Toner for developing electrostatic images, its manufacturing method and electrophotographic image forming method

Abstract

To provide toner for electrostatic charge image development that is excellent in low temperature fixability, prevents tacking, and can reduce glossiness of a fixed image, a method for manufacturing the same, and an electrophotographic image forming method.SOLUTION: Toner for electrostatic charge image development includes a toner base particle that contains at least a binder resin and a mold release agent. A molecular weight that is obtained by gel-permeation chromatography and corresponds to a main peak top of a molecular weight distribution curve of a constituent of the toner for electrostatic charge image development is 15,000 or more. In comparison between area ratios of peaks in the molecular weight distribution curve, the binder resin contains an amorphous material of a low molecular weight component having a weight average molecular weight of 300 or more and less than 1,000 within an area ratio range of 10-20% based on the total amount of the binder resin.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a toner for developing electrostatic images, a method for producing the same, and a method for forming an electrophotographic image, and more particularly to a toner for developing electrostatic images which has excellent low-temperature fixing properties, prevents tackiness, and can suppress the gloss of fixed images. [Background technology]

[0002] In recent years, due to market demands for faster and more energy-efficient image forming apparatuses, there has been a demand for electrostatic image developing toners (hereinafter simply referred to as "toners") that have excellent low-temperature fixing properties and can provide high-quality images. In the case of toner, lowering the melting temperature or melt viscosity of the binder resin can achieve low-temperature fixing, but this can cause problems such as the wax contained in the toner being more likely to seep out onto the image, making the gloss of the image too high and exceeding the desired range.

[0003] For example, Patent Document 1 discloses a method of using a polyester resin having sharp melting properties as the binder resin of a toner, or a crystalline resin that has the property of suddenly softening from a crystallized state at the melting point and ensures heat-resistant storage below the melting point. However, the pursuit of low-temperature fixability has led to a problem that the melt viscosity of the toner is rapidly reduced, resulting in high gloss of the fixed image.

[0004] Furthermore, Patent Document 2 discloses that a toner having a core-shell structure consisting of a core containing a first polyester resin and a shell layer containing a second polyester resin having a high content of metaphenylene skeletons can achieve both sufficient low-temperature fixing property and excellent heat-resistant storage stability, and can form fixed images with low gloss. However, since the toner described in Patent Document 2 provides a low-gloss image, it is necessary to change the toner when a high-gloss image is desired.

[0005] Furthermore, as described above, when low-temperature fixing is attempted by lowering the melting temperature or melt viscosity of the binder resin using a crystalline substance, there is a problem that tacking occurs on the paper discharge tray of the image forming apparatus. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2014-174262 A [Patent Document 2] JP 2015-121661 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above problems and circumstances, and an object of the present invention is to provide a toner for developing electrostatic images, which has excellent low-temperature fixing properties, prevents tackiness, and suppresses the gloss of fixed images, a method for producing the toner, and a method for forming an electrophotographic image. [Means for solving the problem]

[0008] In order to solve the above problems, the present inventors have investigated the causes of the above problems and have found that the above problems can be solved by controlling, within a certain range, the molecular weight corresponding to the main peak top of the molecular weight distribution curve of the components of a toner for developing electrostatic images and the area ratio of the peak of the amorphous material of the low molecular weight component in the molecular weight distribution curve, and have arrived at the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0009] 1. A toner for developing electrostatic images, comprising toner base particles containing at least a binder resin and a release agent, wherein the molecular weight corresponding to the main peak top of a molecular weight distribution curve of the components of the toner for developing electrostatic images, obtained by gel permeation chromatography, is 15,000 or more, and in comparison of the area ratios of each peak in the molecular weight distribution curve, the binder resin contains an amorphous material of a low molecular weight component having a weight average molecular weight of 300 or more and less than 1,000 within an area ratio range of 10 to 20% relative to the total amount of the binder resin. The content ratio of the release agent to the amorphous material of the low molecular weight component is within a range of 0.5 to 0.7. 2. A toner for developing electrostatic images.

[0010] 2. The toner for developing electrostatic images according to claim 1, wherein the binder resin contains a styrene-acrylic resin.

[0011] 3. The toner for developing electrostatic images according to item 1 or 2, wherein the release agent is an ester wax.

[0013] 4 .Items 1 to 5 3 Item 1. A method for producing a toner for developing an electrostatic image according to any one of items 1 to 9, wherein the toner base particles are produced by an emulsion aggregation method having at least a maturing step.

[0014] 5 The aging step is carried out at a temperature within a range of −5 to 15° C. below the melting point of the release agent. 4 2. A method for producing the toner for developing electrostatic images according to claim 1.

[0015] 6 An electrophotographic image forming method having at least an image carrier charging step, an electrostatic latent image forming step, an electrostatic latent image developing step, a toner image transferring step, a toner image fixing step, and a cleaning step, comprising the steps of: 3 3. An electrophotographic image forming method, comprising using the toner for developing an electrostatic image according to claim 1. Effect of the Invention

[0016] According to the above-mentioned means of the present invention, it is possible to provide a toner for developing electrostatic images, which has excellent low-temperature fixing property, prevents tackiness, and suppresses the gloss of fixed images, a method for producing the toner, and a method for forming an electrophotographic image. Although the mechanism by which the effects of the present invention are expressed or the mechanism of action has not been clarified, it is speculated as follows.

[0017] It is believed that if the molecular weight of the components of the toner for developing electrostatic images is large, the decrease in the melt viscosity of the binder resin due to the heat applied during image fixing can be suppressed, and the fixed image will not be smooth and will have low gloss. Therefore, in the present invention, the molecular weight corresponding to the main peak top of the molecular weight distribution curve of the components of the toner for developing electrostatic images, obtained by gel permeation chromatography, is set to 15,000 or more, thereby making the fixed image low gloss. In addition, since the low molecular weight component is amorphous, tacking can be suppressed. Therefore, by introducing an amorphous material of a low molecular weight component having an average molecular weight of 300 or more and less than 1000 as an additive into the toner for developing electrostatic images so that the amount of the amorphous material is within a range of 10 to 20% of the total amount of the binder resin in comparison of the area ratio of each peak in the molecular weight distribution curve, the sharp melt property of the toner is improved. [Brief description of the drawings]

[0018] [Figure 1] Schematic diagram showing the relationship between the molecular weight distribution curve and peaks [Diagram 2] Schematic diagram for understanding the improvement of sharp melting property of toner [Diagram 3] FIG. 1 is a schematic cross-sectional view showing an example of an internal configuration of an image forming apparatus main body. [Figure 4] FIG. 1 is a diagram for explaining a method for evaluating tacking in the examples. [Diagram 5] FIG. 1 is a diagram for explaining a method for evaluating tacking in the examples. [Figure 6] FIG. 1 is a diagram for explaining a method for evaluating tacking in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The toner for developing electrostatic images of the present invention is a toner for developing electrostatic images comprising toner base particles containing at least a binder resin and a release agent, characterized in that a molecular weight corresponding to a main peak top of a molecular weight distribution curve of components of the toner for developing electrostatic images obtained by gel permeation chromatography is 15,000 or more, and in that, in comparison of the area ratios of each peak in the molecular weight distribution curve, the binder resin contains an amorphous material of a low molecular weight component having a weight average molecular weight of 300 or more and less than 1000 within an area ratio range of 10 to 20% relative to the total amount of the binder resin. This feature is a technical feature common to or corresponding to each of the following embodiments (aspects).

[0020] As an embodiment of the present invention, it is preferable that the binder resin contains a styrene-acrylic resin from the viewpoint of the balance of thermal properties, exudation of the release agent, and compatibility with additives.

[0021] The release agent is preferably an ester wax from the viewpoint of improving the sharp melting property of the toner.

[0022] From the viewpoint of achieving both high gloss and low-temperature fixability of an image, it is preferable that the content ratio of the release agent to the amorphous material of the low-molecular-weight component is within a range of 0.5 to 0.7.

[0023] It is preferable to produce the toner base particles by an emulsion aggregation method having at least an aging step from the viewpoints of uniformity of particle size, controllability of shape, and ease of forming a core-shell structure or a domain-matrix structure.

[0024] It is preferable to carry out the aging step at a temperature within a range of −5 to 15° C. lower than the melting point of the release agent, from the viewpoints of suppressing the glossiness and ensuring releasability from the fixing belt.

[0025] The toner for developing electrostatic images of the present invention is suitably used in an electrophotographic image forming method (hereinafter also referred to as an "image forming method").

[0026] The present invention, its components, and embodiments for carrying out the present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after the symbol "to" are included as the lower limit and upper limit.

[0027] [Outline of the toner for developing electrostatic images of the present invention] The toner for developing electrostatic images of the present invention (hereinafter, also simply referred to as "toner") is a toner for developing electrostatic images comprising toner base particles containing at least a binder resin and a release agent, characterized in that the molecular weight corresponding to the main peak top of a molecular weight distribution curve of the components of the toner for developing electrostatic images obtained by gel permeation chromatography is 15,000 or more, and in comparison of the area ratios of each peak in the molecular weight distribution curve, the binder resin contains an amorphous material of a low molecular weight component having a weight average molecular weight of 300 or more and less than 1000 within an area ratio range of 10 to 20% relative to the total amount of the binder resin.

[0028] (Top of the main peak) In this specification, the term "main peak" refers to a peak having the maximum area ratio, preferably a peak having an area ratio of 50% or more, among peaks in a molecular weight distribution curve of the components of the toner for developing electrostatic images, obtained by gel permeation chromatography (hereinafter also referred to as "GPC") (see FIG. 1), and the term "main peak top" refers to a point at which the vertical coordinate value is the largest, i.e., the maximum value, in the main peak of the molecular weight distribution curve. The term "peak" means "a portion protruding from the baseline" and refers to a maximum point in a molecular weight distribution curve. In the present invention, a "peak" is defined as a portion having an area of ​​3% or more of the entire peak area of ​​the molecular weight distribution curve obtained by the above GPC measurement.

[0029] (Method of calculating molecular weight) The molecular weight corresponding to the main peak top of the molecular weight distribution curve of the components of the toner for developing electrostatic images can be calculated from the molecular weight of the components of the toner for developing electrostatic images calculated in terms of polystyrene by GPC from an integrated molecular weight distribution curve by GPC. In addition, the content ratio of the amorphous material of a low molecular weight component having a weight average molecular weight of 300 or more and less than 1000 to the total amount of the binder resin can also be calculated by the same method as above, and appears as a subpeak or a shoulder of the main peak in the molecular weight distribution curve (see Figure 1). For example, when a peak top appears in the portion marked "Low" in FIG. 1, it can be determined that the sample contains a low molecular weight component having a weight average molecular weight of 300 or more and less than 1,000. The term "sub-peak" refers to a peak other than the main peak in the molecular weight distribution curve.

