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Title:
TONER PARTICLE CONTAINING POLYESTER RESIN
Document Type and Number:
WIPO Patent Application WO/2022/046235
Kind Code:
A1
Abstract:
A toner particle contains a binder resin, a colorant, and a wax. The binder resin contains a first amorphous polyester resin having a pendant group, a second amorphous polyester resin having no pendant group, and a crystalline polyester resin. The toner particle is associated with a temperature range in which |dlogG*(t)/dt| is 0.2 or more when the temperature range represents a temperature t of the toner particle that varies between a lower limit t1 and an upper limit t2. The toner particle has a G''(t)/G'(t) ratio of 0.6 to 1.75 at the temperature range of t1 to t2. G*(t) is a complex elastic modulus of the toner particle at the temperature t, G'(t) is a storage elastic modulus of the toner particle at the temperature t, and G''(t) is a loss elastic modulus of the toner particle at the temperature t.

Inventors:
DANNO TAKAHIRO (JP)
IEDA OSAMU (JP)
ISHIKAWA KEIICHI (JP)
TERADA AKINORI (JP)
Application Number:
PCT/US2021/035692
Publication Date:
March 03, 2022
Filing Date:
June 03, 2021
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
HEWLETT PACKARD DEVELOPMENT CO (US)
International Classes:
G03G9/087; G03G9/08; G03G9/093
Domestic Patent References:
WO2020018177A12020-01-23
Foreign References:
US9804515B22017-10-31
JP2007025525A2007-02-01
US5955234A1999-09-21
Attorney, Agent or Firm:
KO, Steve Sokbong et al. (US)
Download PDF:
Claims:
CLAIMS 1. A toner particle comprising: a binder resin comprising: a first amorphous polyester resin having a pendant group;a second amorphous polyester resin having no pendant group; and a crystalline polyester resin; a colorant; and a wax, wherein, the toner particle is associated with a temperature range in which |dlogG*(t)/dt| is 0.2 or more, wherein the temperature range represents a temperature t of the toner particle that varies between a lower limit t1 and an upper limit t2, and wherein the toner particle has a G''(t)/G'(t) ratio of 0.6 to 1.75 in the temperature range of t1 to t2, wherein G*(t) is a complex elastic modulus of the toner particle at the temperature t, wherein G'(t) is a storage elastic modulus of the toner particle at the temperature t, and wherein G''(t) is a loss elastic modulus of the toner particle at the temperature t. 2. The toner particle according to claim 1, wherein the lower limit t1 of the temperature range is approximately 20°C or more, and wherein the upper limit t2 of the temperature range is approximately 100 °C or less.

3. The toner particle according to claim 1, wherein the first amorphous polyester resin comprises, as monomer units: a polyhydric alcohol; a first polycarboxylic acid having a branch chain having 3 or more carbon atoms, the branch chain constituting the pendant group; and a second polycarboxylic acid having no branch chain having 3 or more carbon atoms. 4. The toner particle according to claim 1, wherein the second amorphous polyester resin comprises, as monomer units: a polyhydric alcohol; and a polycarboxylic acid having no branch chain having 3 or more carbon atoms. 5. The toner particle according to claim 4, wherein the second amorphous polyester resin has no pendant group. 6. The toner particle according to claim 1, wherein a weight average molecular weight of the second amorphous polyester resin is greater than a weight average molecular weight of the first amorphous polyester resin. 7. The toner particle according to claim 1, wherein a weight average molecular weight of the first amorphous polyester resin is approximately 5,000 to 30,000. 8. The toner particle according to claim 1, wherein a weight average molecular weight of the second amorphous polyester resin is approximately 30,000 to 80,000. 9. The toner particle according to claim 1, wherein a weight average molecular weight of the crystalline polyester resin is approximately 5,000 to 15,000. 10. The toner particle according to claim 1, comprising: a core comprising the first amorphous polyester resin, the second amorphous polyester resin, the crystalline polyester resin, the colorant, and the wax; and a shell covering the core, wherein the first amorphous polyester resin is additionally contained in the shell. 11. The toner particle according to claim 10, wherein a content of the crystalline polyester resin in the core is approximately 10% by mass to 40% by mass, based on a total content of the first amorphous polyester resin, the second amorphous polyester resin, and the crystalline polyester resin in the core. 12. The toner particle according to claim 10, wherein a mass ratio of a content of the first amorphous polyester resin to a content of the second amorphous polyester resin in the core is 60/40 or more. 13. The toner particle according to claim 10, wherein the second amorphous polyester resin is additionally contained in the shell.

14. The toner particle according to claim 13, wherein a mass ratio of a content of the first amorphous polyester resin to a content of the second amorphous polyester resin in the shell is 60/40 or greater. 15. A toner cartridge comprising a container accommodating a toner particle, wherein the toner particle comprising: a binder resin comprising: a first amorphous polyester resin having a pendant group; a second amorphous polyester resin having no pendant group; and a crystalline polyester resin; a colorant; and a wax, wherein the toner particle is associated with a temperature range in which |dlogG*(t)/dt| is 0.2 or more, wherein the temperature range represents a temperature t of the toner particle that varies between a lower limit t1 and an upper limit t2, and wherein the toner particle has a G''(t)/G'(t) ratio of 0.6 to 1.75 in the temperature range of t1 to t2, wherein G*(t) is a complex elastic modulus of the toner particle at the temperature t, wherein G'(t) is a storage elastic modulus of the toner particle at the temperature t, and wherein G''(t) is a loss elastic modulus of the toner particle at the temperature t.

