Toner for electrostatic charge image development, manufacturing method of toner for electrostatic charge image development, two-component development for electrostatic charge image development, image forming method and image forming system

Abstract

To provide toner for electrostatic charge image development having both low-temperature fixability and hot offset resistance.SOLUTION: Toner for electrostatic charge image development includes toner base particles containing binder resin. The toner for electrostatic charge image development is characterized in that the binding resin contains at least an amorphous polyester containing a structural unit derived from a polyhydric carboxylic acid and a polyhydric alcohol, and a crystalline polyester containing a structural unit derived from a polyhydric carboxylic acid and a polyhydric alcohol, the structural unit derived from the polyhydric alcohol of the amorphous polyester includes at least one selected from a structural unit derived from a linear aliphatic polyhydric alcohol and a structural unit derived from an alicyclic polyhydric alcohol, and the amorphous polyester and the crystalline polyester are a modified amorphous polyester and a modified crystalline polyester, respectively, modified with at least one selected from a styrene compound and a (meth)acrylic acid ester.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a toner for developing electrostatic images, a method for producing a toner for developing electrostatic images, a two-component developer for developing electrostatic images, an image forming method, and an image forming system. More specifically, the present invention relates to a toner for developing electrostatic images that combines low-temperature fixability and hot offset resistance. [Background technology]

[0002] From the viewpoint of energy saving, improved low-temperature fixability is desired for electrostatic image developing toners, but in addition, sufficient hot offset resistance is also required for electrostatic image developing toners. As electrostatic image developing toners that can achieve both low-temperature fixability and hot offset resistance, electrostatic image developing toners that use a combination of amorphous polyester and crystalline polyester as binder resins are known.

[0003] Patent Document 1 discloses a technology for a toner for developing electrostatic images, which uses a combination of an amorphous polyester and a crystalline polyester as a binder resin and has a storage modulus that satisfies a specific condition. Examples of polyhydric alcohol components constituting the amorphous polyester that satisfy the condition include aromatic diols, and specifically, bisphenol A derivatives.

[0004] However, after further investigation, it was found that amorphous polyesters containing structural units derived from aromatic diols, especially bisphenol A derivatives, have low affinity with crystalline polyesters, and therefore there is room for improvement in low-temperature fixability and hot offset resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-66018 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above problems and circumstances, and the problem to be solved is to provide a toner for developing electrostatic images that combines low-temperature fixing properties and hot offset resistance, a method for manufacturing a toner for developing electrostatic images, a two-component developer for developing electrostatic images, an image forming method, and an image forming system. [Means for solving the problem]

[0007] The present inventors have investigated the causes of the above problems in order to solve the above problems, and as a result, have found that in a toner for developing electrostatic images, both low-temperature fixability and hot offset resistance can be achieved by including a polyester having a specific structure in the binder resin of the toner base particles, which has led to the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0008] 1. A toner for developing electrostatic images, comprising toner base particles containing a binder resin, the binder resin contains at least an amorphous polyester containing a structural unit derived from a polycarboxylic acid and a polyhydric alcohol, and a crystalline polyester containing a structural unit derived from a polycarboxylic acid and a polyhydric alcohol, the polyhydric alcohol-derived structural unit of the amorphous polyester includes at least one selected from a linear aliphatic polyhydric alcohol-derived structural unit and an alicyclic polyhydric alcohol-derived structural unit; The amorphous polyester and the crystalline polyester are modified with at least one selected from styrenes and (meth)acrylic acid esters, respectively. 1. A toner for developing electrostatic images, comprising:

[0009] 2. The binder resin contains styrene-acrylic resin in a range of 30 to 60% by mass as solid content. 2. The toner for developing electrostatic images according to claim 1,

[0010] 3. The binder resin contains styrene-acrylic resin in a range of 50 to 60 mass % as solid content. 3. The toner for developing electrostatic images according to claim 2.

[0011] 4. In the modified amorphous polyester, the total content of the structural units derived from the linear aliphatic polyhydric alcohol and the alicyclic polyhydric alcohol relative to the total number of moles of the structural units derived from the polyhydric alcohol is 80 mol % or more. 3. The toner for developing electrostatic images according to claim 1 or 2.

[0012] 5. In the modified amorphous polyester, the structural unit derived from the polyhydric alcohol contains at least one structural unit selected from the group consisting of the linear aliphatic polyhydric alcohol and the alicyclic polyhydric alcohol, each having 5 or more carbon atoms. 3. The toner for developing electrostatic images according to claim 1 or 2.

[0013] 6. The melting point Tm of the modified crystalline polyester is within the range of 70 to 95°C. 3. The toner for developing electrostatic images according to claim 1 or 2.

[0014] 7. The binder resin contains the modified amorphous polyester in an amount of 20% by mass or more as a solid content. 3. The toner for developing electrostatic images according to claim 1 or 2.

[0015] 8.Has a core-shell structure 3. The toner for developing electrostatic images according to claim 1 or 2.

[0016] 9. A method for producing the toner for developing electrostatic images according to item 1 or 2, comprising the steps of: preparing a dispersion of particles of the binder resin by emulsion polymerization; and a step of mixing a dispersion of colorant particles with a dispersion of the binder resin particles, and aggregating, associating, and fusing the colorant particles and the binder resin particles to form toner base particles; 1. A method for producing a toner for developing electrostatic images, comprising:

[0017] 10. A toner for developing electrostatic images according to item 1 or 2, and a carrier. A two-component developer for developing electrostatic images.

[0018] 11. The two-component developer for developing electrostatic images described in item 10 is used. An image forming method comprising:

[0019] 12. The two-component developer for developing electrostatic images according to item 10 is provided. An image forming system comprising: [Effects of the Invention]

[0020] The above-described means of the present invention can provide a toner for developing electrostatic images that achieves both low-temperature fixability and hot offset resistance, a method for producing a toner for developing electrostatic images, a two-component developer for developing electrostatic images, an image forming method, and an image forming system.

[0021] Although the mechanism by which the effects of the present invention are manifested or the mechanism of action are not clearly understood, it is speculated as follows: Hereinafter, "toner for developing electrostatic images" will also be simply referred to as "toner".

[0022] In electrophotographic image formation, toner is first applied as a developer to an electrostatic image formed on a photosensitive drum. The toner is then transferred to paper, and the toner is then fixed to the paper by heating. Specifically, the toner-transferred paper passes through a fixing section consisting of a heated fixing roller, a fixing belt, and a pressure roller, thereby fixing the toner to the paper.

[0023] When paper passes through the fixing unit, some of the toner may not be fixed to the paper and may instead adhere to the fixing belt. When the fixing belt makes one full rotation, the toner that has adhered to the fixing belt may come into contact with the paper again and adhere to the paper again. This is called "offset." When offset occurs, image defects and stains may occur.

[0024] "Low temperature offset" refers to offset that occurs when the heating temperature during fixing is low. If the heating temperature is too low, the toner does not soften sufficiently, and therefore is not fixed to the paper, resulting in low temperature offset. "Hot offset" refers to offset that occurs when the heating temperature during fixing is high. If the heating temperature is too high, the toner softens sufficiently, reducing its elasticity. This causes internal breakage of the toner particles, causing some of the toner particles to separate from the paper, resulting in a loss of adhesion between the toner and the paper. Furthermore, the adhesion between the toner and the fixing belt becomes greater than the adhesion between the toner and the paper. This causes the toner to adhere to the fixing belt, resulting in hot offset.

[0025] Since amorphous polyester has a polar group at the molecular end, molecular chains tend to become entangled, and it is easy to exhibit elasticity even with a relatively low molecular weight. In other words, by including amorphous polyester, the toner can be softened even at a relatively low temperature, while at the same time, the toner is not softened too much even at a relatively high temperature, and a certain degree of hardness can be imparted to the toner.

[0026] Crystalline polyester is very hard below its glass transition point and becomes liquid, i.e., very soft, above its melting point. Therefore, by including crystalline polyester, the toner can be sufficiently softened by heating during fixing, and then hardened as the toner temperature drops, resulting in sufficient adhesion between the toner and paper. In other words, excellent fixing properties can be achieved.

[0027] The binder resin contained in the toner of the present invention contains both an amorphous polyester and a crystalline polyester. This allows the above-mentioned advantages to be exhibited, and both low-temperature offset and high-temperature offset can be suppressed. That is, the toner can achieve both low-temperature fixability and hot-offset resistance.

[0028] In the present invention, the amorphous polyester further contains at least one polyhydric alcohol-derived structural unit selected from the group consisting of a linear aliphatic polyhydric alcohol-derived structural unit and an alicyclic polyhydric alcohol-derived structural unit. This reduces the polarity difference between the main chain of the amorphous polyester and the main chain of the crystalline polyester. As a result, the affinity between the amorphous polyester and the crystalline polyester can be increased, and the compatibility or dispersibility of the two can be improved.

[0029] The amorphous polyester and the crystalline polyester are modified with at least one selected from styrenes and (meth)acrylic acid esters, respectively, to form a modified amorphous polyester and a modified crystalline polyester, which increases the affinity between the modified portions of the amorphous polyester and the crystalline polyester, thereby improving the compatibility or dispersibility of the two.

[0030] By limiting the structures of the amorphous polyester and the crystalline polyester as described above, the compatibility or dispersibility of the two is dramatically improved. This allows the two to be uniformly compatible or dispersed in the portion of the toner base particle where the two are mixed. As a result, it is believed that the toner can achieve both high levels of low-temperature fixability and hot offset resistance. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus 100 according to an embodiment of the present invention. [Figure 2] Explains how to calculate the temperature T50 in heat resistance evaluation DETAILED DESCRIPTION OF THE INVENTION

[0032] The electrostatic image developing toner of the present embodiment is a toner for developing electrostatic images that contains toner base particles containing a binder resin. The binder resin contains at least an amorphous polyester containing structural units derived from a polycarboxylic acid and a polyhydric alcohol, and a crystalline polyester containing structural units derived from a polycarboxylic acid and a polyhydric alcohol. The polyhydric alcohol-derived structural unit of the amorphous polyester includes at least one selected from a linear aliphatic polyhydric alcohol-derived structural unit and an alicyclic polyhydric alcohol-derived structural unit. The amorphous polyester and the crystalline polyester are modified with at least one selected from styrenes and (meth)acrylic acid esters, to give a modified amorphous polyester and a modified crystalline polyester. This feature is a technical feature common to or corresponding to the following embodiments.

[0033] In the present embodiment, from the viewpoint of improving low-temperature fixability and hot offset resistance, the binder resin preferably contains a styrene-acrylic resin in a range of 30 to 60% by mass, more preferably 50 to 60% by mass, in terms of solid content.

[0034] In this embodiment, from the viewpoint of improving low-temperature fixability and hot offset resistance, it is preferable that in the modified amorphous polyester, the total content of the structural units derived from the linear aliphatic polyhydric alcohol and the alicyclic polyhydric alcohol is 80 mol % or more relative to the total number of moles of the structural units derived from the polyhydric alcohol.