[0030] (Molecular weight distribution curve obtained by GPC) In the present invention, the molecular weight distribution curve of the components of the toner for developing electrostatic images measured by GPC is determined as follows.

[0031] All components of the toner for developing electrostatic images are added to tetrahydrofuran (THF) to a concentration of 1 mg / mL, and the mixture is dispersed for 15 minutes at 40°C using an ultrasonic disperser. The mixture is then passed through a membrane filter with a pore size of 0.2 μm to prepare a sample solution. Using a GPC apparatus HLC-8220GPC (manufactured by Tosoh Corporation) and a column TSKguardcolumn+TSKgel SuperHZM-M triplet (manufactured by Tosoh Corporation), the column temperature was maintained at 40° C., and tetrahydrofuran was run as a carrier solvent at a flow rate of 0.2 mL / min. Inject 10 μL of the prepared sample solution together with the carrier solvent into the GPC device, detect the sample using a refractive index detector (RI detector), and calculate the molecular weight distribution of the sample using a calibration curve measured using monodisperse polystyrene standard particles. The calibration curve is for molecular weights of 6 × 10 2 , 2.1×10 3 , 4×103 , 1.75×10 4 , 5.1×10 4 , 1.1×10 5 , 3.9×10 5 , 8.6×10 5 , 2×10 6 , 4.48×10 6 This is prepared by measuring ten polystyrene standard particles (manufactured by Pressure Chemical Co.). At this time, when a peak due to the above-mentioned filter was confirmed in the data analysis, the region before the peak was set as the baseline.

[0032] In addition, a molecular weight distribution curve can be obtained by plotting the molecular weight distribution obtained as described above on a graph with molecular weight (logarithmic) on the X-axis and signal intensity (the sum of the peak areas is 1) on the Y-axis (see Figure 1). In the molecular weight distribution curve, the peak area in each molecular weight range indicates the mass fraction.

[0033] (Amorphous materials) The amorphous material according to the present invention includes, for example, an amorphous resin, a thermoplastic elastomer, and a low molecular weight natural rubber, and contains an additive having a different composition from the main resin. The binder resin according to the present invention contains an amorphous material of a low molecular weight component having a weight average molecular weight of 300 or more and less than 1000 in an area ratio within a range of 10 to 20% relative to the total amount of the binder resin, in comparison of the area ratio of each peak in the molecular weight distribution curve. If the ratio is less than 10%, low-temperature fixability cannot be ensured, whereas if the ratio is more than 30%, the increase in the glossiness of the image cannot be suppressed.

[0034] 1. Toner base particles The toner base particles according to the present invention may contain other components such as other colorants, charge control agents, and external additives in addition to the binder resin and release agent. In the present invention, the term "toner particles" refers to toner base particles to which an external additive has been added, and an aggregate of toner particles is called "toner". Generally, the toner base particles can be used as they are as toner particles, but in the present invention, the toner base particles to which an external additive has been added are used as toner particles. In the following description, when there is no need to particularly distinguish between toner base particles and toner particles, they are also simply referred to as "toner particles". Hereinafter, each of the constituent materials of the toner base particles according to the present invention will be described in detail.

[0035] (1.1) Binder resin "Binding resin (also called "binder resin")" refers to a resin that is used as a medium or matrix (parent body) for dispersing and retaining internal additives (wax, charge control agent, pigment, etc.) and external additives (silica, titanium oxide, etc.) contained in toner particles, and has the function of adhering to a recording medium (e.g. paper) during the fixing process of a toner image.

[0036] The toner for developing electrostatic images of the present invention is a toner for developing electrostatic images comprising toner base particles containing at least a binder resin and a release agent, and is characterized in that the molecular weight corresponding to the main peak top of a molecular weight distribution curve of the components of the toner for developing electrostatic images obtained by gel permeation chromatography is 15,000 or more. The main peak is derived from the binder resin, and in the present invention, it is preferable that at least an amorphous resin is contained.

[0037] It is preferable that the amorphous resin contains a styrene-acrylic resin from the viewpoint of the balance between thermal properties, exudation of the release agent, and compatibility with additives. In addition, when the binder resin is a styrene-acrylic resin and the release agent is an ester-based agent, the compatibility of the three, including the low molecular weight amorphous material, is well balanced, making it easier to achieve low temperature fixing properties, suppression of tacking, and low gloss. In the toner of the present invention, as the binder resin, a conventionally known binder resin, such as an amorphous resin or a crystalline resin, can be used.

[0038] (1.1.1) Amorphous resin The amorphous resin according to the present invention is a resin that does not have crystallinity, as described below. For example, an amorphous resin is a resin that does not have a melting point and has a relatively high glass transition temperature (Tg) when differential scanning calorimetry (DSC) of the amorphous resin or toner particles is performed.

[0039] The Tg of the amorphous resin is preferably within the range of 35 to 80°C, and more preferably within the range of 45 to 65°C.

[0040] The glass transition temperature can be measured in accordance with the method (DSC method) specified in ASTM (American Society for Testing and Materials) D3418-82. For the measurement, a DSC-7 differential scanning calorimeter (manufactured by PerkinElmer), a TAC7 / DX thermal analyzer controller (manufactured by PerkinElmer), or the like can be used.

[0041] The amorphous resin may be one or more kinds. Examples of the amorphous resin include vinyl resin, urethane resin, urea resin, and amorphous polyester resin such as styrene-acrylic modified polyester.

[0042] In the present invention, from the viewpoint of easily controlling thermoplasticity, the amorphous resin preferably contains a vinyl resin as a main component in the binder resin, and preferably also contains an amorphous polyester resin.

[0043] The electrostatic image developing toner of the present invention is characterized in that the molecular weight corresponding to the main peak top of the molecular weight distribution curve of its constituent components is 15,000 or more, and when an amorphous resin is used as the amorphous material of the low molecular weight component, the weight average molecular weight of the amorphous resin is 300 or more and less than 1,000. The number average molecular weight (Mn) of the amorphous resin as the main resin is preferably within a range of 5,000 to 150,000, and more preferably within a range of 8,000 to 70,000. The molecular weight of the amorphous resin can be measured in the same manner as in the above-mentioned method for measuring the molecular weight distribution.

[0044] (Vinyl resin) The vinyl resin is, for example, a polymer of a vinyl compound, and examples thereof include an acrylic ester resin, a styrene-acrylic ester resin, and an ethylene-vinyl acetate resin. Among these, styrene-acrylic ester resins (styrene-acrylic resins) are preferred from the viewpoint of plasticity during thermal fixing.

[0045] Styrene-acrylic resin Styrene-acrylic resin is formed by addition polymerization of at least a styrene monomer and a (meth)acrylic acid ester monomer. Styrene monomers include styrene, which has the structural formula CH2=CH-C6H5, as well as styrene derivatives having known side chains or functional groups in the styrene structure.

[0046] In addition, the (meth)acrylic acid ester monomer is CH(R1)=CHCOOR2 (R1 is R represents a hydrogen atom or a methyl group, and R2 represents an alkyl group having 1 to 24 carbon atoms), as well as acrylate and methacrylate derivatives having known side chains or functional groups in the structure of these esters.

[0047] Examples of styrene monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, and pn-dodecylstyrene.

[0048] Examples of the (meth)acrylic acid ester monomer include acrylic acid ester monomers such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate (2EHA), stearyl acrylate, lauryl acrylate, and phenyl acrylate; and methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, and dimethylaminoethyl methacrylate.

[0049] In this specification, the term "(meth)acrylic acid ester monomer" is a general term for "acrylic acid ester monomer" and "methacrylic acid ester monomer", and means either or both of them. For example, "methyl (meth)acrylate" means one or both of "methyl acrylate" and "methyl methacrylate."

[0050] The (meth)acrylic acid ester monomer may be one or more kinds. For example, it is possible to form a copolymer using a styrene monomer and two or more acrylate monomers, to form a copolymer using a styrene monomer and two or more methacrylate monomers, or to form a copolymer using a styrene monomer in combination with an acrylate monomer and a methacrylate monomer.

[0051] The amorphous resin may further contain a structural unit derived from a monomer other than the styrene monomer and the (meth)acrylic acid ester monomer.

[0052] "others" The other monomer is preferably a compound that forms an ester bond with a hydroxy group (-OH) derived from a polyhydric alcohol or a carboxy group (-COOH) derived from a polycarboxylic acid. That is, the amorphous resin is preferably a polymer which is capable of addition polymerization with the above-mentioned styrene monomer and (meth)acrylic acid ester monomer, and is further polymerized with a compound having a carboxy group or a hydroxy group (amphoteric compound).

[0053] Examples of the amphoteric compound include compounds having a carboxy group, such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, and the like; and compounds having a hydroxy group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and polyethylene glycol mono(meth)acrylate.

[0054] The styrene-acrylic resin can be synthesized by polymerizing monomers using a known oil-soluble or water-soluble polymerization initiator. Examples of the oil-soluble polymerization initiator include azo- or diazo-based polymerization initiators, and peroxide-based polymerization initiators.

[0055] Examples of the azo or diazo polymerization initiator include 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile and azobisisobutyronitrile.

[0056] Examples of the peroxide polymerization initiator include benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis-(4,4-t-butylperoxycyclohexyl)propane, and tris-(t-butylperoxy)triazine.

[0057] In addition, when synthesizing styrene-acrylic resin particles using the emulsion polymerization method, a water-soluble radical polymerization initiator can be used as the polymerization initiator. Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, and hydrogen peroxide.

[0058] When an amorphous resin is used as the amorphous material contained in the toner for developing electrostatic caustic images of the present invention, the weight average molecular weight (Mw) of the amorphous resin is set to 300 or more and less than 1,000, whereby the low temperature fixability and low gloss of the amorphous resin can be achieved at the same time. The above Mw can be determined from the molecular weight distribution measured by gel permeation chromatography (GPC).

