photoreceptor).

(Monodisperse)
The degree of dispersion in the particle size distribution of particles such as spherical silica particles can be discussed by the standard deviation with respect to the number average particle size including aggregates. Here the standard deviation of number-average primary particle diameter D ₅₀ is a "monodispersed" what is "D ₅₀ × 0.22 or less". The standard deviation is obtained as described above (measurement of number average particle diameter of spherical silica particles).

(True specific gravity)
The two kinds of spherical silica particles according to the present invention have different true specific gravity as described above, and the difference is preferably 0.1 or more.
If the true specific gravity of the two types of spherical silica particles is 1.9 or less, the silica particle skeleton can be prevented from being dense and hard, and it can be prevented from becoming excessively strong against physical deformation. As a result, it is possible to suppress the silica particles from being appropriately deformed and easily agglomerate, and thus it is preferable because a loose agglomerate can be easily formed.
The true specific gravity is preferably small, but is preferably 1.4 or more. When the true specific gravity is 1.4 or more, the void ratio in the spherical silica particles does not become too high, it is strong against physical impact, and deformation or crushing due to stress in the developing machine or machine can be prevented. In addition, the rolling property can be suitably achieved, and as a result, the entrance to the contact portion (blade nip portion) between the image carrier and the cleaning blade is not suppressed, and a stationary layer can be suitably formed. It can be expressed.

(Measurement of true specific gravity of spherical silica particles)
The true specific gravity of the spherical silica particles was measured using a Le Chatelier specific gravity bottle in accordance with JIS standards (JIS-K-0061 5-2-1) as follows.
(1) About 250 ml of ethyl alcohol is put into a Lechatelier specific gravity bottle and adjusted so that the meniscus is at the position of the scale. Next, the Lechatelier specific gravity bottle is immersed in a constant temperature water tank, and when the liquid temperature reaches 20.0 ± 0.2 ° C., the position of the meniscus is accurately read with the scale of the Lechatelier specific gravity bottle (accuracy is 0.025 ml). ).
(2) About 100 g of spherical silica particles (with a mass of W) are put into a Le Chatelier specific gravity bottle to remove bubbles.
The Lechatelier specific gravity bottle is immersed in a constant temperature water tank, and when the liquid temperature reaches 20.0 ± 0.2 ° C., the position of the meniscus is accurately read on the scale of the specific gravity bottle (accuracy is 0.025 ml).
(3) The true specific gravity can be calculated by the following equation.
D = W / (L2-L1)
S = D / 0.9982
In the above formula, D represents the density (g / cm ³ ) of spherical silica particles at 20 ° C. S represents the true specific gravity of the spherical silica particles at 20 ° C. W represents the apparent mass (g) of spherical silica particles. L1 represents the meniscus reading (ml) before the spherical silica particles (20 ° C.) are placed in the density bottle. L2 represents the meniscus reading (ml) after the spherical silica particles (20 ° C.) are placed in the specific gravity bottle. 0.9982 is the density of water at 20 ° C. (g / cm ³ ).

(Addition amount of spherical silica particles)
The addition amount of the two types of spherical silica particles according to the present invention is preferably 0.3 to 1.5 parts by mass with respect to the toner base particles. When the added amount is 0.3 parts by mass or more, that is, when the total is 0.6 parts or more, the adhesion of the toner particles does not become too strong, and formation of an aggregate (stationary layer) at the blade nip part. This is preferable because it can be appropriately controlled and can exhibit suitable cleaning properties.
Further, if the number of each added part is 1.5 parts by mass or less, that is, the total is 3.0 parts by mass or less, it is possible to suppress the detachment of the spherical silica particles from the toner particles, and the spherical silica particles in the blade nip part. In addition to being able to prevent slipping, the torque can be made suitable, and the surface of the photoreceptor can be prevented from being damaged. In order to maintain the interchangeability of the two types of spherical silica particles at the cleaning blade portion, the ratio of the added mass portion is preferably 1: 1 to 2: 8.

(Method of adding spherical silica particles)
As a method of adding the spherical silica particles to the toner base particles according to the present invention, an ordinary method of adding and mixing external additives to the toner base particles can be used. For example, as a method for adding spherical silica particles, there is a dry method in which spherical silica particles are added as powder to dried toner base particles, and as a mixing device, a mechanical mixing device such as a Henschel mixer or a coffee mill is used. Is mentioned. Further, as will be described later, other general external additives can be added in the same manner for the purpose of improving charging performance and fluidity.

<Method for producing spherical silica particles by sol-gel method>
Here, the case where the sol-gel method is adopted will be described as an example of the method for producing spherical silica particles according to the present invention.
For the spherical silica particles according to the present invention, a known silica particle production method can be used. In this case, the silica of the present invention is mainly produced through three steps of hydrolysis, polycondensation, and hydrophobization treatment. Further, other steps such as drying may be combined.

  Next, the outline of the production process of the spherical silica particles according to the present invention by the sol-gel method will be described below. First, alkoxysilane is dropped and stirred while adding a catalyst and applying temperature in the presence of water and alcohol. Next, the silica sol suspension obtained by the reaction is centrifuged to separate into wet silica gel, alcohol and aqueous ammonia. A solvent is added to wet silica gel to form a silica sol again, and a hydrophobizing agent is added to hydrophobize the silica surface. Alternatively, after the sol is dried to obtain a dry sol, a hydrophobizing agent is added, and the silica surface is hydrophobized.

  As the hydrophobizing agent, a general coupling agent, silicone oil, fatty acid, fatty acid metal salt, or the like can be used. Next, the spherical silica particles of the present invention can be obtained by removing the solvent from the hydrophobized silica sol and drying it. Further, the spherical silica particles thus obtained may be subjected to a hydrophobic treatment again.