[0035] In this embodiment, from the viewpoint of improving low-temperature fixability and hot offset resistance, it is preferable that in the modified amorphous polyester, the polyhydric alcohol-derived structural unit contains at least one structural unit selected from the group consisting of the linear aliphatic polyhydric alcohol and the alicyclic polyhydric alcohol, each having 5 or more carbon atoms.

[0036] In this embodiment, the melting point Tm of the modified crystalline polyester is preferably within a range of 70 to 95°C, from the viewpoint of improving low-temperature fixability and heat resistance.

[0037] In the present embodiment, from the viewpoint of improving low-temperature fixability, it is preferable that the binder resin contains the modified amorphous polyester in an amount of 20% by mass or more in terms of solid content.

[0038] In this embodiment, it is preferable that the toner has a core-shell structure from the viewpoint of improving low-temperature fixability and hot offset resistance.

[0039] The method for producing a toner for developing electrostatic images according to the present embodiment is a method for producing the toner for developing electrostatic images. The manufacturing method includes: preparing a dispersion of particles of the binder resin by emulsion polymerization; and a step of mixing a dispersion of colorant particles with a dispersion of the binder resin particles to aggregate, associate, and fuse the colorant particles with the binder resin particles to form toner base particles; The present invention is characterized by having the following.

[0040] The two-component developer for developing electrostatic images of this embodiment is characterized by containing the toner for developing electrostatic images and a carrier.

[0041] The image forming method of this embodiment is characterized by using the two-component developer for developing electrostatic images.

[0042] The image forming system of this embodiment is characterized by including the two-component developer for developing electrostatic images.

[0043] Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the disclosed embodiments. In this application, the symbol "to" is used to mean that the numerical values before and after it are included as the lower limit and upper limit.

[0044] 1. Overview of electrostatic image developing toner The toner for developing electrostatic images of the present embodiment is a toner for developing electrostatic images that includes toner base particles containing a binder resin, and has the following characteristics. The binder resin contains at least an amorphous polyester containing structural units derived from a polycarboxylic acid and a polyhydric alcohol, and a crystalline polyester containing structural units derived from a polycarboxylic acid and a polyhydric alcohol. The structural unit derived from a polyhydric alcohol of the amorphous polyester contains at least one selected from a structural unit derived from a linear aliphatic polyhydric alcohol and a structural unit derived from an alicyclic polyhydric alcohol. The amorphous polyester and the crystalline polyester are modified with at least one selected from styrenes and (meth)acrylic acid esters, to give modified amorphous polyesters and modified crystalline polyesters.

[0045] In this specification, the term "toner for developing electrostatic images" refers to an aggregate of toner particles. "Toner for developing electrostatic images" may also be simply referred to as "toner."

[0046] The toner particles may be composed of only toner base particles. Alternatively, the toner particles may be composed of toner base particles and an external additive attached to the surface of the toner base particles. "Toner base particles" refer to particles that form the base of the toner particles.

[0047] 2. Composition of toner base particles In this embodiment, the toner base particles contain a binder resin, and the binder resin contains at least an amorphous polyester and a crystalline polyester. The toner base particles may also contain other additives, such as a release agent (wax), a colorant, and a charge control agent, as needed.

[0048] (1) Binder resin The binder resin may contain, as necessary, other resins in addition to the amorphous polyester and crystalline polyester. The other resins may be amorphous resins or crystalline resins, and known resins used for binder resins can be used. Examples of the other resins include vinyl resins such as styrene-acrylic resins.

[0049] The composition of the binder resin can be analyzed, for example, by pyrolysis gas chromatography / mass spectrometry (GC / MS). Specifically, it can be quantified by the standard addition method using a column and detector that have been confirmed to be capable of detecting monomers having a specific structure. An example of detailed pyrolysis conditions and GC / MS measurement conditions is shown below.

[0050] (Pyrolysis conditions) Measurement device: "PY-2020iD" (manufactured by Frontier Labs Co., Ltd.) Measurement mass: 0.1 mg Heating temperature: 550℃ Heating time: 0.5 minutes

[0051] (GC / MS measurement conditions) Measuring device: "QP2010" (Shimadzu Corporation) Column: "UltraALLOY-5" (inner diameter: 0.25 mm, length: 30 m, thickness: 0.25 μm, manufactured by Frontier Labs, Inc.) Temperature range: 40℃ to 320℃ (maintain at 320℃) Heating rate: 20°C / min

[0052] (1.1) Polyester Polyesters can be synthesized by esterifying polycarboxylic acids and polyhydric alcohols through polycondensation, and therefore contain structural units derived from polycarboxylic acids and polyhydric alcohols in their structures.

[0053] Note that bisphenols can be esterified in the same manner as polyhydric alcohols, and therefore, in this embodiment, bisphenols are also included in the "polyhydric alcohol".

[0054] Each structural unit constituting the polyester can be analyzed by a nuclear magnetic resonance (NMR) device. Specifically, for example, toner particles to be measured are dissolved in a deuterium solvent and analyzed using a proton nuclear magnetic resonance (H-NMR) device.

[0055] The content of each structural unit constituting a polyester can be determined by the following method: Pretreatment using chemical decomposition. There are various types of chemical decomposition, but methods effective for analyzing the composition of polyester, which is a condensation resin, include alkaline hydrolysis and supercritical methanol decomposition. Examples of alkaline hydrolysis methods include the following: Toner and hydrolysis liquid (alkali agent, water, and organic solvent) are placed in a high-pressure wet decomposition crucible and heated in an oven at 80 to 150°C for 3 hours. The oven temperature and heating time may be changed depending on the composition of the sample. Examples of alkaline agents include sodium hydroxide and potassium hydroxide. Examples of organic solvents include methanol and DMSO (dimethyl sulfoxide). A small autoclave may be used as the container. The decomposition liquid obtained after hydrolysis of the toner as described above is measured by proton nuclear magnetic resonance (1H-NMR). The molar ratio of each constituent component can be calculated from the peaks derived from each polyhydric alcohol in the proton nuclear magnetic resonance (1H-NMR) spectrum of this decomposition liquid. If the molar ratio of each constituent component cannot be calculated from the 1H-NMR spectrum due to the influence of matrix components, it is also possible to analyze the composition of the polyhydric alcohol from the GC chromatogram of the decomposition liquid. The molar ratio of carboxylic acids can be similarly analyzed by derivatizing the decomposition liquid. The carbon number and content (ratio) of the constituent components (constituent units) of the polyester can be determined by pyrolysis gas chromatography (GC / MS: Gas Chromatography / Mass Spectrometry) in addition to 1H-NMR measurement.

[0056] (1.1.1) Amorphous polyester "Amorphous" means that it does not have a melting point. In other words, "amorphous" means that it does not have a clear endothermic peak when heated in an endothermic curve obtained by differential scanning calorimetry (DSC). Here, a "clear endothermic peak" refers to a peak with a half-width of 15°C or less in an endothermic curve when heated at a heating rate of 10°C / min.

[0057] The amorphous polyester can be synthesized by esterifying a polycarboxylic acid and a polyhydric alcohol through polycondensation using a known esterification catalyst.

[0058] The polycarboxylic acid is not particularly limited, and examples thereof include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, naphthalene-2,6-dicarboxylic acid, malonic acid, mesaconic acid, dimethyl isophthalate, fumaric acid, dodecenylsuccinic acid, 1,10-dodecanedicarboxylic acid, etc. Among these, terephthalic acid, fumaric acid, and dodecenylsuccinic acid are preferred.

[0059] In this embodiment, the structural unit derived from a polyhydric alcohol of the amorphous polyester includes at least one selected from a structural unit derived from a linear aliphatic polyhydric alcohol and a structural unit derived from an alicyclic polyhydric alcohol.

[0060] The linear aliphatic polyhydric alcohol is not particularly limited. The number of carbon atoms is preferably 5 or more, more preferably in the range of 5 to 10, and even more preferably in the range of 5 to 8. When the number of carbon atoms is 5 or more, the polarity difference between the main chain of the amorphous polyester and the main chain of the crystalline polyester can be further reduced, and as a result, both low-temperature fixability and hot offset resistance can be improved.

[0061] Examples of linear aliphatic polyhydric alcohols 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. These may be used alone or in combination of two or more.

[0062] The alicyclic polyhydric alcohol is not particularly limited. The number of carbon atoms is preferably 5 or more, more preferably in the range of 5 to 10, and even more preferably in the range of 5 to 8. When the number of carbon atoms is 5 or more, the polarity difference between the main chain of the amorphous polyester and the main chain of the crystalline polyester can be further reduced, and as a result, both the low-temperature fixability and the hot offset resistance can be improved.

[0063] Examples of the alicyclic polyhydric alcohol include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,2-cyclohexanedimethanol. These may be used alone or in combination of two or more.

[0064] The content of structural units derived from linear aliphatic polyhydric alcohols and alicyclic polyhydric alcohols relative to the total number of moles of structural units derived from polyhydric alcohols is preferably 80 mol % or more, which improves the affinity or dispersibility between the amorphous polyester and the crystalline polyester, thereby improving both low-temperature fixability and hot offset resistance.

[0065] The structural units derived from polyhydric alcohols may include structural units derived from polyhydric alcohols other than linear aliphatic polyhydric alcohols and alicyclic polyhydric alcohols. The other polyhydric alcohols are not particularly limited, and examples thereof include propylene glycol, 2,3-butanediol, diethylene glycol, triethylene glycol, neopentyl glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, glycerin, sorbitol, 1,4-sorbitan, and trimethylolpropane. These may be used alone or in combination of two or more.

[0066] Furthermore, in amorphous polyesters, structural units derived from aliphatic polyhydric alcohols having 5 or more carbon atoms have a high degree of freedom of molecular motion. Therefore, the presence of such structural units facilitates charge migration within the molecules of the amorphous polyester. As a result, toner fogging can be further suppressed.

[0067] The amorphous polyester of this embodiment is a modified amorphous polyester modified with at least one selected from styrenes and (meth)acrylic acid esters. In this embodiment, "styrenes" refers to compounds having a styrene structure. The amorphous polyester is preferably modified to an extent that does not impair its properties. Both the amorphous polyester and the crystalline polyester are modified with at least one selected from styrenes and (meth)acrylic acid esters, and the modified portions have high affinity with each other, resulting in improved low-temperature fixability and hot offset resistance.

[0068] Furthermore, when the binder resin contains a vinyl resin such as a styrene-acrylic resin, the modified moiety has a high affinity with the vinyl resin, thereby improving both low-temperature fixability and hot offset resistance. The styrenes and (meth)acrylic acid esters used as the modifiers can be monomers used in the styrene-acrylic resins described below.