[0059] (Amorphous polyester resin) When the toner base particles have a core-shell structure, it is preferable to use the amorphous polyester resin as the shell, since it has excellent heat resistance without impairing fixability. The amorphous polyester resin is a polyester resin which does not have a melting point and has a relatively high glass transition temperature (Tg) when subjected to differential scanning calorimetry (DSC). Moreover, since the monomers constituting the amorphous polyester resin are different from the monomers constituting the crystalline polyester resin, the amorphous polyester resin can be distinguished from the crystalline polyester resin by analysis such as NMR.

[0060] The amorphous polyester resin is obtained by a polycondensation reaction between a divalent or higher carboxylic acid (polycarboxylic acid) and a divalent or higher alcohol (polyhydric alcohol). There are no particular limitations on the specific amorphous polyester resin, and any amorphous polyester resin conventionally known in the art can be used.

[0061] The specific method for producing the amorphous polyester resin is not particularly limited, and the resin can be produced by polycondensing (esterifying) a polyvalent carboxylic acid and a polyhydric alcohol using a known esterification catalyst.

[0062] The catalyst usable in the production, the polycondensation (esterification) temperature, and the polycondensation (esterification) time are not particularly limited, and are the same as those for the crystalline polyester resin described below.

[0063] (1.1.2) Crystalline resins In the present invention, a crystalline resin refers to a resin that shows a clear endothermic peak, not a stepwise endothermic change, in differential scanning calorimetry (DSC). Specifically, a clear endothermic peak means a peak whose half-width is within 15° C. when measured by differential scanning calorimetry (DSC) at a heating rate of 10° C. / min.

[0064] The toner base particles according to the present invention may contain a crystalline resin as a binder resin. The content of the crystalline resin in the toner base particles is preferably within a range of 1 to 40% by mass, and more preferably within a range of 7 to 15% by mass, from the viewpoint of obtaining sufficient low-temperature fixing ability.

[0065] When the content is 1% by mass or more, a sufficient plasticizing effect is obtained, and low-temperature fixability is sufficient. When the content is 20% by mass or less, the toner has sufficient thermal stability and stability against physical stress.

[0066] The crystalline resin is not particularly limited, but may include polyolefin-based resins, polydiene-based resins, and polyester-based resins. Among these, crystalline polyester resins are preferred from the viewpoints of obtaining sufficient low-temperature fixability and gloss uniformity, and of ease of use.

[0067] The number average molecular weight (Mn) of the crystalline resin is preferably within the range of 2,500 to 5,000, and more preferably within the range of 3,000 to 4,500. From the viewpoint of low-temperature fixing ability and gloss stability, the number average molecular weight (Mn) of the crystalline resin is preferably within the range of 3000 to 12500, and more preferably within the range of 4000 to 11000. Moreover, the weight average molecular weight (Mw) of the crystalline resin is preferably within the range of 10000 to 100000, more preferably within the range of 15000 to 80000, and even more preferably within the range of 20000 to 50000.

[0068] When Mw and Mn are within the above ranges, the fixing property and heat resistance are easily balanced. In addition, sufficient strength is obtained in the fixed image. Furthermore, in the production of the toner, the crystalline resin is not pulverized during stirring of the emulsion, and the glass transition temperature Tg of the toner is kept constant, so that the thermal stability of the toner is maintained. Mw and Mn can be determined from the molecular weight distribution measured by the above-mentioned gel permeation chromatography (GPC).

[0069] (Crystalline polyester resin) The crystalline polyester resin is obtained by a polycondensation reaction between a divalent or higher carboxylic acid (polycarboxylic acid) and a divalent or higher alcohol (polyhydric alcohol).

[0070] <Polycarboxylic acids> Examples of polycarboxylic acids include dicarboxylic acids, which may be one or more kinds, are preferably aliphatic dicarboxylic acids, and may further include aromatic dicarboxylic acids. The aliphatic dicarboxylic acid is preferably a straight-chain type from the viewpoint of enhancing the crystallinity of the crystalline polyester.

[0071] Examples of the aliphatic dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid (dodecanedioic acid), 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, lower alkyl esters thereof, and acid anhydrides thereof.

[0072] Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, t-butylisophthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-biphenyldicarboxylic acid.

[0073] <Polyhydric alcohol> Examples of the polyhydric alcohol component include diols. The diol may be one or more kinds, is preferably an aliphatic diol, and may further contain other diols. The aliphatic diol is preferably a straight-chain type from the viewpoint of enhancing the crystallinity of the crystalline polyester.

[0074] Examples of the aliphatic diol include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, and 1,20-eicosanediol.

[0075] Examples of the other diols include diols having a double bond and diols having a sulfonic acid group.Specific examples of the diols having a double bond include 2-butene-1,4-diol, 3-hexene-1,6-diol, and 4-octene-1,8-diol.

[0076] The content of the aliphatic diol-derived constituent units relative to the diol-derived constituent units in the crystalline polyester resin is preferably 50 mol % or more, more preferably 70 mol % or more, even more preferably 80 mol % or more, and particularly preferably 100 mol %, from the viewpoint of improving the low-temperature fixability of the toner and the glossiness of the image finally formed.

[0077] The ratio of the diol and the dicarboxylic acid in the monomer of the crystalline polyester resin is preferably within the range of 2.0 / 1.0 to 1.0 / 2.0, more preferably within the range of 1.5 / 1.0 to 1.0 / 1.5, and particularly preferably within the range of 1.3 / 1.0 to 1.0 / 1.3, in terms of the equivalent ratio [OH] / [COOH] of the hydroxy group [OH] of the diol to the carboxy group [COOH] of the dicarboxylic acid.

[0078] "others" The monomers constituting the crystalline polyester resin preferably contain linear aliphatic monomers in an amount of 50% by mass or more, and more preferably 80% by mass or more. When an aromatic monomer is used, the melting point of the crystalline polyester resin tends to be high, whereas when a branched aliphatic monomer is used, the crystallinity tends to be low. Therefore, it is preferable to use a straight-chain aliphatic monomer as the above monomer.

[0079] From the viewpoint of maintaining the crystallinity of the crystalline polyester resin in the toner, it is preferable to use 50% by mass or more of the straight-chain aliphatic monomer, and more preferably 80% by mass or more.

[0080] The crystalline polyester resin can be synthesized by polycondensing (esterifying) the above-mentioned polyvalent carboxylic acid and polyhydric alcohol using a known esterification catalyst.

[0081] The catalyst usable in the synthesis of the crystalline polyester resin may be one or more kinds, and examples thereof include alkali metal compounds such as sodium and lithium; compounds containing Group 2 elements such as magnesium and calcium; metal compounds such as aluminum, zinc, manganese, antimony, titanium, tin, zirconium, and germanium; phosphorous compounds; phosphoric acid compounds; and amine compounds.

[0082] The polymerization temperature for the crystalline polyester resin is preferably within a range of 150 to 250° C. The polymerization time is preferably within a range of 0.5 to 10 hours. During the polymerization, the reaction system may be depressurized as necessary.

[0083] The crystalline resin according to the present invention may be of one kind or two kinds.

[0084] (1.2) Toner base particles with a core-shell structure The electrostatic image developing toner according to the present invention may be a toner base particle having a core-shell structure. Here, the term "core-shell structure" refers to a form in which the resin that forms the shell layer on the surface of the core particle is aggregated and fused.

[0085] It is preferable that the crystalline substance and the amorphous resin are used as core particles, and the amorphous polyester resin or the hybrid amorphous polyester resin in which a vinyl-based polymerization segment and a polyester-based polymerization segment are bonded is used as a shell layer, which is disposed on the core particle.

[0086] The vinyl polymer segment refers to a portion derived from the vinyl resin. That is, it means a molecular chain having the same chemical structure as the molecular chain constituting the above-mentioned vinyl resin. The polyester polymer segment means a portion derived from the polyester resin. That is, it means a molecular chain having the same chemical structure as the molecular chain constituting the above-mentioned polyester resin.

[0087] The shell layer does not have to cover the entire surface of the core particle, and the core particle may be partially exposed. The cross section of the core-shell structure can be observed by known observation means such as a transmission electron microscope (TEM) or a scanning probe microscope (SPM).

[0088] In the case of a core-shell structure, the glass transition point, melting point, hardness, and other properties can be made different between the core particle and the shell layer, making it possible to design toner particles according to specific purposes. For example, it is preferable to form a shell layer by aggregating and fusing a resin having a relatively high glass transition point (Tg) onto the surface of a core particle containing a binder resin, a colorant, a release agent, etc. and having a relatively low glass transition point (Tg).

[0089] For a method for producing toner particles having a core-shell structure, refer to JP 2016-161780 A. To obtain toner particles having a core-shell structure by the emulsion aggregation method, first, binder resin fine particles for the core particles, a crystalline substance, and a colorant are aggregated (and fused) to produce core particles, and then binder resin fine particles for the shell portion are added to a dispersion of the core particles, and the binder resin fine particles for the shell portion are aggregated and fused to the surface of the core particles to form a shell portion that covers the surface of the core particles.

[0090] (1.3) Toner base particles with domain-matrix structure The toner for developing electrostatic images according to the present invention may be toner base particles having a domain-matrix structure.

[0091] Here, the "domain-matrix structure" is also called an "island-sea structure," and refers to a structure in which island-shaped dispersed phases (domains) with closed interfaces (boundaries between phases) exist in the continuous phase (matrix: equivalent to the sea) of the toner base particle.

[0092] The toner base particles having the domain-matrix structure according to the present invention show a state in which there is a portion in which the amorphous polyester resin or the hybrid amorphous polyester resin is introduced in an immiscible manner into the amorphous resin. The domains may contain a lamellar crystal structure. This structure can be observed as follows. It is also preferable that a release agent such as wax is added to the domain or matrix in addition to the resin.

[0093] Equipment: Electron microscope "JSM-7401F" (manufactured by JEOL Ltd.) Sample: Section of toner particle stained with ruthenium tetroxide (RuO4) (section thickness: 60-100 nm) Acceleration voltage: 30 kV Magnification: 50000x Observation conditions: Transmission electron detector, bright field image

[0094] When the electrostatic image developing toner according to the present invention has a domain-matrix structure, the average diameter of the domains is preferably within a range of 50 to 150 nm. The average diameter of the domains can be measured by observing and analyzing the domains stained by the above method using an electron microscope and an image processing analyzer (for example, "LUZEX (registered trademark) AP" (manufactured by Nireco Corporation). The average diameter of the domains referred to here means the average value of the major axis of the domains.

[0095] (1.4) Release agent From the viewpoint of achieving both image gloss and low-temperature fixability, it is preferable that the content ratio of the release agent to the amorphous material of the low molecular weight component according to the present invention is within the range of 0.5 to 0.7.