  For example, a dry method such as a spray drying method in which a treatment agent or a solution containing a treatment agent is sprayed on particles suspended in a gas phase, or a wet method in which particles are immersed in a solution containing a treatment agent and dried. Alternatively, a treatment process using a mixing method in which a treatment agent and particles are mixed by a mixer may be added.

As the silane compound used as the hydrophobizing agent, a water-soluble compound can be used. As such a silane compound, those represented by the following structural formula (1) can be used.
Structural formula (1)
R _a SiX _4-a
Here, in the structural formula (1), a is an integer of 0 to 3, R represents an organic group such as a hydrogen atom, an alkyl group, and an alkenyl group, and X represents a hydrous such as a chlorine atom, a methoxy group, and an ethoxy group. Represents a degradable group.

  Examples of the compound represented by the structural formula (1) include chlorosilane, alkoxysilane, silazane, and a special silylating agent. Specifically, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, Methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, N, O- (bistrimethylsilyl) acetamide, N, N-bis (Trimethylsilyl) urea, tert-butyldimethylchlorosilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxy Silane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercapto Representative examples include propyltrimethoxysilane and γ-chloropropyltrimethoxysilane.

Particularly preferably, the hydrophobizing agent used in the present invention includes dimethyldimethoxysilane, hexamethyldisilazane (HMDS), methyltrimethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane and the like.
Specific examples of silicone oils include, for example, cyclic compounds such as organosiloxane oligomers, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, tetramethylcyclotetrasiloxane, tetravinyltetramethylcyclotetrasiloxane, linear or Mention may be made of branched organosiloxanes. Alternatively, a highly reactive silicone oil in which a modifying group is introduced into a side chain, one end or both ends, a side chain piece end, or both side chain ends may be used. Examples of the modifying group include, but are not particularly limited to, alkoxy, carboxyl, carbinol, higher fatty acid modification, phenol, epoxy, methacryl, amino and the like. Further, for example, it may be a silicone oil having several kinds of modifying groups such as amino / alkoxy modification. Further, dimethyl silicone oil, these modified silicone oils, and other surface treatment agents may be mixed or combined. Examples of the treating agent used in combination include silane coupling agents, titanate coupling agents, aluminate coupling agents, various silicone oils, fatty acids, fatty acid metal salts, esterified products thereof, rosin acid, and the like. .

(Production of spherical silica particles with different number average particle diameter and true specific gravity)
The monodispersed spherical silica particles having a number average particle size of 30 to 200 nm in the present invention can be preferably produced by the sol-gel method which is the wet method described above.
Since the true specific gravity is produced by a wet method and without firing, the true specific gravity can be controlled to be lower than that of the vapor phase oxidation method. Further, the true specific gravity can be further adjusted by controlling the type of hydrophobic treatment agent or the amount of treatment in the hydrophobization treatment step. The number average particle size can be adjusted by controlling the mass ratio, the reaction rate, the stirring rate, and the supply rate of the alkoxysilane, ammonia, alcohol, and water in the hydrolysis and polycondensation steps of the sol-gel method. In addition, according to the sol-gel method, the monodispersion and the sphericity can be adjusted and manufactured.

[Toner base particles]
It is preferable that the toner base particles contain a crystalline polyester resin because the flexibility of the toner base particles is improved and the spherical silica particles are preferably fixed easily, and also from the viewpoint of low-temperature fixability. .
The toner base particles according to the present invention preferably contain at least a binder resin, a colorant, and a release agent.
Examples of the method for producing toner base particles include a pulverization method, an emulsion polymerization aggregation method, a suspension polymerization method, a dissolution suspension method, and an emulsion aggregation method. Examples of a method for producing toner base particles preferable in the present invention include an emulsion aggregation method and an emulsion polymerization aggregation method.

  In particular, the toner base particles according to the present invention are prepared by mixing a dispersion liquid in which fine colorant particles are dispersed in an aqueous medium and a dispersion liquid in which binder resin fine particles are dispersed in an aqueous medium. It is preferably obtained by a process of agglomerating and fusing the fine particles and the binder resin fine particles, that is, obtained by a production method such as an emulsion aggregation method. The reason why such a production method is preferable is that the colorant fine particles are excellent in dispersibility in the colorant dispersion liquid contained in the toner base particles, and the colorant fine particles and the binder resin fine particles are aggregated and fused. Even in this case, the toner base particles can be formed while the fine colorant particles retain excellent dispersibility.

  The toner base particles according to the present invention preferably have a core / shell structure.

  Further, the particle size of the toner base particles according to the present invention is preferably small for the purpose of improving the image quality, but the number average particle size of the toner base particles is in the range of 2 to 8 μm. The fluidity and adhesion can be suitably achieved, and therefore, development, transfer and cleaning are not difficult, which is preferable. The particle size of the toner base particles is more preferably in the range of 4 to 7 μm from the above viewpoint.

  The circularity of the toner base particles is preferably closer to a spherical shape from the viewpoint of rising of charge and fluidity, but the cleaning property becomes difficult. From this point, 0.970 or less is preferable.

(Circularity of toner base particles)
The circularity of the toner base particles is a value measured using a flow type particle image analyzer “FPIA-2100” (manufactured by Sysmex).

  Specifically, the toner base particles are moistened in a surfactant aqueous solution, and ultrasonic dispersion is performed for 1 minute. After dispersion, the HPF is used in the measurement condition HPF (high magnification imaging) mode using “FPIA-2100”. Measurement is performed at an appropriate concentration of 3000 to 10,000 detections. Within this range, reproducible measurement values can be obtained. The circularity is calculated by the following formula.