Description:
TONER PARTICLE CONTAINING CRYSTALLINE POLYESTER RESIN AND AMORPHOUS POLYESTER RESIN BACKGROUND [0001] Methods for graphically outputting image information through electrostatically charged images, such as electrophotography, have been utilized in a variety of fields. In electrophotography, the surface of a photoreceptor is charged to a given potential, and an electrostatically charged image is subsequently formed on the photoreceptor surface to form an electrostatic latent image which is then developed with a developer including toner particles, so as to graphically output a toner image of the electrostatic latent image. Subsequently, this toner image is transferred and fixed onto the surface of a recording medium, and thereby an image is formed. The developer that may be used, may be a two-component developer composed of toner particles and a carrier in some examples, or a one-component developer that includes either a magnetic toner or a non-magnetic toner according to other examples. BRIEF DESCRIPTION OF DRAWINGS [0002] FIG.1 is a graph showing complex elastic modulus properties G*(t) and |dlogG*(t)/dt| of the toner particles of Test Example 1. FIG. 2 is a graph showing a ratio of the viscous component to the elastic component tanδ(t) of the toner particles of Test Example 1. FIG. 3 is a graph showing a complex elastic modulus property |dlogG*(t)/dt| relative to a ratio of the viscous component to the elastic component tanδ(t) in the toner particles of Test Examples 1 to 3. FIG. 4 is a graph showing a complex elastic modulus property |dlogG*(t)/dt| relative to a ratio of the viscous component to the elastic component tanδ(t) in the toner particles of TestExamples 4 to 6. FIG. 5 is a graph showing a complex elastic modulus property |dlogG*(t)/dt| relative to a ratio of the viscous component to the elastic component tanδ(t) in the toner particles of Test Examples 7 to 9. FIG. 6 is a graph showing a complex elastic modulus property |dlogG*(t)/dt| relative to a ratio of the viscous component to the elastic component tanδ(t) in the toner particles of comparative Test Examples 1 to 3. FIG. 7 is a graph showing a complex elastic modulus property |dlogG*(t)/dt| relative to a ratio of the viscous component to the elastic component tanδ(t) in the toner particles of comparative Test Examples 4 to 6. DETAILED DESCRIPTION [0003] In the following description, examples of a toner particle will be described. The toner particle according to examples contains a binder resin, a colorant, and a wax. [0004] Binder resin The binder resin includes a first amorphous polyester resin having a pendant group, a second amorphous polyester resin that is different from the first amorphous polyester resin, and a crystalline polyester resin. The amorphous polyester resin may be a polyester resin which does not have a clear endothermic peak in differential scanning calorimetry (DSC). The amorphous polyester resin may be defined as, for example, a polyester resin showing a stepwise endothermic change when measurement is made by differential scanning calorimetry at a rate of temperature increase of 10 °C/min, or a polyester resin having an endothermic peak with a half-value width greater than 15 °C. [0005] The amorphous polyester resin is, for example, a reaction product of a polyhydric alcohol and a polycarboxylic acid. In other words, the amorphous polyester resin may contain a polyhydric alcohol and a polycarboxylic acid as monomer units. [0006] The first amorphous polyester resin may contain a polyhydric alcohol as monomer units, a first polycarboxylic acid having a branch chain of 3 or more carbon atoms, and a second polycarboxylic acid that does not have a branch chain of 3 or more carbon atoms. The branch chain in the first polycarboxylic acid constitutes a pendant group for the first amorphous polyester resin. [0007] The polyhydric alcohol may be, for example, a diol. Examples of the diol include aliphatic diols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, and glycerin, alicyclic diols such as cyclohexanediol, cyclohexanedimethanol, and hydrogenated bisphenol A, and aromatic diols such as an ethylene oxide adduct of bisphenol A and a propylene oxide adduct of bisphenol A. One kind among these examples may be employed as the polyhydric alcohol of the first amorphous polyester resin in some example toner particles. In other example toner particles, a combination of two or more kinds thereof may be employed as the polyhydric alcohol. The diol may be an aromatic diol or an alicyclic diol. According to some examples, the diol is an aromatic diol. In order to form a crosslinked structure or a branched structure that has a sufficient fixability, the polyhydric alcohol may further include, in addition to a diol, a polyhydric alcohol having a valency of 3 or more (for example, glycerin, trimethylolpropane, or pentaerythritol). [0008] The content of the polyhydric alcohol may be within a range having a minimum of 45% by mole, 47% by mole, or 50% by mole, and having a maximum of 55% by mole, 54% by mole, or 53% by mole, based on the total amount of the monomer units in the first amorphous polyester resin. [0009] In a chain having two carboxyl groups in a polycarboxylic acid that is employed as the main chain, a chain that is branched out from this main chain may be referred to as the branch chain in the first polycarboxylic acid. The branch chain may be a chain-like hydrocarbon group and may be, for example, an alkyl group or an alkenyl group. The number of carbon atoms of the branch chain may be within a range having a minimum of 4, 6, 8, 10, or 12, and having a maximum of 30, 28, 26, 24, 22, 20, 18, 16, 14, or 12. [0010] The first polycarboxylic acid may be, for example, a dicarboxylic acid having a branch chain having 3 or more carbon atoms, and may include an anhydride of a dicarboxylic acid having a branch chain having 3 or more carbon atoms. Examples of the first polycarboxylic acid include a succinic acid having an alkyl group having 3 or more carbon atoms, a succinic acid having an alkenyl group having 3 or more carbon atoms, an alkyl bis(succinic acid) having an alkyl group having 3 or more carbon atoms, an alkenyl bis(succinic acid) having an alkenyl group having 3 or more carbon atoms, and anhydrides thereof. Specific examples of the polycarboxylic acid include octyl succinic acid, decyl succinic acid, dodecyl succinic acid, tetradecyl succinic acid, hexadecyl succinic acid, octadecyl succinic acid, isooctadecyl succinic acid, hexenyl succinic acid, octenyl succinic acid, decenyl succinic acid, dodecenyl succinic acid, tetrapropenyl succinic acid, tetradecenyl succinic acid, hexadecenyl succinic acid, isooctadecenyl succinic acid, octadecenyl succinic acid, and nonenyl succinic acid. One kind among these examples may be employed as the first polycarboxylic acid of the first amorphous polyester resin in some example toner particles. In other example toner particles, two or more kinds thereof may be employed as the first polycarboxylic acid. [0011] In order to increase the dispersibility of the crystalline polyester resin in the first amorphous polyester resin, the content of the first polycarboxylic acid may be within a range having a minimum of 1% by mole, 2% by mole, 3% by mole, 4% by mole, or 5% by mole, and having a maximum of 20% by mole, 18% by mole, 16% by mole, or 14% by mole, based on the total amount of the monomer units in the first amorphous polyester resin. [0012] The second polycarboxylic acid may be, for example, a dicarboxylic acid that does not have a branch chain having 3 or more carbon atoms, and includes an anhydride of a dicarboxylic acid that does not have a branch chain having 3 or more carbon atoms. Examples of the second polycarboxylic acid include adipic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylene-2-acetic acid, m-phenylene diglycolic acid, p-phenylene diglycolic acid, o-phenylene diglycolic acid, diphenylacetic acid, diphenyl-p,p'-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracene dicarboxylic acid, cyclohexane dicarboxylic acid, and anhydrides of these polycarboxylic acids. One kind among these examples may be employed as the second polycarboxylic acid of the first amorphous polyester