Electrostatic charge image developing toner, and manufacturing method for the same

Abstract

To provide an electrostatic charge image developing toner that is excellent in shatter resistance and fixability, and a manufacturing method of the electrostatic charge image developing toner.SOLUTION: In an electrostatic charge image developing toner including at least a toner particle, the toner particle is manufactured that uses a dispersion fluid including at least a coloring agent particle, and the dispersion fluid contains a coloring agent, a dispersant, an aqueous medium and a surfactant, a Rsp value of the dispersion fluid is within a range of 3.0 to 4.5, and the toner particle is manufactured by fusing a resin particle with the coloring agent particle using a divalent or more cations.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a toner for electrostatic charge image development and a method for manufacturing the same. More specifically, the present invention relates to a toner for electrostatic charge image development having excellent crush resistance and fixability and a method for manufacturing the same.

Background Art

[0002] In recent years, with the increase in printing speed, contamination inside the actual machine and large charge fluctuations have become problems. These problems are considered to be caused by the affinity between colorants contained in the toner for electrostatic charge image development used in printing and the affinity between the colorant and the binder resin.

[0003] Conventional toners for electrostatic charge image development containing a colorant and a binder resin are likely to cause the above problems of contamination inside the actual machine and large charge fluctuations. For example, when the colorant is carbon black showing weak acid properties and the binder resin is a styrene-acrylic resin, this problem becomes more prominent.

[0004] The reason is considered to be that the toner particles are crushed due to the weak affinity between the colorants and the weak affinity between the colorant and the binder resin.

[0005] As a conventional technique for improving the crush resistance of toner particles, a method of synthesizing a vinyl polymer by crosslinking with a crosslinking agent in the binder resin contained in the toner for electrostatic charge image development can be considered. However, the binder resin synthesized by this method has too high strength, which may cause an excessive increase in the softening point and loss of low-temperature fixability.

[0006] To improve the crush resistance of toner particles, there is a method of increasing the amount of flocculant used in the production of toner particles, that is, the amount of cations. However, in this method, the effect of the flocculant on the binding of the resin is higher than the effect on the binding of the colorants, which may deteriorate the fixing property (crack fixing property). In addition, the flocculant also has a higher effect on the binding of the resins than on the binding of the colorant and the resin, and the fixing property (crack fixing property) may deteriorate as described above.

[0007] As another technique for improving the crush resistance of toner particles, for example, as disclosed in Patent Document 1, there is an example in which the shell layer of toner particles is formed including polyamide and polyester. However, there is still room for improvement in terms of achieving both crush resistance and fixing property.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention has been made in view of the above problems and situations, and the problem to be solved is to provide an electrostatic charge image developing toner excellent in crush resistance and fixing property and a method for manufacturing the same.

Means for Solving the Problems

[0010] As a result of studying the cause of the above problems in order to solve the above problems, the present inventor has found that the above problems can be solved by using toner particles prepared using a dispersion liquid containing colorant particles and having an Rsp value in the range of 3.0 to 4.5, and thus has reached the present invention. That is, the above problems according to the present invention are solved by the following means.

[0011] 1. A method for manufacturing an electrostatic charge image developing toner containing at least toner particles, wherein the toner particles are produced using a dispersion liquid containing at least colorant particles, the dispersion liquid contains a colorant, a dispersant, an aqueous medium, and a surfactant, the Rsp value of the dispersion liquid is in the range of 3.0 to 4.5, and the toner particles are produced by fusing resin particles and the colorant particles using a divalent or higher cation. A method for manufacturing an electrostatic charge image developing toner, characterized by the above.

[0012] 2. The method for manufacturing an electrostatic charge image developing toner according to claim 1, wherein the dispersant is an alkaline solution. A method for manufacturing an electrostatic charge image developing toner according to claim 1, characterized by the above.

[0013] 3. The method for manufacturing an electrostatic charge image developing toner according to claim 2, wherein the alkaline solution contains at least sodium hydroxide. A method for manufacturing an electrostatic charge image developing toner according to claim 2, characterized by the above.

[0014] 4. The dielectric loss tangent tanδ measured at a frequency of 100 kHz in an environment of a temperature of 25°C and a relative humidity of 50% RH is in the range of 0.02 to 0.04. A method for manufacturing an electrostatic charge image developing toner according to claim 1, characterized by the above.

[0015] 5. The colorant is carbon black having an acid value in the range of 5.0 to 14.0 mgNaOH / g. A method for manufacturing an electrostatic charge image developing toner according to claim 1, characterized by the above.

[0016] 6. An electrostatic charge image developing toner containing at least toner particles, wherein the toner particles contain at least composite particles of resin particles and colorant particles, the composite particles are composite particles fused by a divalent or higher cation, and The dielectric loss tangent tanδ measured at a frequency of 100 kHz in an environment of a temperature of 25°C and a relative humidity of 50% RH is in the range of 0.02 to 0.04. An electrostatic charge image developing toner characterized by the above.

[0017] 7. The colorant particles are carbon black particles having an acid value in the range of 5.0 to 14.0 mg NaOH / g. The electrostatic charge image developing toner according to Item 6, characterized by the above.

Advantages of the Invention

[0018] By the above means of the present invention, it is possible to provide an electrostatic charge image developing toner excellent in crush resistance and fixability and a method for producing the same. Regarding the mechanism or action mechanism for the expression of the effects of the present invention, it is not clearly defined, but it is presumed as follows.

[0019] The method for producing an electrostatic charge image developing toner of the present invention is a method for producing an electrostatic charge image developing toner containing at least toner particles, wherein the toner particles are produced using a dispersion liquid containing at least colorant particles, the dispersion liquid contains a colorant, a dispersant, an aqueous medium, and a surfactant, the Rsp value of the dispersion liquid is in the range of 3.0 to 4.5, and the toner particles are produced by fusing resin particles and the colorant particles using a divalent or higher cation.

[0020] As an approach for improving crush resistance, in Patent Document 1 mentioned above, the composition of the resin used in the existing toner material is changed, but in the present invention, toner particles are produced using the existing toner material as it is.

[0021] For example, when changing the toner material as in the technique disclosed in Patent Document 1, the influence on the fusion and shape control of resin particles and colorant particles and the time required for the toner particles to reach a desired particle size and roundness is great.

[0022] In contrast, in the present invention, for example, by simply changing the timing of adding a dispersant such as a sodium hydroxide solution, it is possible to produce an electrostatic charge image developing toner without changing the toner material, and thus it is possible to minimize the impact on toner productivity.

[0023] As described above, the main factors of the problems caused by the conventional electrostatic charge image developing toner are the weak affinity between colorants and the weak affinity between the colorant and the binder resin.

[0024] Therefore, in order to improve the above-mentioned weak affinity, the inventors of the present invention set the Rsp value, which is an index of the wettability of the dispersion liquid containing the colorant particles, within the range of 3.0 to 4.5 in the dispersion liquid containing the colorant particles. As a result, since the above-mentioned weak affinity can be improved, it is presumed that both the crush resistance and the fixability of the toner particles can be achieved.

Embodiments for Carrying Out the Invention

[0025] The method for manufacturing an electrostatic charge image developing toner of the present invention is a method for manufacturing an electrostatic charge image developing toner containing at least toner particles, wherein the toner particles are produced using a dispersion liquid containing at least colorant particles, the dispersion liquid contains a colorant, a dispersant, an aqueous medium, and a surfactant, the Rsp value of the dispersion liquid is within the range of 3.0 to 4.5, and the toner particles are produced by fusing resin particles and the colorant particles using a divalent or higher cation. This feature is a technical feature common to or corresponding to the following respective embodiments (aspects).

[0026] As an embodiment of the present invention, it is preferable from the viewpoint of improving the wettability of the dispersion liquid that the dispersant is an alkaline solution.

[0027] It is more preferable from the viewpoint of improving the wettability of the dispersion liquid that the alkaline solution contains at least sodium hydroxide.

[0028] It is preferable that the dielectric loss tangent tanδ measured at a frequency of 100 kHz in an environment of a temperature of 25°C and a relative humidity of 50% RH is in the range of 0.02 to 0.04 from the viewpoint of imparting excellent fixing property while maintaining good dispersibility of the colorant.

[0029] It is preferable that the colorant is carbon black having an acid value in the range of 5.0 to 14.0 mg NaOH / g from the viewpoint of improving the affinity between the colorant particles and between the colorant and the binder resin.

[0030] The toner for electrostatic charge image development of the present invention is a toner for electrostatic charge image development containing at least toner particles, wherein the toner particles contain at least composite particles of resin particles and colorant particles, the composite particles are composite particles fused by a divalent or higher cation, and the dielectric loss tangent tanδ measured at a frequency of 100 kHz in an environment of a temperature of 25°C and a relative humidity of 50% RH is in the range of 0.02 to 0.04.

[0031] It is preferable that the colorant particles are carbon black particles having an acid value in the range of 5.0 to 14.0 mg NaOH / g from the viewpoint of improving the affinity between the colorant particles and between the colorant and the binder resin.

[0032] Hereinafter, the present invention, its components, and the embodiments and modes for carrying out the present invention will be described in detail. In the present application, "~" is used in the meaning of including the numerical values described before and after as the lower limit value and the upper limit value.

[0033] [ Outline of the method for manufacturing a toner for electrostatic charge image development ] The toner for electrostatic charge image development of the present invention is a method for manufacturing a toner for electrostatic charge image development containing at least toner particles, wherein the toner particles are produced using a dispersion containing at least colorant particles, the dispersion contains a colorant, a dispersant, an aqueous medium, and a surfactant, the Rsp value of the dispersion is in the range of 3.0 to 4.5, and the toner particles are produced by fusing resin particles and the colorant particles using a divalent or higher cation.

[0034] As described above, it is considered that the problems of contamination in the actual machine and large charge fluctuations are caused by the weak affinity between colorants and the weak affinity between the colorant and the binder resin. In the present invention, in order to improve the above-mentioned weak affinity, in the dispersion containing colorant particles, the Rsp value, which is an index of the wettability of the dispersion containing the colorant particles, is set within the range of 3.0 to 4.5. Thereby, since the above-mentioned weak affinity can be improved, it is possible to achieve both the crush resistance and the fixability of the toner particles.

[0035] Hereinafter, first, before explaining the method for manufacturing the toner for electrostatic charge image development according to the present invention, a dispersion containing colorant particles, which is a main component in the present invention, and the dielectric loss tangent will be explained.

[0036] 1. Dispersion containing colorant particles (1.1) Wettability of the dispersion and the Rsp value The toner for electrostatic charge image development according to the present invention is produced using a dispersion containing colorant particles, and the Rsp value of the dispersion is in the range of 3.0 to 4.5. By setting the Rsp value of the dispersion containing colorant particles within such a range, the affinity between the colorant particles in the dispersion is increased, and both the crush resistance and the fixability can be achieved.