Circularity = (perimeter of a circle having the same projection area as the particle image) / (perimeter of the particle projection image)
The average circularity is an arithmetic average value obtained by adding the circularity of each particle and dividing by the total number of particles measured.

<Crystalline polyester resin>
The crystalline polyester resin according to the present invention is a portion derived from a known polyester resin obtained by a polycondensation reaction between a divalent or higher carboxylic acid (polyvalent carboxylic acid) and a divalent or higher alcohol (polyhydric alcohol). In the differential scanning calorimetry (DSC) of the toner, the resin unit has a clear endothermic peak instead of a stepwise endothermic change.
The clear endothermic peak specifically means a peak in which the half-value width of the endothermic peak is within 15 ° C. when measured at a rate of temperature increase of 10 ° C./min in differential scanning calorimetry (DSC). To do.

  The crystalline polyester resin is not particularly limited as long as it is a resin as defined above. For example, the crystalline polyester resin itself may be contained. Alternatively, as a hybrid resin having a crystalline polyester resin unit, a resin having a structure in which other components are copolymerized on the main chain of the crystalline polyester resin unit, or a crystalline polyester resin unit is copolymerized on the main chain composed of other components A resin having such a structure that the toner containing the resin exhibits a clear endothermic peak as described above may be contained.

  Furthermore, in the case of a hybrid resin having a crystalline polyester resin unit, the content of the crystalline polyester resin unit is preferably 50% by mass or more and less than 98% by mass with respect to the total amount of the hybrid resin. By setting it as the above range, sufficient crystallinity can be imparted to the hybrid resin. In addition, the structural component and content rate of each unit in a hybrid resin can be specified by NMR measurement and methylation reaction P-GC / MS measurement, for example.

  Here, the hybrid resin includes an amorphous resin unit other than the polyester resin in addition to the crystalline polyester resin unit. The hybrid resin may be in any form such as a block copolymer or a graft copolymer as long as it includes the crystalline polyester resin unit and an amorphous resin unit other than the polyester resin. A coalescence is preferable. By using a graft copolymer, the orientation of the crystalline polyester resin unit can be easily controlled, and sufficient crystallinity can be imparted to the hybrid resin.

  The amorphous resin unit is preferably composed of the same kind of resin as the amorphous resin (that is, a resin other than the hybrid resin) contained in the binder resin. By adopting such a form, the affinity between the hybrid resin and the amorphous resin is further improved, the hybrid resin is more easily taken into the amorphous resin, and the charging uniformity and the like are further improved.

  Here, “the same kind of resin” means that a characteristic chemical bond is commonly contained in the repeating unit. Here, “characteristic chemical bond” is described in the National Institute for Materials Science (NIMS) Substance / Material Database (http://polymer.nims.go.jp/PoLyInfo/guide/jp/term_polymer.html). According to “Polymer classification”.

<Binder resin>
As the binder resin contained in the toner base particles according to the present invention, for example, when the toner base particles are produced by a pulverization method, a dissolution suspension method, an emulsion aggregation method, or the like, a styrenic resin or (meth) acrylic resin is used. Resin, styrene- (meth) acrylic copolymer resin, vinyl resin such as olefin resin, polyester resin, polyamide resin, carbonate resin, polyether, polyvinyl acetate resin, polysulfone, epoxy resin, polyurethane Various known resins such as resins and urea resins can be used. These can be used alone or in combination of two or more.

  For example, when the toner base particles are produced by suspension polymerization method, emulsion polymerization aggregation method, miniemulsion polymerization aggregation method, etc., as a polymerizable monomer for obtaining a binder resin, for example, styrene, o- Methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert -Styrene or styrene derivatives such as butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene; methyl methacrylate, methacryl Ethyl acetate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, Methacrylic acid ester derivatives such as t-butyl tacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate; methyl acrylate , Ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, etc. Acrylic ester derivatives; Olefins such as ethylene, propylene and isobutylene; Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride and vinylidene fluoride Vinyl esters such as vinyl propionate, vinyl acetate and vinyl benzoate; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl hexyl ketone; N-vinyl carbazole N-vinyl compounds such as N-vinyl indole and N-vinyl pyrrolidone; Vinyl compounds such as vinyl naphthalene and vinyl pyridine; Acrylic acid such as acrylonitrile, methacrylonitrile, acrylamide, etc. A polymer can be mentioned. These vinyl monomers can be used alone or in combination of two or more.

  Further, as the polymerizable monomer for obtaining the binder resin, it is preferable to use a combination of the polymerizable monomer having an ionic dissociation group. The polymerizable monomer having an ionic dissociation group has, for example, a substituent such as a carboxy group, a sulfonic acid group, and a phosphoric acid group as a constituent group, and specifically includes acrylic acid, methacrylic acid, maleic acid. Acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrenesulfonic acid, allylsulfosuccinic acid, 2-acrylamido-2-methylpropanesulfonic acid, acid phosphooxyethyl methacrylate And 3-chloro-2-acid phosphooxypropyl methacrylate.

  Furthermore, as a polymerizable monomer, divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl A binder resin having a crosslinked structure can also be obtained using a polyfunctional vinyl such as glycol diacrylate.

  The binder resin that can be suitably used for the toner base particles of the present invention preferably contains a binder resin having a hydrophilic polar group as a constituent component, and the hydrophilic polar group is preferably a carboxy group.

  Specific examples of the polymerizable monomer having a carboxy group used in the binder resin include acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, and maleic acid monoalkyl ester. And itaconic acid monoalkyl ester.