resin in some example toner particles. In other example toner particles, a combination of two or more kinds thereof may be employed as the second polycarboxylic acids. [0013] The second polycarboxylic acid may also be a polycarboxylic acid having a valency of 3 or more, which does not have a branch chain having 3 or more carbon atoms. Examples of this polycarboxylic acid include trimellitic acid, pyromellitic acid, naphthalene tricarboxylic acid, naphthalene tetracarboxylic acid, pyrene tricarboxylic acid, pyrene tetracarboxylic acid, and acid anhydrides, acid chlorides, or esters of these carboxylic acids. [0014] The content of the second polycarboxylic acid may be within a range having a minimum of 30% by mole, 32% by mole, or 34% by mole, and having a maximum of 50% by mole, 48% by mole, or 46% by mole, based on the total amount of the monomer units in the first amorphous polyester resin. [0015] The weight average molecular weight of the first amorphous polyester resin may be less than the weight average molecular weight of the second amorphous polyester resin described below. In order to increase the dispersibility of the crystalline polyester resin in the first amorphous polyester resin, the weight average molecular weight of the first amorphous polyester resin may be within a range having a minimum of 5,000, 6,000, or 8,000, and having a maximum of 40,000, 30,000, 25,000, 18,000, or 16,000. [0016] The weight average molecular weight of the first amorphous polyester resin described herein, is measured according to gel permeation chromatography (GPC) of a tetrahydrofuran (THF)-soluble fraction. For example, the weight average molecular weight may be determined by the following method. Waters e2695 (manufactured by Nihon Waters K.K.) is used as a measuring apparatus, and two sets of Inertsil CN-325 cm (manufactured by GL Sciences, Inc.) are used as columns. A filtrate obtained by introducing 10 mg of a first amorphous polyester resin into 10 mL of tetrahydrofuran (THF) (containing a stabilizer, manufactured by Wako Pure Chemical Industries, Ltd.), stirring the mixture for one hour, and then filtering the mixture through a 0.2 μm filter, is used as a sample. A sample solution in tetrahydrofuran (THF) is injected into the measuring apparatus in an amount of 20 PL, and measurement is made under the conditions of 40 °C and a flow rate of 1.0 mL/min. [0017] The content of the first amorphous polyester resin may be within a range having a minimum of 55% by mass, 60% by mass, or 70% by mass, and having a maximum of 90% by mass, 85% by mass, or 80% by mass, based on the total amount of the binder resin. The content of the first amorphous polyester resin may be within a range having a minimum of 48% by mass or 56% by mass, and having a maximum of 72% by mass or 64% by mass, based on the total amount of the toner particle. [0018] The second amorphous polyester resin may contain a polyhydric alcohol and a polycarboxylic acid that does not have a branch chain having 3 or more carbon atoms as monomer units. The monomer units constituting the second amorphous polyester resin are different from the monomer units constituting the first amorphous polyester resin. Specific examples of the polyhydric alcohol and of the polycarboxylic acid that does not have a branch chain having 3 or more carbon atoms correspond to the same examples as those listed above for the polyhydric alcohols and for the polycarboxylic acid that does not have a branch chain having 3 or more carbon atoms (second polycarboxylic acid), respectively, in the description of the first amorphous polyester resin. One kind of polyhydric alcohol among the corresponding examples may be employed as the polyhydric alcohol of the second amorphous polyester resin according to some example toner particles, or in other example toner particles, a combination of two or more kinds thereof may be employed. In addition, one kind of polycarboxylic acid that does not have a branch chain having 3 or more carbon atoms, among the corresponding examples may be employed according to some example toner particles, or in other example toner particles, a combination of two or more kinds thereof may be employed. [0019] The content of the polyhydric alcohol may be within a range having a minimum of 46% by mole, 48% by mole, or 50% by mole, and having a maximum of 56% by mole, 54% by mole, or 52% by mole, based on the total amount of the monomer units in the second amorphous polyester resin. [0020] The content of the polycarboxylic acid that does not have a branch chain having 3 or more carbon atoms may be within a range having a minimum of 30% by mole, 35% by mole, 40% by mole, 45% by mole, or 48% by mole, and having a maximum of 55% by mole, 53% by mole, or 50% by mole, based on the total amount of the monomer units in the second amorphous polyester resin. [0021] The second amorphous polyester resin may further contain a polycarboxylic acid having a branch chain having 3 or more carbon atoms as monomer units. In this case, the second amorphous polyester resin has a pendant group constituted by the branch chain having 3 or more carbon atoms of the polycarboxylic acid. Namely, the second amorphous polyester resin may have the pendant group in some examples, and may have no pendant group in other examples. Specific examples of the polycarboxylic acid having the branch chain having 3 or more carbon atoms are the same as those previous listed in the description of the polycarboxylic acid having the branched chain having 3 or more carbon atoms (first polycarboxylic acid) in the first amorphous polyester. One kind of polycarboxylic acid having the branch chain having 3 or more carbon atoms among the corresponding examples may be employed according to some example toner particles. In other example toner particles, a combination of two or more kinds thereof may be employed. [0022] The content of the branched polycarboxylic acid having 3 or more carbon atoms may be within a range having a minimum of 5% by mole, 10% by mole, or 15% by mole, and having a maximum of 30% by mole, 25% by mole, or 20% by mole, based on the total amount of monomer units in the second amorphous polyester resin. [0023] In order to inhibit a decrease in the strength of the binder resin and a decrease in the glass transition temperature of the toner particle, and to increase the low-temperature fixability, the intensity of images fixed on paper, and the preservability of the toner particle, the weight average molecular weight of the second amorphous polyester resin may be within a range having a minimum of 30,000, 40,000, or 45,000, and having a maximum of 80,000, 70,000, or 60,000. The weight average molecular weight of the second amorphous polyester resin is measured by the same method as that for the weight average molecular weight of the first amorphous polyester resin. [0024] The content of the second amorphous polyester resin may be within a range having a minimum of 5% by mass, 10% by mass, or 15% by mass, and having a maximum of 40% by mass, 35% by mass, or 30% by mass, based on the total amount of the binder resin. The content of the second amorphous polyester resin may be within a range having a minimum of 5% by mass or 10% by mass, and having a maximum of 40% by mass or 35% by mass, based on the total amount of the toner particle. [0025] The mass ratio of the content of the first amorphous polyester resin to the content of the second amorphous polyester resin (content (mass) of first amorphous polyester resin/content (mass) of second amorphous polyester resin) may be within a range having a minimum of 60/40, 65/35, or 70/30, and having a maximum of 90/10, 85/15, or 80/20. [0026] The total content of the first amorphous polyester resin and the second amorphous polyester resin may be within a range having a minimum of 60% by mass, 70% by mass, or 80% by mass, and having a maximum of may be 92% by mass, 90% by mass, or 85% by mass, based on the total amount of the binder resin. The total content of the first amorphous polyester resin and the second amorphous polyester resin may be within a range having a minimum of 48% by mass or 56% by mass, and having a maximum of may be 72% by mass or 64% by mass, based on the total amount of the toner