[0037] Pulse NMR (nuclear magnetic resonance) can be used to measure the Rsp value of the dispersion. Here, the "Rsp value" is an index of the affinity between the particles and water molecules. In this specification, the "Rsp value of the dispersion containing colorant particles" is an index of the affinity between the colorant particles and the solvent constituting the dispersion, and can also be referred to as the wettability of the dispersion containing colorant particles. When the wettability is high, the Rsp value of the above dispersion becomes high, and when the wettability is low, the Rsp value of the above dispersion becomes low.

[0038] Hereinafter, in this specification, the "Rsp value of the dispersion containing colorant particles" is also simply referred to as the "Rsp value of the dispersion".

[0039] (1.1.1) Measurement principle of pulse NMR and evaluation of wettability NMR (nuclear magnetic resonance) is generally well-known as an evaluation apparatus for measuring chemical shifts and performing structural analysis of organic compounds. However, many pieces of information other than chemical shifts can also be obtained from the NMR spectrum, and one of them is relaxation. The "relaxation" mentioned here refers to the process in which the energy once absorbed decays.

[0040] The nuclear spin excited by radio waves relaxes due to the surrounding environment and the energy exchange of the nuclear spin, and the time is measured as the relaxation time. It is possible to evaluate the molecular mobility from the relaxation time by the pulse NMR method.

[0041] The liquid in contact with or adsorbed on the particles is, in other words, the "liquid on the particle surface". The response to the change in the magnetic field is different between this "liquid on the particle surface" and the "liquid in a free state not in contact with the particle surface". The above "liquid in a free state not in contact with the particle surface" is also referred to as the "bulk liquid".

[0042] In this specification, when the liquid on the particle surface is a solvent, for convenience, "liquid molecules" are also referred to as "solvent molecules". In that case, "liquid molecules on the particle surface" are also referred to as "solvent molecules on the particle surface", and "liquid molecules in a free state not in contact with the particle surface" are also referred to as "solvent molecules in the bulk liquid".

[0043] Generally, the movement of "liquid molecules in contact with or adsorbed on the particle surface" is restricted. For example, the hydroxyl groups on the particle surface and water molecules are bound by hydrogen bonds or the like. Therefore, "liquid molecules in contact with or adsorbed on the particle surface" can also be regarded as "bound liquid molecules".

[0044] In contrast, the movement of "liquid molecules in the bulk liquid" is not restricted and can move freely. As a result, the relaxation time of "liquid molecules in contact with or adsorbed on the particle surface" is shorter than that of "liquid molecules in the bulk liquid".

[0045] (Specific example) For the evaluation of wettability, it is suitable to observe protium ( 1 H) which is the most abundant in the world. Therefore, the observed atomic nucleus here is protium ( 1 H).

[0046] Here, when water is used as the solvent, considering a system in which particles are dispersed in water, if hydroxyl groups exist on the particle surface in the dispersion containing particles, it is considered that there are two types of water in the particle dispersion. The first is water in which the above-mentioned hydroxyl groups and water molecules are bound by hydrogen bonds or the like. The second is free water other than that.

[0047] The bound water is prone to energy exchange and has a short relaxation time for protium ( 1 H). In contrast, free water is less prone to energy exchange and has a long relaxation time for protium ( 1 H).

[0048] That is, a state with good wettability is a state in which many hydrogen bonds exist and there is a large amount of bound water. Note that the solvent is not limited to water, and if light hydrogen ( 1 H) is contained in the chemical structure of the solvent, it can be used for evaluating wettability.

[0049] (Various parameters) The "reciprocal of the relaxation time T" obtained by measuring a dispersion containing particles is the relaxation rate (hereinafter also referred to as the "relaxation time constant"). At this time, let the relaxation time constant of the bound liquid molecules (adsorbed phase liquid molecules on the particle surface) be Rs, and the relaxation time constant of the liquid molecules in the bulk liquid be Rb.

[0050] Also, let the volume concentration of particles etc. in the liquid molecules (bound liquid molecules) on the particle surface be Ps, and the volume concentration of particles etc. in the free liquid molecules (liquid molecules in the bulk liquid) not in contact with the particle surface be Pb.

[0051] At this time, since the dispersion containing particles is composed of the above-mentioned bound liquid molecules and the liquid molecules in the bulk liquid, the average relaxation rate Rav in the dispersion containing the particles is represented by the following formula (1).

[0052] Formula (1) Rav = Ps·Rs + Pb·Rb

[0053] Here, consider the application to a dispersion containing coloring agent particles according to the present invention (hereinafter also referred to as a "dispersion containing coloring agent particles").

[0054] For example, when evaluating the wettability of a dispersion containing coloring agent particles containing carbon black particles as coloring agent particles and further containing silica particles as inorganic particles, Rav, Rs, Rb, Ps, and Pb in the above formula (1) are defined as follows, and the Rsp value can be obtained by using the following formula (2).

[0055] Rav: Reciprocal of the average relaxation time of the dispersion containing coloring agent particles Ps: Volume concentration of a solution containing coloring agent particles and also containing other inorganic particles other than the coloring agent particles Rs: Reciprocal of the relaxation time of a solution containing other inorganic particles other than the coloring agent particles (relaxation time constant of the adsorbed solvent molecules on the surface of the coloring agent particles) Pb: Volume concentration of a solution (blank solution) containing neither the coloring agent particles nor other inorganic particles other than the coloring agent particles Rb: Reciprocal of the relaxation time of a solution (blank solution) containing neither the coloring agent particles nor other inorganic particles other than the coloring agent particles (relaxation time constant of the solvent molecules in the solvent bulk)

[0056] Equation (2) Rsp = (Rav - Rb) / (Rb)

[0057] (1.1.2) Measurement conditions and measurement method for the Rsp value For the measurement of the Rsp value of the dispersion, for example, a pulsed NMR particle interface property evaluation apparatus "Acorn Area" (manufactured by Xigo nanotools) is used. Specifically, it can be measured under the following measurement conditions and measurement method, for example.

[0058] <Measurement conditions> Measurement temperature: 25 °C 90° pulse width: 6.37 μs Delay time: 8.0 μs Repetition time: 2.0 s Number of integrations: 32 times

[0059] <Measurement method> For example, 0.5 ml of a dispersion containing coloring agent particles is put into an NMR sample tube, set in the apparatus, and the relaxation time is measured. Note that, for example, carbon black is used as the coloring agent.

[0060] Also, as the blank solution used for dispersion, a mixed solution of a surfactant, water, and an aqueous sodium hydroxide solution is used. Then, the relaxation time of the blank solution is measured.

[0061] Using the above measurement results and by using the aforementioned equations (1) and (2), the Rsp value is obtained.

[0062] In the present invention, when the calculation is performed using the above formula (2) with Rav being the reciprocal of the average relaxation time of the dispersion liquid containing the colorant particles and Rb being the reciprocal of the relaxation time of the blank solution, Rsp is within the range of 3.0 to 4.5.

[0063] From the viewpoint of achieving both crush resistance and fixing property, it is more preferable that the above range is within the range of 3.5 to 4.0.

[0064] (1.2) Colorant As the colorant according to the present invention, there is no particular limitation and known ones can be used. However, when a colorant showing the properties of a weak acid is used, if the binder resin contained in the toner for electrostatic charge image development is a styrene-acrylic resin, the effects of the present invention are enhanced.

[0065] Specifically, the effect is to suppress the crushing of toner particles due to the weak affinity between colorants showing the properties of a weak acid and the weak affinity between a colorant showing the properties of a weak acid and a styrene-acrylic resin.

[0066] As the colorant, for example, known inorganic or organic colorants used for coloring color toners are used. Examples of the colorant include carbon black, magnetic materials, pigments, and dyes. In addition, acid dye-based pigments such as peacock blue lake, eosin lake, and quinoline yellow lake can also be used, and these colorants may be used alone or in combination.

[0067] Among them, it is preferable that the colorant is carbon black, and it is preferable that the colorant particles constituting the colorant are carbon black particles with an acid value within the range of 5.0 to 14.0 mgNaOH / g from the viewpoint of improving the affinity between the colorant particles and between the colorant and the binder resin.

[0068] Examples of the carbon black include channel black, furnace black, acetylene black, thermal black, and lamp black. Further, there are no particular restrictions on the magnetic material, pigment, and dye, and general known materials can be used.

[0069] (1.3) Degree of contribution to the affinity and wettability between colorants and between the colorant and the binder resin Regarding the affinity between colorants and between the colorant and the binder resin, an example in which carbon black is used as the colorant and a styrene-acrylic resin is used as the binder resin will be specifically described below.

[0070] On the surface of the carbon black particles constituting the carbon black, various functional groups such as hydroxy groups, sulfonic acid groups, and carboxy groups are present. It is presumed that the amount of carboxy groups mainly contributes to the wettability.

[0071] When the wettability is low, that is, in a state where the Rsp value is low, the degree of deviation of the weak acid groups (for example, COOH and SO 3 H) present in the carbon black from COO - and H + and SO 3 - and H + is very small.

[0072] On the other hand, in the dispersion according to the present invention, the above carbon black particles are dispersed in the dispersion by adding a dispersant described later. At this time, for example, by adding sodium hydroxide as the dispersant, the degree of deviation of the weak acid groups (for example, COOH and SO 3 H) present in the carbon black from COO - and H + and SO 3 - and H + becomes large. And thereby, the wettability of the dispersion can be made high (a state where the Rsp value is high).

[0073] The toner particles according to the present invention are produced by fusing resin particles and colorant particles using a divalent or higher cation. Note that the resin particles are the resin particles contained in the binder resin.

[0074] As described above, when the wettability is high (the Rsp value is high), the weak acid groups present in the carbon black, particularly COOH, are sufficiently dissociated, and as a result, the number of metal ions (here, Mg 2+ ) that bind to the carbon black particles increases. Therefore, the affinity between carbon blacks and between carbon black and the binder resin is enhanced by the aggregated salt (metal ions), and the crush resistance is improved.

[0075] On the other hand, if the affinity is too high, that is, if the Rsp value becomes too high, the number of metal ions (here, Mg 2+ ) that bind to the carbon black particles increases too much. And as a result, the resin becomes too hard due to the interaction with the metal ions, and the fixability deteriorates. Therefore, the upper limit of the Rsp value is 4.5, and by controlling not to exceed this value, it is possible to appropriately impart crush resistance to the toner particles and at the same time suppress the deterioration of the fixability.

[0076] (Acid value of carbon black) In this specification, the "acid value" is defined as the mass of sodium hydroxide in mg required to neutralize the weak acid contained in 1 g of carbon black.