<Colorant>
A colorant can be added to the toner of the present invention. A known colorant can be used as the colorant.

  Specifically, examples of the colorant contained in the yellow toner include C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Pigment yellow 14, 17, 74, 93, 94, 138, 155, 180, 185, and the like. These can be used alone or in combination of two or more. Among these, C.I. I. Pigment Yellow 74 is preferable.

  The content of the colorant contained in the yellow toner is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass with respect to 100 parts by mass of the binder resin.

  Specifically, examples of the colorant contained in the magenta toner include C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Pigment Red 5, 48: 1, 53: 1, 57: 1, 122, 139, 144, 149, 166, 177, 178, 222, and the like. These can be used alone or in combination of two or more. Among these, C.I. I. Pigment Red 122 is preferable.

  The content of the colorant contained in the magenta toner is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass with respect to 100 parts by mass of the binder resin.

  Specifically, examples of the colorant contained in the cyan toner include C.I. I. Pigment blue 15: 3.

  The content of the colorant contained in the cyan toner is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass with respect to 100 parts by mass of the binder resin.

  Examples of the colorant contained in the black toner include carbon black, magnetic material, and titanium black. Examples of carbon black include channel black, furnace black, acetylene black, thermal black, and lamp black. Examples of magnetic materials include ferromagnetic metals such as iron, nickel, and cobalt, alloys containing these ferromagnetic metals, compounds of ferromagnetic metals such as ferrite and magnetite, and ferromagnetic materials that do not contain ferromagnetic metals but are heat treated. The alloy shown etc. are mentioned. Examples of alloys that exhibit ferromagnetism by heat treatment include Heusler alloys such as manganese-copper-aluminum and manganese-copper-tin, and chromium dioxide.

  The content of the colorant contained in the black toner is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass with respect to 100 parts by mass of the binder resin.

  The toner of the present invention can contain an internal additive such as a charge control agent and a release agent and other external additives as necessary.

<Charge control agent>
The charge control agent is not particularly limited as long as it can give positive or negative charge by frictional charging, and various known positive charge control agents and negative charge control agents can be used.

  The content of the charge control agent is preferably 0.01 to 30 parts by mass, more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the binder resin.

<Release agent>
Various known waxes can be used as the release agent.

  Examples of the wax include polyolefin waxes such as polyethylene wax and polypropylene wax, branched hydrocarbon waxes such as microcrystalline wax, long chain hydrocarbon waxes such as paraffin wax and sazol wax, and dialkyls such as distearyl ketone. Ketone wax, carnauba wax, montan wax, behenate behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanedioldi Ester waxes such as stearate, tristearyl trimellitic acid, distearyl maleate, ethylenediamine behenylamide, tristearyl trimellitic acid Such as amide-based waxes such as bromide and the like.

  It is preferable that content of a mold release agent is 0.1-30 mass parts with respect to 100 mass parts of binder resin, More preferably, it is 1-10 mass parts.

[Other external additives]
In addition to the spherical silica particles according to the present invention, other external additives may be added to the toner of the present invention in order to improve fluidity and chargeability as long as the effect is not inhibited. As other external additives, for example, inorganic fine particles such as silica fine particles having a particle size of less than 30 nm, alumina fine particles, titanium oxide fine particles, inorganic stearate compound fine particles such as aluminum stearate fine particles, zinc stearate fine particles, Alternatively, inorganic fine particles such as inorganic titanate compound fine particles such as strontium titanate and zinc titanate can be used.

<Surface treatment of external additive>
From the viewpoint of heat-resistant storage stability and environmental stability, the external additive that can be used in the present invention is preferably one whose surface has been subjected to a hydrophobic treatment with a known surface treatment agent such as a coupling agent. The surface treating agent that can be used is particularly preferably dimethyldimethoxysilane, hexamethyldisilazane (HMDS), methyltrimethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane, or the like.

  Specific examples of silicone oils include, for example, cyclic compounds such as organosiloxane oligomers, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, tetramethylcyclotetrasiloxane, tetravinyltetramethylcyclotetrasiloxane, linear or Mention may be made of branched organosiloxanes. Alternatively, a highly reactive silicone oil in which a modifying group is introduced at a side chain or one end or both ends, a side chain piece end, or both side chain ends may be used. Examples of the modifying group include, but are not particularly limited to, alkoxy, carboxyl, carbinol, higher fatty acid modification, phenol, epoxy, methacryl, amino and the like. Further, for example, it may be a silicone oil having several kinds of modifying groups such as amino / alkoxy modification.

  Further, dimethyl silicone oil, these modified silicone oils, and other surface treatment agents may be mixed or combined. Examples of the treating agent used in combination include silane coupling agents, titanate coupling agents, aluminate coupling agents, various silicone oils, fatty acids, fatty acid metal salts, esterified products thereof, rosin acid, and the like. .

≪Toner production method≫
The method for producing the toner according to the present invention is not particularly limited, and a known method can be adopted, but an emulsion polymerization aggregation method or an emulsion aggregation method can be preferably employed.

  The emulsion polymerization aggregation method preferably used in the method for producing a toner according to the present invention is a dispersion of fine particles of a binder resin produced by an emulsion polymerization method (hereinafter also referred to as “binder resin fine particles”) as a colorant. The fine particles (hereinafter also referred to as “colorant fine particles”) are mixed with a dispersion liquid of a release agent such as a dispersion liquid and wax, and the toner particles are aggregated until a desired particle diameter is obtained. In this method, toner particles are manufactured by controlling the shape by fusing.