particle. [0027] The crystalline polyester resin may be a polyester resin having a clear endothermic peak in modified differential scanning calorimetry (MDSC). The binder resin may include a crystalline polyester resin, in order to increase the image glossiness of the toner and to increase the low-temperature fixability. [0028] A crystalline polyester resin is, for example, a reaction product between a polyhydric alcohol and a polycarboxylic acid. In other words, a crystalline polyester resin includes a polyhydric alcohol and a polycarboxylic acid as monomer units. [0029] According to examples, the polyhydric alcohol is a diol. In order to more easily achieve a crystalline polyester having a suitable melting point for the toner particle, the number of carbon atoms of the polyhydric alcohol may be within a range having a minimum of 4, 5, or 6, having a maximum of 12, 11, or 10. Examples of the polyhydric alcohol include 1,6-hexanediol and 1,9-nonanediol. [0030] The polycarboxylic acid may be an aliphatic polycarboxylic acid in some examples, or may be a dicarboxylic acid in other examples. In order to increase the linearity of the structure of the crystalline polyester resin, and to increase the affinity with the first amorphous polyester resin, the polycarboxylic acid may be an aliphatic dicarboxylic acid. In order to more easily achieve a crystalline polyester having a suitable melting point for the toner particle, the number of carbon atoms of the polycarboxylic acid (provided that the number of carbons except for the carbons constituting a carboxyl group) may be within a range having a minimum of 6, 7, or 8, having a maximum of 12, 11, or 10. Examples of the polycarboxylic acid include 1,8-octane dicarboxylic acid, 1,10-decane dicarboxylic acid and 1,12-dodecane dicarboxylic acid. [0031] In order to inhibit a decrease in the strength of the binder resin and a decrease in the glass transition temperature of the toner particle, and to increase the low-temperature fixability, the intensity of images fixed on paper, and the preservability of the toner particle, the weight average molecular weight of the crystalline polyester resin may be within a range having a minimum of 5,000, 5,100, or 5,400, and having a maximum of 15,000, 10,000, 8,000, 5,900, or 5,700. The weight average molecular weight of the crystalline polyester resin is measured by the same method as that for the weight average molecular weight of the first amorphous polyester resin. [0032] The content of the crystalline polyester resin may be within a range having a minimum of 8% by mass, 10% by mass, or 12% by mass, and having a maximum of 30% by mass, 25% by mass, or 23% by mass, based on the total amount of the binder resin. The content of the crystalline polyester resin may be within a range having a minimum of 6% by mass or 8% by mass, and having a maximum of 20% by mass or 10% by mass, based on the total amount of the toner particle. [0033] The mass ratio of the content of the amorphous polyester resins to the content of the crystalline polyester resins (content (mass) of amorphous polyester resins/content (mass) of crystalline polyester resins) may be within a range having a minimum of 80/20 or 85/15, and having a maximum of 95/5 or 90/10. [0034] The binder resin may consist of the first amorphous polyester resin, the second amorphous polyester resin, and the crystalline polyester resin, in some examples, or may further include other resins in addition to the first amorphous polyester resin, second amorphous polyester resin, and crystalline polyester resin, according to other examples. [0035] Examples of the other resins may include a styrene-(meth)acrylic copolymer, an epoxy resin, and a styrene-butadiene copolymer. The styrene-(meth)acrylic copolymer may be a copolymer of a styrene-based monomer and a (meth)acrylic acid ester-based monomer. Examples of the styrene-based monomer include styrene, o- (m-, p-) methylstyrene and m- (p-) ethylstyrene. Examples of the (meth)acrylic acid ester-based monomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and diethylaminoethyl (meth)acrylate. [0036] The total content of the first amorphous polyester resin, second amorphous polyester resin, and crystalline polyester resin in the binder resin may be within a range having a minimum of 80% by mass, 85% by mass, or 90% by mass, and having a maximum of may be 98% by mass or 95% by mass, based on the total amount of the binder resin. [0037] The content of the binder resin in the toner particle may be within a range having a minimum of 40% by mass, 45% by mass, or 50% by mass, and having a maximum of 90% by mass, 85% by mass, or 75% by mass, based on the total amount of the toner particle. [0038] Colorant The colorant may include at least one colorant selected from, for example, a black colorant, a cyan colorant, a magenta colorant, and a yellow colorant. Regarding the colorant, one kind of colorant may be used in some examples, or in other examples, two or more kinds may be used as a mixture, in consideration of hue, chroma, brightness, weather-resistance, dispersibility in toner, and the like. [0039] The black colorant may be carbon black or aniline black. The yellow colorant may be a condensed nitrogen compound, an isoindolinone compound, an anthraquine compound, an azo metal complex, or an allylimide compound. Specific examples of the yellow colorant include C.I. Pigment Yellow 12, 13, 14, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 168, and 180. [0040] The magenta colorant may be a condensed nitrogen compound, anthraquine, a quinacridone compound, a basic dye lake compound, a naphthol compound, a benzimidazole compound, a thioindigo compound, or a perylene compound. Specific examples of the magenta colorant include C.I. Pigment Red 2, 3, 5, 6, 7, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 122, 144, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221, and 254. [0041] The cyan colorant may be a copper phthalocyanine compound or a derivative thereof, an anthraquine compound, or the like. Specific examples of the cyan colorant include C.I. Pigment Blue 1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, and 66. [0042] In order to sufficiently exhibit a coloration effect, the content of the colorant may be within a range having a minimum of 0.5% by mass, 1% by mass, or 2% by mass, based on the total amount of the toner particle. Additionally, in order to achieve a sufficient amount of frictional electrification without having significant influence on the increase in the production cost of the toner particle, the range of the content of the colorant may have a maximum of 15% by mass, 12% by mass, or 10% by mass, based on the total amount of the toner particle. [0043] Wax A wax can function as a mold release agent, for example. Since a mold release agent enhances low-temperature fixability, final image durability, and abrasion resistance characteristics of the toner particle, the type and content of the wax that serves as a mold release agent can be determined by taking the characteristics of the toner into account. [0044] The wax may be a natural wax or a synthetic wax. Although the type of the wax is not limited to such waxes, the wax can be selected from the group consisting of, for example, a polyethylene-based wax, a polypropylene-based wax, a silicon wax, a paraffin-based wax, an ester-based wax, a carnauba wax, beeswax, and a metallocene wax. Specific examples include solid paraffin wax, microwax, rice wax, a fatty acid amide-based wax, a fatty acid-based wax, an aliphatic monoketone, a fatty acid metal salt-based wax, a fatty acid ester-based wax, a partially saponified fatty acid ester-based wax, a silicone varnish, a higher alcohol, and carnauba wax. Furthermore, a polyolefin such as a low-molecular weight polyethylene or polypropylene, or the like can also be used. [0045] The wax may be an ester-based wax containing an ester group. Specific examples thereof include, for example, a mixture of an ester-based wax and a non-ester-based wax, and an ester group-containing wax obtained by incorporating an ester group into a non-ester-based wax. [0046] With regard to an ester-based wax component, since an ester group has high affinity with a latex