[0096] It is preferable that the content ratio of the release agent to the amorphous material of the low molecular weight component is 0.7 or less, particularly from the viewpoint of the glossiness of the image. Moreover, it is particularly preferable from the viewpoint of releasability that the ratio of the release agent added is 0.5 or more. For example, separation from the fixing belt during the image forming process is good, and the fixing performance is not deteriorated.

[0097] The release agent applicable to the toner base particles according to the present invention is not particularly limited, and for example, various known waxes can be used. From the viewpoint of improving the sharp melting property of the toner, it is preferable to use an ester-based wax.

[0098] (Sharp melting property) In this specification, the term "sharp melting property of a toner" refers to a state in which the difference between the melting start temperature and the melting end temperature in a DSC curve measured at a constant heating rate in a differential scanning calorimeter is small and the peak of the DSC curve is sharp. Alternatively, in measuring the dynamic viscoelasticity of a toner, when observing the temperature change in viscoelasticity (e.g., complex viscosity) at a constant heating rate, it represents the degree of change in viscoelasticity (e.g., complex viscosity) relative to temperature change; the greater the degree of change in viscoelasticity (complex viscosity) relative to temperature change, the greater the sharp melting property of the toner. In addition, if the toner has a high sharp melting property, it has a high sensitivity to heat and can be fixed at a low temperature.

[0099] FIG. 2 is a schematic diagram for understanding the improvement in the sharp melting property of the toner in the present invention. FIG. 2 is a graph with the toner temperature on the horizontal axis and the complex viscosity of the toner on the vertical axis. It is preferable to use a method and measurement conditions that are generally used for toners in the past as a method for measuring the dynamic viscoelasticity, and it is preferable to measure, for example, by the following method.

[0100] (Measurement method) As a measurement sample, a certain amount (e.g., 0.2 g) of toner in which external additives have been arbitrarily added to toner base particles is weighed out, and a certain pressure (e.g., 25 MPa) is applied in a compression molding machine to perform pressure molding, thereby producing a pellet of a certain shape (e.g., a cylindrical shape with a diameter of 10 mm) made of the above toner. Next, using a rheometer (e.g., ARES G2 manufactured by TA Instruments), a set of parallel plates with a constant diameter (e.g., 8 mm) on top and a parallel plate with a constant diameter (e.g., 20 mm) on the bottom is used to perform temperature rise measurements at a constant frequency (e.g., 1 Hz). Next, the sample is set at a constant temperature (for example, 100° C.), and the plate distance (gap) is once set to 1.4 mm, after which any sample sticking out from between the plates is scraped off. Thereafter, the distance between the plates is set to a fixed distance (e.g., 1.2 mm), and the temperature is lowered to the measurement start temperature (e.g., 30°C) while applying axial force. The axial force is then stopped, and the complex viscosity is measured at a fixed temperature increase rate (e.g., 3°C / min) from the measurement start temperature (30°C) to a fixed temperature (e.g., 190°C).

[0101] As can be seen from Figure 2, when comparing the toner before and after the introduction of low molecular weight components, for example, the complex viscosity of 1.0 × 10 6 When focusing on [Pa s], it can be seen that even with the same complex viscosity, the toner temperature is lower, and the slope (rate of change) of the change in complex viscosity relative to temperature change at 60 to 70°C is larger. Therefore, it is understood from the above that the sharp melting property is improved by introducing a low molecular weight component into the toner.

[0102] (Examples of ester wax) Examples of ester waxes include carnauba wax, montan wax, behenyl behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitate, and distearyl maleate.

[0103] (Melting Point) The melting point of the release agent is preferably within the range of 60 to 90°C. This ensures a balance between heat-resistant storage property and fixability, as well as toner manufacturability.

[0104] (1.5) Colorants In the toner base particles according to the present invention, a dye and a pigment generally known as a colorant can be used in combination as a colorant.

[0105] The colorant according to the present invention may be one or more types. Examples of typical colorants include colorants for the colors magenta, yellow, cyan and black.

[0106] Examples of colorants for magenta include CI Pigment Red 2, 3, 5, 6, 7, 15, 16, 48:1, 53:1, 57:1, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 139, 144, 149, 150, 163, 166, 170, 177, 178, 184, 202, 206, 207, 209, 222, 238, and 269.

[0107] Examples of colorants for yellow include CI Pigment Orange 31, CI Pigment Orange 43, CI Pigment Yellow 12, CI Pigment Yellow 14, CI Pigment Yellow 15, CI Pigment Yellow 17, CI Pigment Yellow 74, CI Pigment Yellow 83, CI Pigment Yellow 93, CI Pigment Yellow 94, CI Pigment Yellow 138, CI Pigment Yellow 155, CI Pigment Yellow 162, CI Pigment Yellow 180, and CI Pigment Yellow 185.

[0108] Examples of colorants for cyan include CI Pigment Blue 2, 3, 15, 15:2, 15:3, 15:4, 16, 17, 60, 62, 66 and CI Pigment Green 7.

[0109] Examples of colorants for black include carbon black and magnetic particles. Examples of carbon black include channel black, furnace black, acetylene black, thermal black and lamp black. Examples of the magnetic material of the magnetic particles include ferromagnetic metals such as iron, nickel, and cobalt; alloys containing these metals, and compounds of ferromagnetic metals such as ferrite and magnetite; chromium dioxide; and alloys that do not contain ferromagnetic metals but exhibit ferromagnetism when heat treated. Examples of alloys that become ferromagnetic upon heat treatment include Heusler alloys such as manganese-copper-aluminum and manganese-copper-tin.

[0110] The content of the colorant in the toner base particles can be determined appropriately and independently. For example, from the viewpoint of ensuring color reproducibility of the image, the content is preferably within a range of 1 to 30% by mass, and more preferably within a range of 2 to 20% by mass.

[0111] The particle size of the colorant, in terms of volume average particle size, is preferably within the range of, for example, 10 to 1000 nm, more preferably within the range of 50 to 500 nm, and even more preferably within the range of 80 to 300 nm.

[0112] The volume average particle diameter may be a catalog value, and for example, the volume average particle diameter (median diameter based on volume) of the colorant can be measured using "UPA-150" (manufactured by Microtrack Bell Co., Ltd.).

[0113] (1.6) Charge control agents The charge control agent applicable to the toner base particles according to the present invention is not particularly limited, and various known compounds can be used, such as nigrosine dyes, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, and metal salicylate salts.

[0114] The amount of the charge control agent added is usually within a range of 0.1 to 10% by mass, and preferably 0.5 to 5% by mass, based on 100% by mass of the finally obtained toner base particles.

[0115] The size of the charge control agent particles is, in number average primary particle diameter, 10 to 1000 nm, preferably 50 to 500 nm, and more preferably within the range of 80 to 300 nm.

[0116] (1.7) External additives The toner particles can be used as they are, but may be treated with external additives such as a fluidizing agent and a cleaning aid in order to improve flowability, chargeability, cleaning properties, and the like.

[0117] Examples of external additives include inorganic oxide fine particles such as silica fine particles, alumina fine particles, and titanium oxide fine particles; inorganic stearic acid compound fine particles such as aluminum stearate fine particles and zinc stearate fine particles; and inorganic titanic acid compound fine particles such as strontium titanate and zinc titanate. These may be used alone or in combination of two or more.

[0118] From the viewpoint of improving heat-resistant storage stability and environmental stability, it is preferable that these inorganic particles are surface-treated with a silane coupling agent, a titanium coupling agent, a higher fatty acid, a silicone oil, or the like.

[0119] The amount of the external additive added (the total amount added when multiple external additives are used) is preferably within a range of 0.05 to 5 parts by mass, and more preferably within a range of 0.1 to 3 parts by mass, per 100 parts by mass of the toner base particles.

[0120] 2. Properties of toner for developing electrostatic images (Toner particle size) The average particle size of the toner particles is the volume-based median diameter (d 50 ) is preferably in the range of 3 to 15 μm, and more preferably in the range of 4 to 8 μm.

[0121] Within the above range, high reproducibility can be obtained even for extremely fine dot images at the 1200 dpi level.

[0122] The average particle size of the toner particles can be controlled by the concentration of the coagulant used during production, the amount of organic solvent added, the fusion time, the composition of the binder resin, and the like.

[0123] To measure the volume-based median diameter (d50) of toner particles, a measuring device consisting of a Multisizer 3 (manufactured by Beckman Coulter) connected to a computer system equipped with data processing software Software V3.51 can be used. Alternatively, its successor (eg, Multisizer IV) may be used.

[0124] Specifically, the measurement sample (toner) is added to a surfactant solution (a surfactant solution prepared by diluting, for example, a neutral detergent containing a surfactant component 10 times with pure water in order to disperse toner particles) and allowed to mix, and then ultrasonic dispersion is performed to prepare a toner particle dispersion. This toner particle dispersion is poured into a beaker containing ISOTON II (manufactured by Beckman Coulter) in a sample stand using a pipette until the concentration indicated by the measuring device reaches 8%. By using this concentration, reproducible measurement values ​​can be obtained. The measurement device counted 25,000 particles and had an aperture diameter of 100 μm. The measurement range of 2 to 60 μm was divided into 256 parts to calculate the frequency value. The particle diameter of 50% of the particles with the largest volume fraction was determined as the volume-based median diameter (d 50 ) is obtained.

[0125] (Average circularity of toner particles) From the viewpoint of improving the stability of the charging characteristics and low-temperature fixability, the toner particles preferably have an average circularity in the range of 0.930 to 1.000, and more preferably in the range of 0.950 to 0.995.

[0126] When the average circularity is within the above range, the individual toner particles are less likely to be crushed. This makes it possible to suppress contamination of the frictional charging member and stabilize the chargeability of the toner, and also to improve the quality of the formed image.

[0127] The average circularity of the toner particles can be measured using an FPIA-3000 (manufactured by Sysmex Corporation).

[0128] Specifically, the measurement sample (toner) is soaked in an aqueous solution containing a surfactant, and then dispersed by ultrasonic dispersion treatment for 1 minute. Thereafter, images are taken using an FPIA-3000 (manufactured by Sysmex) under the measurement conditions of HPF (high magnification imaging) mode at an appropriate concentration of 3,000 to 10,000 HPF detection numbers. If the number of HPF detections is within the above range, reproducible measurement values ​​can be obtained. From the photographed particle images, the circularity of each toner particle is calculated according to the following formula (I), and the circularity of each toner particle is added and divided by the total number of toner particles to obtain an average circularity.