[0069] Examples of catalysts that can be used in the synthesis of amorphous polyesters include metal-containing compounds, phosphorous compounds, phosphoric acid compounds, amine compounds, etc. Examples of metals contained in metal-containing compounds include sodium, lithium, magnesium, calcium, aluminum, zinc, manganese, antimony, titanium, tin, zirconium, germanium, etc. These may be used alone or in combination of two or more.

[0070] Specific examples of tin-containing compounds include dibutyltin oxide, tin octoate, tin dioctoate, and salts thereof.

[0071] Examples of titanium-containing compounds include titanium alkoxides, titanium acylates, and titanium chelates. Examples of titanium alkoxides include tetra-normal-butyl titanate (Ti(On-Bu)4), tetraisopropyl titanate, tetramethyl titanate, and tetrastearyl titanate. Examples of titanium acylates include polyhydroxytitanium stearate. Examples of titanium chelates include titanium tetraacetylacetonate, titanium lactate, and titanium triethanolamine.

[0072] Examples of germanium-containing compounds include germanium dioxide. Examples of aluminum-containing compounds include polyaluminum hydroxide, aluminum alkoxide, tributylaluminate, and the like.

[0073] The polymerization conditions for synthesizing the amorphous polyester are not particularly limited. In particular, the polymerization temperature is preferably within the range of 150 to 250°C. The polymerization time is preferably within the range of 0.5 to 10 hours. During the polymerization, the reaction system may be reduced in pressure as needed.

[0074] From the viewpoint of achieving both sufficient low-temperature fixability and heat-resistant storage stability, the glass transition temperature Tg of the amorphous polyester is preferably within a range of 25 to 60° C., and more preferably within a range of 35 to 55° C. The glass transition temperature Tg can be measured using a differential scanning calorimeter, for example, a Diamond DSC (manufactured by PerkinElmer Co., Ltd.).

[0075] The weight average molecular weight Mw of the amorphous polyester is not particularly limited, and is preferably within the range of 10000 to 100000. The weight average molecular weight Mw can be measured using gel permeation chromatography (GPC).

[0076] The content of the amorphous polyester is preferably in the range of 30 to 100% by mass, more preferably in the range of 30 to 70% by mass, based on the total mass of the binder resin.

[0077] (1.1.2) Crystalline polyester "Crystalline" means having a melting point. In other words, "crystalline" means having a clear endothermic peak when heated in an endothermic curve obtained by differential scanning calorimetry (DSC). Here, a "clear endothermic peak" refers to a peak with a half-width of 15°C or less in an endothermic curve when heated at a heating rate of 10°C / min.

[0078] The crystalline polyester can be synthesized by esterifying a polycarboxylic acid and a polyhydric alcohol through polycondensation using a known esterification catalyst. The polycarboxylic acid and the polyhydric alcohol are not particularly limited.

[0079] Examples of polycarboxylic acids include saturated aliphatic dicarboxylic acids, unsaturated aliphatic dicarboxylic acids, and unsaturated aromatic dicarboxylic acids.

[0080] Examples of saturated aliphatic dicarboxylic acids 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 (dodecanedioic acid), 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, and 1,18-octadecanedicarboxylic acid.

[0081] Examples of unsaturated aliphatic dicarboxylic acids include methylenesuccinic acid, fumaric acid, maleic acid, 3-hexenedioic acid, 3-octenedioic acid, and dodecenylsuccinic acid.

[0082] Examples of unsaturated aromatic dicarboxylic acids include phthalic acid, terephthalic acid, isophthalic acid, t-butylisophthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-phenylene diacetic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and anthracene dicarboxylic acid.

[0083] Lower alkyl esters or acid anhydrides of these dicarboxylic acids may also be used as the polycarboxylic acid. These may be used alone or in combination of two or more.

[0084] Other examples of trivalent or higher polyvalent carboxylic acids include trimellitic acid and pyromellitic acid.

[0085] Examples of polyhydric alcohols include saturated aliphatic diols, unsaturated aliphatic diols, and aromatic diols.

[0086] Examples of saturated aliphatic diols include ethylene glycol, 1,2-propanediol, 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, 1,20-eicosanediol, and neopentyl glycol.

[0087] Examples of unsaturated aliphatic diols include 2-butene-1,4-diol, 3-butene-1,4-diol, 2-butyne-1,4-diol, 3-butyne-1,4-diol, and 9-octadecene-7,12-diol.

[0088] Examples of aromatic diols include bisphenols, alkylene oxide adducts of bisphenols, etc. Examples of bisphenols include bisphenol A and bisphenol F. Examples of alkylene oxide adducts of bisphenols include ethylene oxide adducts of bisphenols and propylene oxide adducts of bisphenols. Derivatives of these diols may also be used as polyhydric alcohols.

[0089] As a combination of polycarboxylic acid and polyhydric alcohol, from the viewpoint of heat-resistant storage stability and charge build-up property, a combination of an aliphatic dicarboxylic acid having 6 to 14 carbon atoms and an aliphatic diol having 6 to 14 carbon atoms is preferred.

[0090] This will be explained from the viewpoint of heat-resistant storage properties. The smaller the number of carbon atoms in the polycarboxylic acid and the polyhydric alcohol, the easier the toner base particles melt, improving low-temperature fixability. On the other hand, if the toner base particles are made too easy to melt, the heat-resistant storage stability is likely to deteriorate. For example, if the heat-resistant storage stability is poor, the toner is likely to aggregate when stored in a developing device under heat. Therefore, by setting the number of carbon atoms in both the polycarboxylic acid and the polyhydric alcohol to within the range of 6 to 14, the toner can achieve both high-temperature storage stability and low-temperature fixability.

[0091] This will be explained from the viewpoint of the rise in charge amount. The larger the carbon number of the polycarboxylic acid and polyhydric alcohol, the lower the polarity of the crystalline polyester, making it less compatible with other resins and resulting in larger domains in the binder resin.On the other hand, the smaller the carbon number of the polycarboxylic acid and polyhydric alcohol, the higher the polarity of the crystalline polyester, making it more compatible with other resins and resulting in more fine dispersion in the binder resin.

[0092] The appropriate dispersion state of the crystalline polyester shortens the distance between domains. When the distance between domains shortens, the resistance to charge transfer in the toner particles decreases, making it easier for the charge amount to build up. Therefore, by setting the carbon numbers of both the polycarboxylic acid and the polyhydric alcohol to within the range of 6 to 14, the charge amount can be improved.

[0093] The crystalline polyester of the present embodiment is a modified crystalline polyester modified with at least one selected from styrenes and (meth)acrylic acid esters. The crystalline polyester is preferably modified to an extent that does not impair its properties. The styrenes and (meth)acrylic acid esters used as the modifiers can be monomers used in the styrene-acrylic resins described below.

[0094] For the synthesis of crystalline polyester, the above-mentioned catalysts that can be used for the synthesis of amorphous polyester can be used.

[0095] The polymerization conditions for synthesizing the crystalline polyester are not particularly limited. In particular, the polymerization temperature is preferably within the range of 70 to 250°C. The polymerization time is preferably within the range of 0.5 to 10 hours. During the polymerization, the reaction system may be reduced in pressure as needed.

[0096] The melting point of the crystalline polyester is not particularly limited, but is preferably within the range of 70 to 95° C. A melting point of 70° C. or higher can improve heat resistance, and a melting point of 95° C. or lower can improve low-temperature fixability. The melting point can be measured using a differential scanning calorimeter, for example, a Diamond DSC (manufactured by PerkinElmer Co., Ltd.).

[0097] The weight average molecular weight Mw of the crystalline polyester is preferably within a range of 1000 to 29000. The weight average molecular weight Mw can be measured by gel permeation chromatography (GPC).

[0098] The content of the crystalline polyester is preferably in the range of 5 to 30% by mass, more preferably in the range of 10 to 20% by mass, based on the total mass of the binder resin.

[0099] (1.2) Vinyl resin In this embodiment, the term "vinyl resin" refers to an amorphous polymer of a monomer having a vinyl group. Hereinafter, the "monomer having a vinyl group" may also be referred to as a "vinyl monomer."

[0100] The vinyl resin is not particularly limited, and examples thereof include styrene-acrylic resin, styrene resin, acrylic resin, etc. Among them, the vinyl resin is preferably a styrene-acrylic resin. By using a styrene-acrylic resin, the affinity between the amorphous polyester and the modified portion of the crystalline polyester is high, and both low-temperature fixability and hot offset resistance can be improved. Note that the styrene-acrylic resin is an amorphous resin. In this embodiment, the term "acrylic resin" also includes methacrylic resin in its category.

[0101] The vinyl monomer is not particularly limited, and examples thereof include the following compounds: These may be used alone or in combination of two or more.

[0102] (1) Styrenes In this embodiment, the term "styrenes" refers to compounds having a styrene structure. Examples of styrenes 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, pn-dodecylstyrene, etc. Derivatives of these styrenes are also included in the styrenes.

[0103] (2) (Meth)acrylic acid ester In this embodiment, the term "(meth)acrylic acid ester" refers to at least one of an acrylic acid ester and a methacrylic acid ester. Examples of (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, phenyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, etc. Derivatives of these esters are also included in the (meth)acrylic acid esters.

[0104] (3) Vinyl esters Examples of vinyl esters include vinyl propionate, vinyl acetate, and vinyl benzoate. (4) Vinyl ethers Examples of vinyl ethers include vinyl methyl ether and vinyl ethyl ether. (5) Vinyl ketones Examples of vinyl ketones include vinyl methyl ketone, vinyl ethyl ketone, and vinyl hexyl ketone. (6) N-vinyl compounds Examples of N-vinyl compounds include N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone. (7) Other Other vinyl monomers include vinyl compounds (vinylnaphthalene, vinylpyridine, etc.), acrylic acid (acrylonitrile, methacrylonitrile, acrylamide, etc.), methacrylic acid derivatives, and the like.

[0105] The vinyl monomer preferably has an ionically dissociable group such as a carboxy group, a sulfonic acid group, or a phosphoric acid group, since this makes it easier to control the affinity with the crystalline polyester.

[0106] Examples of the monomer having a carboxy group include acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, and itaconic acid monoalkyl ester.

[0107] Examples of the monomer having a sulfonic acid group include styrene sulfonic acid, allyl sulfosuccinic acid, and 2-acrylamido-2-methylpropane sulfonic acid.

[0108] Examples of the monomer having a phosphate group include acidophosphooxyethyl methacrylate.

[0109] The vinyl monomer may be a polyfunctional vinyl from the viewpoint of obtaining a polymer having a crosslinked structure. Examples of the polyfunctional vinyl include divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, and neopentyl glycol diacrylate.

[0110] The content of the vinyl resin is preferably in the range of 30 to 60% by mass, more preferably in the range of 50 to 60% by mass, based on the total mass of the binder resin.