component of toner particle, the wax can distributed substantially uniformly in the toner particle, so as to effectively exhibit the action of the wax. A non-ester-based wax component tends to suppress the excessive plasticizing action in a case in which the wax is composed of ester-based waxes exclusively, as a result of mold release action with latex. Consequently, a mixture of an ester-based wax and a non-ester-based wax tends to maintain a suitable developability of toner for a long period of time. [0047] The ester-based wax may be an ester of a fatty acid having 15 to 30 carbon atoms and a monohydric alcohol to a pentahydric alcohol, such as behenyl behenate, stearyl stearate, stearic acid ester of pentaerythritol, and montanic acid glyceride. The alcohol component constituting the ester may be a monohydric alcohol having 10 to 30 carbon atoms or a polyhydric alcohol having 3 to 30 carbon atoms. Examples of the non-ester-based wax include a polyethylene-based wax, a polypropylene-based wax, a silicon wax, and a paraffin-based wax. [0048] Examples of the ester-based wax containing an ester group include a mixture of a paraffin-based wax and an ester-based wax, and an ester group-containing paraffin-based wax, and specific examples thereof include, for example, product names P-212, P-280, P-318, P-319, and P-419 of CHUKYO YUSHI CO., LTD. [0049] In order to sufficiently maintain the compatibility with a latex that is used at the time of production of toner particles when the wax is a mixture of a paraffin-based wax and an ester-based wax, , the content of the ester-based wax may be within a range having a minimum of 1% by mass, 5% by mass, 10% by mass, or 15% by mass, based on the total amount of the mixture of a paraffin-based wax and an ester-based wax. Additionally, in order to achieve a suitable plasticity of the toner particle and to achieve long-term maintenance of developability, the range of the content of the ester-based wax may have a maximum of 50% by mass, based on the total amount of the toner particle. [0050] The melting temperature of the wax may be within a range having a minimum of 60°C or 70°C, and having a maximum of 100°C or 90°C. The wax component may be a component that physically adheres tightly to toner particle but does not form covalent bonding with the toner particle. [0051] In order to achieve a suitable low-temperature fixability and a suitable fixing temperature range, the content of the wax may be within a range having a minimum of 1% by mass, 2% by mass, or 3% by mass, based on the total amount of the toner particle. Additionally, in order to increase preservability and economic efficiency, the range of the content of the wax may have a maximum of 20% by mass, 16% by mass, or 12% by mass, based on the total amount of the toner particle. [0052] Other components The toner particle may further include a charge control agent in some examples. The charge control agent may be internally added or externally added to the toner particle. The charge control agent may be a negative charge control agent or a positive charge control agent. [0053] Examples of the negative charge control agent include a salicylic acid metal compound, a naphthoic acid metal compound, a dicarboxylic acid metal compound, a polymer type compound having sulfonic acid or carboxylic acid in a side chain, a polymer type compound having a sulfonic acid salt or a sulfonic acid esterification product in a side chain, a polymer type compound having a carboxylic acid salt or a carboxylic acid esterification product in a side chain, a boron compound, a urea compound, a silicon compound, and a calixarene. [0054] Examples of the positive charge control agent include a quaternary amount salt, a polymer type compound having a quaternary ammonium salt in a side chain, a guanidine compound, and an imidazole compound. [0055] The toner particle may further include inorganic microparticles in some examples. The inorganic microparticles may be internally added or externally added to the toner particles. Examples of the inorganic microparticles include silica microparticles, titanium oxide microparticles, and aluminum oxide microparticles. These inorganic microparticles may be, for example, hydrophobized with a hydrophobizing agent such as a silane compound, a silicone oil, or a mixture thereof. [0056] The specific surface area of the inorganic microparticles may be within a range having a minimum of 10 m 2 /g or 50 m 2 /g, and having a maximum of 400 m 2 /g or 50 m 2 /g. The content of the inorganic microparticles may be within a range having a minimum of 0.1% by mass and having a maximum of 10% by mass, based on the total amount of the toner particle. [0057] The toner particle may contain iron element, silicon element, and sulfur element, and in addition to these elements, fluorine element may also be further incorporated if necessary. The iron element and the silicon element may be components originating from an aggregating agent and the like. Sulfur element may be a component originating from a production catalyst for a self-adhesive resin, an aggregating agent, and the like. Fluorine element may be a component originating from a production catalyst for a self-adhesive resin and the like. [0058] In order to achieve a toner particle that is more suitable for developing an electrostatically charged image, the content of iron element may be within a range having a minimum of 1.0x10 3 ppm, and having a maximum of 1.0x10 4 ppm or 5.0x10 3 ppm. In order to achieve a toner particle that is more suitable for developing an electrostatically charged image, the content of silicon element may be within a range having a minimum of 1.0x10 3 ppm or 1.5x10 3 ppm, and having a maximum of 5.0x10 3 ppm or 4.0x10 3 ppm. The contents of iron element and silicon element can be controlled by regulating the type, amount, and the like of the aggregating agent to be used. [0059] From the viewpoint that the toner particle can be more suitably used for developing an electrostatically charged image, the content of sulfur element may be within a range having a minimum of 500 ppm or 1,000 ppm, and having a maximum of 3,000 ppm. The content of sulfur element can be controlled by regulating the types, amounts, and the like of the catalyst and aggregating agent to be used. [0060] In order to achieve a toner particle that is more suitable for developing an electrostatically charged image, the content of fluorine atom may be within a range having a minimum of 1.0u10 3 ppm or 5.0u10 3 ppm, and having a maximum of 1.0x10 4 ppm or 8.0x10 3 ppm. The content of fluorine atom can be controlled by regulating the type and amount of the catalyst to be used. [0061] The contents of the various elements in the toner particle can be measured by, for example, fluorescent X-ray analysis. For example, an X-ray analyzer EDX-720 (manufactured by SHIMADZU CORPORATION) is used as a measuring apparatus, and measurement can be performed under the conditions of an X-ray tube voltage of 50 kV and an amount of sample molding of 30.0 g. The contents of various elements can be determined by utilizing the intensity (cps/PA) from the quantification results derived by fluorescent X-ray analysis. [0062] The average particle size of the toner particles may be, for example, within a range having a minimum of 4 μm or 5 μm, and having a maximum of 7 μm or 6 μm. The average particle size of the toner particles is a volume average particle size that may be determined by the following method. Namely, the volume average particle size of the toner particles is measured by a pore electrical resistance method. According to the method, a measurement is performed on 30,000 particles using a Coulter counter (manufactured by Beckman Coulter, Inc.) as a measuring apparatus, ISOTON II (manufactured by Beckman Coulter, Inc.) as an electrolytic solution, and an aperture tube having an aperture diameter of 100 μm. The particles that are measured accordingly are classified in size ranges. A particle size distribution represents the numbers of particles counted in each particle size range, from a smallest diameter range to largest diameter range. Each size range is associated with a volume representing the volume occupied by the particles of