[0077] When the acid value of the carbon black used as the colorant is 5.0 mg NaOH / g or more, it is possible to sufficiently secure the amount of sodium hydroxide added until the dispersion becomes neutral. Therefore, the interaction between carbon blacks and between carbon black and styrene-acrylic resin is strengthened, and as a result, an electrostatic charge image developing toner excellent in crush resistance can be produced.

[0078] On the one hand, if the acid value of the carbon black used as the colorant is 14.0 mgNaOH / g or less, the amount of sodium hydroxide added until the dispersion becomes neutral is not too much, and the styrene-acrylic resin does not become too hard, so the fixing property does not deteriorate.

[0079] From the above, it is preferable that the colorant particles are carbon black particles having an acid value in the range of 5.0 to 14.0 mgNaOH / g from the viewpoint of improving the affinity between the colorant particles and between the colorant and the binder resin.

[0080] To measure the acid value of carbon black, for example, an automatic titrator "TITSTATION TS-1700" manufactured by HIRANUMA can be used, and specifically, the acid value is calculated as follows.

[0081] First, draw a conductivity curve with the amount of sodium hydroxide on the horizontal axis and the conductivity on the vertical axis, and calculate the amount of sodium hydroxide when COOH in the carbon black dispersion starts to deviate from COO - and H + and the amount of sodium hydroxide when the deviation of COOH is completed. Calculate the acid value based on these calculated amounts.

[0082] Note that the amount of sodium hydroxide dropped from the start of the deviation of COOH to the completion of the deviation of COOH corresponds to the amount of sodium hydroxide required to neutralize the weak acid in the carbon black. As described above, the "acid value" is the mass of sodium hydroxide required to neutralize the weak acid contained in 1 g of carbon black, expressed in mg.

[0083] Also, the titration conditions are as follows. The concentration of the sodium hydroxide solution used for titration is 0.05 mol / L, and the solution for measurement is a solution prepared by adding pure water to 12.5 g of the carbon black dispersion prepared above to make 50 g.

[0084] <Titration conditions> Continuous dropping amount: 0.25 mL Maximum dropping amount: 20 mL Waiting time: 5 seconds

[0085] (1.4) Dispersant As the dispersant according to the present invention, known ones can be used without particular limitation, but it is preferable that the dispersant is an alkaline solution from the viewpoint of improving the wettability of the dispersion liquid.

[0086] As the alkaline compound contained in the alkaline solution, known ones can be used without particular limitation, and for example, hydroxides of alkali metals such as potassium hydroxide and sodium hydroxide can be used. Among these, from the viewpoint of improving the dispersion stability of the resin particles, hydroxides showing strong alkalinity such as potassium hydroxide or sodium hydroxide are preferable. Further, among them, it is more preferable that the alkaline solution contains at least sodium hydroxide from the viewpoint of improving the wettability of the dispersion liquid.

[0087] (1.5) Surfactant The surfactant contained in the dispersion liquid according to the present invention is used for the aqueous medium used at the time of polymerization of the colorant fine particle dispersion liquid and the core binder resin fine particles described later.

[0088] Examples of the surfactant include anionic surfactants, cationic surfactants, and nonionic surfactants, and these may be used alone or in combination of two or more.

[0089] Examples of the anionic surfactant include sulfate ester salts, sulfonates, and phosphate esters. Specifically, for example, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium alkylnaphthalenesulfonate, and sodium dialkylsulfosuccinate can be mentioned.

[0090] Examples of the cationic surfactant include amine salt types and quaternary ammonium salt types. Specifically, for example, alkylbenzyldimethylammonium chloride, alkyltrimethylammonium chloride, and distearylammonium chloride can be mentioned.

[0091] Examples of nonionic surfactants include polyethylene glycol-based, alkylphenol ethylene oxide adduct-based, polyhydric alcohol-based, etc. Specifically, for example, polyoxyethylene alkyl ether, glycerin fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, and polyoxyethylene fatty acid ester can be mentioned.

[0092] (1.6) Aqueous medium The aqueous medium contained in the dispersion according to the present invention is used during the polymerization of the coloring agent fine particle dispersion and the core binder resin fine particles described later. Here, the "aqueous medium" refers to a medium composed of 50 to 100% by mass of water and 0 to 50% by mass of a water-soluble organic solvent. Examples of the water-soluble organic solvent include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, tetrahydrofuran, etc. Among these, an alcohol-based organic solvent that does not dissolve the resin to be produced is preferred.

[0093] 2. Dielectric loss tangent The ideal state as the electrical property of the toner for electrostatic charge image development is that the charge can be retained regardless of the frequency of the applied electric field.

[0094] The dielectric loss tangent tanδ is calculated by ε′′ / ε′, where ε′ represents the storage ability of electrical energy and ε′′ represents the loss of electrical energy. The smaller the value of tanδ, which is the ratio of these, the easier it is to retain the charge. That is, the smaller the dielectric loss tangent tanδ, the less likely the charge is to leak and the easier it is to maintain the chargeability.

[0095] Also, the smaller the frequency dependence of the dielectric loss tangent tanδ, the more likely the toner for electrostatic charge image development is to faithfully respond to the applied electric field and retain the charge in various processes such as the development process and the transfer process, and the latent image reproducibility can be improved.

[0096] Since the toner of the present invention has good dispersibility of carbon black in the mother particles, the tanδ measured at a frequency of 100 kHz in an environment of a temperature of 25°C and a relative humidity of 50%RH has a high value.

[0097] The dielectric loss tangent tanδ varies with the dispersion time. However, for an electrostatic charge image developing toner with too high a dielectric loss tangent tanδ, while the dispersion of carbon black improves, the amount of deviation of the carboxyl groups of the resin also increases, resulting in the resin becoming hard and leading to deterioration of the fixing property.

[0098] Therefore, from the viewpoint of imparting excellent fixing property while maintaining good dispersibility of the colorant, it is preferable that the dielectric loss tangent tanδ measured at a frequency of 100 kHz in an environment of a temperature of 25°C and a relative humidity of 50%RH is in the range of 0.02 to 0.04.

[0099] <Measurement method> The measurement method of the dielectric loss tangent tanδ is specifically shown below.

[0100] First, as a measurement sample, a 40 mmφ disc-shaped sample (thickness: about 2 mm) formed by applying a load of 100 kgf / cm 2 for 10 seconds to 2 g of the electrostatic charge image developing toner is used.

[0101] The thickness of each disc-shaped sample is measured with a vernier caliper. The dielectric loss tangent tanδ is measured using an "LCR meter 65120P" (manufactured by Toyo Technica Co., Ltd.) in an environment of a temperature of 25°C and a relative humidity of 50%RH.

[0102] Using the attached software "WITNESS-6000", the measurement frequency is set from 1 kHz to 100 kHz, the number of one-digit points is set to 5, and the averaging times is set to 3, and the thickness of the disc-shaped sample is input for measurement.

[0103] 3. Manufacturing process of the electrostatic charge image developing toner As the manufacturing process of the toner for electrostatic charge image development of the present invention, any known process can be adopted as long as it is the aforementioned manufacturing method, but from the viewpoints of particle size uniformity and shape controllability, it is preferable to adopt a process by an emulsification aggregation method. Hereinafter, the process by an emulsion polymerization method will be described.

[0104] The emulsification aggregation method is a method using a dispersion of particles of a binder resin (hereinafter also referred to as "binder resin particles") dispersed by a surfactant or a dispersion stabilizer. Then, if necessary, it is mixed with a dispersion of particles of a colorant (hereinafter also referred to as "colorant particles"), aggregated until a desired toner particle size is obtained, and further shape control is performed by fusing between the binder resin particles to produce toner particles. Here, the particles of the binder resin may optionally contain a release agent, a charge control agent, and the like.

[0105] In the manufacturing method of the toner for electrostatic charge image development of the present invention, it is essential to use the dispersion of the colorant particles.

[0106] When the toner has a core - shell structure, its manufacturing method will be specifically described below by dividing it into steps (1) to (9).

[0107] (1) Colorant fine particle dispersion preparation step of preparing a dispersion of colorant fine particles in which the colorant is dispersed in fine particle form (2 - 1) Core binder resin fine particle polymerization step of obtaining core binder resin fine particles composed of a core binder resin containing a main wax and internal additives, etc., and preparing this dispersion (2 - 2) Shell binder resin fine particle polymerization step of obtaining shell binder resin fine particles composed of a shell binder resin, and preparing this dispersion (3) Aggregation - fusion step of aggregating and fusing the core binder resin fine particles and the colorant fine particles in an aqueous medium to form associated particles to be core particles (4) First aging step of aging the associated particles by thermal energy to control the shape and obtain core particles (5) A shell layer forming step of adding shell binder resin fine particles to be formed into a shell layer into a dispersion of core particles, aggregating and fusing the shell binder resin fine particles onto the surface of the core particles to form particles having a core-shell structure. (6) A second aging step of aging the particles having a core-shell structure by thermal energy to control the shape and obtaining toner particles having a core-shell structure. (7) A filtration and washing step of solid-liquid separating the toner particles from the cooled dispersion system (aqueous medium) of the toner particles and removing surfactants and the like from the toner particles. (8) It is composed of a drying step of drying the washed toner particles, and if necessary, after the drying step, (9) An external additive treatment step of adding an external additive to the dried toner particles may be added.

[0108] To obtain toner particles having a core-shell structure, first, binder resin particles for core particles and colorant particles are aggregated and fused to produce core particles. Next, binder resin particles for the shell layer are added to the dispersion of the core particles, and the binder resin particles for the shell layer are aggregated and fused onto the surface of the core particles to form a shell layer covering the surface of the core particles. Thereby, toner particles having a core-shell structure can be obtained.

[0109] However, for example, in the step (4) above, toner particles formed from single-layer particles can be similarly manufactured without adding a shell resin particle dispersion liquid.

[0110] (1) A step of preparing a colorant particle dispersion liquid In this step, a treatment of preparing a dispersion liquid of colorant fine particles in which the colorant is dispersed in fine particle form is performed by adding a colorant to an aqueous medium and performing a dispersion treatment with a disperser. Specifically, the dispersion treatment of the colorant is performed in an aqueous medium in a state where the surfactant concentration is at or above the critical micelle concentration (CMC). The surfactant used for the aqueous medium is as described above.

[0111] The disperser used for the dispersion treatment is not particularly limited, but preferably, an ultrasonic disperser, a mechanical homogenizer, a pressure disperser such as a Manton Gorin or a pressure-type homogenizer, a sand grinder, a media-type disperser such as a Getzmann mill or a diamond fine mill, etc.

[0112] The dispersion diameter of the colorant fine particles in this colorant fine particle dispersion liquid is preferably in the range of 40 to 200 nm in terms of the volume-based median diameter.