Further, the emulsion aggregation method preferably used as a method for producing the toner according to the present invention is a method in which a binder resin solution dissolved in a solvent is dropped into a poor solvent to obtain a resin particle dispersion, and the resin particle dispersion and the colorant dispersion And a release agent dispersion such as wax, and agglomerate until a desired toner particle diameter is obtained. Further, the shape is controlled by fusing the binder resin fine particles to produce toner particles. Is the method.
Either method can be applied to the toner of the present invention.

An example of using the emulsion polymerization aggregation method as a method for producing the toner of the present invention is shown below.
(1) Step of preparing a dispersion liquid in which fine particles of colorant are dispersed in an aqueous medium (2) Dispersion in which binder resin fine particles containing an internal additive are dispersed in an aqueous medium as required Step of preparing liquid (3) Step of preparing dispersion of binder resin fine particles by emulsion polymerization (4) Mixing dispersion of fine particles of colorant and dispersion of binder resin fine particles, Step of forming toner base particles by agglomerating, associating and fusing the fine particles of the resin and the binder resin fine particles (5) The toner base particles are filtered off from the dispersion system (aqueous medium) of the toner base particles to obtain a surfactant, etc. (6) Step of drying toner base particles (7) Step of adding external additive to toner base particles

  In the case of producing a toner by the emulsion polymerization aggregation method, the binder resin fine particles obtained by the emulsion polymerization method may have a multilayer structure of two or more layers made of binder resins having different compositions. For example, a binder resin fine particle having a two-layer structure is prepared by preparing a dispersion of resin particles by emulsion polymerization treatment (first-stage polymerization) according to a conventional method, and adding a polymerization initiator to the dispersion. It can be obtained by adding a polymerizable monomer and polymerizing this system (second stage polymerization).

  In addition, toner particles having a core / shell structure can be obtained by an emulsion polymerization aggregation method. Specifically, the toner particles having a core / shell structure are firstly binder resin fine particles for core particles and fine particles of colorant. The core particles are prepared by agglomerating, associating and fusing, and then the binder resin fine particles for the shell layer are added to the core particle dispersion to agglomerate the binder resin fine particles for the shell layer on the core particle surface. , And can be obtained by forming a shell layer that covers the surface of the core particles by fusing.

An example of using a pulverization method as a method for producing the toner of the present invention is shown below.
(1) A step of mixing a binder resin, a colorant and, if necessary, an internal additive by a Henschel mixer or the like (2) a step of kneading the obtained mixture while heating with an extrusion kneader or the like (3) obtained Step of coarsely pulverizing the kneaded product with a hammer mill or the like, and further pulverizing with a turbo mill pulverizer or the like (4) The obtained pulverized product is finely classified using, for example, an airflow classifier utilizing the Coanda effect. Step of forming toner base particles (5) Step of adding external additive to toner base particles

[Particle size of toner particles]
The particle diameter of the toner particles constituting the toner of the present invention is preferably 4 to 10 μm, and more preferably 5 to 9 μm, for example, in terms of volume-based median diameter.

  When the volume-based median diameter is in the above range, the transfer efficiency is increased, the image quality of halftone is improved, and the image quality of fine lines and dots is improved.

  The volume-based median diameter of the toner particles is measured and calculated using a measuring apparatus in which a data processing computer system (Beckman Coulter, Inc.) is connected to “Multisizer 3” (Beckman Coulter, Inc.).

  Specifically, 0.02 g of toner is added to 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 toner particles). Then, ultrasonic dispersion treatment was performed for 1 minute to prepare a toner particle dispersion, and this toner particle dispersion was placed in “ISOTON II” (Beckman Coulter, Inc.) in the sample stand. Pipette into beaker until display concentration of measuring device is 5% to 10%. Here, a reproducible measurement value can be obtained by setting the concentration range. In the measuring apparatus, the measurement particle count is set to 25000, the aperture diameter is set to 50 μm, and the frequency value is calculated by dividing the range of 1 μm to 30 μm, which is the measurement range, into 256. % Is the volume-based median diameter.

≪Overview of two-component developer for electrostatic latent image development≫
The toner for developing an electrostatic latent image of the present invention can be used as a non-magnetic one-component developer, but can be suitably used for a two-component developer for developing an electrostatic latent image containing a carrier.

[Career]
The carrier is composed of a magnetic material, but resin-coated carrier particles in which the surface of a carrier core made of the magnetic material is coated with a resin, or a resin-dispersed type in which magnetic fine powder is dispersed in a resin. It can also be composed of carrier particles. From the viewpoint of controlling the true specific gravity to 4.25 to 5 g / cm ³ and the porosity to 8% or less, it is preferably constituted by resin-coated carrier particles.
The carrier particles may contain an internal additive such as a resistance adjuster as necessary.

<Carrier core>
The carrier core that constitutes the carrier particles is made of, for example, various kinds of ferrite in addition to metal powder such as iron powder. Among these, ferrite is preferable.
As the ferrite, ferrite containing heavy metals such as copper, zinc, nickel and manganese and light metal ferrite containing alkali metals or alkaline earth metals are preferable.
Ferrite is a compound represented by the formula: (MO) _x (Fe ₂ O ₃ ) _y , and the molar ratio y of Fe ₂ O ₃ constituting the ferrite is preferably 30 to 95 mol%. Ferrite having a composition ratio y in the above range has a merit that a desired magnetization can be easily obtained, so that a carrier that hardly causes carrier adhesion can be produced. M in the formula is manganese (Mn), magnesium (Mg), strontium (Sr), calcium (Ca), titanium (Ti), copper (Cu), zinc (Zn), nickel (Ni), aluminum (Al) , Silicon (Si), zirconium (Zr), bismuth (Bi), cobalt (Co), lithium (Li) and the like, and these can be used alone or in combination.