that size range. A particle size Dv50 is associated with a point in the distribution curve that corresponds to a cumulative volume of 50% of the total cumulative volume. Namely, based on the particle size distribution of the particles measured, the volumes occupied by the particles included in the divided particle size ranges are cumulated from the smaller diameter side, and the cumulative 50% particle size is designated as the volume average particle size Dv50. [0063] According to some examples, the toner particle may have a core-shell structure. For example. the toner particle may include: a core containing the first amorphous polyester resin, the second amorphous polyester resin, the crystalline polyester resin, the colorant, and the wax; and a shell containing the first amorphous polyester resin and covering the core. The first amorphous polyester resin contained in the shell may be of the same kind (or kinds) as the first amorphous polyester resin contained in the core, according to some examples. In other examples, the shell and the core contain different kinds of the first amorphous polyester resin. [0064] The content of the crystalline polyester resin in the core may be within a range having a minimum of 10% by mass, 15% by mass, or 20% by mass, and having a maximum of 40% by mass, 35% by mass, or 30% by mass, based on the total content of the first amorphous polyester, the second amorphous polyester, and the crystalline polyester in the core. [0065] The mass ratio of the content of the first amorphous polyester resin to the content of the second amorphous polyester resin (content (mass) of first amorphous polyester resin/content (mass) of second amorphous polyester resin) in the core may be within a range having a minimum of 60/40, 65/35, or 70/30, and having a maximum of 95/5, 90/10, 85/15, or 80/20. [0066] The shell may further contain the second amorphous polyester resin. In this case, the mass ratio of the content of the first amorphous polyester resin to the content of the second amorphous polyester resin (content (mass) of first amorphous polyester resin/content (mass) of second amorphous polyester resin) in the shell may be within a range having a minimum of 60/40, 65/35, or 70/30, and having a maximum of 95/5, 90/10, 85/15, or 80/20. The second amorphous polyester resin contained in the shell may be of the same kind (or kinds) as the second amorphous polyester resin contained in the core, according to some examples. In other examples, the shell and the core contain different kinds of the second amorphous polyester resin. [0067] The proportion of the core in a toner particle may be within a range having a minimum of 60% by mass, 65% by mass, or 70% by mass, based on the total amount of the toner particle, in order to increase fixability, and in order to increase heat-resistant storability, the range of the proportion of the core may be have a maximum of 90% by mass, 80% by mass, or 75% by mass, based on the total amount of the toner particle. The proportion of the shell in the toner particle may be within a range having a minimum of 10% by mass, 20% by mass, or 25% by mass, based on the total amount of the toner particle, in order to increase heat-resistant storability. In order to increase fixability, the range of the proportion of the core may have a maximum of 40% by mass, 35% by mass, or 30% by mass, based on the total amount of the toner particle. [0068] The content of the binder resin in the core may be within a range having a minimum of 50% by mass, 60% by mass, or 65% by mass, and may have a maximum of 90% by mass, 80% by mass, or 75% by mass, based on the content of the binder resin in the toner particle. The content of the binder resin in the shell may be within a range having a minimum of 10% by mass, 20% by mass, or 25% by mass, and having a maximum of 50% by mass, 40% by mass, or 35% by mass, based on the content of the binder resin in the toner particle. [0069] In the toner particle described above, given that the complex elastic modulus of the toner particle at the temperature t is represented as G*(t), the storage elastic modulus of the toner particle at the temperature t is represented as G'(t), and the loss elastic modulus of the toner particle at the temperature t is represented as G"(t), there is a temperature range of t1 to t2 at which |dlogG*(t)/dt| is 0.2 or more, and the toner particle has a G''(t)/G'(t) ratio of 0.6 to 1.75 at any temperature t that is within the temperature range of t1 to t2. Consequently, the low-temperature fixability, the fixable temperature range, and the heat-resistant storability of the toner particles are increased. The term “dlogG*(t)/dt” represents a variation of the logarithm of G*(t) (logG*(t)) for a temperature variation dt, and is usually a negative value. The term “|dlogG*(t)/dt|” represents the absolute values of the variation dlogG*(t)/dt. The term G''(t)/G'(t) may also be expressed as tanδ(t) and represents the ratio of the viscous component to the elastic component. [0070] The complex elastic modulus G*(t), the storage elastic modulus G'(t), and the loss elastic modulus G''(t) of the toner particles are measured using a rheometer (for example, a rotating plate rheometer “ARES” (manufactured by TA INSTRUMENTS)) as a measurement apparatus, and a sample obtained by pressure-molding 0.25g of the toner particles at 20 MPa for 1 minute using a tablet molding machine. Then, G*(t), G'(t), and G''(t) are measured at intervals of 1 °C from 20 °C to 180 °C under the conditions of a frequency of 10 Hz, a strain amount control mode (a strain amount of 0.01%-3%), and a heating rate of 2 °C/min. [0071] The temperature range of t1 to t2 may be set within a range of 20 to 100 °C. Namely, the temperature range may have a minimum (lower limit t1) of 20 °C, 30 °C, 40 °C, or 50 °C, for example, and a maximum (upper limit t2) of 100 °C, 90 °C, 80 °C, or 70 °C, for example. [0072] The lower limit of the ratio G''(t)/G'(t) in the temperature range of t1 to t2 may be 0.7, 0.8, 0.9, or 1.0, for example. The upper limit of the ratio G''(t)/G'(t) in the temperature range of t1 to t2 may be 1.7, 1.6, 1.5, 1.4, 1.3, or 1.2, for example. [0073] The toner particle can be used as a one-component system developer. In order to further enhance dot reproducibility and to supply stable images over a long period of time, the toner particle can be mixed with a magnetic carrier and used as a two-component system developer. [0074] Examples of the magnetic carrier include iron oxide; metal particle such as iron, lithium, calcium, magnesium, nickel, copper, zinc, cobalt, manganese, chrome, and rare earth elements; particle of alloys thereof, particle of oxides thereof; magnetic bodies such as ferrites; and a magnetic body-dispersed resin carrier (so-called resin carrier) containing a magnetic body and a binder resin that maintains the magnetic body in a dispersed state. [0075] In a case in which the toner particles are mixed with a magnetic carrier and are used as a two-component system developer, the content of the toner particle may be within a range having a minimum of 2% by mass or 4% by mass, and having a maximum of 15% by mass or 13% by mass, based on the total amount of the two-component system developer. [0076] The toner particle may be accommodated in, for example, a toner cartridge. For example, the toner particle may be accommodated within a container in a toner cartridge. Namely, an example toner cartridge may include a container that accommodates the toner particle described above. Test Examples [0077] Hereinafter, the toner particle will be described by way of Test Examples. [0078] Preparation of first amorphous polyester resins 1A to 1E and comparative amorphous polyester resin 1a Polyhydric alcohols, polycarboxylic acids, and esterification catalysts in the respective feed amounts shown in Table 1 were introduced into a 5-liter four-necked flask equipped with a nitrogen inlet tube, a dewatering tube, a stirrer, and a thermocouple, and the components were caused to react at 230 °C in a nitrogen atmosphere. Thus, first amorphous polyester resins 1A to 1E and comparative amorphous polyester resins 1a, having the respective weight average molecular weights shown in Table 1, were obtained.