[0129] Formula (I): Circularity of a toner particle = (perimeter of a circle having the same projected area as a particle image) / (perimeter of a particle projected image)

[0130] 3. Developer The toner for developing electrostatic images according to the present invention can be used as a magnetic or non-magnetic one-component developer, but may also be mixed with a carrier and used as a two-component developer. When the toner is used as a two-component developer, the carrier may be magnetic particles made of conventionally known materials such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead, with ferrite particles being particularly preferred.

[0131] As the carrier, a coated carrier in which the surface of magnetic particles is coated with a coating agent such as resin, or a dispersion type carrier in which fine magnetic powder is dispersed in a binder resin may be used.

[0132] The volume-based median diameter of the carrier (d 50 ) is preferably in the range of 20 to 100 μm, and more preferably in the range of 25 to 80 μm.

[0133] The volume-based median diameter of the carrier (d 50 ) can be measured, for example, by a laser diffraction particle size distribution measuring device HELOS (manufactured by SYMPATEC) equipped with a wet disperser.

[0134] [Method of manufacturing toner for developing electrostatic images] In the toner for developing electrostatic images of the present invention, it is preferable to produce the toner base particles by an emulsion aggregation method having at least a maturation step, from the viewpoints of uniformity of particle size, controllability of shape, and ease of forming a core-shell structure or a domain-matrix structure. From the viewpoint of suppressing glossiness, it is preferable to carry out the aging step at a temperature within a range of −5 to 15° C. lower than the melting point of the release agent.

[0135] If the aging process during emulsion aggregation is carried out at a temperature equal to or higher than the melting point of the release agent, which is −5° C., the wax crystallizes and is incompatible with the amorphous material of the low molecular weight component and no longer exists. As a result, the amount of wax in the toner becomes less than the amount added at the time of formulation, and the wax does not exist in large amounts in the toner. As a result, the amount of wax that seeps out onto the image does not increase, and high gloss can be suppressed.

[0136] On the other hand, if the aging step during emulsion aggregation is carried out at a temperature set to be 15° C. lower than the melting point of the release agent, the wax in the toner does not melt and become miscible with the nearby amorphous material of the low molecular weight component, and the amount of wax present as crystals in the toner does not decrease. For example, poor separation of the toner from the fixing belt during image formation does not occur, and deterioration of fixability and low gloss can be suppressed.

[0137] From the above, by carrying out the aging process during emulsion aggregation within a range of −5 to 15° C. of the melting point of the release agent, the compatibility of the wax and the additives can be controlled within a desired range, the bleeding of the wax into the image during toner fixing can be suppressed, and the glossiness can be controlled within a desired range.

[0138] Examples of the method for producing the toner for developing electrostatic images of the present invention include, in addition to the above-mentioned emulsion aggregation method, a kneading and pulverizing method, a suspension polymerization method, a dissolution suspension method, a polyester elongation method, a dispersion polymerization method, and other known methods. The emulsion aggregation method will be described below.

[0139] 4.Emulsification aggregation method The method for producing the toner particles according to the present invention using the emulsion aggregation method is, for example, a method in which an aqueous dispersion of a crystalline substance, an aqueous dispersion of amorphous vinyl resin particles, an aqueous dispersion of amorphous polyester resin particles or hybrid amorphous polyester resin particles, and an aqueous dispersion of colorant particles are mixed together, and the amorphous resin particles, the amorphous polyester resin particles or hybrid amorphous polyester resin particles, and the colorant particles are aggregated to form toner particles.

[0140] The emulsion aggregation method is a method in which a dispersion of fine resin particles (hereinafter also referred to as "resin fine particles") dispersed with a surfactant or dispersion stabilizer is mixed with a dispersion of toner particle constituent components such as fine colorant particles, and an aggregating agent is added to aggregate the particles to the desired toner particle size, and thereafter, or simultaneously with the aggregation, the resin fine particles are fused together and the shape is controlled to form toner particles.

[0141] Here, the resin particles can be toner particles having a core-shell structure made of resins with different compositions, or composite particles formed of multiple layers having a domain-matrix structure.

[0142] The resin fine particles can be produced, for example, by an emulsion polymerization method, a mini-emulsion polymerization method, a phase inversion emulsification method, or the like, or by a combination of several production methods. When a release agent is contained in the resin fine particles, it is preferable to use the mini-emulsion polymerization method.

[0143] When a release agent is contained in the toner particles according to the present invention, the resin fine particles may contain the release agent. Alternatively, a dispersion of release agent fine particles consisting of only the release agent may be separately prepared, and the release agent fine particles may be aggregated together with the resin fine particles when the resin fine particles are aggregated.

[0144] Furthermore, the emulsion aggregation method can also be used to obtain toner particles having a domain-matrix structure. Specifically, toner particles having a domain-matrix structure can be obtained by first aggregating (and fusing) binder resin fine particles for the matrix particles and a colorant to produce matrix particles, and then adding binder resin fine particles for the domains to a dispersion of the matrix particles, and aggregating and fusing the binder resin fine particles for the domains from the inside to the surface of the matrix particles to form domains in the matrix particles.

[0145] An example of the steps of a toner manufacturing method using the emulsion aggregation method will be described below.

[0146] (4.1) Toner manufacturing process by emulsion aggregation method (1) In the step (1), an aqueous dispersion of crystalline resin particles is prepared as a dispersion of the crystalline resin particles.

[0147] Specifically, a crystalline resin is synthesized and dissolved or dispersed in an organic solvent to prepare an oil phase liquid, and this oil phase liquid is emulsified by phase inversion to disperse crystalline resin particles in an aqueous medium. After controlling the particle size of the oil droplets to a desired particle size, the organic solvent is removed to obtain an aqueous dispersion of the crystalline resin.

[0148] The organic solvent used in the oil phase liquid is preferably one that has a low boiling point and low solubility in water, from the viewpoint of facilitating removal treatment after the formation of oil droplets. Specific examples include methyl acetate, ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, toluene, and xylene. These may be used alone or in combination of two or more.

[0149] The amount of the organic solvent used is usually within the range of 1 to 300 parts by mass with respect to 100 parts by mass of the crystalline resin.

[0150] The emulsification and dispersion of the oil phase liquid can be carried out by utilizing mechanical energy.

[0151] (4.2) Toner manufacturing process by emulsion aggregation method (2) In the step (2), an aqueous dispersion of amorphous vinyl resin particles is prepared as the dispersion of the amorphous resin. At this stage, it is preferable to incorporate a release agent into the amorphous vinyl resin particles.

[0152] Specifically, an amorphous vinyl resin can be synthesized in an aqueous system to obtain an aqueous dispersion of the amorphous vinyl resin.

[0153] (4.3) Toner manufacturing process by emulsion aggregation method (3) In the step (3), an aqueous dispersion of amorphous polyester resin particles or hybrid amorphous polyester resin is prepared.

[0154] The aqueous dispersion of the amorphous polyester resin particles or the hybrid amorphous polyester resin particles can be prepared in the same manner as described above.

[0155] The average particle size of the amorphous polyester resin particles or the hybrid amorphous polyester resin particles is the volume-based median diameter (d 50 ) in the range of 30 to 400 nm. The volume-based median diameter (d 50 ) can be measured using a Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.).

[0156] (4.4) Toner manufacturing process by emulsion aggregation method (4) In step (4), the colorant is dispersed in the form of fine particles in an aqueous medium to prepare an aqueous dispersion of colorant particles.

[0157] The aqueous dispersion of colorant particles can be obtained by dispersing the colorant in an aqueous medium to which a surfactant has been added at a critical micelle concentration (CMC) or higher.

[0158] The colorant can be dispersed by utilizing mechanical energy. The dispersing machine to be used is not particularly limited, but preferred examples include ultrasonic dispersing machines, mechanical homogenizers, pressure dispersing machines such as Manton-Gaulin and pressure homogenizers, sand grinders, and media-type dispersing machines such as Getzmann mills and diamond fine mills.

[0159] The colorant particles in the aqueous dispersion have a volume-based median diameter (d 50 ) is preferably within the range of 10 to 300 nm, more preferably within the range of 100 to 200 nm, and particularly preferably within the range of 100 to 150 nm.

[0160] The volume-based median diameter of the colorant particles (d 50 ) can be measured using a Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.).

[0161] (4.5) Toner manufacturing process by emulsion aggregation method (5) In step (5), the crystalline material particles, the amorphous vinyl resin particles, the amorphous polyester resin particles, the colorant particles and other toner component particles are aggregated to form toner particles.

[0162] Specifically, a flocculant at or above the critical flocculation concentration is added to a system obtained by mixing an aqueous medium and an aqueous dispersion of each particle, and the mixture is flocculated by heating to a temperature above the glass transition temperature (Tg) of the amorphous resin particles.

[0163] (Flocculant) The flocculant is not particularly limited, but is preferably selected from metal salts such as alkali metal salts and alkaline earth metal salts. Examples of metal salts include monovalent metal salts such as sodium, potassium, and lithium; divalent metal salts such as calcium, magnesium, manganese, and copper; and trivalent metal salts such as iron and aluminum. Specific examples of metal salts include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, and manganese sulfate. Among these, it is particularly preferable to use divalent metal salts because they can promote aggregation more stably. These may be used alone or in combination of two or more.

[0164] (4.6) Toner manufacturing process by emulsion aggregation method (6) In step (6), the toner particles formed in step (5) are subjected to a maturation treatment to control the toner particles into a desired shape. Step (6) can be performed as necessary.

[0165] Specifically, the dispersion liquid of the toner particles obtained in the step (5) is heated and stirred, and the heating temperature, stirring speed, heating time, etc. are adjusted so that the toner particles have a desired circularity.

[0166] <Step (5B) of the toner manufacturing method using the emulsion aggregation method> In the step (5B), the toner particles obtained in the step (5) or (6) may be used as matrix particles, and domains may be formed at least partially from the inside to the surface of the matrix particles. The step (5B) may be carried out when forming toner particles having a domain-matrix structure.

[0167] When forming toner particles with a domain-matrix structure, the resin that constitutes the domain is dispersed in an aqueous medium to prepare a dispersion of the resin particles of the domain, and the resin particles of the domain are aggregated and fused from the inside to the surface of the matrix particle. This makes it possible to obtain a dispersion of toner particles having a domain-matrix structure.

[0168] A heat treatment step can be carried out in order to more firmly aggregate and fuse the resin particles of the domains to the matrix particles. The heat treatment may be carried out until toner particles having a desired circularity are obtained.