[0113] The volume-based median diameter of this colorant fine particle is measured under the following measurement conditions using "MICROTRAC UPA-150 (manufactured by HONEYWELL)".

[0114] <Measurement conditions> ·Sample refractive index 1.59 ·Sample specific gravity 1.05 (converted to spherical particles) ·Solvent refractive index 1.33 ·Solvent viscosity 0.797 (30 °C), 1.002 (20 °C) ·Zero-point adjustment: The measurement cell was filled with ion-exchanged water and adjusted.

[0115] (2-1) Core binder resin fine particle polymerization step In this step, a treatment is performed to prepare a dispersion liquid of core binder resin fine particles composed of a core binder resin containing a main wax, an internal additive, etc. by performing a polymerization treatment.

[0116] In a preferred example of the polymerization treatment in this step, a polymerizable monomer solution containing a main wax, an internal additive, etc. as necessary is added to an aqueous medium containing a surfactant below the critical micelle concentration (CMC), mechanical energy is applied to form droplets, then a water-soluble polymerization initiator is added, and the polymerization reaction is allowed to proceed in the droplets. Note that an oil-soluble polymerization initiator may be contained in the droplets. Also, the surfactant used for the aqueous medium is as described above.

[0117] (Coinitiator) As the coinitiator used in the step of polymerizing core binder resin fine particles, for example, water-soluble coinitiators or oil-soluble coinitiators can be mentioned.

[0118] Examples of water-soluble coinitiators include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropanoate, azobiscyanovaleric acid and its salts, hydrogen peroxide, and the like.

[0119] Examples of oil-soluble coinitiators include azo-based or diazo-based coinitiators such as 2,2′-azobis-(2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis(cyclohexane-1-carbonitrile), 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile; peroxide-based coinitiators such as benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxydicarbonate, 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-(t-butylperoxy)triazine; and polymer initiators having a peroxide in the side chain.

[0120] (Chain transfer agent) For the purpose of adjusting the molecular weight of the obtained core binder resin, a chain transfer agent can be used in the step of preparing the core resin particle dispersion. As the chain transfer agent, generally used chain transfer agents can be used.

[0121] The chain transfer agent is not particularly limited. For example, mercaptans such as n-octyl mercaptan, n-decyl mercaptan, tert-dodecyl mercaptan; mercaptopropionic acid esters such as n-octyl 3-mercaptopropionate; terpinolene; and α-methylstyrene dimer are used.

[0122] (2-2) Shell Binder Resin Fine Particle Polymerization Process In this process, a polymerization treatment is carried out in the same manner as in the process of preparing the core resin particle dispersion liquid to prepare a dispersion liquid of shell binder resin fine particles composed of the shell binder resin.

[0123] (3) Aggregation / Fusion Process In this process, a treatment is carried out to aggregate and fuse the core binder resin fine particles and the colorant fine particles in an aqueous medium to form associated particles to be core particles.

[0124] As the method of aggregation and fusion in this process, the salting-out / fusion method using the colorant fine particles obtained by the colorant fine particle dispersion liquid preparation process in (1) and the core binder resin fine particles obtained by the core binder resin fine particle polymerization process in (2-1) is preferable.

[0125] Also, in the aggregation / fusion process, internal additive fine particles such as wax fine particles and charge control agents can be aggregated and fused together with the core binder resin fine particles and the colorant fine particles.

[0126] Here, "salting-out / fusion" means proceeding with aggregation and fusion in parallel, adding an aggregation terminator when growth reaches the desired particle size to stop particle growth, and further continuing heating as necessary to control the particle shape.

[0127] The salting-out / fusion method is as follows. First, a salting-out agent composed of an alkali metal salt, an alkaline earth metal salt, a trivalent salt, etc. is added as a flocculant at a concentration equal to or higher than the critical flocculation concentration into the aqueous medium in which the core binder resin fine particles and the colorant fine particles are present. Next, heating is carried out at a temperature equal to or higher than the glass transition point of the core binder resin fine particles and equal to or higher than the melting peak temperature of the core binder resin fine particles and the colorant fine particles to proceed with salting-out and at the same time carry out aggregation / fusion.

[0128] Here, the alkali metal salts and alkaline earth metal salts as salting - out agents include, as alkali metals, lithium, potassium, sodium, etc., and as alkaline earth metals, magnesium, calcium, strontium, barium, etc. Among them, preferably potassium, sodium, magnesium, calcium, and barium are mentioned. When the aggregation / fusion step in (3) is carried out by salting - out / fusion, it is preferable to make the time for standing after adding the salting - out agent as short as possible.

[0129] The reason for this is not clear, but problems occur such that the aggregation state of the particles fluctuates depending on the standing time after salting - out, the particle size distribution becomes unstable, or the surface property of the fused toner fluctuates.

[0130] Also, as the temperature for adding the salting - out agent, it is necessary to be at least below the glass transition point of the core - used binder resin fine particles.

[0131] The reason for this is that if the temperature for adding the salting - out agent is above the glass transition point of the core - used binder resin fine particles, although the salting - out / fusion of the core - used binder resin fine particles proceeds rapidly, problems occur such that the particle size cannot be controlled and large - sized particles are generated.

[0132] This addition temperature range may be below the glass transition point of the binder resin, but generally it is within the range of 5 - 55°C, preferably within the range of 10 - 45°C.

[0133] Also, add the salting - out agent below the glass transition point of the core - used binder resin fine particles, then heat up as quickly as possible, and heat to a temperature above the glass transition point of the core - used binder resin fine particles and above the melting peak temperature (°C) of the core - used binder resin fine particles and the colorant fine particles.

[0134] The time until this temperature rise is preferably less than 1 hour. Further, it is necessary to rapidly raise the temperature, and the rate of temperature rise is preferably 0.25 °C / min or more. Although the upper limit is not particularly clear, if the temperature is raised instantaneously, salting out proceeds rapidly, and there is a problem that it is difficult to control the particle size. Therefore, it is preferably 5 °C / min or less.

[0135] By the above salting out / fusion method, a dispersion of aggregated particles (core particles) in which the core binder resin fine particles and optional fine particles are salted out / fused is obtained.

[0136] (4) First aging step In this step, a treatment for aging the aggregated particles by thermal energy is performed. By controlling the heating temperature in the aggregation / fusion step in (3) and particularly the heating temperature and time in the first aging step in (4), it is possible to control the surface of the core particles to have a smooth but uniform shape with a constant particle size and a narrow distribution.

[0137] Specifically, in the aggregation / fusion step in (3), the heating temperature is lowered to suppress the progress of fusion between the core binder resin fine particles and promote homogenization. In the first aging step, the heating temperature is lowered and the time is lengthened to control the surface of the core particles to have a uniform shape.

[0138] (5) Shell layer formation step In this step, a dispersion of shell binder resin fine particles is added to the dispersion of core particles, and the shell binder resin fine particles are aggregated and fused on the surface of the core particles to coat the surface of the core particles with the shell binder resin fine particles to form a core-shell structured particle. A shelling treatment is performed.

[0139] This step is a preferable production condition for imparting both low-temperature fixing property and heat-resistant storage property. Further, when forming a color image, it is preferable to perform this shell layer formation in order to obtain high color reproducibility for secondary colors.

[0140] Specifically, while maintaining the heating temperature in the aggregation and fusion step (3) and the first aging step (4) of the core particle dispersion, a dispersion of shell binder resin fine particles is added, and the shell binder resin fine particles are slowly coated on the surface of the core particles over several hours while continuing heating and stirring to form core-shell structured particles. The heating and stirring time is preferably in the range of 1 to 7 hours, and particularly preferably in the range of 3 to 5 hours.

[0141] (6) Second aging step In this step, when the particles with a core-shell structure reach a predetermined particle size in the shell layer formation step (5), a terminator such as sodium chloride is added to stop particle growth, and then heating and stirring are continued for several hours to fuse the shell binder resin fine particles attached to the core particles.

[0142] And the thickness of the layer formed by the shell binder resin fine particles covering the surface of the core particles is in the range of 100 to 300 nm. In this way, the shell binder resin fine particles are fixed on the surface of the core particles to form a shell layer, and toner particles with a core-shell structure that are rounded and have a uniform shape are formed.

[0143] (7) Filtration and washing step In this step, first, a process of cooling the dispersion of toner particles is performed. As the cooling treatment conditions, it is preferable to cool at a cooling rate within the range of 1 to 20 °C / min. The cooling treatment method is not particularly limited, and examples include a method of introducing a refrigerant from the outside of the reaction vessel for cooling and a method of directly injecting cold water into the reaction system for cooling.

[0144] Next, the toner particles are separated from the dispersion of toner particles cooled to a predetermined temperature, and then a washing treatment is performed to remove deposits such as surfactants and salting-out agents from the separated toner cake (an aggregate obtained by aggregating wet toner particles into a cake shape).

[0145] Here, the filtration method is not particularly limited, and examples include centrifugation, vacuum filtration using a Nutsche filter, etc., and filtration using a filter press, etc.

[0146] (8) Drying step In this step, the washed toner cake is dried. Examples of the dryer used in this step include spray dryers, vacuum freeze dryers, vacuum dryers, etc., and it is preferable to use stationary shelf dryers, mobile shelf dryers, fluidized bed dryers, rotary dryers, stirring dryers, etc.

[0147] The moisture content of the dried toner particles is preferably 5% by mass or less, more preferably 2% by mass or less. In addition, when the dried toner particles are aggregated by weak interparticle attraction, the aggregates may be crushed. Here, as the crushing device, mechanical crushing devices such as jet mills, Henschel mixers, coffee mills, and food processors can be used.

[0148] (9) External additive treatment step In this step, an external additive is added to the toner particles dried in the drying step (8). As a method for adding the external additive, for example, it can be added using a mechanical mixing device such as a Henschel mixer or a coffee mill.

[0149] [Outline of toner for electrostatic charge image development] The toner for electrostatic charge image development of the present invention is a toner for electrostatic charge image development containing at least toner particles, wherein the toner particles contain at least composite particles of resin particles and colorant particles, the composite particles are composite particles fused by a divalent or higher cation, and the dielectric loss tangent tanδ measured at a frequency of 100 kHz in an environment of temperature 25°C and relative humidity 50%RH is in the range of 0.02 to 0.04.

[0150] The electrostatic charge image developing toner (hereinafter also referred to as "toner") refers to an aggregate of "toner particles". Further, the toner particles contain at least toner base particles, and the toner particles refer to the toner base particles themselves or those obtained by adding at least an external additive to the toner base particles.