[0111] (2) Release agent The toner base particles may contain a release agent as needed. By containing the release agent, the toner base particles can improve the fixing separation property. The release agent is not particularly limited, and various known waxes can be used.

[0112] Examples of the release agent include branched chain hydrocarbon waxes, long chain hydrocarbon waxes, dialkyl ketone waxes, ester waxes, and amide waxes.

[0113] Examples of branched-chain hydrocarbon waxes include polyolefin waxes (polyethylene wax, polypropylene wax, etc.) and microcrystalline wax. Examples of long-chain hydrocarbon waxes include paraffin wax and sazol wax. Examples of dialkyl ketone waxes include distearyl ketone. 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, distearyl maleate, and stearyl stearate. Examples of amide waxes include ethylenediamine behenylamide and tristearyl trimellitate amide. These may be used alone or in combination of two or more.

[0114] Examples of commercially available release agents include "HNP-0190, HNP-51, FNP-0090" (manufactured by Nippon Seiro Co., Ltd.) and "C80" (manufactured by Sasol Corporation).

[0115] The melting point Tm of the release agent is preferably within the range of 70 to 91°C. When the melting point Tm is 91°C or less, the release agent easily exudes from the toner particles during fixing, and the amount of release agent on the surface of the image increases. This improves separability from the fixing roller and improves low-temperature fixability. Furthermore, when the melting point Tm is 70°C or more, due to the difference in viscosity with the binder resin, the release agent is less likely to be disposed on the surface of the toner particles during production, improving the heat-resistant storage stability of the toner particles.

[0116] The melting point Tm of the release agent can be determined by differential scanning calorimetry (DSC) using, for example, the following procedure.

[0117] A differential scanning calorimeter "DSC7000X" (Hitachi High-Tech Corporation) and a thermal analysis controller "AS3 / DX" (Hitachi High-Tech Corporation) were used. 0.5 mg of the measurement sample was placed in an AI autosampler sample container φ6.8 H2.5 mm (Hitachi High-Tech Corporation) and sealed using an AI autosampler cover (Hitachi High-Tech Corporation). This was then placed in the sample holder of the "AS3 / DX."

[0118] The measurement conditions are a measurement temperature of 0 to 200°C, a temperature increase rate of 10°C / min, and a temperature decrease rate of 10°C / min. Heat-cool-heat temperature control is performed, and the data from the first heat is analyzed. An empty aluminum pan is used for the reference measurement. The above procedure allows the melting point of the crystalline resin contained in the measurement sample to be measured. The crystalline resin contains the release agent as well as the crystalline polyester. Therefore, when the measurement sample is a toner, peaks derived from the crystalline polyester as well as the release agent may be detected. The peak top temperature of the endothermic peak derived from the crystalline resin in the first heat is taken as the melting point Tm of the release agent. If multiple endothermic peaks are detected, the peak top temperature of the highest endothermic peak is taken as the melting point Tm of the release agent.

[0119] From the viewpoint of fixation and separation properties, the content of the release agent is preferably in the range of 1 to 30 parts by mass, and more preferably in the range of 5 to 20 parts by mass, relative to 100 parts by mass of the binder resin.

[0120] (3) Coloring agent The toner base particles may contain a colorant, if necessary. The colorant is not particularly limited, and may be a known inorganic or organic colorant. Specific examples of the colorant include carbon black, magnetic powder, organic pigments, inorganic pigments, and dyes.

[0121] The content of the colorant is preferably in the range of 1 to 30% by mass, more preferably in the range of 2 to 20% by mass, based on the total mass of the binder resin.

[0122] (4) Charge control agent The toner base particles may contain a charge control agent as needed. By containing a charge control agent, the toner base particles can improve their charging properties. Examples of charge control agents include known compounds such as nigrosine dyes, metal salts of naphthenic acid, metal salts of higher fatty acids, alkoxylated amines, quaternary ammonium salts, azo metal complexes, and metal salicylate salts.

[0123] The content of the charge control agent is preferably within the range of 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the binder resin.

[0124] 3. Toner base particle structure The structure of the toner base particle according to this embodiment is not particularly limited. It may have a single-layer structure consisting of only toner base particles containing the above-described components. Alternatively, it may have a multi-layer structure such as a core-shell structure, in which a toner base particle containing the above-described components is used as a core particle and a shell layer covering the surface of the core particle.

[0125] The shell layer does not need 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 confirmed by known observation means, such as a transmission electron microscope (TEM) or a scanning probe microscope (SPM).

[0126] In a core-shell structure, the core particle and the shell layer can have different properties such as glass transition point, melting point, and hardness, making it possible to design toner base particles according to the purpose. For example, a shell layer can be formed by aggregating and fusing a resin with a relatively high glass transition point to the surface of a core particle that contains a binder resin, a colorant, a release agent, etc. and has a relatively low glass transition point.

[0127] From the viewpoint of suppressing fogging, the release agent may be present in the vicinity of the surface of the toner base particles, but not exposed on the surface of the toner base particles.

[0128] In the toner base particles according to this embodiment, the binder resin of the core particles preferably contains the crystalline polyester, and more preferably contains both the amorphous polyester and the crystalline polyester. This allows both low-temperature fixability and hot offset resistance to be achieved. When the toner base particles contain a vinyl resin, the vinyl resin is preferably contained in the core particles.

[0129] In the toner base particles according to this embodiment, the binder resin of the shell layer preferably contains primarily the amorphous polyester. By covering the surface of the toner base particle with the amorphous polyester, the surface of the toner base particle does not soften excessively even in a high-temperature environment, and hot offset resistance can be further improved. Furthermore, by containing the amorphous polyester in the shell layer, the affinity between the shell layer and the core particle is also increased. As a result, it is believed that the crystalline polyester in the core particle is less likely to be exposed, and hot offset resistance can be further improved.

[0130] The average circularity of the toner base particles is preferably in the range of 0.935 to 0.995, more preferably in the range of 0.945 to 0.990, and even more preferably in the range of 0.955 to 0.980. By being within the above range, individual toner particles are less likely to be crushed, the charge amount is stable, and high-quality images can be obtained. The average circularity can be measured using, for example, a flow-type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation).

[0131] The specific measurement method is to wet the toner base particles in a surfactant aqueous solution and disperse them by ultrasonic dispersion for 1 minute. After that, using the "FPIA-2100", the measurement is performed in the HPF (high magnification imaging) mode under measurement conditions at an appropriate concentration with an HPF detection count of 4,000 particles. The circularity is calculated using the following formula. (Formula) Circularity = (perimeter of a circle with the same projected area as the particle image) / (perimeter of the particle projected image) The average circularity is an arithmetic mean value obtained by adding up the circularity of each particle and dividing the sum by the total number of particles measured.

[0132] 4.External additives The toner of this embodiment preferably contains an external additive. That is, the external additive is preferably added to the surface of the toner base particles. By containing the external additive, the toner can control the chargeability, fluidity, antiblocking properties, etc. of the toner.

[0133] The external additive is not particularly limited, and examples thereof include inorganic oxide particles, inorganic stearic acid compound particles, inorganic titanic acid compound particles, zirconia particles, etc. These may be used alone or in combination of two or more.

[0134] Examples of inorganic oxide particles include silica particles, alumina particles, titanium oxide particles, zinc oxide particles, chromium oxide particles, cerium oxide particles, antimony oxide particles, tungsten oxide particles, tin oxide particles, tellurium oxide particles, manganese oxide particles, and boron oxide particles.

[0135] Examples of inorganic stearic acid compound particles include aluminum stearate particles and zinc stearate particles.

[0136] Examples of inorganic titanate compound particles include strontium titanate particles and zinc titanate particles.

[0137] The content of the external additive is preferably in the range of 0.05 to 5 parts by mass, more preferably in the range of 0.1 to 3 parts by mass, per 100 parts by mass of the toner base particles. When multiple external additives are used, the total content of the external additives is preferably in the above range.

[0138] Among these, the external additive is preferably silica particles or strontium titanate particles.

[0139] (1) Silica particles Silica particles are particles whose main component is silica (SiO2). Silica particles may be either crystalline or amorphous. Silica particles may be particles produced using silicon compounds such as water glass or alkoxysilane as raw materials, or may be particles obtained by pulverizing quartz.

[0140] Examples of silica particles include sol-gel silica particles, aqueous colloidal silica particles, alcoholic silica particles, fumed silica particles obtained by a gas phase method, etc., fused silica particles, etc. Among these, sol-gel silica particles are preferred.

[0141] Sol-gel silica particles can be obtained, for example, as follows: Tetraalkoxysilane (such as TMOS) is dropped into an alkaline catalyst solution containing alcohol and aqueous ammonia. The tetraalkoxysilane is hydrolyzed and condensed to obtain a suspension containing sol-gel silica particles. The solvent is removed from the suspension to obtain granules. The granules are dried to obtain sol-gel silica particles.

[0142] The silica particles may be treated with a hydrophobic treatment agent. Examples of the hydrophobic treatment agent include known organosilicon compounds having an alkyl group (e.g., a methyl group, an ethyl group, a propyl group, a butyl group, etc.). Specific examples of the hydrophobic treatment agent include an alkoxysilane compound, a siloxane compound, a silazane compound, etc. Among these, the hydrophobic treatment agent is preferably at least one of a siloxane compound and a silazane compound.

[0143] Examples of siloxane compounds include silicone oil and silicone resin. Examples of silicone oil include dimethylsilicone oil. Examples of silazane compounds include hexamethyldisilazane and tetramethyldisilazane. The silazane compound is preferably hexamethyldisilazane (HMDS). These compounds may be used alone or in combination of two or more.

[0144] The amount of the hydrophobic treatment agent attached to the surface of the silica particles is preferably within a range of 0.01 to 5 mass %, more preferably within a range of 0.05 to 3 mass %, and even more preferably within a range of 0.10 to 2 mass %, relative to the total mass of the silica particles. By having the amount of the hydrophobic treatment agent attached to the surface within the above range, the degree of hydrophobicity of the silica particles can be improved.

[0145] Examples of methods for hydrophobizing silica particles include the following methods. [I] A method in which a hydrophobic treatment agent is dissolved in supercritical carbon dioxide and the solution is applied (for example, sprayed or coated) to the surface of silica particles. [II] A method in which a solution containing a hydrophobic treatment agent is applied (for example, sprayed, coated, etc.) to the surface of silica particles in the atmosphere. [III] A method in which a solution containing a hydrophobic treatment agent is added to a silica particle dispersion in the atmosphere, the mixture is maintained, and then the mixture is dried.

[0146] The number-average particle diameter of the silica particles is preferably within the range of 90 to 130 nm. When the number-average particle diameter is 90 nm or more, the silica particles are likely to exert a spacer effect with other toner particles. As a result, even when the toner base particles have high melting properties, coalescence of the toner particles is unlikely to occur, improving heat-resistant storage stability. When the number-average particle diameter is 130 nm or less, the silica particles are unlikely to detach from the toner base particles, preventing deterioration of heat-resistant storage stability due to exposure of the toner base particles.