<Carrier coating resin>
By using a highly hydrophobic alicyclic methacrylic acid ester compound as a monomer for obtaining a coating resin, the moisture adsorption amount of the carrier particles is reduced, and the environmental difference in chargeability is reduced. A decrease in charge amount in a wet environment is suppressed. In addition, a resin obtained by polymerizing a monomer containing an alicyclic methacrylic acid ester compound has an appropriate mechanical strength, and the surface of the carrier particles is refreshed by appropriate film abrasion as a coating material. The
As the alicyclic methacrylic acid ester compound, those having a cycloalkyl group having 5 to 8 carbon atoms are preferable. Specific examples include cyclopentyl methacrylate, cyclohexyl methacrylate, cycloheptyl methacrylate, cyclooctyl methacrylate and the like. It is done. Among these, cyclohexyl methacrylate is particularly preferable from the viewpoint of mechanical strength and environmental stability of the charge amount.

≪Image formation method≫
The toner of the present invention can be suitably used in a general electrophotographic image forming method together with black toner, yellow toner, magenta toner and cyan toner.

  The embodiments to which the present invention can be applied are not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "mass part" or "mass%" is represented.

[Preparation of spherical silica particles 1 to 7]
Spherical silica particles 1 to 7 (external additives) were produced as follows.

<Preparation of spherical silica particles 1>
(1) 630 parts by mass of methanol and 90 parts by mass of water were added to and mixed with a 3 liter reactor equipped with a stirrer, a dropping funnel, and a thermometer. While stirring this solution, 950 parts by mass of tetramethoxysilane was hydrolyzed to obtain a suspension of silica particles. Subsequently, it heated at 60-70 degreeC, 390 mass parts of methanol was distilled off, and the aqueous suspension of the silica particle was obtained.
(2) To this aqueous suspension, 11.6 parts by mass of methyltrimethoxysilane (corresponding to 0.1 molar ratio with respect to tetramethoxysilane) was added dropwise at room temperature to hydrophobize the surface of the silica particles. .
(3) After adding 1400 parts by mass of methyl isobutyl ketone to the dispersion thus obtained, the mixture was heated to 80 ° C. to distill off methanol water. To the obtained dispersion, 280 parts by mass of hexamethyldisilazane was added at room temperature, heated to 120 ° C. and reacted for 3 hours to trimethylsilylate the silica particles. Thereafter, the solvent was distilled off under reduced pressure to prepare spherical silica particles 1.
When the number average primary particle size and true specific gravity of the spherical silica particles obtained by the above method were measured, spherical silica particles 1 having a number average primary particle size of 100 nm and a true specific gravity of 1.7 were obtained.

(Measurement of number average particle diameter)
The number average particle diameter (median diameter based on the number) was measured by the following method.
Using a scanning electron microscope (SEM) “JEM-7401F” (manufactured by JEOL Ltd.), an SEM photograph of the toner magnified 30,000 times was taken, and the SEM photograph was observed to observe primary particles of spherical silica particles. The particle size (Ferret diameter) was measured. The two types of spherical silica particles can be easily discriminated from the shape and size, and by measuring the particle size, it can be discriminated that there are two types of particles having different average diameters. For the measurement of the particle size, a region where the total number of particles is 500 in the SEM image was selected, and the average was obtained to obtain the number average particle size (number average primary particle size).

(Calculation of sphericity)
As the sphericity, Wadell's true sphericity was obtained from the following formula (1).

Formula (1) Degree of spheroidization = (surface area of sphere having the same volume as actual particle) / (surface area of actual particle)
Here, the “surface area of a sphere having the same volume as the actual particles” was obtained by arithmetic calculation from the number average particle diameter.
The “surface area of the actual particles” was substituted with the BET specific surface area determined using “Powder Specific Surface Area Measuring Device SS-100” (manufactured by Shimadzu Corporation).
The spherical silica particles 1 had a sphericity of 0.6 or more and were spherical.
In addition, spherical silica particles 2 to 7 described later were all 0.6 or more and spherical.

(Measurement of true specific gravity)
The true specific gravity of the spherical silica particles was measured using a Le Chatelier specific gravity bottle in accordance with JIS standards (JIS-K-0061 5-2-1) as follows.
(1) About 250 ml of ethyl alcohol was put into a Lechatelier specific gravity bottle and adjusted so that the meniscus was at the position of the scale. Next, the Lechatelier specific gravity bottle was immersed in a constant temperature water tank, and when the liquid temperature reached 20.0 ± 0.2 ° C., the position of the meniscus was accurately read on the scale of the Lechatelier specific gravity bottle (accuracy 0.025 ml) To do).
(2) About 100 g of spherical silica particles (assumed to be mass W) was placed in a Le Chatelier specific gravity bottle to remove bubbles.
The Lechatelier specific gravity bottle was immersed in a constant temperature water bath, and when the liquid temperature reached 20.0 ± 0.2 ° C., the position of the meniscus was accurately read on the scale of the specific gravity bottle (accuracy 0.025 ml).
(3) The true specific gravity was calculated by the following formula.
D = W / (L2-L1)
S = D / 0.9982
In the above formula, D represents the density (g / cm ³ ) of spherical silica particles at 20 ° C. S represents the true specific gravity of the spherical silica particles at 20 ° C. W represents the apparent mass (g) of spherical silica particles. L1 represents the meniscus reading (ml) before the spherical silica particles (20 ° C.) are placed in the density bottle. L2 represents the meniscus reading (ml) after the spherical silica particles (20 ° C.) are placed in the specific gravity bottle. 0.9982 is the density of water at 20 ° C. (g / cm ³ ).