[0080] 300 g of a first amorphous polyester resin or of a comparative amorphous polyester resin, 250 g of methyl ethyl ketone, and 50 g of isopropyl alcohol were introduced into a 3-liter double-jacketed reactor, and the interior of the reaction vessel was stirred using a semi-moon type impeller, in an environment of approximately 30°C, so as to dissolve the resin. While a resin solution thus obtained was stirred, 20 g of a 5% aqueous solution of ammonia was slowly added into the reaction vessel, and subsequently 1,200 g of water was added at a rate of 20 g/min to thereby produce an emulsion. Subsequently, a mixed solvent of methyl ethyl ketone and isopropyl alcohol was removed from the emulsion by a reduced pressure distillation method until the concentration of the first amorphous polyester resin or the comparative amorphous polyester resin as a solid component reached 20% by mass, to obtain a latex of the first amorphous polyester resin or of the comparative amorphous polyester resin. [0081] Preparation of second amorphous polyester resins 2A to 2C Second amorphous polyester resins 2A to 2C having the respective weight average molecular weights shown in Table 2 were synthesized in a similar manner as in the case of the first amorphous polyester resins 1A to 1E, with the exception that the polyhydric alcohols and polycarboxylic acids were used in the respective feed amounts shown in Table 2, to obtain latexes of these resins. [0082] Table 2 [0083] Preparation of crystalline polyester resin The polyhydric alcohol and the polycarboxylic acid in the respective feed amounts shown in Table 3 and the esterifying catalyst, were placed in a 5-liter four-necked flask equipped with a nitrogen-introducing tube, a dehydrating tube, a stirrer, and a thermocouple, to react, at 97 °C under a nitrogen atmosphere, in order to obtain crystalline polyester resins 3A to 3C having the respective weight average molecular weights shown in Table 3. In addition, latexes of the resins of the crystalline polyester resins 3A to 3C were obtained in the same manner as the first amorphous polyester resins 1A to 1E. [0084] Table 3 [0085] Preparation of colorant dispersion liquid 10 g of an anionic reactive emulsifier (HS-10: manufactured by DKS Co. Ltd.) was introduced into a milling bath together with 60 g of a Cyan pigment (C.I. Pigment Blue 15:3: manufactured by Clariant AG). Into this, 400 g of glass beads having a diameter of 0.8 to 1 mm were introduced, and milling was performed at normal temperature. As a result, a colorant dispersion liquid was obtained. [0086] Preparation of toner particles In a 3-liter reactor, 800g of a mixed latex obtained by mixing the latexes of the first amorphous polyester resin, the second amorphous polyester resin, and the crystalline polyester resin, and 500 g of deionized water were added so that the solid contents are as shown at "composition of binder resin in core (mass ratio)" in Tables 4 and 5, and subsequently, 60 g of the colorant dispersion liquid, 80 g of a wax dispersion liquid (SELOSOL P-212: manufactured by CHUKYO YUSHI CO., LTD.), and 70 g of polysilicato-iron (PSI-100, manufactured by SUIDO KIKO KAISHA, LTD.) as an aggregating agent, were added. While these were stirred using a homogenizer (ULTRA-TURRAX T50 (trade name) manufactured by IKA-Werke GmbH & CO. KG), the temperature of the mixed solution in the flask was increased to 45 °C at a rate of 1 °C/min. Subsequently, the temperature of the aggregate reaction liquid was increased at a rate of 0.2 °C/min to continue an aggregation reaction, and primary aggregated particles (cores) having a volume average particle size of 4 to 6 μm were obtained. Furthermore, each of the latexes of the first amorphous polyester resin and the second amorphous polyester resin were added so that the solid contents are as shown at "composition of binder resin in core (mass ratio)" and "binder resin in core/binder resin in shell (mass ratio)" in Tables 4 and 5, the mixture was caused to aggregate for 30 minutes, and the shell was formed so as to cover the primary aggregated particles. [0087] Subsequently, a 0.1 N aqueous solution of NaOH was added, and the pH of the mixed liquid was adjusted to 9.5. After 20 minutes elapsed, the temperature of the mixed liquid was increased, the mixed liquid was subjected to fusing for 3 hours or longer and 5 hours or shorter, so as to obtain secondary aggregated particles having a volume average particle size of 4 to 7 μm. Ice of deionized water was added to this aggregated reaction solution at a cooling rate shown in Tables 4 and 5, and the solution was cooled to 28 °C or less. Subsequently, particles were separated through a filtration process and dried, so as to obtain a toner particle precursor. [0088] To 100 parts by mass of the toner particle precursor obtained as described above, 1.3 parts by mass of small particle-sized silica R8200 (average particle size 12 nm, manufactured by NIPPON AEROSIL CO., LTD.), 1.7 parts by mass of medium particle-sized silica RX50 (volume average particle size 40 nm, manufactured by NIPPON AEROSIL CO., LTD.), 1.0 part by mass of large particle-sized silica (X24-9600A-80, volume average particle size 80 nm, manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.5 part by mass of titanium oxide (volume average particle size 15 nm, JMT150IB, manufactured by Tayca Corporation) were added, and the mixture was mixed for 3 minutes at 6,000 rpm using a Powder mixer (Model No. KM-LS-2K, manufactured by KM TECH Co., Ltd.). As a result, toner particles were obtained. [0089] Measurement of Dynamic Viscoelasticity The complex elastic modulus G*(t), the storage elastic modulus G'(t), and the loss elastic modulus G''(t) of each of the obtained toner particles were measured. Specifically, a rotating plate rheometer "ARES" (manufactured by TA Instruments) was used as a measurement apparatus. A measurement sample was obtained by pressure-molding 0.25g of the toner particles at 20 MPa for 1 minute using a tablet molding machine. Then, G*(t), G'(t), and G''(t) were measured from the sample, at intervals of 1 °C from 20 °C to 180 °C under the conditions