[0169] (4.7) Toner manufacturing process by emulsion aggregation method (7) In step (7), the dispersion of toner particles is subjected to a cooling treatment. As a condition for the cooling treatment, it is preferable to cool at a cooling rate of 1 to 20° C. / min. The specific method for the cooling treatment is not particularly limited, and examples thereof include a method of cooling by introducing a refrigerant from the outside of the reaction vessel, and a method of cooling by directly introducing cold water into the reaction system.

[0170] (4.8) Toner manufacturing process by emulsion aggregation method (8) In step (8), the toner particles are separated from the cooled toner particle dispersion liquid, and the toner cake (toner particles in a wet state formed into a cake shape) obtained by solid-liquid separation is washed to remove any attached substances such as surfactants and coagulants.

[0171] The solid-liquid separation is not particularly limited, and may be performed by centrifugation, reduced pressure filtration using a Nutsche or the like, filtration using a filter press or the like, or the like. In addition, in the washing, it is preferable to wash with water until the electrical conductivity of the slurry becomes 10 μS / cm.

[0172] (4.9) Toner manufacturing process by emulsion aggregation method (9) In step (9), the washed toner cake is dried. The toner cake can be dried using a spray dryer, a vacuum freeze dryer, a reduced pressure dryer, or the like, and it is preferable to use a stationary shelf dryer, a mobile shelf dryer, a fluidized bed dryer, a rotary dryer, an agitator dryer, or the like.

[0173] The moisture content of the toner particles after drying is preferably 5% by mass or less, and more preferably 2% by mass or less.

[0174] In addition, in the case where the toner particles after drying are aggregated due to a weak interparticle attractive force, the aggregates may be subjected to a crushing treatment. As the disintegration device, a mechanical disintegration device such as a jet mill, a Henschel mixer, a coffee mill, or a food processor can be used.

[0175] (4.10) Toner manufacturing process by emulsion aggregation method (10) In step (10), an external additive is added to the toner particles. Step (10) can be carried out as necessary.

[0176] For the addition of the external additives, a mechanical mixer such as a Henschel mixer or a coffee mill can be used. 5. Electrophotographic Image Forming Method Each step in the electrophotographic image forming method in which the toner for developing electrostatic images of the present invention can be used will be described below. The image formation steps are preferably steps used in general electrophotographic image formation methods, such as a charging step, a step of forming an electrostatic latent image, a developing step, a fixing step, and a cleaning step.

[0177] (Electrifying process) In this step, the electrophotographic photoreceptor is charged. The method of charging is not particularly limited, and may be a known method such as a charging roller method in which an electrophotographic photosensitive member is charged by a charging roller.

[0178] (Process for forming electrostatic latent images) In this process, an electrostatic latent image is formed on an electrophotographic photoreceptor (electrostatic latent image bearing member). The electrophotographic photoreceptor is not particularly limited, but may be, for example, a drum-shaped one made of an organic photoreceptor such as polysilane or phthalopolymethine.

[0179] The electrostatic latent image is formed, for example, by uniformly charging the surface of the electrophotographic photosensitive member by a charging means and exposing the surface of the electrophotographic photosensitive member to imagewise light by an exposing means. The "electrostatic latent image" is an image formed on the surface of an electrophotographic photoreceptor by such a charging means.

[0180] The charging means and the exposure means are not particularly limited, and those generally used in the electrophotographic system can be used.

[0181] (Developing process) The developing step is a step in which the electrostatic latent image is developed with a toner (generally, a dry developer containing a toner) to form a toner image. The toner image is formed, for example, by using a dry developer containing toner, using a developing means including a stirrer that charges the toner by friction stirring, and a rotatable magnet roller.

[0182] Specifically, in the developing means, for example, toner and a carrier are mixed and stirred, and the toner becomes charged by friction during this process and is held on the surface of a rotating magnet roller, forming a magnetic brush. Since the magnet roller is disposed in the vicinity of the electrophotographic photosensitive member, a part of the toner constituting the magnetic brush formed on the surface of the magnet roller moves to the surface of the electrophotographic photosensitive member by electrical attraction. As a result, the electrostatic latent image is developed with toner to form a toner image on the surface of the electrophotographic photosensitive member.

[0183] (Transfer process) In this step, the toner image is transferred onto a recording medium. The toner image is transferred onto a transfer material by peeling and charging the toner image onto the transfer material.

[0184] As the transfer means, for example, a corona transfer device using corona discharge, a transfer belt, a transfer roller, or the like can be used.

[0185] The transfer step can be carried out, for example, by using an intermediate transfer member, performing primary transfer of a toner image onto the intermediate transfer member, and then secondary transfer of the toner image onto a transfer material, or by directly transferring a toner image formed on an electrophotographic photosensitive member onto a transfer material.

[0186] (Fixing process) The fixing process according to the present invention includes a step of fixing the unfixed image (toner image) formed using toner onto the transfer material by passing the transfer material between a heated fixing belt or fixing roller and a pressure roller which is a pressure member.

[0187] As for the type of the fixing process, as described above, there can be mentioned the belt fixing type or roller fixing type, which is constituted by a fixing belt or a fixing roller as a fixing rotor, and a pressure roller as a pressure member provided in a state of being in pressure contact with the fixing belt or the fixing roller so as to form a fixing nip portion.

[0188] In the fixing step according to the present invention, the toner adhesion amount of the fixed toner image is 2.0 g / m 2 It is preferable for the ink to have the following range in terms of good halftone dot reproducibility.

[0189] (Cleaning process) In this step, the developer that has not been used for image formation or that has not been transferred and remains on the developer carrying member such as the photoreceptor or intermediate transfer member is removed from the developer carrying member.

[0190] The cleaning method is not particularly limited, but it is preferable to use a method in which a blade is used, the tip of which is in contact with the object to be cleaned, such as a photoconductor, and which scrapes the surface of the photoconductor.

[0191] 6. Electrophotographic Image Forming Apparatus The image forming apparatus of the present invention has an image forming unit that forms a toner image on a transfer material using the electrostatic image developing toner of the present invention, a fixing member that faces the upper surface of the transfer material, a pressure member that faces the fixing member to form a fixing nip, a drive source that drives each of the fixing member and the pressure member, and a drive control unit that controls the surface speeds of the fixing member and the pressure member.

[0192] As an example of the image forming apparatus of the present invention, a schematic configuration of a color tandem type image forming apparatus 100 including a fixing member and a pressure member will be described with reference to FIG. This image forming apparatus is a multifunction machine equipped with functions such as a scanner, copier, and printer, and is called an MFP (Multi Function Peripheral or Multi Function Printer).

[0193] As shown in FIG. 3, the image forming apparatus 100 is provided with an annular intermediate transfer belt 108 wound around two rollers 102 and 106 and moving in the circumferential direction, approximately at the center of a main body casing 101.

[0194] Of the two rollers 102 and 106, one roller 102 is disposed on the left side in FIG. 3, and the other roller 106 is disposed on the right side in FIG. The intermediate transfer belt 108 is supported by these rollers 102 and 106 and is driven to rotate in the direction of the arrow X.

[0195] Below the intermediate transfer belt 108, image forming segments 110Y, 110M, 110C, and 110K corresponding to the toner colors yellow (Y), magenta (M), cyan (C), and black (K) are arranged in order from the left in FIG.

[0196] Each of the image forming segments 110Y, 110M, 110C, and 110K is configured similarly to one another except for the toner colors that they handle.

[0197] For example, the yellow image forming segment 110Y is configured by integrating a photoconductor drum 190, a charging device 191, an exposure device 192, a developing device 193 that develops with toner, and a cleaner device 195.

[0198] A primary transfer roller 194 is provided at a position facing the photoconductor drum 190 with the intermediate transfer belt 108 interposed therebetween.

[0199] When forming an image, first the surface of the photoconductor drum 190 is uniformly charged by the charging device 191, and then the surface of the photoconductor drum 190 is exposed by the exposure device 192, and a latent image is formed thereon. Next, the latent image on the surface of the photoconductor drum 190 is developed by the developing device 193 into a toner image. This toner image is transferred to the intermediate transfer belt 108 by applying a voltage between the photoconductor drum 190 and the primary transfer roller 194 . Residual toner remaining on the surface of the photoconductor drum 190 is cleaned by a cleaner device 195 .

[0200] As the intermediate transfer belt 108 moves in the direction of the arrow X, four color toner images are formed as an output image on the intermediate transfer belt 108 by the image forming segments 110Y, 110M, 110C, and 110K in a superimposed manner.

[0201] On the left side of the intermediate transfer belt 108, a cleaning device 125 that removes residual toner from the surface of the intermediate transfer belt 108, and a toner recovery box 126 that recovers the toner removed by the cleaning device 125 are provided.

[0202] A secondary transfer roller 112 is provided on the right side of the intermediate transfer belt 108 with a conveying path 124 for the transfer material therebetween. A transport roller 120 is provided at a position on the transport path 124 that corresponds to the upstream side of the secondary transfer roller 112 . An optical density sensor 115 is provided for detecting the toner pattern on the intermediate transfer belt 108 .

[0203] A fixing device 130 for fixing the toner onto the transfer material is provided in the upper right portion inside the main casing 101 .

[0204] The fixing device 130 includes a pair of fixing members, a fixing roller, and a pressure roller, which are pressure members, extending perpendicularly to the paper surface in FIG. In FIG. 3, there is a heating roller 132 as a fixing roller, and the other is a pressure roller 131 .

[0205] Heat roller 132 and pressure roller 131 each have a drive unit (not shown) and a drive control unit (control unit 200 in FIG. 3) that control the surface speed of heat roller 132 and pressure roller 131 that are driven to rotate.

[0206] The heating roller 132 is heated by the heater 133 to a predetermined target temperature (for example, a fixing temperature within a range of 180 to 200° C.). The pressure roller 131 is biased toward the heating roller 132 by a spring (not shown). As a result, the pressure roller 131 and the heating roller 132 form a nip portion for fixing.

[0207] When the transfer material 90 onto which the toner image has been transferred passes through this nip portion, the toner image is fixed onto the transfer material 90 . The temperatures of the pressure roller 131 and the heating roller 132 are detected by temperature sensors 135 and 136, respectively.

[0208] At the bottom of the main casing 101, paper feed cassettes 116A and 116B for accommodating transfer materials 90 are provided in two stages. FIG. 3 shows a state in which the transfer material 90 is contained only in the paper feed cassette 116A.