[0147] The number average particle diameter of the silica particles can be determined, for example, by the following procedure. (i) Toner particles are dispersed in methanol, stirred at room temperature (23°C), and then treated in an ultrasonic bath to separate the external additives from the toner base particles. The toner base particles are precipitated by centrifugation, and the dispersion liquid in which the external additives are dispersed is recovered. Methanol is distilled off from the dispersion liquid, and the external additives are extracted.

[0148] (ii) The extracted external additive is dispersed in resin particles (polyester, weight average molecular weight Mw=50,000) having a volume average particle diameter of 100 μm. (iii) An image of the resin particles in which the external additives are dispersed is taken at a magnification of 40,000 times. The apparatus used is, for example, an energy dispersive X-ray analyzer (EDX apparatus) called "EMAX Evolution X-Max 80mm" 2 A scanning electron microscope (SEM) "S-4800" (Hitachi High-Technologies Corporation) equipped with a "Horiba, Ltd." (Horiba, Ltd.) was used. At this time, EDX analysis was used to identify 300 or more primary silica particles within one field of view based on the presence of Si. SEM observations were performed at an acceleration voltage of 15 kV, an emission current of 20 μA, and a working distance of 15 mm. EDX analysis was performed under the same conditions with a detection time of 60 minutes.

[0149] (iv) The obtained image is imported into an image analyzer "LUZEX III" (manufactured by Nireco Corporation). The area of each particle is determined by analyzing the imported image. (v) From this measured area value, the particle diameter of the silica particles is calculated as the circle equivalent diameter. (vi) Select 100 silica particles having a circle-equivalent diameter of 80 nm or more. (vii) The number average particle size is calculated from the particle sizes of the selected silica particles.

[0150] (2) Strontium titanate particles Strontium titanate particles are particles whose main component is strontium titanate (SrTiO3). Strontium titanate particles are positively charged. Therefore, by using strontium titanate particles as an external additive, the strontium titanate particles promote the negative charging of the toner base particles, thereby suppressing fogging.

[0151] The number-average primary particle diameter of the strontium titanate particles is preferably within the range of 30 to 100 nm, more preferably within the range of 30 to 80 nm, and even more preferably within the range of 30 to 60 nm. By having a number-average primary particle diameter of 30 nm or more, embedding of the particles in the toner base particles is suppressed. By having a number-average primary particle diameter of 100 nm or less, the surface coverage of the toner base particles is easily increased.

[0152] 5.Method for manufacturing toner for developing electrostatic images The method for producing the toner base particles is not particularly limited, and includes known methods such as a kneading and pulverization method, a suspension polymerization method, an emulsion aggregation method, a solution suspension method, a polyester elongation method, and a dispersion polymerization method. Among these, the emulsion aggregation method is preferred from the viewpoints of uniformity of particle size, controllability of shape, and ease of forming a core-shell structure. The emulsion aggregation method will be described below.

[0153] The method for producing a toner for developing electrostatic images using an emulsion aggregation method preferably includes the following steps (I) and (II). (I) A step of preparing a dispersion of binder resin particles by emulsion polymerization (II) A step of mixing a dispersion of colorant particles with a dispersion of binder resin particles to aggregate, associate, and fuse the colorant particles and the binder resin particles to form toner base particles.

[0154] The binder resin particles may be composite particles. Composite particles are formed of two or more layers of resins with different compositions. The binder resin particles can be formed by, for example, emulsion polymerization, mini-emulsion polymerization, phase inversion emulsification, or the like. The binder resin particles can also be formed by combining several of these manufacturing methods. Among these, the binder resin particles are preferably formed by emulsion polymerization from the viewpoint of being able to control the shape. Thereafter, it is preferable to disperse the binder resin particles formed by emulsion polymerization using a surfactant or a dispersion stabilizer to prepare a dispersion liquid.

[0155] In the emulsion aggregation method, first, various dispersions of the components contained in the toner base particles are mixed. Specifically, a dispersion of colorant particles and a dispersion of binder resin particles are mixed. If necessary, a dispersion of particles of a release agent or the like may be mixed. Furthermore, if the toner base particles do not contain a colorant, it is not necessary to mix in a dispersion of colorant particles. Next, an aggregating agent is added to this mixture, causing aggregation and association until the desired toner base particle diameter is achieved. Subsequently, or simultaneously, fusion between binder resin particles is performed, and shape control is performed to form toner base particles.

[0156] The emulsion aggregation method can produce toner base particles having a core-shell structure. Specifically, first, various particles of components contained in the core particles are aggregated, associated, and fused to form core particles. Next, a dispersion of binder resin particles for the shell layer is added to a dispersion of the core particles, and the binder resin particles for the shell layer are aggregated, associated, and fused to the surface of the core particles to form a shell layer that covers the surface of the core particles.

[0157] The method for drying the toner base particles is not particularly limited, but from the viewpoint of productivity, freeze drying, flash jet drying, vibration type fluidized drying, etc. are preferred.

[0158] An example of a method for adding an external additive to toner base particles is a dry method in which the external additive is added in powder form to dried toner base particles. Examples of a mixing device include mechanical mixing devices such as a Henschel mixer and a coffee mill.

[0159] 6. Developer The toner of this embodiment may be used alone as a magnetic or non-magnetic one-component developer for developing electrostatic images. Alternatively, the toner of this embodiment may be mixed with carrier particles to be used as a two-component developer for developing electrostatic images. By using a two-component developer, the charging stability can be improved. As a result, a uniform image can be formed before fixing, and the image quality and low-temperature fixability are excellent.

[0160] As the carrier particles, for example, magnetic particles made of conventionally known materials can be used. Examples of magnetic particles include metal particles such as iron, ferrite, and magnetite. Also included are particles of alloys of these metals with metals such as aluminum and lead. Ferrite particles are particularly preferred as the carrier particles.

[0161] The carrier particles may be coated carrier particles in which the surfaces of magnetic particles are coated with a coating agent such as a resin, or dispersed carrier particles in which magnetic fine powder is dispersed in a binder resin. From the viewpoint of suppressing adhesion of the carrier particles to the photoreceptor, the carrier particles are preferably coated carrier particles.

[0162] The volume-based median diameter of the carrier particles is preferably within a range of 20 to 100 μm, and more preferably within a range of 25 to 80 μm. The volume-based median diameter of the carrier particles can be measured, for example, using a laser diffraction particle size distribution analyzer "HELOS" (manufactured by SYMPATEC Corporation) equipped with a wet disperser.

[0163] An appropriate amount of carrier particles may be mixed with the toner of this embodiment. Examples of a mixing device used for mixing include a Nauta mixer, a W-type mixer, and a V-type mixer.

[0164] In the two-component developer, the toner content is preferably within a range of 8 to 10% by mass relative to the total mass of the two-component developer (total mass of the toner and carrier).

[0165] 7.Image forming method The image forming method of this embodiment uses the above-mentioned developer. In particular, the image forming method of this embodiment preferably uses a two-component developer for developing electrostatic images. Specifically, the image forming method of this embodiment can be carried out using the above-mentioned two-component developer for developing electrostatic images and an electrophotographic image forming apparatus. Any known electrophotographic image forming apparatus can be used, and details will be described later.

[0166] 8. Image Formation System The image forming system of this embodiment includes the developer. In particular, the image forming system of this embodiment preferably includes a two-component developer for developing electrostatic images. Specifically, the image forming system of this embodiment includes the two-component developer for developing electrostatic images in a developing device of an electrophotographic image forming apparatus. Examples of electrophotographic image forming apparatuses include well-known ones.

[0167] An image forming apparatus in which the two-component developer for developing electrostatic images of this embodiment is suitably used will be described. Hereinafter, the "two-component developer for developing electrostatic images" will also be simply referred to as "developer." For example, the image forming apparatus may be a four-cycle image forming apparatus configured with four color developing devices (yellow, magenta, cyan, and black) and one electrophotographic photosensitive member. Alternatively, the image forming apparatus may be a tandem image forming apparatus configured with four color developing devices (yellow, magenta, cyan, and black) and four electrophotographic photosensitive members provided for each color. The developer of this embodiment can be used as any of yellow, magenta, cyan, and black developers.

[0168] 1 is a schematic diagram showing an example of an image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 shown in FIG. 1 includes an image reading unit 110, an image processing unit 30, an image forming unit 40, a paper conveying unit 50, and a fixing device 60.

[0169] Image forming section 40 has image forming units 41Y, 41M, 41C, and 41K that form images using toner of each color: Y (yellow), M (magenta), C (cyan), and K (black). These units all have the same configuration except for the toner they contain, so hereinafter, the symbols representing the colors may be omitted.

[0170] The image forming unit 41 includes an exposure device 411, a development device 412, an electrophotographic photosensitive member (image carrier) 413, a charging device 414, and a drum cleaning device 415. The charging device 414 is, for example, a corona charger. The charging device 414 may be a contact charging device that charges the electrophotographic photosensitive member 413 by bringing a contact charging member (such as a charging roller, a charging brush, or a charging blade) into contact with the electrophotographic photosensitive member 413. The exposure device 411 includes, for example, a semiconductor laser as a light source and an optical deflection device (polygon motor) that irradiates the electrophotographic photosensitive member 413 with laser light corresponding to the image to be formed. The electrophotographic photosensitive member 413 is a negatively charged organic photosensitive member having photoconductivity. The electrophotographic photosensitive member 413 is charged by the charging device 414.

[0171] Developing device 412 is a two-component developing device. Developing device 412 has a developing container, a developing roller, a partition wall, a transport roller, and an agitating roller. The developing container contains a developer. The developing roller (magnetic roller) is rotatably arranged at the opening of the developing container. The partition wall divides the inside of the developing container so that the developer can communicate with each other. The transport roller transports the developer on the opening side of the developing container toward the developing roller. The agitating roller agitates the developer in the developing container. [Example]

[0172] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass." In the following examples, unless otherwise specified, all operations were carried out at room temperature (25°C).

[0173] Toner base particles having a core-shell structure were prepared by the following procedure. First, dispersions of binder resins (amorphous polyester, crystalline polyester, and styrene-acrylic resin), colorants, and release agents were prepared. Next, the dispersions of binder resins, colorants, and release agents were mixed and aggregated to form core particles. After that, a dispersion of amorphous polyester was further added to the dispersion of core particles to form a shell layer, thereby obtaining toner base particles.