(Preparation of spherical silica particles 2)
The spherical silica particles 1 were prepared in the same manner except that the tetramethoxysilane was changed to 650 parts by mass and the hexamethyldisilazane was changed to 200 parts by mass. The number average particle diameter was 60 nm and the true specific gravity was 1.5. Spherical silica particles 2 were obtained.

(Production of spherical silica particles 3 to 7)
In the production of the spherical silica particles 1 or 2, the true specific gravity is adjusted by controlling the hydrophobizing agent species or the treatment amount in the hydrophobizing treatment step, and the hydrolysis, polycondensation step alkoxysilane, ammonia, alcohol, The number average particle size was adjusted by controlling the mass ratio of water, the reaction rate, the stirring rate, and the supply rate to prepare spherical silica particles 3 to 7 shown in Table 1.

<Preparation of Toner 1>
(Preparation of colorant fine particle dispersion)
A solution obtained by stirring and dissolving 11.5 parts by mass of sodium n-dodecyl sulfate in 160 parts by mass of ion-exchanged water was stirred, and 24.5 parts by mass of copper phthalocyanine was gradually added to the solution. Subsequently, by performing a dispersion treatment using a stirring device “Clearmix W Motion CLM-0.8” (manufactured by M Technique Co., Ltd.), a “colorant fine particle dispersion having a volume-based median diameter of 126 nm [ A1] "was prepared.

(Preparation of crystalline polyester resin)
In a three-necked flask, 300 g of 1,9-nonanediol, 250 g of dodecanedioic acid, and catalyst Ti (OBu) ₄ (0.014% by mass with respect to the carboxylic acid monomer) were added, Air was depressurized. Further, under an inert atmosphere with nitrogen gas, the mixture was refluxed at 180 ° C. for 6 hours with mechanical stirring. Thereafter, unreacted monomer components were removed by distillation under reduced pressure, and the temperature was gradually raised to 220 ° C., followed by stirring for 12 hours. Crystalline polyester resin [B1] was obtained by cooling when it became a viscous state. The obtained crystalline polyester resin [B1] had a weight average molecular weight (Mw) of 19,500 and a melting point of 75 ° C.

(First stage polymerization)
4 g of polyoxyethylene (2) sodium dodecyl ether sulfate and 3000 g of ion-exchanged water are charged into a 5 L reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen introduction device, and stirred at a stirring speed of 230 rpm under a nitrogen stream. The internal temperature was raised to 80 ° C. After raising the temperature, 10 g of potassium persulfate dissolved in 200 g of ion-exchanged water was added to obtain a liquid temperature of 75 ° C.
・ Styrene 568g
・ 164 g of n-butyl acrylate
・ Methacrylic acid 68g
After the monomer mixed liquid consisting of 1 was added dropwise over 1 hour, polymerization was carried out by heating and stirring at 75 ° C. for 2 hours to prepare a dispersion of resin particles [C1].

(Second stage polymerization)
A 5 L reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen introducing device was charged with a solution prepared by dissolving 2.0 g of sodium polyoxyethylene (2) sodium dodecyl ether sulfate in 3000 g of ion-exchanged water and brought to 80 ° C. After heating, 42 g of the above resin particles [C1] (in terms of solid content), 70 g of wax “HNP-0190” (manufactured by Nippon Seiwa Co., Ltd.) and 70 g of the above crystalline polyester resin [B1]
・ Styrene 195g
・ 91g of n-butyl acrylate
・ Methacrylic acid 20g
n-Octyl mercaptan 3g
A solution prepared by dissolving the monomer solution at 80 ° C. in a monomer solution is mixed and dispersed for 1 hour by a mechanical disperser “CLEARMIX” (manufactured by M Technique Co., Ltd.) having a circulation path. A dispersion liquid containing oil droplets) was prepared.

  Next, an initiator solution in which 5 g of potassium persulfate was dissolved in 100 g of ion-exchanged water was added to this dispersion, and the system was heated and stirred at 80 ° C. for 1 hour to carry out polymerization, whereby resin particles [ C2] dispersion was prepared.

(3rd stage polymerization)
A solution prepared by dissolving 10 g of potassium persulfate in 200 g of ion-exchanged water was further added to the dispersion of the resin particles [C2].
・ 298 g of styrene
・ 137g of n-butyl acrylate
・ N-stearyl acrylate 50g
・ Methacrylic acid 64g
・ 6g of n-octyl mercaptan
A monomer mixture consisting of was added dropwise over 1 hour. After completion of the dropwise addition, polymerization was performed by heating and stirring for 2 hours, and then cooled to 28 ° C. to obtain a dispersion of core resin fine particles [C3].

(Production of resin for shell)
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction device, a surfactant solution in which 2.0 g of sodium polyoxyethylene dodecyl ether sulfate was dissolved in 3000 g of ion-exchanged water was charged, and the flow rate was 230 rpm under a nitrogen stream. The internal temperature was raised to 80 ° C. while stirring at a stirring speed.
To this solution was added an initiator solution in which 10 g of potassium persulfate was dissolved in 200 g of ion-exchanged water,
・ Styrene 564g
・ 140 g of n-butyl acrylate
・ Methacrylic acid 96g
・ 12g of n-octyl mercaptan
A polymerizable monomer mixed solution obtained by mixing the compounds consisting of was dropped over 3 hours. After the dropping, this system was heated and stirred at 80 ° C. for 1 hour for polymerization to obtain a dispersion of shell resin fine particles [D1].