[0209] Each of the paper feed cassettes 116A and 116B is provided with a paper feed roller 118 for feeding out the transfer material, and a paper feed sensor 117 for detecting the fed out transfer material.

[0210] Inside the main body casing 101, there is provided a control unit 200 including a CPU (Central Processing Unit) that controls the operation of the entire image forming apparatus. The control unit 200 also has a function of controlling the rotational drive of the drive source, and changes the difference between the surface speed of the fixing member and the surface speed of the pressure member when an image is clamped between the fixing member and the pressure member and fixed by inputting conditions in advance.

[0211] During image formation, the transfer material 90 is sent out one by one from the paper feed cassette 116A to the transport path 124 by the paper feed roller 118 under the control of the control unit 200. The transfer material 90 sent to the conveying path 124 is fed to the toner transfer position between the intermediate transfer belt 108 and the secondary transfer roller 112 by the conveying roller 120 at the timing determined by the resist sensor 114 .

[0212] Meanwhile, as described above, four-color toner images are formed on the intermediate transfer belt 108 by the image forming segments 110Y, 110M, 110C, and 110K, and the four-color toner images on the intermediate transfer belt 108 are transferred by the secondary transfer roller 112 to the transfer material 90 sent to the toner transfer position.

[0213] The transfer material 90 onto which the toner image has been transferred is conveyed through a nip portion formed by a pressure roller 131 and a heating roller 132 of a fixing device 130, and is subjected to heat and pressure. As a result, the toner image is fixed onto the transfer material 90 .

[0214] Finally, the transfer material 90 on which the toner image has been fixed is discharged by a discharge roller 121 through a discharge path 127 onto a discharge tray portion 122 provided on the upper surface of the main body casing 101 .

[0215] In addition, the image forming apparatus 100 is provided with a switchback conveying path 128 for feeding the transfer material 90 again to the toner transfer position in the case of double-sided printing.

[0216] As described above, the pressure roller 131 constitutes one of the fixing rollers, and a silicone rubber roller is used here.

[0217] The embodiments to which the present invention can be applied are not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit of the present invention.

[0218] In the above description, the fixing member is a heating roller, and the pressure member is a pressure roller. However, a conventionally known fixing belt type can also be manufactured and used in the same manner. The fixing belt in this specification is a fixing belt made of silicone rubber and used when fixing toner to a transfer material in an image forming apparatus.

[0219] Specifically, this refers to known fixing belts used in fixing devices, such as those described in JP-A-2017-194550, JP-A-2017-173445, and JP-A-2017-97187. EXAMPLES

[0220] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In the examples, the terms "parts" and "%" are used, but they represent "parts by mass" or "% by mass" unless otherwise specified.

[0221] <<Toner Production>> [Preparation of Toner 1] <Preparation of fine particle dispersion (A1) of styrene-acrylic resin (1)> (1) First-stage polymerization (preparation of "resin fine particle (a1)" dispersion) A reaction vessel equipped with a stirrer, a temperature sensor, a temperature controller, a cooling tube, and a nitrogen introducing device was charged with an anionic surfactant prepared by dissolving 2.0 parts by mass of the anionic surfactant "sodium lauryl sulfate" in 2,900 parts by mass of ion-exchanged water, and the internal temperature was raised to 80°C while stirring at a stirring speed of 230 rpm under a nitrogen stream. To this surfactant solution, 9.0 parts by mass of a polymerization initiator "potassium persulfate (KPS)" was added, and the internal temperature was raised to 78°C. Then, a monomer solution (1) having the following composition was added dropwise over 3 hours. After completion of the addition, the mixture was heated and stirred at 78°C for 1 hour to carry out polymerization (first stage polymerization), thereby preparing a dispersion of "resin microparticles (a1)".

[0222] (Monomer solution (1)) Styrene 540 parts by weight n-Butyl acrylate 270 parts by weight Methacrylic acid 65 parts by mass n-Octyl mercaptan 17 parts by mass

[0223] (2) Second-stage polymerization: Formation of the intermediate layer ("resin fine particles (a 11 Preparation of Dispersion of In a flask equipped with a stirrer, 57 parts by mass of ester wax (manufactured by NOF Corporation, WEP-3, melting point: 77° C.) as a release agent and 90 parts by mass of disproportionated rosin ester (manufactured by Arakawa Chemical Industries, A-100) as an amorphous material were added to a monomer solution (2) having the following composition, which was then heated to 85° C. to dissolve, thereby preparing a monomer solution (2).

[0224] (Monomer solution (2)) Styrene 225 parts by weight n-Butyl acrylate 42.2 parts by weight 2-Ethylhexyl acrylate 42.2 parts by mass Methacrylic acid 31.4 parts by mass n-Octyl mercaptan 5 parts by mass

[0225] On the other hand, a surfactant solution in which 2 parts by mass of the anionic surfactant "sodium lauryl sulfate" was dissolved in 1,100 parts by mass of ion-exchanged water was heated to 90°C, and a dispersion of "resin fine particles (a1)" was added to this surfactant solution in an amount of 40 parts by mass, calculated as the solid content of "resin fine particles (a1)". The monomer solution (2) was then mixed and dispersed for 60 minutes using a mechanical disperser "Clearmix" (manufactured by M Technique Co., Ltd.) with a circulation path, to prepare a dispersion containing emulsified particles with a dispersed particle diameter of 350 nm.

[0226] To this dispersion, an aqueous initiator solution in which 4.9 parts by mass of the polymerization initiator "KPS" was dissolved in 110 parts by mass of ion-exchanged water was added, and the system was heated and stirred at 90°C for 2 hours to carry out polymerization (second stage polymerization) to obtain "resin fine particles (a 11 A dispersion of " was prepared.

[0227] (3) Third-stage polymerization: Formation of the outer layer (preparation of fine particle dispersion (A1) of styrene-acrylic resin (1)) The above "Resin fine particles (a 11 To the dispersion of "KPS", 5.7 parts by mass of the polymerization initiator "KPS" was dissolved in 110 parts by mass of ion-exchanged water, and a monomer solution (3) having the following composition was added dropwise over a period of 2 hours at a temperature of 80°C.

[0228] (Monomer solution (3)) Styrene 355 parts by weight n-Butyl acrylate 151 parts by weight Methacrylic acid 44 parts by mass n-Octyl mercaptan 9 parts by mass

[0229] After the dropwise addition was completed, the mixture was heated and stirred for 1 hour to carry out polymerization (third-stage polymerization). The mixture was then cooled to 28°C to prepare a "styrene-acrylic resin (1) microparticle dispersion (A1)" in which microparticles (volume average particle size: 232 nm) of styrene-acrylic resin (1) were dispersed in the anionic surfactant solution. The glass transition temperature of this styrene-acrylic resin (1) was 40°C as measured by the above-mentioned method using a DSC (Diamond DSC, manufactured by PerkinElmer).

[0230] <Preparation of colorant (carbon black) particle dispersion [Bk]> 90 g of sodium dodecyl sulfate was dissolved in 1600 g of ion-exchanged water with stirring, and 420 g of carbon black (furnace black) "REGAL (registered trademark) 330R" (manufactured by Cabot Corporation) was gradually added while stirring the solution. Next, a dispersion treatment was carried out using a stirring device "CLEARMIX (registered trademark)" (manufactured by M-Technique Co., Ltd.) to prepare a colorant particle dispersion liquid [Bk] in which colorant particles [Bk] were dispersed.

[0231] The volume-based median diameter of the colorant particles [Bk] in the colorant particle dispersion [Bk] was measured using an electrophoretic light scattering photometer "ELS-800" (manufactured by Otsuka Electronics Co., Ltd.) and was found to be 120 nm.

[0232] <Preparation of toner base particles 1> (1) Agglomeration / fusion process In a reaction vessel equipped with a stirrer, a temperature sensor, and a cooling tube, 126 parts by mass of "styrene-acrylic resin (1) particle dispersion (A1)" (calculated as solid content) as a binder resin particle dispersion and 100 parts by mass of ion-exchanged water were added, and then a 5 mol / L aqueous sodium hydroxide solution was added to adjust the pH to 10 and the liquid temperature to 20°C. Furthermore, 11 parts by mass of "colorant (carbon black) particle dispersion liquid [Bk]" was added in terms of solid content, and the pH was adjusted to 10 again with an aqueous sodium hydroxide solution. Next, an aqueous solution prepared by dissolving 12.8 parts by mass of magnesium chloride in 12.8 parts by mass of ion-exchanged water was added thereto at 20° C. over a period of 10 minutes with stirring. After that, the system was left to stand for 3 minutes, and then heating was started. The system was heated to 70° C. over 60 minutes, and the particle growth reaction was continued while maintaining the temperature at 70° C. In this state, the particle size of the associated particles (toner base particle precursor) was measured using a Multisizer 4 (manufactured by Beckman Coulter), and when the volume-based median diameter (D50% diameter) reached 6.2 μm, the stirring speed was increased to stop particle growth. The temperature was then further increased and the particles were stirred at 82°C while being heated to promote fusion of the particles. When the average circularity reached 0.950 (HPF detection count: 4,000 particles) using a flow particle image analyzer "FPIA-3000" (Sysmex Corporation), the mixture was cooled to 30°C to obtain a "dispersion of toner base particle 1."

[0233] (2) Washing and drying process The "dispersion of toner base particles 1" produced in the aggregation and fusion process was subjected to solid-liquid separation in a centrifuge to remove coarse particles and fine particles, and a wet cake of toner base particles 1 was formed. The wet cake was washed with ion-exchanged water at 35°C until the electrical conductivity of the slurry in 10 times the amount of ion-exchanged water reached 5 μS / cm, and then transferred to a "Flash Jet Dryer" (manufactured by Seishin Enterprise Co., Ltd.) and dried until the moisture content was 0.5% by mass to produce "toner base particle 1".

[0234] (3) External additive processing process To the above "toner base particles 1", 2.5 parts by mass of hydrophobic silica particles (silica particles surface-modified with HMDS, number average primary particle diameter = 120 nm), 1.0 part by mass of hydrophobic silica particles (silica particles surface-modified with HMDS, number average primary particle diameter = 12 nm), and 0.6 part by mass of hydrophobic titania particles (number average primary particle diameter = 20 nm) were added as external additives relative to 100 parts by mass of toner base particles 1, and mixed using a Henschel mixer to prepare "toner 1".