[0174] 1. Preparation of various dispersions (1) Preparation of amorphous polyester particle dispersion (1.1) Preparation of amorphous polyester particle dispersion [A1] (Synthesis of amorphous polyester particles [a1]) A mixed liquid of the following components (modifier and polymerization initiator) was placed in a dropping funnel. Note that n-butyl acrylate is an acrylic acid ester. Styrene 80.0 parts by mass n-Butyl acrylate 20.0 parts by mass Acrylic acid 10.0 parts by mass Di-t-butyl peroxide (polymerization initiator) 16.0 parts by mass

[0175] The following amorphous polyester monomers were placed in a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer and a thermocouple, and heated to 170° C. to dissolve. Polycarboxylic acids Terephthalic acid 100.0 parts by mass Fumaric acid 15.0 parts by mass Dodecenyl succinic acid 130.0 parts by mass Polyhydric alcohol Ethylene glycol 37.0 parts by mass (0.60 mole parts) Pentanediol 63.0 parts by mass (0.61 mol parts)

[0176] The mixture in the dropping funnel was added dropwise to a four-necked flask over 90 minutes while stirring, and after aging for 60 minutes, unreacted monomer was removed under reduced pressure (8 kPa). Then, 0.003 parts by mass of Ti(OBu)4 as an esterification catalyst per 100 parts by mass of the polycarboxylic acid component was added to the four-necked flask.

[0177] The mixture in the four-neck flask was heated to 235°C and reacted under normal pressure (101.3 kPa) for 5 hours and then under reduced pressure (8 kPa) for 1 hour. The mixture in the four-neck flask was then cooled to 200°C and reacted under reduced pressure (20 kPa) for 1 hour. Thereafter, the solvent was removed from the reaction product in the four-neck flask to obtain amorphous polyester particles [a1]. The amorphous polyester particles [a1] obtained had a glass transition point of 45° C. and a weight average molecular weight of 8,500.

[0178] (Preparation of amorphous polyester particle dispersion [A1]) The following ingredients were dissolved by stirring at 70°C for 30 minutes. Amorphous polyester particles [a1] 108.0 parts by mass Methyl ethyl ketone 64.0 parts by mass

[0179] To this solution was added an aqueous solution obtained by mixing the following components. Ion-exchanged water 26.0 parts by mass Sodium polyoxyethylene lauryl ether sulfate Amount that makes the concentration of the aqueous solution 1% by mass

[0180] The following ingredients were then added: 3.4 parts by mass of 25% sodium hydroxide aqueous solution

[0181] The resulting solution was placed in a reaction vessel equipped with a stirrer, and the following components were added dropwise over 70 minutes while stirring. The liquid in the vessel became cloudy during the addition, and after the entire amount was added, a uniform emulsion was obtained. 270.0 parts by mass of ion-exchanged water heated to 70°C

[0182] Next, while keeping the emulsion at 70°C, it was stirred for 1 hour under a reduced pressure of 15 kPa (150 mbar) using a diaphragm vacuum pump "V-700" (manufactured by BUCHI Corporation). This allowed methyl ethyl ketone to be distilled off from the emulsion. The resulting mixture was then cooled to prepare a dispersion [A1] containing amorphous polyester particles.

[0183] The resulting amorphous polyester dispersion [A1] had a solids content of 25% by mass. Measurement using a particle size distribution analyzer revealed that the volume average particle size of the amorphous polyester particles in the dispersion [A1] was 94 nm.

[0184] (1.2) Preparation of amorphous polyester particle dispersions [A2] to [A7] (Synthesis of amorphous polyester particles [a2] to [a7]) Amorphous polyester particles [a2] to [a7] were obtained in the same manner as in the synthesis of amorphous polyester particles [a1], except that the type and parts by mass of the polyhydric alcohol were changed as shown in Table I.

[0185] (Synthesis of amorphous polyester particles [a8]) In the synthesis of the amorphous polyester particles [a8], no modifier was used.

[0186] The following amorphous polyester monomers were placed in a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer and a thermocouple, and heated to 170° C. to dissolve. Polycarboxylic acids Terephthalic acid 100.0 parts by mass Fumaric acid 15.0 parts by mass Dodecenyl succinic acid 130.0 parts by mass Polyhydric alcohol Ethylene glycol 37.0 parts by mass Pentanediol 63.0 parts by mass

[0187] The mixture in the dropping funnel was added dropwise to a four-necked flask over 90 minutes while stirring, and after aging for 60 minutes, unreacted monomer was removed under reduced pressure (8 kPa). Then, 0.003 parts by mass of Ti(OBu)4 as an esterification catalyst per 100 parts by mass of the polycarboxylic acid component was added to the four-necked flask.

[0188] The mixture in the four-neck flask was heated to 235°C and reacted under normal pressure (101.3 kPa) for 5 hours and then under reduced pressure (8 kPa) for 1 hour. The mixture in the four-neck flask was then cooled to 200°C and reacted under reduced pressure (20 kPa) for 1 hour. Thereafter, the solvent was removed from the reaction product in the four-neck flask to obtain amorphous polyester particles [a8]. The amorphous polyester particles [a8] thus obtained had a glass transition temperature of 47° C. and a weight average molecular weight of 8,900.

[0189] (Preparation of amorphous polyester particle dispersions [A2] to [A8]) Amorphous polyester particle dispersions [A2] to [A8] were prepared in the same manner as in the preparation of amorphous polyester particle dispersion [A1], except that the amorphous polyester particle [a1] was changed to [a2] to [a8].

[0190] Table I below shows the polyhydric alcohols used in the synthesis of the amorphous polyester particles [a1] to [a8]. Ethylene glycol and 1,5-pentanediol are linear aliphatic polyhydric alcohols. 1,4-Cyclohexanediol and 1,4-cyclohexanedimethanol are alicyclic polyhydric alcohols. In Table I below, only linear aliphatic polyhydric alcohols or alicyclic polyhydric alcohols are shown by their carbon number. "*1" in the table indicates the content of linear aliphatic polyhydric alcohol and alicyclic polyhydric alcohol relative to the total number of moles of polyhydric alcohol. The content ratio of each alcohol in the amorphous polyester particles [a1] to [a8] was measured using the method for measuring the content of each structural unit constituting a polyester described above. The content ratio obtained by the measurement and the ratio of the amount of each alcohol added during the synthesis of the amorphous polyester particles [a1] to [a8] were consistent.

[0191] [Table 1]

[0192] (2) Preparation of crystalline polyester particle dispersion (2.1) Preparation of crystalline polyester particle dispersion [C1] (Synthesis of crystalline polyester particles [c1]) A mixed liquid of the following components (modifier and polymerization initiator) was placed in a dropping funnel. Note that n-butyl acrylate is an acrylic acid ester. Styrene 40.0 parts by mass n-Butyl acrylate 16.0 parts by mass Acrylic acid 3.5 parts by mass Polymerization initiator (di-t-butyl peroxide) 8.0 parts by mass

[0193] The following crystalline polyester monomers were placed in a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer and a thermocouple, and heated to 170° C. to dissolve them. Polycarboxylic acids Tetradodecanedioic acid 400.0 parts by mass Polyhydric alcohol 1,4-butanediol 130.0 parts by mass

[0194] The mixture in the dropping funnel was added dropwise to a four-necked flask over 90 minutes while stirring, and after aging for 60 minutes, unreacted monomer was removed under reduced pressure (8 kPa). Then, 0.003 parts by mass of Ti(OBu)4 as an esterification catalyst per 100 parts by mass of the polycarboxylic acid component was added to the four-necked flask.

[0195] The mixture in the four-neck flask was heated to 235°C and reacted under normal pressure (101.3 kPa) for 5 hours and then under reduced pressure (8 kPa) for 1 hour. The mixture in the four-neck flask was then cooled to 200°C and reacted under reduced pressure (20 kPa) for 1 hour. Thereafter, the solvent was removed from the reaction product in the four-neck flask to obtain crystalline polyester particles [c1]. The melting point of the resulting crystalline polyester particles [c1] was 77°C.

[0196] (Preparation of Crystalline Polyester Particle Dispersion [C1]) The following ingredients were dissolved by stirring at 70°C for 30 minutes. Crystalline polyester particles [c1] 174.0 parts by mass Methyl ethyl ketone 102.0 parts by mass

[0197] To this solution was added an aqueous solution obtained by mixing the following components. Ion-exchanged water 26.0 parts by mass Sodium polyoxyethylene lauryl ether sulfate Amount that makes the concentration of the aqueous solution 1% by mass

[0198] The following ingredients were then added: 4.6 parts by mass of 25% sodium hydroxide aqueous solution

[0199] The resulting solution was placed in a reaction vessel equipped with a stirrer, and the following components were added dropwise over 70 minutes while stirring. The liquid in the vessel became cloudy during the addition, and after the entire amount was added, a uniform emulsion was obtained. 375.0 parts by mass of ion-exchanged water heated to 70°C

[0200] Next, while keeping the emulsion at 70°C, it was stirred for 1 hour under a reduced pressure of 15 kPa (150 mbar) using a diaphragm vacuum pump "V-700" (manufactured by BUCHI Corporation). This allowed methyl ethyl ketone to be distilled off from the emulsion. The resulting mixture was then cooled to prepare a dispersion [C1] containing crystalline polyester particles.

[0201] The solid content of the resulting crystalline polyester particle dispersion [C1] was 25% by mass. Furthermore, as a result of measurement using a particle size distribution analyzer, the volume average particle size of the crystalline polyester particles in the dispersion [C1] was 202 nm.

[0202] (2.2) Preparation of crystalline polyester particle dispersions [C2] to [C5] (Synthesis of crystalline polyester particles [c2] to [c5]) Crystalline polyester particles [c2] to [c5] were obtained using the same procedure as for synthesizing crystalline polyester particles [c1], except that the types and parts by mass of polycarboxylic acids and polyhydric alcohols were changed as shown in Table II.

[0203] (Synthesis of crystalline polyester particles [c6]) In the synthesis of the crystalline polyester particles [c6], no modifier was used.

[0204] The following crystalline polyester monomers were placed in a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer and a thermocouple, and heated to 170° C. to dissolve them. Polycarboxylic acids Tetradodecanedioic acid 400.0 parts by mass Polyhydric alcohol 1,4-butanediol 130.0 parts by mass

[0205] The mixture in the dropping funnel was added dropwise to a four-necked flask over 90 minutes while stirring, and after aging for 60 minutes, unreacted monomer was removed under reduced pressure (8 kPa). Then, 0.003 parts by mass of Ti(OBu)4 as an esterification catalyst per 100 parts by mass of the polycarboxylic acid component was added to the four-necked flask.

[0206] The mixture in the four-neck flask was heated to 235°C and reacted under normal pressure (101.3 kPa) for 5 hours and then under reduced pressure (8 kPa) for 1 hour. The mixture in the four-neck flask was then cooled to 200°C and reacted under reduced pressure (20 kPa) for 1 hour. Thereafter, the solvent was removed from the reaction product in the four-neck flask to obtain crystalline polyester particles [c6]. The melting point of the resulting crystalline polyester particles [c6] was 75°C.

[0207] (Preparation of Crystalline Polyester Particle Dispersions [C2] to [C6]) Crystalline polyester particle dispersions [C2] to [C6] were prepared using the same procedure as for preparing the crystalline polyester particle dispersion [C1], except that the crystalline polyester particle [c1] was changed to [c2] to [c6].