(Aggregation / fusion process)
In a 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction device, 360 g of a dispersion of resin particles for core [C3] (in terms of solid content), 1100 g of ion-exchanged water, and dispersion of colorant particles Liquid [A1] (50 g) was charged and the liquid temperature was adjusted to 30 ° C., and then 5N sodium hydroxide aqueous solution was added to adjust the pH to 10. Next, an aqueous solution in which 60 g of magnesium chloride was dissolved in 60 g of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After holding for 3 minutes, the temperature was started to rise, and the system was heated to 85 ° C. over 60 minutes, and the particle growth reaction was continued while maintaining 85 ° C. In this state, the particle size of the associated particles was measured with “Multisizer 3” (manufactured by Beckman Coulter). When the number-based median diameter reached 5.7 μm, 40 g of sodium chloride was added to 160 g of ion-exchanged water. The aqueous solution dissolved in the solution is added to stop the particle growth, and as a ripening step, the particles are heated and stirred at a liquid temperature of 80 ° C. for 1 hour to promote fusion between the particles, whereby the core particles [1] Formed.

  Next, 80 g of resin fine particles for shell [D1] (solid content conversion) are added, and stirring is continued at 80 ° C. for 1 hour to fuse the resin fine particles for shell [D1] to the surface of the core particles [1]. To form a shell layer. Here, an aqueous solution in which 150 g of sodium chloride is dissolved in 600 g of ion-exchanged water is added, aging treatment is performed at 80 ° C., and when the circularity reaches 0.960, the solution is cooled to 30 ° C. (1) was obtained. The number-based median diameter of the toner after cooling was 5.8 μm, and the circularity was 0.960.

(Washing / drying process)
The dispersion (1) of the toner base particles produced in the aggregation / fusion process was subjected to solid-liquid separation with a centrifuge to form a wet cake of toner base particles. The wet cake was washed with ion-exchanged water at 35 ° C. until the electric conductivity of the filtrate reached 5 μS / cm in the centrifuge, and then transferred to “Flash Jet Dryer” (manufactured by Seishin Enterprise Co., Ltd.). The toner was dried until the amount became 0.8% by mass to prepare “toner base particles 1”.

(External additive addition process)
Toner base particles 1 include 0.3 parts by mass of spherical silica particles 1 (number average particle size = 100 nm, silica A described in Table 2) and spherical silica particles 2 (number average particle size = 60 nm, silica described in Table 2). B) Toner 1 was prepared by adding 1.5 parts by mass and 12 nm silica particles (hydrophobic silica particles R805 manufactured by Aerosil) and mixing for 20 minutes with a Henschel mixer.

[Production of Toners 2 to 8]
Toner 1 was prepared in the same manner as in the preparation of toner 1 except that the spherical silica particles (silica A and silica B shown in Table 2) to be added to toner base particles 1 and the number of parts added were changed to those shown in Table 2. 2-8 were produced.

<< Evaluation Method of Toners 1-8 >>
[Production of developer]
Each of the toners was mixed with a ferrite carrier having a volume average particle size of 30 μm and a toner concentration of 6.5% by mass to prepare developers 1 to 8 and used for evaluation of toners 1 to 8 below. . The mixer was mixed for 20 minutes using a V-type mixer.

<Toner slip-through>
In a normal temperature and humidity environment (20 ° C., 50% RH), the developer was replaced with bizhub C754 manufactured by Konica Minolta Co., Ltd. as shown in Table 2, and the following evaluation was made on toner slipping after 10,000 sheets of continuous shooting. Was performed visually.
◎: No toner slipping out, no problem at all ○: Toner slipping out is recognized, but no problem in practical use △: Toner slipping out is recognized, but somehow practical use ×: Toner slipping out is recognized, practical problem Yes (results in image defects)

<Scratches on photoconductor>
A halftone image was printed on the entire surface of A3 paper, and the following evaluation was performed.

A: There is no visible scratch on the surface of the photoreceptor, and no defect is observed in the halftone image (good).
○: No noticeable scratches observed on the surface of the photoconductor, and no image defects corresponding to the photoconductor scratches were observed in the halftone image (no problem in practical use).
Δ: Minor scratches are visually observed on the photoreceptor surface, but no image defects corresponding to the photoreceptor scratches are observed in the halftone image (practical)
X: The occurrence of scratches is clearly observed on the surface of the photoreceptor, and the occurrence of image defects corresponding to the scratches is also observed in the halftone image (there is a problem in practical use).

(Summary)
As is clear from the above results, the toners 1 to 5 of the present invention maintain cleaning properties compared to the toners 6 to 8 as comparative examples, and the toner and external additives slip through the surface of the photoreceptor. It turns out that it can suppress that a crack arises.

DESCRIPTION OF SYMBOLS 1 Toner particle 10 Toner base particle 100 Photoconductor 101 Cleaning blade 102 Nip part 103 Static layer 104 Toner particle 105 Space | gap A, B Spherical silica particle

Claims (4)

An electrostatic latent image developing toner containing at least toner particles composed of toner base particles and an external additive,
As the external additive, at least the number average particle diameter contains two types of spherical silica particles in the range of 30 to 200 nm,
An electrostatic latent image developing toner, wherein the two types of spherical silica particles have different number average particle diameters and true specific gravity.   2. The electrostatic latent image according to claim 1, wherein a spherical silica particle having a larger number average particle diameter of the two types of spherical silica particles has a number average particle diameter in a range of 60 to 150 nm. Development toner.   3. The electrostatic latent image developing toner according to claim 1, wherein the toner base particles contain a crystalline polyester resin.   A two-component developer for developing an electrostatic latent image, comprising the toner for developing an electrostatic latent image according to any one of claims 1 to 3 and a carrier.

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