[0151] The binder resin contained in the above toner base particles preferably contains an amorphous resin and a crystalline resin. Further, the toner base particles contain a colorant, and may contain other components such as a release agent (wax) and a charge control agent as necessary. Note that the colorant according to the present invention and the above dielectric loss tangent tanδ are as described above.

[0152] By mixing the toner base particles with a crystalline resin and an amorphous resin to be described in detail below, the crystalline resin and the amorphous resin are compatibilized during heat fixing. As a result, low-temperature fixing of the toner can be achieved, and energy saving can be achieved.

[0153] [1] Binder resin The binder resin contained in the toner according to the present invention may be a resin containing at least one acid group (a group having one or more hydrogen atoms capable of substituting with a cation). Examples of the acid group include a sulfonic acid group and a carboxy group. Examples of the resin include styrene-acrylic resins, acrylic resins, methacrylic resins, and polyester resins.

[0154] [1-1] Amorphous resin Conventionally known amorphous resins in the art can be used. Among them, the amorphous resin preferably contains an amorphous vinyl resin. Particularly preferred is a styrene-acrylic copolymer resin formed using a styrene monomer and a (meth)acrylate monomer or acrylic acid.

[0155] By emulsifying and aggregating styrene-acrylic resin to form toner, the toner moisture content becomes moderately high, the adhesion of the toner to the photoreceptor is improved, it becomes difficult for the toner to detach from the photoreceptor, and scavenging can be suppressed.

[0156] As the vinyl monomer for forming the amorphous vinyl resin, one or more selected from styrene monomers, (meth)acrylate monomers, vinyl esters, vinyl ethers, vinyl ketones, N-vinyl compounds, etc. can be used. In addition to this, vinyl compounds such as vinyl naphthalene and vinyl pyridine, and acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide can also be used.

[0157] In addition, as the vinyl monomer, it is preferable to use a monomer having an ionic dissociative group such as a carboxy group, a sulfonic acid group, or a phosphoric acid group. Furthermore, as the vinyl monomer, polyfunctional vinyls can be used to make the amorphous vinyl resin have a crosslinked structure.

[0158] As described above, as a preferable form of the amorphous resin, the vinyl resin has been described in detail, but it is not limited to this, and an amorphous polyester resin or the like may be used as the amorphous resin.

[0159] [1-2] Crystalline resin The "crystalline resin" refers to a resin having a distinct endothermic peak instead of a stepwise endothermic change in differential scanning calorimetry (DSC). Specifically, the distinct endothermic peak means a peak whose half-width at half maximum of the endothermic peak is within 15 °C when measured at a heating rate of 10 °C / min in differential scanning calorimetry (DSC).

[0160] The crystalline resin is not particularly limited as long as it has the above characteristics, and conventionally known crystalline resins in the technical field can be used. Specific examples thereof include crystalline polyester resins, crystalline polyurethane resins, crystalline polyurea resins, crystalline polyamide resins, and Examples include crystalline polyether resins and the like. The crystalline resin can be used alone or in combination of two or more.

[0161] Among them, the crystalline resin is preferably a crystalline polyester resin. Here, the "crystalline polyester resin" is a resin that satisfies the above endothermic characteristics among known polyester resins obtained by polycondensation reaction of a dicarboxylic acid (polyvalent carboxylic acid) having two or more valences and its derivatives, and a diol (polyvalent alcohol) having two or more valences and its derivatives.

[0162] The melting point of the crystalline polyester resin is not particularly limited, but is preferably in the range of 55 to 90 °C. When the melting point of the crystalline polyester resin is within the above range, sufficient low-temperature fixability can be obtained. From such a viewpoint, it is more preferably in the range of 60 to 85 °C. The melting point of the crystalline polyester resin can be controlled by the resin composition. In addition, in this specification, the melting point of the resin is the value measured by the method described in the examples.

[0163] The valences of the polyvalent carboxylic acid and polyvalent alcohol constituting the crystalline polyester resin are preferably 2 to 3, respectively, and particularly preferably 2, respectively. Therefore, hereinafter, the case where the valences are both 2 (that is, the dicarboxylic acid component and the diol component) will be described in detail.

[0164] As the dicarboxylic acid component, it is preferable to use an aliphatic dicarboxylic acid, and an aromatic dicarboxylic acid may be used in combination as necessary. As the aliphatic dicarboxylic acid, a linear one is preferably used. By using a linear one, there is an advantage that the crystallinity is improved. The dicarboxylic acid component may be used alone or in combination of two or more.

[0165] From the viewpoint of ensuring both sufficient low-temperature fixability and excellent long-term heat-resistant storage stability, the weight-average molecular weight (Mw) of the crystalline polyester resin is preferably in the range of 3,000 to 100,000. More preferably, it is in the range of 4,000 to 50,000, and particularly preferably in the range of 5,000 to 20,000.

[0166] The method for producing the crystalline polyester resin is not particularly limited, and it can be produced by polycondensing (esterifying) the above-mentioned dicarboxylic acid and dialcohol using a known esterification catalyst.

[0167] The polymerization temperature is not particularly limited, but it is preferably in the range of 150 to 250 °C. Also, the polymerization time is not particularly limited, but it is preferably in the range of 0.5 to 15 hours. During the polymerization, the inside of the reaction system may be depressurized as necessary.

[0168] When the binder resin contains a crystalline resin (preferably a crystalline polyester resin), the content of the crystalline resin in the binder resin is not particularly limited, but it is preferably less than 50% by mass based on the total amount of the binder resin. More preferably, it is 30% by mass or less, and particularly preferably 10% by mass or less.

[0169] When the crystalline resin is a crystalline polyester resin, by setting the content to less than 50% by mass, the environmental dependence of the charge amount due to the hygroscopicity of the crystalline polyester resin can be reduced. On the other hand, the lower limit value of the content is not particularly limited, but when the binder resin contains a crystalline resin (preferably a crystalline polyester resin), it is preferably 5% by mass or more. If the content of the crystalline resin is 5% by mass or more based on the total amount of the binder resin, a toner excellent in low-temperature fixability can be obtained.

[0170] [2] Release agent As the release agent, various known waxes can be used. 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 Sasol wax, dialkyl ketone waxes such as distearyl ketone, ester waxes such as carnauba wax, montan wax, behenyl behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitate, and distearyl maleate, and amide waxes such as ethylenediamine behenylamide and tristearyl trimellitate amide.

[0171] The content of the release agent is preferably in the range of 0.1 to 30 parts by mass, more preferably 1 to 10 parts by mass, based on 100 parts by mass of the binder resin. These can be used alone or in combination of two or more. Further, the melting point of the release agent is preferably in the range of 50 to 95°C from the viewpoints of low-temperature fixability and releasability of the toner in electrophotography.

[0172] [3] Charge control agent As the charge control agent, known charge control agent particles that can be dispersed in an aqueous medium can be used. Specifically, nigrosine-based dyes, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, quaternary ammonium salt compounds, azo-based metal complexes, metal salts of salicylic acid, or metal complexes thereof can be mentioned.

[0173] [4] Exterior additive In order to improve the fluidity, chargeability, cleaning property, etc. of the toner, exterior additives such as fluidizing agents and cleaning aids, which are so-called post-treatment agents, can be added to the surface of the toner mother particles.

[0174] The external additive according to the present invention may be one kind or more than one kind. The external additive is not particularly limited, and known ones can be used. For example, silica particles, titania particles, alumina particles, zirconia particles, zinc oxide particles, chromium oxide particles, cerium oxide particles, antimony oxide particles, tungsten oxide particles, tin oxide particles, tellurium oxide particles, manganese oxide particles, and boron oxide particles can be used.

[0175] It is more preferable that the above external additive contains silica particles produced by the sol-gel method. Since the silica particles produced by the sol-gel method have the characteristic of a narrow particle size distribution, they are preferable from the viewpoint of suppressing the variation in the adhesion strength of the external additive to the toner base particles.

[0176] Also, the number average primary particle diameter of the above silica particles is preferably in the range of 70 to 200 nm. The silica particles with the number average primary particle diameter within the above range are larger than other external additives. Therefore, they serve as spacers in the two-component developer. Thus, it is preferable from the viewpoint of preventing smaller other external additives from being embedded in the toner base particles when the two-component developer is being stirred in the developing device. Also, it is preferable from the viewpoint of preventing the fusion of toner base particles with each other.

[0177] The number average primary particle diameter of the above external additive can be determined, for example, by image processing of an image taken with a transmission electron microscope, and can be adjusted, for example, by classification or mixing of classified products.

[0178] It is preferable that the surface of the above external additive is hydrophobically treated. Known surface treatment agents are used for the hydrophobic treatment. The surface treatment agent may be one kind or more than one kind, and examples thereof include silane coupling agents, silicone oils, titanate-based coupling agents, aluminate-based coupling agents, fatty acids, fatty acid metal salts, their esterified products, and rosin acids.

[0179] Examples of the above silane coupling agent include dimethyldimethoxysilane, hexamethyldisilazane (HMDS), methyltrimethoxysilane, isobutyltrimethoxysilane, and decyltrimethoxysilane.

[0180] Examples of the above silicone oil include cyclic compounds, linear or branched organosiloxanes, and the like. More specifically, organosiloxane oligomers, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, tetramethylcyclotetrasiloxane, and tetravinyltetramethylcyclotetrasiloxane are included.

[0181] In addition, examples of the above silicone oil include highly reactive silicone oils modified at least at the ends, with a modifying group introduced at the side chain or one end or both ends, side chain one end, side chain both ends, etc. The type of the above modifying group may be one kind or more than one kind, and examples thereof include alkoxy, carboxyl, carbinol, higher fatty acid modification, phenol, epoxy, methacryl, and amino.

[0182] The addition amount of the above external additive is preferably in the range of 0.1 to 10.0% by mass based on the whole toner particles. More preferably, it is in the range of 1.0 to 3.0% by mass.

[0183] [5] Physical properties of toner particles [5-1] Structure of toner particles The toner base particles according to the present invention may have a single-layer structure of only toner particles, but preferably have a core-shell structure. Thereby, low-temperature fixability and heat-resistant storage stability can be made better.

[0184] The toner base particles having a core-shell structure refer to toner base particles having a multilayer structure including core particles and a shell covering the surface of the core particles. The shell does not necessarily cover the entire surface of the core particles, and the core particles may be partially exposed. The cross-section of the core-shell structure can be confirmed by known observation means such as a transmission electron microscope (TEM) and a scanning probe microscope (SPM).

[0185] In the case of a core-shell structure, the properties such as the glass transition point, melting point, and hardness can be made different between the core particles and the shell, and it is possible to design toner particles according to the purpose. For example, a resin having a relatively high glass transition point can be aggregated and fused on the surface of core particles containing a binder resin, a colorant, a release agent, etc. and having a relatively low glass transition point to form a shell. As the shell, an amorphous polyester resin can be used as described above, and among them, an amorphous polyester resin modified with a styrene-acrylic resin can be preferably used.