[0208] The polycarboxylic acids and polyhydric alcohols used in the synthesis of the crystalline polyester particles [c1] to [c6] are shown in Table II below. The carboxylic acid and alcohol content ratios of the crystalline polyester particles [c1] to [c6] were measured using the method for measuring the content of each structural unit constituting a polyester described above. The content ratios obtained by the measurement matched the ratios of the amounts of carboxylic acid and alcohol added during the synthesis of the crystalline polyester particles [c1] to [c6].

[0209] [Table 2]

[0210] (3) Preparation of colorant particle dispersion [P1] The following ingredients were mixed and dissolved: Sodium dodecyl sulfate 226.0 parts by mass Ion-exchanged water 1600.0 parts by mass

[0211] The resulting solution was stirred while the following ingredients were gradually added: Colorant: Copper phthalocyanine (CI Pigment Blue 15:3) 420.0 parts by mass

[0212] The resulting mixture was dispersed using a mechanical dispersion device "Clearmix (registered trademark)" (manufactured by M Technique Co., Ltd.) to prepare colorant particle dispersion [P1]. The volume-based median diameter of the colorant particles in the dispersion was 110 nm.

[0213] (4) Preparation of release agent particle dispersion [W1] The following ingredients were mixed: Release agent: behenyl behenate (melting point 73°C) 50.0 parts by mass Anionic surfactant "Neogen (registered trademark) RK" (Dai-ichi Kogyo Seiyaku Co., Ltd.) 5.0 parts by mass Ion-exchanged water 200.0 parts by mass

[0214] The resulting mixture was heated to 110°C and dispersed using a homogenizer "Ultra Turrax T50" (manufactured by IKA Corporation). The dispersion was then dispersed using a Manton-Gaulin high-pressure homogenizer (manufactured by Gaulin Corporation) to obtain a release agent particle dispersion [W1]. The release agent concentration in the release agent particle dispersion [W1] was 26% by mass. Furthermore, as a result of measurement using a particle size distribution measuring device "Microtrac UPA-150" (manufactured by Nikkiso Co., Ltd.), the volume average particle diameter of the release agent particles in the dispersion was 215 nm.

[0215] (5) Preparation of styrene-acrylic resin particle dispersion [S1] The styrene-acrylic resin particle dispersion liquid [S1] was prepared by polymerizing styrene-acrylic resin particles in three stages.

[0216] (First stage polymerization) The following components were placed in a 5 L reaction vessel equipped with a stirrer, a temperature sensor, a condenser, and a nitrogen inlet. The internal temperature of the reaction vessel was raised to 80°C while stirring the following components at a stirring speed of 230 rpm under a nitrogen stream. Sodium dodecyl sulfate 8.0 parts by mass Ion-exchanged water 3000.0 parts by mass

[0217] The following components were dissolved to obtain a solution, which was then added to the reaction vessel after heating. Potassium persulfate 10.0 parts by mass Ion-exchanged water 200.0 parts by mass

[0218] The liquid temperature in the reaction vessel was again raised to 80° C., and the following mixed liquid of monomers was added dropwise over 1 hour. Styrene 480.0 parts by mass n-Butyl acrylate 250.0 parts by mass Methacrylic acid 68.0 parts by mass

[0219] After the dropwise addition of the mixed liquid, the resulting mixed liquid was heated and stirred at 80° C. for 2 hours to polymerize the monomers, thereby preparing a styrene-acrylic resin particle dispersion liquid [s1].

[0220] (Second stage polymerization) The following components were placed in a 5 L reaction vessel equipped with a stirrer, a temperature sensor, a condenser, and a nitrogen inlet, and heated to 87°C. Ion-exchanged water 1100.0 parts by mass Styrene-acrylic resin particle dispersion prepared by first-stage polymerization [s1] Amount equivalent to 55.0 parts by mass in solid content

[0221] The following monomers, chain transfer agent, and release agent were dissolved at 85° C. to obtain a mixed liquid. Styrene (St) 256.5 parts by mass 2-Ethylhexyl acrylate (2-EHA) 95.3 parts by mass Methacrylic acid (MAA) 38.2 parts by mass Release agent: "WEP-5" (NOF Corporation) 144.0 parts by mass Chain transfer agent: n-octyl-3-mercaptopropionate 4.0 parts by mass

[0222] The resulting mixture was dispersed for 10 minutes using a mechanical dispersion device with a circulation path, "Clearmix (registered trademark)" (manufactured by M Technique Co., Ltd.), to prepare a dispersion containing emulsified particles (oil droplets). This dispersion was added to the 5 L reaction vessel.

[0223] The following components were dissolved to prepare a polymerization initiator solution, which was then added to the 5 L reaction vessel. Potassium persulfate 5.4 parts by mass Ion-exchanged water 103.0 parts by mass

[0224] The mixture in the reaction vessel was heated and stirred at 87° C. for 1 hour to carry out polymerization, thereby preparing a styrene-acrylic resin particle dispersion liquid [s1′].

[0225] (Third stage polymerization) The following components were dissolved to obtain a solution, which was then added to the styrene-acrylic resin particle dispersion liquid [s1'] obtained by the second-stage polymerization. Potassium persulfate 7.3 parts by mass Ion-exchanged water 157.9 parts by mass

[0226] To the resulting mixture, a mixture of the following monomers and chain transfer agent was added dropwise over 90 minutes at a temperature of 84°C. Styrene (St) 370.0 parts by mass n-Butyl acrylate (BA) 165.0 parts by mass Methacrylic acid (MAA) 40.0 parts by mass Methyl methacrylate (MMA) 47.2 parts by mass Chain transfer agent: n-octyl-3-mercaptopropionate 8.6 parts by mass

[0227] After the dropwise addition was completed, the mixture was heated and stirred for 2 hours to carry out polymerization. The mixture was then cooled to 28°C to obtain a styrene-acrylic resin particle dispersion liquid [S1]. The solid content of the obtained styrene-acrylic resin particle dispersion liquid [S1] was 25% by mass.

[0228] 2. Preparation of toner base particles (1) Preparation of toner base particles 1 (agglomeration process) The following components were placed in a 4 L reaction vessel equipped with a thermometer, pH meter, and stirrer. The temperature inside the reaction vessel was adjusted to 25°C, and 1.0% nitric acid was added to adjust the pH inside the reaction vessel to 3.0. Note that in the preparation of toner base particles 1, the styrene-acrylic resin particle dispersion liquid [S1] was not added (0.0 parts by mass). Amorphous polyester resin particle dispersion [A1] 800.0 parts by mass Crystalline polyester resin particle dispersion [C1] 110.0 parts by mass Styrene-acrylic resin particle dispersion [S1] 0.0 parts by mass Colorant particle dispersion liquid [P1] 187.0 parts by mass Release agent particle dispersion liquid [W1] 160.0 parts by mass Anionic surfactant "Dowfax2A1 20% aqueous solution" (manufactured by The Dow Chemical Company) 40.0 parts by mass Ion-exchanged water 1500.0 parts by mass

[0229] Next, the mixture in the reaction vessel was dispersed at 3000 rpm using a homogenizer "Ultra Turrax T50" (manufactured by IKA Corporation), while the flocculant below was added over 30 minutes. After the dropwise addition was completed, the mixture in the reaction vessel was stirred for 10 minutes to thoroughly mix the raw materials and flocculant. Flocculant: Aluminum sulfate aqueous solution (2% by mass) 100.0 parts by mass

[0230] A stirrer and mantle heater were then installed in the reaction vessel, and the stirrer's rotation speed was adjusted so that the mixture was thoroughly stirred. The mixture was heated at a rate of 0.2°C / min up to 40°C, and then at a rate of 0.05°C / min after reaching 40°C. The particle size of the particles in the mixture was measured every 10 minutes using a precision particle size distribution analyzer, Coulter Multisizer 3 (aperture diameter 100 μm, manufactured by Beckman Coulter, Inc.).

[0231] The temperature was maintained when the volume average particle size of the particles (core particles) in the mixed solution reached 5.5 μm, and a mixed solution of the following components, which had been mixed in advance, was added to the reaction vessel over 20 minutes. Amorphous polyester particle dispersion [A1] 200.0 parts by mass Anionic surfactant "Dowfax2A1 20% aqueous solution" (manufactured by The Dow Chemical Company) 15.0 parts by mass

[0232] Next, the temperature inside the reaction vessel was maintained at 50°C for 30 minutes, and then the following components were added to the reaction vessel. EDTA (ethylenediaminetetraacetic acid) 20% solution 8.0 parts by mass

[0233] A 1 mol / L aqueous solution of sodium hydroxide was added to control the pH of the mixture in the reaction vessel at 9.0, and the mixture was then heated to 85°C at a rate of 1°C / min while adjusting the pH to 9.0 every 5°C, and maintained at 85°C.

[0234] (cooling process) When the shape factor of the particles in the mixture reached 0.970, the mixture was cooled at a temperature drop rate of 10°C / min to obtain toner base particle dispersion 1. The shape factor of the particles was confirmed using an automatic flow particle imaging analyzer "FPIA-3000" (manufactured by Sysmex Corporation).

[0235] (filtration, washing and drying processes) The toner base particle dispersion 1 was filtered and thoroughly washed with ion-exchanged water. The filtered residue was then dried at 40°C to obtain toner base particles 1. The obtained toner base particles 1 had a volume average particle size of 6.0 μm and an average circularity of 0.971.

[0236] (2) Preparation of toner base particles 2 to 15 and 17 to 19 The types and amounts of the amorphous polyester dispersion, crystalline polyester dispersion, and styrene-acrylic resin dispersion were changed as shown in Table 3. Other than this, toner base particles 2 to 15 and 17 to 19 were produced using the same procedure as for producing toner base particle 1.

[0237] As shown in the preparation of toner base particles 1, the amorphous polyester particle dispersion was added twice, in the first half and the second half. For example, in the preparation of toner base particles 2, 570.0 parts by mass was added to the core particles (first half) and 200.0 parts by mass to the shell layer (second half).

[0238] (3) Preparation of toner base particles 16 The amorphous polyester particle dispersion was added only in the first half, and not in the second half. That is, only core particles were formed, and no shell layer was formed. Except for this, toner base particles 16 were prepared using the same procedure as toner base particles 1.