[0235] [Preparation of Toner 2] Toner 2 was prepared in the same manner as Toner 1, except that (2) the amount of the release agent in the second polymerization step was 122.4 parts by mass and the amount of the amorphous material was 204 parts by mass.

[0236] [Preparation of Toner 3] Toner 3 was prepared in the same manner as Toner 1, except that the ripening temperature after particle growth in the process of preparing the toner base particles was set to 72°C. [Preparation of Toner 4] Toner 4 was prepared in the same manner as Toner 1, except that the temperature was not increased after particle growth in the process of preparing the toner base particles but was maintained at 70°C. [Preparation of Toner 5] Toner 5 was prepared in the same manner as Toner 1, except that (2) the release agent in the second polymerization step was a hydrocarbon release agent, HNP-51 (melting point: 77° C.).

[0237] [Preparation of Toner 6] Toner 6 was prepared in the same manner as Toner 1, except that (2) the amount of the release agent in the second polymerization step was 37 parts by mass and the amount of the amorphous material was 98 parts by mass.

[0238] [Preparation of Toner 7] Toner 7 was prepared in the same manner as Toner 1, except that (2) the amount of the release agent in the second polymerization step was 67 parts by mass and the amount of the amorphous material was 86 parts by mass.

[0239] [Preparation of Toner 8] Toner 8 was prepared in the same manner as Toner 1, except that (2) the amorphous material of the second polymerization step was not added.

[0240] [Preparation of Toner 9] Toner 9 was prepared in the same manner as Toner 1, except that (2) the amount of the release agent in the second polymerization step was 142.8 parts by mass and the amount of the amorphous material was 238 parts by mass.

[0241] [Preparation of Toner 10] Toner 10 was prepared in the same manner, except that the amount of n-octyl mercaptan in the monomer solution (2) was 7.5 parts by mass, and the amount of n-octyl mercaptan in the monomer solution (3) was 13.5 parts by mass.

[0242] [Preparation of Toner 11] Toner 11 was prepared in the same manner as Toner 1, except that the following crystalline polyester resin [C1] was added instead of the amorphous material.

[0243] (Synthesis of crystalline polyester resin) A 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introducing device was charged with 300 parts by mass of a polycarboxylic acid compound: sebacic acid (molecular weight 202.25) and 170 parts by mass of a polyhydric alcohol compound: 1,6-hexanediol (molecular weight 118.17). The internal temperature of the system was raised to 190°C over one hour while stirring. After confirming that the system was in a uniformly stirred state, Ti(OBu)4 was added as a catalyst in an amount of 0.003% by mass relative to the amount of the polycarboxylic acid compound charged. Thereafter, while distilling off the water produced, the internal temperature was raised from 190°C to 240°C over a period of 4 hours, and the dehydration condensation reaction was continued at 240°C for a further 6 hours to carry out polymerization, thereby obtaining a crystalline polyester resin [C1]. The resulting crystalline polyester resin [C1] had a melting point (Tm) of 77° C. and a number average molecular weight of 5,000.

[0244] Preparation of the developer The toners 1 to 11 prepared as described above were mixed with a ferrite carrier having a volume average particle size of 40 μm coated with a copolymer resin of cyclohexyl methacrylate and methyl methacrylate (monomer mass ratio = 1:1) to prepare developers 1 to 11 by making the toner concentration 6 mass%. The mixer was a V-type mixer, and the mixture was mixed for 30 minutes.

[0245] [Each evaluation method and evaluation criteria] The evaluation methods and criteria were as follows. The results are shown in Table I. be. In Table I, Example 6 and Example 7 should be read as Reference Example 6 and Reference Example 7, respectively.

[0246] [Table 1]

[0247] (1) Low-temperature fixability (Evaluation method) As the image forming apparatus, a commercially available full-color multifunction printer "bizhub PRO C6500" (manufactured by Konica Minolta) was used, which was modified so that the surface temperature of the upper fixing belt could be changed. The black two-component developer is equipped with developer 1 to 11, and the recording material is "NPi wood-free paper 128g / m 2 " (Nippon Paper Industries) with a black toner adhesion of 11.3 g / m 2 A test was conducted in which a solid image (black) was output at a fixing speed of 300 mm / sec. The temperature of the upper fixing belt was decreased in increments of 5°C from 200°C, and the test was repeated until under-offset occurred.

[0248] The term "under-offset" used here refers to an image defect in which a solid toner image is not sufficiently melted by the heat applied when passing through a fixing device, causing the image to peel off from a transfer material such as recording paper.

[0249] The lowest surface temperature of the upper fixing belt at which under-offset did not occur was investigated, and this was taken as the lower limit temperature for fixing to evaluate low-temperature fixing performance. In each test, the fixing temperature refers to the surface temperature of the upper fixing belt, and the surface temperature of the lower fixing roller was set to 70°C. The low-temperature fixability was evaluated according to the following evaluation criteria.

[0250] (Evaluation Criteria) The lower the minimum fixing temperature (the temperature at which under-offset occurs), the better the low-temperature fixing property. In this evaluation, a temperature of 125°C or less was deemed to be acceptable as follows. The minimum fixing temperature is 125°C or less. × The minimum fixing temperature is higher than 125°C.

[0251] (2) Tacking ability (Evaluation method) As an image forming device, a commercially available full-color multifunction printer "bizhub PRESS C1070" (manufactured by Konica Minolta) was used, and a HAMMERMILL Laser Print 24lb (grammage 90g / m2) A4 size was printed on the paper in an environment of normal temperature and humidity (temperature 20°C, humidity 50% RH). 2 ) on which the image shown in FIG. 4 (toner adhesion amount 10.0 g / m 2 ) was formed. Next, the surface temperature of the pressure roller of the fixing device was set to 100°C, and the surface temperature of the heating roller was set to the temperature at which image staining due to fixing offset was no longer visually confirmed in the low-temperature fixing test + 25°C, and fixing was performed on two sheets. As shown in FIG. 5, a weight (201), an aluminum plate (202), a paper insert (203), and a thermocouple (204) are set up. The interleaved paper (203) was made of five A4 HAMMERMILL Laser Print 24 lb sheets stacked together, the edges of which were secured with tape (205). The thermocouple (204) is inserted between the third and fourth sheets from the top of the interleaving paper (203). The clamping jig is placed in the ADVANTEC oven "DRM420DD" and heated. Preheat for 2 hours at a temperature higher than the target temperature, then adjust to the set temperature. Once it has been confirmed that the set temperature is stable, the oven is opened, and the two fixed images (206), (206) are placed on top of each other so that the image portions overlap, as shown in Figure 6, and then clamped with a clamping jig. The oven is then closed and the sheets are left as they are. Once you have confirmed that the temperature inside the oven has stabilized at the set temperature, leave it for one minute. Thereafter, the superimposed fixed images (206), (206) were taken out and evaluated for whether the images were stuck to each other.

[0252] (Evaluation Criteria) None: No tacking occurred. Yes: Tacking occurred.

[0253] (3) Glossiness (Evaluation method) The image forming device was a commercially available full-color multifunction printer "bizhub PRO C6500" (manufactured by Konica Minolta) and the transfer material was "POD gloss coated paper 128g / m 2 " (Oji Paper Co., Ltd.) with a toner adhesion of 4.5 g / m 2 Solid image patches (2.5 cm x 4 cm) were fixed at three locations in the longitudinal direction of the paper and at the center image in the width direction under standard temperature conditions. The obtained image was measured with a gloss meter (60° manufactured by Gardner Co., Ltd.) and the average value of three points was calculated.

[0254] (Evaluation Criteria) ○: Glossiness is 15° or less. ×: Glossiness is greater than 15°.

[0255] (4) The area ratio of low molecular weight amorphous materials to the total amount of binder resin in the molecular weight distribution curve of the toner components for developing electrostatic caustic images (referred to as the GPC area ratio of amorphous materials in Table I).

[0256] (Evaluation method) The calculation method (evaluation method) of the area ratio of the amorphous material of the low molecular weight component to the total amount of the binder resin in the molecular weight distribution curve of the toner components for developing electrostatic caustic images is omitted since it has been described above.

[0257] (Evaluation Criteria) ○: GPC area ratio is within the range of 10 to 20%. ×: GPC area ratio is outside the range of 10 to 20%.

[0258] As is clear from Table I, the examples are superior to the comparative examples. [Explanation of symbols]

[0259] 90 Transfer material 100 Image forming device 101 Main casing 108 Intermediate transfer belt 110Y, 110M, 110C, 110K Image forming segments 112 Secondary transfer roller 120 Transport roller 125 Cleaning device 126 Toner collection box 130 Fixing device 131 Pressure roller 132 Heating roller 190 Photoconductor drum 191 Charging device 192 Exposure Equipment 193 Developing device 194 Primary transfer roller 195 Cleaning Equipment 200 Control section 201 Weight 202 Aluminum plate 203 Inserting paper 204 Thermocouple 205 Tape 206 Fixed Image

Claims

1. A toner for developing an electrostatic image, comprising toner base particles containing at least a binder resin and a release agent, The molecular weight corresponding to the main peak top of the molecular weight distribution curve of the constituent components of the toner for developing electrostatic images, which is obtained by gel permeation chromatography, is 15,000 or more; and In comparison of the area ratios of the peaks in the molecular weight distribution curve, the binder resin contains an amorphous material of a low molecular weight component having a weight average molecular weight of 300 or more and less than 1000 in an area ratio range of 10 to 20% relative to the total amount of the binder resin, The content ratio of the release agent to the amorphous material of the low molecular weight component is within a range of 0.5 to 0.

7.

2. A toner for developing electrostatic images.

2. The binder resin contains a styrene-acrylic resin.

2. The toner for developing electrostatic images according to claim 1.

3. The release agent is an ester wax.

3. The toner for developing electrostatic images according to claim 1 or 2.

4. A method for producing the toner for developing electrostatic images according to any one of claims 1 to 3, comprising the steps of: The toner base particles are produced by an emulsion aggregation method having at least a maturing step.

2. A method for producing a toner for developing an electrostatic image, comprising the steps of:

5. The aging step is carried out within a range of −5 to 15° C. below the melting point of the release agent. The method for producing a toner for developing an electrostatic image according to claim 4 .

6. An electrophotographic image forming method having at least an image carrier charging step, an electrostatic latent image forming step, an electrostatic latent image developing step, a toner image transferring step, a toner image fixing step, and a cleaning step, The toner for developing electrostatic images according to any one of claims 1 to 3 is used.

2. A method for forming an electrophotographic image comprising:

Images