[0186] [5-2] Average particle diameter of toner particles The volume average particle diameter (Dv) of the toner particles according to the present invention is preferably in the range of 3.00 to 8.00 μm, more preferably in the range of 4.00 to 6.50 μm.

[0187] In the present invention, the particle diameter of the toner particles is treated as being equal to the particle diameter of the toner base particles.

[0188] The volume average particle diameter can be measured using a measuring device connected to a computer system equipped with Software V4.03 for data processing on a Coulter Multisizer 4e (manufactured by Beckman Coulter, Inc.). Specifically, the measurement is performed as follows.

[0189] First, 0.02 g of the sample (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-fold with pure water for the purpose of dispersing toner particles) and allowed to mix. Then, ultrasonic dispersion treatment is performed for 1 minute to prepare a dispersion of the toner.

[0190] This dispersion of the toner is pipetted into a beaker containing ISOTON II (manufactured by Beckman Coulter) in a sample stand until the display concentration of the measuring device reaches 8%. By setting this concentration, reproducible measurement values can be obtained.

[0191] As the aperture in the Coulter Multisizer, it is necessary to use an appropriate one according to the particle size distribution of the toner. However, for a toner that satisfies the requirements of the present invention, by using an aperture diameter that is about 15 times the most frequent diameter of the volume-based particle size distribution, most of the particles on the small diameter side and the large diameter side can be included in the measurement range.

[0192] Then, in the measuring device, the number of measured particles is set to 25,000, the frequency values are calculated by dividing the standard measurement range of each aperture into 400 logarithmic intervals, and the volume distribution of the toner is measured to calculate the particle size distribution and the volume average particle diameter (Dv). The above measurement range is, for example, a measurement range of 2 to 60 μm when the aperture diameter is 100 μm.

[0193] Similarly, the number average particle diameter (Dn) can be measured using a Coulter Multisizer 4e (manufactured by Beckman Coulter) or the like. The number distribution of the toner is measured to calculate the particle size distribution and the number average particle diameter.

[0194] The ratio Dv / Dn of the volume average particle diameter (Dv) to the number average particle diameter (Dn) of the electrostatic charge image developing toner according to the present invention is preferably in the range of 1.05 to 1.20. In this way, since the particle size distribution of the (small diameter) toner as the main component is sharp, the fluidity of the flowable dam layer becomes good and the cleaning property is improved.

[0195] When the toner has a broad particle size distribution, a stepwise weir layer is formed in the nip portion, and the fluidity of the small-diameter toner present near the nip tip is reduced, thus suppressing the deterioration of the cleaning performance.

[0196] Further, in the particle size distribution based on mass of the toner for electrostatic charge image development, it has at least one maximum value on the larger particle size side than the volume average particle diameter (Dv). Let the particle diameter of the maximum value be Dx, and the particle diameter of the minimum value with a low mass ratio among the minimum values between Dv and Dx be Dy. At this time, it is preferable that Dx and Dy simultaneously satisfy the following formulas (3) and (4).

[0197] Formula (3) 3.0 ≦ Dx / Dv ≦ 6.0 Formula (4) 1.5 ≦ Dy / Dv ≦ 4.0 Furthermore, in the particle size distribution based on mass of the toner for electrostatic charge image development, when the mass ratio at Dx is X and the mass ratio at Dy is Y, it is preferable to further satisfy the following formula (5).

[0198] Formula (5) Y / X ≦ 0.5 The significance of the above formulas (3) to (5) is as follows.

[0199] Here, the particle size distribution based on mass is specifically obtained as follows.

[0200] First, as the sieve mesh, an electroformed sieve with high mesh opening accuracy is used, and sieving is performed with an air jet sieve (manufactured by Hosokawa Alpine, e200LS) for 10 minutes or more until the mass change stops, and the powder mass remaining on the sieve with respect to the total toner mass is obtained.

[0201] Measurement starts with a sieve having a mesh opening corresponding to 6.5 times the volume-based average particle diameter, and measurements are performed with sieves having different mesh openings every 1 μm up to a particle diameter with a mesh opening diameter of 1.5 times the volume-based average particle diameter. Thereby, the full-scale integrated distribution based on mass on the larger diameter side with the mesh opening on the horizontal axis can be obtained.

[0202] By continuously showing the midpoints of each section of the histogram, which has a height proportional to the mass ratio contained in each particle size range per 1 μm from the full-sieved cumulative distribution, the particle size distribution based on mass on the larger diameter side and the maximum and minimum values in the particle size distribution can be obtained. Note that the values of the midpoints of each section, which are representative values, are used for the maximum and minimum values.

[0203] Here, the "maximum value" refers to the point where the value of the mass ratio changes from increasing to decreasing when the value of the particle size is changed in the particle size distribution curve with the particle size on the horizontal axis and the mass ratio on the vertical axis, and the "minimum value" refers to the point where the value of the mass ratio changes from decreasing to increasing.

[0204] Since the particle size component in the region of formula (3) increases the thickness of the dam layer and has a large effect of buffering the impact force on the blade part due to the collision of paper powder etc., it preferably has a maximum value within the range of formula (3).

[0205] At the same time, although the particle size component in the region of formula (4) has an effect of increasing the thickness of the dam layer, it is likely to move through the processes of development and transfer simultaneously with the main component toner. Therefore, since it causes a decrease in the granularity of the image, it preferably has a minimum value within the range of formula (4).

[0206] Furthermore, since it is more likely that the larger diameter component in the region of formula (3) becomes more (within the range of the amount satisfying formula (2)) and the component of formula (4) becomes less, and the cleaning property and image quality can be more surely compatible, it is preferably within the range of the mass ratio represented by formula (5).

[0207] [5-3] Average circularity of toner particles The toner for electrostatic charge image development according to the present invention has an average circularity of toner particles within the range of 0.945 to 0.985, more preferably 0.955 to 0.975, and particularly preferably 0.960 to 0.970. If the average circularity is within the above range, crushing of the toner particles can be suppressed, contamination of the friction charging member can be suppressed, and the chargeability of the toner can be stabilized. In addition, the image formed by the toner has high image quality.

[0208] The above average circularity can be measured as follows. A toner dispersion is prepared in the same manner as when measuring the median diameter. Using FPIA-3000 (manufactured by Sysmex Corporation) or the like, the toner dispersion is photographed in the HPF (high magnification imaging) mode within an appropriate concentration range of 3000 to 10000 HPF detections. Then, the circularity of each toner particle is calculated by the following formula (y).

[0209] The circularities of each toner particle are added, and the average circularity is calculated by dividing the sum of the circularities by the number of each toner particle. If the number of HPF detections is within the above appropriate concentration range, sufficient reproducibility can be obtained. In the following formula (y), L1 represents the perimeter length (μm) of a circle having the same projected area as the particle image, and L2 represents the perimeter length (μm) of the particle projection image.

[0210] Formula (y) Circularity = L1 / L2

[0211] It is preferable that the proportion of toner particles without corners in the toner particles according to the present invention is 50% or more by number. If the proportion of toner having corners is too large, the fluidity in the nip portion is insufficient, and the same toner continues to be stressed, and the torque increases due to the progress of the embedding of the external additive and filming on the photoreceptor is likely to occur. In addition, since excessive stress is applied to the corners and that part is likely to wear, which is also a cause of the occurrence of filming on the photoreceptor, toner particles without corners are preferable.

[0212] In the toner particles constituting the electrostatic charge image developing toner according to the present invention, the proportion of toner particles without corners is preferably 50% or more by number, more preferably 70% or more and 100% or less by number.

[0213] [5-4] Softening point of toner particles From the perspective of low-temperature fixing performance, the softening point of the toner particles is preferably in the range of 80 to 120 °C, more preferably in the range of 95 to 105 °C, and particularly preferably in the range of 97 to 103 °C. The softening point of the toner particles is measured by the flow tester shown below.

[0214] Specifically, first, 1.1 g of a sample (toner particles) is placed in a petri dish, leveled, and left for 12 hours or more in an environment of 20 °C and 50% RH. Then, using a molding machine "SSP-10A" (manufactured by Shimadzu Corporation), it is pressed with a force of 3820 kg / cm 2 (3.75 MPa) for 30 seconds to produce a cylindrical molded sample with a diameter of 1 cm.

[0215] Next, this molded sample is extruded from the hole of the cylindrical die (1 mm diameter × 1 mm) using a piston with a diameter of 1 cm by a flow tester "CFT-500D" (manufactured by Shimadzu Corporation) in an environment of 24 °C and 50% RH starting from the end of preheating. The conditions at this time are a load of 196 N (20 kgf), a starting temperature of 60 °C, a preheating time of 300 seconds, and a heating rate of 6 °C / min.

[0216] Then, the offset method temperature Toffset measured with an offset value of 5 mm set by the melting temperature measurement method of the heating rate method is defined as the above softening point.

Example

[0217] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, the notations "parts" or "%" are used, and unless otherwise specified, they represent "parts by mass" or "% by mass". In the following description, those obtained by subjecting a "colorant solution" to a dispersion treatment are denoted as "colorant particle dispersion liquids" to distinguish the two.

[0218] A. Preparation before toner production (A.1) Preparation of colorant particle dispersion liquid As the colorant particle dispersion liquids, the following colorant particle dispersion liquids [1] to

[20] were prepared.

[0219] (A.1.1) Preparation of Colorant Particle Dispersion [1] (Preparation of Colorant Solution [1]) 90 parts by mass of sodium n-dodecyl sulfate was dissolved in 1600 parts by mass of ion-exchanged water with stirring. While stirring this solution, 420 parts by mass of carbon black "Morgal L" (manufactured by Cabot Corporation, pH 2, room temperature 25°C) was gradually added as a colorant, and further 14 parts by mass of a 25% sodium hydroxide solution was added as a dispersant to prepare a solution, and Colorant Solution [1] was prepared. Note that the residence time in the reaction furnace during the production of the above carbon black "Morgal L" (manufactured by Cabot Corporation, pH 2, room temperature 25°C), that is, the time required for the movement from the raw material introduction point to the reaction stop position, was 80 milliseconds and the acid value was 8.5 mg NaOH / g. In Table I, this carbon black colorant is designated as "CB1".

[0220] 〔Dispersion Treatment〕 Next, the above Colorant Solution [1] was subjected to a dispersion treatment using a mechanical disperser "ClearMix" (manufactured by M. Technique Co., Ltd.) to prepare a colorant particle dispersion [1] in which carbon black particles were dispersed.