[0239] 3. Preparation of Developer (1) Preparation of external additive (silica particles [1]) The following ingredients were added to a 3 L reaction vessel equipped with a stirrer, a dropping funnel, and a thermometer and mixed. Methanol 945.0 parts by mass Ammonia water (28% by mass) 45.0 parts by mass Water 135.0 parts by mass

[0240] The temperature of the resulting solution was adjusted to 35°C, and the following components were added dropwise over 6 hours while stirring. After the addition, the mixture was stirred for 1 hour to carry out hydrolysis, yielding a dispersion of silica particles. This dispersion was distilled under reduced pressure and dried, and the resulting particles were then crushed to obtain silica particles [1]. Tetramethoxysilane 405.0 parts by mass

[0241] (2) Preparation of developer (2.1) Preparation of Developer 1 The following components were mixed using a Henschel mixer (manufactured by Nippon Coke & Engineering Co., Ltd.) at a rotor peripheral speed of 35 mm / sec at 32° C. for 20 minutes to obtain Toner 1, which is an aggregate of Toner Particles 1. Toner base particles [1] 100.0 parts by mass Silica particles [1] 1.5 parts by mass

[0242] Coarse particles were removed from toner [1] using a sieve with 45 μm openings. The toner [1] from which the coarse particles had been removed was mixed with ferrite carrier coated with acrylic resin and having a volume average particle size of 32 μm so that the toner particle concentration was 6 mass %, to prepare developer [1], a two-component developer.

[0243] (2.2) Preparation of Developers 2 to 19 Developers [2] to

[19] were prepared in the same manner as developer [1], except that the toner base particles were changed to [2] to

[19] .

[0244] Table III below shows the binder resin composition of each toner base particle. The "amount added" refers to the amount of each dispersion liquid added in the production of each toner base particle. The "first half" of the amount of the amorphous polyester dispersion added refers to the amount added when the core particles are formed. The "second half" refers to the amount added when the shell layer is formed. The "total amount" refers to the sum of the amount added in the first half and the amount added in the second half. The "content" represents the content of each resin relative to the total mass of the binder resin in each toner base particle. The toner number also corresponds to the toner base particle number and the developer number.

[0245] [Table 3]

[0246] 4. Evaluation (1) Low-temperature fixability The fixing device of the multifunction printer "bizhub PRESS (registered trademark)" (manufactured by Konica Minolta, Inc.) was modified so that the surface temperatures of the upper fixing belt and the lower fixing roller could be changed. The fixing device was also modified so that the fixing temperature, toner adhesion amount, and system speed (rotation speed of the fixing roller) could be freely set. Each developer was loaded into the multifunction printer in sequence.

[0247] Under normal temperature and humidity conditions (temperature 20°C, humidity 50% RH), A4 size high-quality paper "NPI high-quality (127.9 g / m 2 ) (Nippon Paper Industries Co., Ltd.) with a toner adhesion of 10 g / m 2 A fixing experiment was conducted to output a solid image (100mm x 100mm).

[0248] In the fixing experiment, the fixing temperature was changed to fix a 100mm x 100mm solid image. The fixing temperature was increased in 1°C increments from 110°C, and the fixing experiment was repeated until it reached 180°C.

[0249] The lowest fixing temperature at which image defects due to fixing offset were not visually confirmed was defined as the "minimum fixing temperature (UO avoidance temperature)." Here, "image defects" refers to white spots caused by the toner image adhering to the fixing belt. The obtained minimum fixing temperatures were evaluated according to the following criteria. A grade of C or higher (A to C) was considered to be acceptable for practical use.

[0250] A: The minimum fixing temperature is 129°C or lower. B: The minimum fixing temperature is within the range of 130 to 134°C. C: The minimum fixing temperature is within the range of 135 to 139°C. D: The minimum fixing temperature is 140°C or higher.

[0251] (2) Hot offset resistance Each developer was loaded in turn into the modified multifunction machine used for evaluating low-temperature fixability. Under normal temperature and humidity conditions (temperature 20°C, humidity 50% RH), A4 size plain paper "J Paper (64 g / m 2) (Konica Minolta, Inc.) with toner adhesion of 8 g / m 2 A fixing experiment was conducted to output a solid image. Under the conditions of a fixing device nip pressure of 238 kPa and a nip time of 25 milliseconds (process speed 480 mm / s), the fixing temperature was increased in 5°C increments from 100°C, and the fixing experiment was repeated until it reached 200°C.

[0252] The lowest fixing temperature at which image defects due to hot offset were visually confirmed was defined as the "hot offset occurrence temperature." Here, "image defects" refers to white spots caused by the toner image adhering to the fixing belt. The obtained hot offset occurrence temperatures were evaluated according to the following criteria. A rating of C or higher (A to C) was considered to be acceptable for practical use. A: Even when the fixing temperature is 200°C, hot offset does not occur, and the temperature at which hot offset occurs is above 200°C. B: The hot offset temperature is 195°C or 200°C. C: The hot offset temperature is 185°C or 190°C. D: The hot offset temperature is 180° C. or less.

[0253] (3) Heat resistance 0.5 g of each toner was placed in a 10 mL glass bottle with an inner diameter of 21 mm. Note that "toner" here refers to a mixture of toner base particles and silica particles (external additive), and refers to an aggregate of toner particles. The lid of the glass bottle was closed, and the bottle was shaken 600 times at room temperature using a shaker "Tap Denser KYT-2000" (manufactured by Seishin Enterprise Co., Ltd.). The bottle was then left with the lid open in an environment of 55°C and 35% RH for 2 hours.

[0254] Next, the toner was placed on a 48-mesh (350 μm mesh) sieve, taking care not to break up the toner aggregates. The sieve with the toner placed on it was placed in a powder property evaluation device "Powder Tester (registered trademark)" (manufactured by Hosokawa Micron Corporation) and fixed with a pressure bar and knob nut. After applying vibration for 10 seconds with a vibration intensity adjusted to give a feed width of 1 mm, the mass of the toner remaining on the sieve was measured, and the toner aggregation rate R was calculated using the following formula. Formula: Toner cohesion rate R [mass %] = (mass of toner remaining on the sieve [g] / 0.5 [g]) x 100

[0255] The toner cohesion rate R was repeatedly measured using the same procedure except for changing the temperature at which the toner was left. The temperature at which the toner was left was increased in 2.5°C increments from 55°C, and the measurement was stopped when the toner cohesion rate R exceeded 50% by mass.

[0256] The toner is left at a temperature T at which the toner cohesion rate R reaches 50% by mass using the following method. 50 When the toner cohesion rate R is exactly 50% by mass at a certain temperature, the temperature is taken as T 50 It was decided.

[0257] The highest toner storage temperature at which the toner cohesion rate R is less than 50% by mass is defined as T A The lowest temperature at which the toner cohesion rate R exceeds 50% by mass is defined as T B As shown in FIG. 2, the X axis represents temperature [°C], the Y axis represents toner cohesion rate [mass %], and the temperature T A Toner cohesion rate R A , temperature T B Toner cohesion rate R B A straight line is drawn by connecting the two plotted points, and the temperature on this line at which the toner cohesion rate R becomes 50% by mass is designated as T 50 It was decided.

[0258] The obtained temperature T 50 The results were evaluated according to the following criteria, where a grade of C or higher (A to C) was deemed to be acceptable for practical use. A:T 50However, the temperature is above 59°C. B:T 50 However, the temperature is above 58°C and below 59°C. C:T 50 However, the temperature is above 57°C and below 58°C. D:T 50 However, it is below 57°C.

[0259] The evaluation results are shown in Table IV below.

[0260] [Table 4]

[0261] From the examples and comparative examples, it is clear that the toner of this embodiment can achieve both low-temperature fixability and hot offset resistance.

[0262] From Examples 1 to 6, it can be seen that the low-temperature fixability and hot offset resistance can be improved by including a styrene-acrylic resin in the binder resin in a range of 30 to 60 mass %, or even in a range of 50 to 60 mass %, as solid content.

[0263] Examples 5 and 7 to 10 reveal the following. In the modified amorphous polyester, the structural unit derived from a polyhydric alcohol contains at least one structural unit selected from the group consisting of aliphatic polyhydric alcohols and alicyclic polyhydric alcohols having 5 or more carbon atoms, thereby improving both low-temperature fixability and hot offset resistance.

[0264] From Examples 5 and 12 to 15, it is clear that when the melting point Tm of the modified crystalline polyester is within the range of 70 to 95°C, the low-temperature fixability and heat resistance can be improved.

[0265] From Examples 5 and 6, it is clear that the binder resin containing 20% by mass or more of the modified amorphous polyester as a solid content can improve the low-temperature fixability. [Explanation of symbols]

[0266] 100 Image forming device 110 Image reading unit 30 Image processing section 40 Image forming unit 41 Image forming unit 411 Exposure equipment 412 Developing device 413 Electrophotographic photoreceptor 414 Charging device 415 Drum cleaning device 50 Paper transport section 60 Fixing device

Claims

1. A toner for developing electrostatic images, comprising toner base particles containing a binder resin, the binder resin contains at least an amorphous polyester containing a structural unit derived from a polycarboxylic acid and a polyhydric alcohol, and a crystalline polyester containing a structural unit derived from a polycarboxylic acid and a polyhydric alcohol, the polyhydric alcohol-derived structural unit of the amorphous polyester includes at least one selected from a linear aliphatic polyhydric alcohol-derived structural unit and an alicyclic polyhydric alcohol-derived structural unit; The amorphous polyester and the crystalline polyester are modified with at least one selected from styrenes and (meth)acrylic acid esters, respectively.

1. A toner for developing electrostatic images, comprising:

2. The binder resin contains a styrene-acrylic resin in a range of 30 to 60 mass % as a solid content.

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

3. The binder resin contains a styrene-acrylic resin in a range of 50 to 60 mass % as a solid content.

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

4. In the modified amorphous polyester, the total content of the structural units derived from the linear aliphatic polyhydric alcohol and the alicyclic polyhydric alcohol is 80 mol % or more relative to the total number of moles of the structural units derived from the polyhydric alcohol.

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

5. In the modified amorphous polyester, the structural unit derived from the polyhydric alcohol contains at least one structural unit selected from the group consisting of the linear aliphatic polyhydric alcohol and the alicyclic polyhydric alcohol, each having 5 or more carbon atoms.

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

6. The melting point Tm of the modified crystalline polyester is in the range of 70 to 95°C.

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

7. The binder resin contains the modified amorphous polyester in an amount of 20% by mass or more as a solid content.

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

8. Has a core-shell structure 3. The toner for developing electrostatic images according to claim 1 or 2.

9. A method for producing the toner for developing electrostatic images according to claim 1 or 2, comprising the steps of: preparing a dispersion of particles of the binder resin by emulsion polymerization; and a step of mixing a dispersion of colorant particles with a dispersion of the binder resin particles, and aggregating, associating, and fusing the colorant particles and the binder resin particles to form toner base particles; 1. A method for producing a toner for developing electrostatic images, comprising:

10. A toner for developing electrostatic images according to claim 1 or 2, comprising a carrier. A two-component developer for developing electrostatic images.

11. The two-component developer for developing electrostatic images according to claim 10 is used. An image forming method comprising:

12. The two-component developer for developing electrostatic images according to claim 10 is provided. An image forming system comprising:

Images