of a frequency of 10 Hz, a strain amount control mode (strain amount: 0.01%-3%), and a heating rate of 2 °C/min. [0090] Additionally, from the obtained G*(t), the absolute values |dlogG*(t)/dt| of the variation of the logarithm logG*(t) were calculated, and from the obtained G'(t) and G''(t), tanδ(t) = G''(t)/G'(t) was calculated. As a representative example, G*(t) and |dlogG*(t)/dt| at t = 40 to 100 °C of Test Example 1 are shown in FIG. 1, and tanδ(t) at t = 40 to 100 °C of Test Example 1 is shown in FIG.2. [0091] In addition, for each of the toner particles of Test Examples 1 to 9 and Comparative Test Examples 1 to 6, the relationship between |dlogG*(t)/dt| and tanδ(t) is shown in FIGs.3 to 7, and the temperature range (t1 to t2 °C) in which |dlogG*(t)/dt| is 0.2 or more, the maximum value of |dlogG*(t)/dt|, the minimum value of tanδ(t) at t1 to t2 °C, and the maximum value of tanδ(t) at t1 to t2 °C are shown in Tables 4 and 5. [0092] The toner particles of Test Examples 1 to 9 and Comparative Test Examples 1 to 6 were evaluated as follows. The results are shown in Tables 4 and 5. [0093] Evaluation of low-temperature fixability An OHP sheet from which a square having a size of 25 mm u 40 mm had been hollowed out was arranged to face a masked 90 g/m 2 paper, and toner particles were scraped off from above a SUS316 I0.04 u 300 mesh (sieve opening 0.04 mm) at an applied voltage of 1 kV such that the weight of the toner on the paper would be 0.36 mg/cm 2 . [0094] An external fixing device obtained by modifying a fixing device of MultiXpress 7 (manufactured by Samsung Electronics Co., Ltd.) was used, and under the conditions of a heat belt linear velocity of 280 mm/sec, the heat belt surface temperature and the surface temperature of a pressure roller were monitored using a radiation thermometer (H 0.98). When the surface temperature of the pressure roller reached -20°C with respect to the heat belt temperature, paper having an unfixed image printed thereon was fed. [0095] The image density of the image on the fed paper was measured using a colorimeter (X-rite eXact, manufactured by X-Rite, Incorporated). Scotch (registered trademark) tape was attached to the image, a sheet of paper having a basis weight of 60 g/m 3 was interposed therebetween, a weight of 500 g was reciprocated five times, and then the tape was peeled off at 180°. The image density after tape peeling was measured, and the image density after peeling with respect to the image density before peeling was designated as the fixing strength. The above-described operation was carried out by varying the heat belt temperature, and the temperature at which the fixing strength reached 90% was designated as the lowest fixing temperature. The low-temperature fixability is suitable when the lowest fixing temperature is 135°C or less. [0096] Evaluation of fixable temperature range Sheets of paper having an unfixed image printed thereon were fed into the fixing device, each time increasing the heat belt surface temperature by 5°C, in a similar manner as in the evaluation of low-temperature fixability, with the exception that the 90 g/m 2 paper was replaced with a 60 g/m 2 paper. The maximum temperature of the heat belt surface at which the fixing device did not generate an image at the rear end of the paper thus fed, was designated as the highest fixing temperature at which hot offset does not occur. The difference between this highest fixing temperature and the above-described lowest fixing temperature was calculated as the fixable temperature range. A fixable temperature range of 15 °C or more is considered suitable for the fixing operation. [0097] Evaluation of heat-resistant storability The change in the degree of aggregation was measured after leaving the toner particles to stand for 100 hours in an environment at a temperature of 50 °C / a humidity of 80 RH%. For measuring the degree of aggregation, a POWDER TESTER (manufactured by HOSOKAWA MICRON CORPORATION, sieves 53, 45, and 38 μm) was used. The sieves were mounted to be overlapped in the order of, from the top downward, an upper sieve having openings of 53 μm in diameter, a middle sieve having opening of 45 μm in diameter, and a lower sieve having openings of 38 μm in diameter, and 2 g of the toner particles were loaded on the upper sieve. The sieves were vibrated at an amplitude of 1 mm for 40 seconds, and the mass of toner particles remaining on each of the sieves was measured. The degree of aggregation was calculated according to the following formula: Degree of aggregation = (T/2 + C/2 u (3/5) + B/2 u (1/5))/100, wherein T represents the mass of the toner particles remaining on the upper sieve; C represents the mass of toner particles remaining on the middle sieve; and B represents mass of toner particles remaining on the lower sieve. [0098] The ratio of the degree of aggregation represents a ratio of the degree of aggregation measured after leaving the toner particles to stand for 100 hours in the above-described environment, with respect to the degree of aggregation measured before the 100 hours (after /before). A ratio of the degree of aggregation of 20 or less, was found to impart a suitable heat-resistant storability.

Table 4 Table 4 (continued)

[0099] As demonstrated above, in the toner particles containing the first amorphous polyester resin having the pendant group, there may be a temperature range t1 to t2 in which |dlogG*(t)/dt| is 0.2 or more and in which the ratio G''(t)/G'(t) is 0.6 to 1.75, so as to impart the toner particles with increased low-temperature fixability (the lowest fixing temperature is 135 °C or less), increased fixable temperature range (the fixable temperature range is 15 °C or more), and increased heat-resistant storability (the ratio of the degree of aggregation is 20 or less). [0100] It is to be understood that not all aspects, advantages and features described herein may necessarily be achieved by, or included in, any one particular example. Indeed, having described and illustrated various examples herein, it should be apparent that other examples may be modified in arrangement and detail is omitted.