[0221] This "ClearMix" has a rotor (stirring blade) that rotates at high speed and a screen (fixed ring) that surrounds this rotor, and has a structure that imparts shear force, collision force, pressure fluctuation, cavitation, and potential core effects to the liquid to be treated. And by the synergistic function of these actions, carbon black particles can be effectively dispersed.

[0222] When the particle size of the colorant particles <1> in the colorant particle dispersion [1] was measured using a microtrack particle size distribution measuring device "UPA-150" (manufactured by Nikkiso Co., Ltd.), the median diameter based on volume was 85 nm.

[0223] (A.1.2) Preparation of Colorant Particle Dispersions [2] to

[20] The coloring agent solutions [1-2] to [1-5], and [2] to [7] were prepared by the following method, and the coloring agent particle dispersions [2] to

[20] were prepared in the combinations shown in Table I. Also, the dispersion treatment times of the coloring agent solutions [1-2] to [1-5], and [2] to [7] were those described in Table I.

[0224] (Preparation of Coloring Agent Solutions [1-2] to [1-5]) For the coloring agent solutions [1-2] to [1-5], the residence times in the reactor during the production of carbon black "Morgal L" (manufactured by Cabot Corporation, pH 2, room temperature 25°C) were set to 50 milliseconds, 170 milliseconds, 45 milliseconds, and 180 milliseconds as shown in Table I. And the acid values were set to 5.0 mg NaOH / g, 14.0 mg NaOH / g, 4.9 mg NaOH / g, and 14.1 mg NaOH / g. In Table I, these carbon black coloring agents are designated as "CB2", "CB3", "CB4", and "CB5".

[0225] (Preparation of Coloring Agent Solutions [2] to [6]) For the coloring agent solution [2], it was prepared in the same manner as the preparation of the coloring agent solution [1], except that 10 parts by mass of a 25% sodium hydroxide solution was added as a dispersant.

[0226] For the coloring agent solution [3], it was prepared in the same manner as the preparation of the coloring agent solution [1], except that 17 parts by mass of a 25% sodium hydroxide solution was added as a dispersant.

[0227] For the coloring agent solution [4], it was prepared in the same manner as the preparation of the coloring agent solution [1], except that 8 parts by mass of a 25% sodium hydroxide solution was added as a dispersant.

[0228] For the coloring agent solution [5], it was prepared in the same manner as the preparation of the coloring agent solution [1], except that 18 parts by mass of a 25% sodium hydroxide solution was added as a dispersant.

[0229] For the coloring agent solution [6], it was prepared in the same manner as the preparation of the coloring agent solution [1], except that no 25% sodium hydroxide solution was added as a dispersant.

[0230] (Preparation of Colorant Solution [7]) Regarding the colorant solution [7], it was prepared in the same manner as the preparation of the colorant solution [1], except that 420 parts by mass of quinoline yellow (manufactured by Daiwa Kasei Co., Ltd.) was gradually added as a colorant instead of carbon black, and 3 parts by mass of a 25% sodium hydroxide solution was added as a dispersant.

[0231]

Table 1

[0232] (A.2) Preparation of Resin As the resin used for the preparation of the toner, the following crystalline polyester [1] was prepared in advance.

[0233] (Preparation of Crystalline Polyester [1]) A mixed solution containing 300 g of 1,9-nonanediol, 250 g of dodecanedioic acid, and a catalyst Ti(OBu) 4 (0.014% by mass based on the carboxylic acid monomer) was prepared in a three-necked flask, and then the air in the container was decompressed by a decompression operation.

[0234] Furthermore, nitrogen gas was introduced into the three-necked flask to make the inside of the flask an inert atmosphere, and the above mixed solution was refluxed at 180 °C for 6 hours while being mechanically stirred. Then, unreacted monomer components were removed by vacuum distillation, and the temperature was gradually raised to 220 °C and stirred for 12 hours.

[0235] When it became viscous, it was cooled to prepare crystalline polyester [1]. The weight average molecular weight (Mw) of crystalline polyester [1] was 19,500. Also, the melting point of crystalline polyester [1] was 75 °C. The measurement of the weight average molecular weight (Mw) and the melting point measurement were carried out as follows.

[0236] 〔Measurement of Weight Average Molecular Weight〕 The GPC apparatus "HLC-8220" (manufactured by Tosoh Corporation) and the column "TSKguardcolumn + TSKgel SuperHZM-M3 series" (manufactured by Tosoh Corporation) were used. With these, while maintaining the column temperature at 40°C, tetrahydrofuran (THF) was flowed as the carrier solvent at a flow rate of 0.2 mL / min, and 10 μL of the sample solution was injected into the above apparatus.

[0237] Then, detection was performed using a refractive index detector (RI detector), and the molecular weight distribution of the measurement sample was determined by calculating using a calibration curve measured using monodisperse polystyrene standard particles.

[0238] 〔Measurement of melting point of crystalline resin〕 The melting point of the crystalline resin was measured by the following method using a differential scanning calorimeter "Diamond DSC" (manufactured by PerkinElmer).

[0239] 3.0 mg of the sample was sealed in an aluminum pan and set in a holder, and an empty aluminum pan was set as a reference.

[0240] DSC curves were obtained under the measurement conditions (heating and cooling conditions) that go through the first heating process, cooling process, and second heating process in this order. The details of the above first heating process, cooling process, and second heating process are as follows.

[0241] · First heating process: The process of heating from 0°C to 200°C at a rate of 10°C / min · Cooling process: The process of cooling from 200°C to 0°C at a rate of 10°C / min · Second heating process: The process of heating from 0°C to 200°C at a rate of 10°C / min

[0242] Then, based on this DSC curve, the endothermic peak top temperature derived from the crystalline polyester in the first heating process was taken as the melting point.

[0243] B. Preparation of toner (B.1) Preparation of toner 1 (B.1.1) Preparation of Dispersion of Resin Particles [L3] for Core A dispersion of resin microparticles (resin particles [L3] for core) in which binder resin microparticles containing an internal additive were dispersed was prepared by the following first-stage polymerization to third-stage polymerization.

[0244] (1) Preparation of Dispersion of Resin Particles [L1] (First-Stage Polymerization) A 5 L reaction vessel equipped with a stirring device, a temperature sensor, a cooling tube, and a nitrogen introduction device was charged with 4 g of sodium polyoxyethylene (2) dodecyl ether sulfate and 3000 g of ion-exchanged water to obtain a mixture [1].

[0245] Then, while stirring the mixture [1] at a stirring speed of 230 rpm under a nitrogen stream, the temperature of the mixture [1] was raised to 80°C. After the temperature was raised, a solution prepared by dissolving 10 g of potassium persulfate in 200 g of ion-exchanged water was added. Then, the liquid temperature was set to 75°C, and the following monomer [a] was added dropwise over 1 hour.

[0246] [Monomer [a]] Styrene 568 g n-Butyl acrylate 164 g Methacrylic acid 68 g

[0247] Thereafter, the mixture was heated and stirred at 75°C for 2 hours to polymerize the above monomers, thereby preparing a dispersion of resin particles [L1].

[0248] (2) Preparation of Dispersion of Resin Particles [L2] (Second-Stage Polymerization) A 5 L reaction vessel equipped with a stirring device, a temperature sensor, a cooling tube, and a nitrogen introduction device was charged with a solution prepared by dissolving 2 g of sodium polyoxyethylene (2) dodecyl ether sulfate in 3000 g of ion-exchanged water, and the resulting mixture was heated to 80°C to obtain a mixture [2]. On the other hand, the following monomer [b] was dissolved at 80°C to prepare a solution [3] consisting of the monomer [b].

[0249] [Monomer [b]] Resin particles [L1] 42 g (in terms of solid content) 70 g of behenyl behenate 70 g of crystalline polyester [1] 195 g of styrene 91 g of n-butyl acrylate 20 g of methacrylic acid 3 g of n-octyl mercaptan

[0250] Thereafter, the solution [3] composed of the above monomer [b] was added to the above mixture [2], and dispersed and mixed for 1 hour by a mechanical disperser "CLEARMIX" (manufactured by M Technique Co., Ltd.) having a circulation path to prepare a dispersion [4] containing emulsified particles (oil droplets).

[0251] Next, an initiator solution was prepared by dissolving 5 g of potassium persulfate in 100 g of ion-exchanged water. This was added to the dispersion [4] containing the above emulsified particles (oil droplets), and the mixture was heated and stirred at 80°C for 1 hour to polymerize the above monomer [b], thereby preparing a dispersion of resin particles [L2].

[0252] (3) Preparation of dispersion of core resin particles [L3] (third-stage polymerization) To the dispersion of the above resin particles [L2], a solution prepared by dissolving 10 g of potassium persulfate in 200 g of ion-exchanged water was further added, and the resulting dispersion was maintained at 80°C, and the following monomer [c] was dropped into the dispersion over 1 hour.

[0253] [Monomer [c]] 298 g of styrene 137 g of n-butyl acrylate 50 g of n-stearyl acrylate 64 g of methacrylic acid 6 g of n-octyl mercaptan

[0254] After completion of the dropping, the resulting dispersion was heated and stirred for 2 hours to polymerize the above monomer [c]. Thereafter, the dispersion was cooled to 28°C to prepare a dispersion of core resin particles [L3].

[0255] (B.1.2) Preparation of Dispersion of Resin Particles for Shell [S1] Into a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction device, a surfactant solution prepared by dissolving 2.0 g of sodium polyoxyethylene dodecyl ether sulfate in 3000 g of ion-exchanged water was charged. Then, while stirring at a stirring speed of 230 rpm under a nitrogen stream, the temperature of the surfactant solution was raised to 80 °C.

[0256] To this surfactant solution, an initiator solution prepared by dissolving 10 g of potassium persulfate in 200 g of ion-exchanged water was added and mixed to obtain a mixed solution. To this mixed solution, the following monomer [d] was added dropwise over 3 hours.

[0257] <Monomer [d]> Styrene 564 g n-Butyl acrylate 140 g Methacrylic acid 96 g n-Octyl mercaptan 12 g

[0258] After the dropwise addition, the obtained mixed solution was heated and stirred at 80 °C for 1 hour to polymerize the above monomer [d], and a dispersion of resin particles for shell [S1] was prepared.

[0259] (B.1.3) Preparation of Core-Shell Particles [1] (Aggregation / Fusion Process) (Preparation of Core Particle Dispersion) Into a 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction device, 360 g (in terms of solid content) of a dispersion of resin particles for core [L3], 1100 g of ion-exchanged water, and 40 g of the colored agent particle dispersion [1] prepared as described above were charged. Then, after adjusting the temperature of the obtained dispersion to 30 °C, a 5N aqueous sodium hydroxide solution was added to the dispersion to adjust the dispersion to pH 10 at room temperature of 25 °C.

[0260] Next, an aqueous solution prepared by dissolving 60 g of magnesium chloride in 60 g of ion-exchanged water was added to the above dispersion with stirring at 30°C over 10 minutes. After the addition, the dispersion was held at 30°C for 3 minutes and then the temperature was raised. The above dispersion was heated to 85°C over 60 minutes, and the particle growth reaction was continued while maintaining the temperature of the dispersion at 85°C. Thereby, a dispersion of core particles [1] was prepared.

[0261] (Formation of shell layer) 80 g (in terms of solid content) of resin particles [S1] for the shell was added thereto, and stirring was continued at 80°C for 1 hour to fuse the resin particles [S1] for the shell to the surface of the core particles [1] to form a shell layer, thereby obtaining a resin particle dispersion [1] containing core-shell particles [a].

[0262] (Production of core-shell particles) Here, an aqueous solution prepared by dissolving 150 g of sodium chloride in 600 g of ion-exchanged water was added to the obtained resin particle dispersion [1], and aging treatment was performed at a liquid temperature of 80°C. When the average circularity of the core-shell particles [a] in the resin particle dispersion [1] reached 0.960, it was cooled to 30°C to produce core-shell particles [1]. The volume-based median diameter of the core-shell particles [1] after cooling was 5.5 μm.

[0263] <Measurement and calculation method of median diameter based on number> The median diameter of the core-shell particles based on the number is the median diameter in the number particle size distribution, and was measured and calculated by the following measurement procedure using an apparatus in which a computer system for data processing was connected to "Multisizer 3 (manufactured by Beckman Coulter, Inc.)".

[0264] First, 0.02 g of the core-shell particles was wetted with 20 mL of a surfactant solution (a surfactant solution prepared by diluting a neutral detergent containing a surfactant component 10-fold with pure water for the purpose of dispersing the core-shell particles), and then ultrasonic dispersion was performed for 1 minute. Thereby, a core-shell particle dispersion was prepared.

[0265] This core-shell particle dispersion was pipetted into a beaker containing ISOTON II (manufactured by Beckman Coulter) in a sample stand until the measurement concentration reached 5 - 10%.

[0266] Here, by setting the concentration within this range, reproducible measurement values can be obtained. Then, the measured particle count was set to 25,000, the aperture diameter of the Multi-Sizer 3 (manufactured by Beckman Coulter) was set to 100 μm, and the frequency distribution was calculated by dividing the measurement range of 1 - 30 μm into 256 segments. And the particle size at which the cumulative fraction by number was 50% starting from the larger side was taken as the median diameter on a number basis.

[0267] <Method for Measuring Average Circularity> The average circularity of the core-shell particles is the value measured using the flow-type particle image analyzer "FPIA-3000" (manufactured by Sysmex).

[0268] Specifically, the core-shell particles were wetted with an aqueous surfactant solution and subjected to ultrasonic dispersion for 1 minute. After dispersion, using the "FPIA-3000", measurements were carried out at an appropriate concentration with 3000 - 10000 HPF detection counts in the HPF (high magnification imaging) mode. Within this range, reproducible measurement values can be obtained. The circularity was calculated using the following formula.

[0269] Formula: Circularity of core-shell particles = (Perimeter of a circle having the same projected area as the particle image) / (Perimeter of the particle projection image)

[0270] Here, the average circularity is the arithmetic mean value obtained by adding up the circularities of each particle and dividing by the total number of particles measured.

[0271] (B.1.4) Preparation of Toner Base Particles [1] (Washing and Drying Process) The dispersion of the core-shell particles [1] generated in the aggregation and fusion process was separated by solid-liquid separation using a centrifuge to form a wet cake of the core-shell particles [1]. The wet cake was washed with ion-exchanged water at 35 °C using the centrifuge until the electrical conductivity of the filtrate reached 5 μS / cm.

[0272] Thereafter, it was transferred to a "Flash Jet Dryer" (manufactured by Seishin Enterprise Co., Ltd.) and dried until the moisture content reached 0.8% by mass to produce toner base particles [1].

[0273] (B.1.5) Addition of external additive To the obtained toner base particles [1], 1% by mass of hydrophobic silica particles (number-average secondary particle diameter: 30 μm, number-average primary particle diameter: 50 to 200 nm) and 1.2% by mass of hydrophobic titanium oxide particles (number-average secondary particle diameter: 20 μm, number-average primary particle diameter: 50 to 200 nm) were added.

[0274] Then, using a Henschel mixer, mixing was carried out for 20 minutes under the condition of a peripheral speed of the rotating blade of 24 m / s, and the external additive was added by passing through a 400-mesh sieve to produce toner [1]. In the table II, the said external additive is designated as external additive 1.

[0275] (B.2) Preparation of toners [2] to [5] Toners [2] to [5] were produced in the same manner as toner [1], except that the type of the colorant solution and the addition amount of the dispersant were changed as shown in Table I to prepare colorant particle dispersions [2] to [5].

[0276] (B.3) Preparation of toners [6] to

[10] Toners [6] to

[10] were produced in the same manner as toner [1], except that the type of the dispersant was changed from sodium hydroxide to calcium hydroxide as shown in Table II to prepare colorant particle dispersions [6] to

[10] .

[0277] (B.4) Preparation of toners

[11] to

[14] Using colorant solutions [1-2] to [1-5] in which the acid value of carbon black particles was changed by setting the residence time in the reactor during the production of carbon black as the colorant as shown in Table I, toners

[11] to

[14] were produced in the same manner as toner [1], except that colorant particle dispersions

[11] to

[14] were prepared.

[0278] (B.5) Preparation of Toners

[15] to

[18] Toners

[15] to

[18] were prepared in the same manner as toner [1], except that the dispersion treatment time was as shown in Table II, and colorant particle dispersions

[15] to

[18] were prepared.

[0279] (B.6) Preparation of Toner

[19] Toner

[19] was prepared in the same manner as toner [1], except that colorant solution [6] was used, the external additive formulation was as follows, and colorant particle dispersion [1] was changed to colorant particle dispersion

[19] as shown in Table II.

[0280] (External Additive Formulation) To 100 parts by mass of the toner base, 0.15 part by mass of composite oxide particles 1 mixed so that the Mg / Al element ratio was 3.0 and 0.6 part by mass of hydrophobic silica fine particles (number average primary particle size = 10 nm) were added. Then, using a "Henschel mixer" (manufactured by Mitsui Miike Seisakusho), mixing was performed at a peripheral speed of 35 m / sec for 25 minutes. This external additive was used as external additive 2 in Table II.

[0281] (B.7) Preparation of Toner

[20] Toner

[20] was prepared in the same manner as toner [1], except that colorant solution [7] using quinoline yellow (manufactured by Daiwa Kasei) instead of carbon black was used, and colorant particle dispersion [1] was changed to colorant particle dispersion

[20] as shown in Table II.

[0282] C. Evaluation (C.1) Resistance to Crushing (Evaluation Method) The particle size distribution of each prepared toner was measured using "FPIA - 2100", and the amount (number %) of toner particles (crushed toner particles) with a particle size of 2 μm or less was calculated.

[0283] The resistance to crushing was evaluated according to the following criteria based on the amount of crushed toner particles. The evaluation results are shown in Table II. Note that A and B were considered qualified.

[0284] (Evaluation Criteria) A: Less than 2.0% by number. B: 2.0% or more and less than 4.0% by number. C: 4.0% or more by number.

[0285] (C.2) Fixing property (Evaluation method) For image formation, a commercially available multifunction printer "bizhub PRO C6500" (manufactured by Konica Minolta Business Technologies, Inc.) was used.

[0286] Each toner produced was set in the above multifunction printer, and a solid image with a relative density (image density) of 0.8 with respect to white paper was fixed at a fixing temperature of 160 °C on paper "NPi Premium Paper 128 g / m 2 "(manufactured by Nippon Paper Industries Co., Ltd.) to obtain a test print.

[0287] Specifically, when the fixed image of the toner was bent with the inner surface facing inward, the degree of toner peeling at the bent portion was evaluated as the fixing rate.

[0288] The above fixing rate is a value calculated by the following formula from the image densities before and after bending at the fold of the solid image portion after folding the solid image portion with the image surface inside, rubbing it three times with fingers, opening the image, and wiping it three times with a "JK wiper" (manufactured by Kuresia Co., Ltd.).

[0289] Fixing rate [%] = (image density after bending) / (image density before bending) × 100

[0290] From the obtained fixing rate, the fold fixing strength was evaluated as follows. The evaluation results are shown in Table II. Note that A and B were considered qualified.

[0291] (Evaluation criteria) A: The fixing rate at the fold was within the range of 90 to 100% at each temperature. B: The fixing rate at the fold was 80 to less than 90% at each temperature. C: There was one where the fixing rate at the fold was less than 80%.

[0292]

Table 2

[0293] D. General Evaluation As is clear from Table II, it can be seen that the examples are superior to the comparative examples in terms of crush resistance and fixing property.

Claims

1. A method for manufacturing a toner for electrostatic charge image development containing at least toner particles, wherein the toner particles are produced using a dispersion liquid containing at least colorant particles, the dispersion liquid contains a colorant, a dispersant, an aqueous medium, and a surfactant, the Rsp value of the dispersion liquid is within the range of 3.0 to 4.5, and the toner particles are produced by fusing resin particles and the colorant particles using a divalent or higher cation. A method for manufacturing a toner for electrostatic charge image development, characterized by the above.

2. The dispersant is an alkaline solution. A method for manufacturing a toner for electrostatic charge image development according to Claim 1, characterized by the above.

3. The alkaline solution contains at least sodium hydroxide. A method for manufacturing a toner for electrostatic charge image development according to Claim 2, characterized by the above.

4. The dielectric loss tangent tanδ measured at a frequency of 100 kHz in an environment of a temperature of 25°C and a relative humidity of 50% RH is within the range of 0.02 to 0.

04. A method for manufacturing a toner for electrostatic charge image development according to Claim 1, characterized by the above.

5. The colorant is carbon black having an acid value within the range of 5.0 to 14.0 mg NaOH / g. A method for manufacturing a toner for electrostatic charge image development according to Claim 1, characterized by the above.

6. A toner for electrostatic charge image development containing at least toner particles, wherein the toner particles contain at least composite particles of resin particles and colorant particles, the composite particles are composite particles fused by a divalent or higher cation, and the dielectric loss tangent tanδ measured at a frequency of 100 kHz in an environment of a temperature of 25°C and a relative humidity of 50% RH is within the range of 0.02 to 0.

04. A toner for electrostatic charge image development, characterized by the above.

7. The colorant particles are carbon black particles having an acid value within the range of 5.0 to 14.0 mg NaOH / g. A toner for electrostatic charge image development according to Claim 6, characterized by the above.

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