CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Japanese Patent Application No. 2022-077390, filed on May 10, 2022, in the Japan Patent Office, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] Methods for visualizing 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 uniformly charged, an electrostatically charged image is subsequently formed on the photoreceptor surface, an electrostatic latent image is developed with a developer including toner particles, and the electrostatic latent image is thereby visualized as a toner image. The toner image is transferred and fixed onto a surface of a recording medium, and thereby an image is formed. In various examples, a two-component developer composed of toner particles and a carrier, or a one-component developer that includes a magnetic toner or a non-magnetic toner may be used.

DETAILED DESCRIPTION

[0003] Hereinafter, examples of a toner particle will be described. In various examples, the toner particle may include a binder resin having an amorphous polyester resin and a crystalline polyester resin, a colorant, and a release agent.

[0004] In an example, the binder resin may include terephthalic acid and ethylene glycol as monomer units. The terephthalic acid and ethylene glycol may be included as monomer units at least in the amorphous polyester resin. One or both of terephthalic acid and ethylene glycol may be included as monomer units in the crystalline polyester resin.

[0005] In an example, the amorphous polyester resin may be a polyester resin exhibiting no clear endothermic peak in differential scanning calorimetry (DSC). The amorphous polyester resin may be defined as, for example, a polyester resin exhibiting a stepwise endothermic change in response to being measured by differential scanning calorimetry at a temperature rise rate of 10°C/min, or a polyester resin exhibiting an endothermic peak with a half width of more than 15°C.

[0006] The amorphous polyester resin may include terephthalic acid and ethylene glycol as the monomer units. The terephthalic acid and ethylene glycol included as the monomer units in the amorphous polyester resin may be derived from single terephthalic acid and single ethylene glycol, or may be derived from a polyethylene terephthalate (PET). In an example, the amorphous polyester resin may include terephthalic acid and ethylene glycol derived from a polyethylene terephthalate, as terephthalic acid and ethylene glycol. In this case, the toner particle can be produced from a recycled polyethylene terephthalate, and thus an environmentally friendly toner particle can be provided.

[0007] The amorphous polyester resin may further include a carboxylic acid other than terephthalic acid as a monomer unit. The carboxylic acid other than terephthalic acid may be a polycarboxylic acid or an anhydride thereof. The polycarboxylic acid may contain a dicarboxylic acid or an anhydride thereof, may contain a tri- or more carboxylic acid or an anhydride thereof, or may contain a dicarboxylic acid or an anhydride thereof and a tri- or more carboxylic acid or an anhydride thereof.

[0008] Examples of the dicarboxylic acid include adipic acid, phthalic acid, isophthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylene-2-acetic acid, m-phenylenediglycolic acid, p-phenylenediglycolic acid, o-phenylenediglycolic acid, diphenylacetic acid, diphenyl-p,p’-dicarboxylic acid, naphthalene-1 ,4-dicarboxylic acid, naphthalene- 1 ,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracenedicarboxylic acid, cyclohexanedicarboxylic acid, and the like. [0009] The polycarboxylic acid may be a tri- or more carboxylic acid.

Examples of such a polycarboxylic acid include trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, pyrenetetracarboxylic acid, and the like.

[0010] The amorphous polyester resin may further contain an alcohol other than ethylene glycol as a monomer unit. The alcohol other than ethylene glycol may be a polyhydric alcohol. The polyhydric alcohol may be a diol. Examples of the diol include aliphatic diols such as diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, glycerin, and the like; alicyclic diols such as cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, and the like; and aromatic diols such as ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, and the like.

[0011] In an example, the alcohol may comprise an aromatic diol. In various examples, the alcohol may contain 60% by mole or more, 70% by mole or more, 80% by mole or more, or 90% by mole or more of the aromatic diol, based on the total amount of the alcohol. The alcohol may include the aromatic diol.

[0012] In various examples, the content of terephthalic acid may be 20% by mole or more, 25% by mole or more, 30% by mole or more, 35% by mole or more, 65% by mole or less, 60% by mole or less, or 55% by mole or less, based on the total amount of the monomer units in the amorphous polyester resin.

[0013] In various examples, the content of ethylene glycol may be 10% by mole or more, 15% by mole or more, 20% by mole or more, 55% by mole or less, 50% by mole or less, or 45% by mole or less, based on the total amount of the monomer units in the amorphous polyester resin.

[0014] In various examples, the content of ethylene glycol in the amorphous polyester resin may be 17 to 37 parts by mass, the lower limit thereof may be 20 parts by mass, 23 parts by mass, or 26 parts by mass, and the upper limit thereof may be 35 parts by mass, 33 parts by mass, or 30 parts by mass, with respect to 100 parts by mass of the content of terephthalic acid in the amorphous polyester resin.

[0015] In various examples, the content of the carboxylic acid other than terephthalic acid may be 0% by mole or more, 0.5% by mole or more, 1 % by mole or more, 45% by mole or less, 40% by mole or less, or 35% by mole or less, based on the total amount of the monomer units in the amorphous polyester resin. [0016] In various examples, the content of the alcohol other than ethylene glycol may be 2% by mole or more, 5% by mole or more, 10% by mole or more, 80% by mole or less, 75% by mole or less, or 70% by mole or less, based on the total amount of the monomer units in the amorphous polyester resin.

[0017] In various examples, the weight average molecular weight (Mw) of the amorphous polyester resin may be 4000 or more, 6000 or more, 7000 or more, 20,000 or less, 15,000 or less, or 12,000 or less. The weight average molecular weight (Mw) of the amorphous polyester resin may be measured by example methods as described herein.

[0018] In various examples, the glass transition temperature of the amorphous polyester resin may be 50°C or more and may be 80°C or less. In various examples, the acid value of the amorphous polyester resin may be 5 mgKOH/g or more and may be 20 mgKOH/g or less. The glass transition temperature and acid value of the amorphous polyester resin may be measured by example methods as described herein.

[0019] In various examples, the content of the amorphous polyester resin may be 80 parts by mass or more, 85 parts by mass or more, 90 parts by mass or more, 98 parts by mass or less, 96 parts by mass or less, or 95 parts by mass or less, with respect to 100 parts by mass of the binder resin. In various examples, the content of the amorphous polyester resin may be 70% by mass or more, 75% by mass or more, 80% by mass or more, 95% by mass or less, 90% by mass or less, or 85% by mass or less, based on the total amount of the toner particle.

[0020] The crystalline polyester resin may be a polyester resin exhibiting a clear endothermic peak in modulated differential scanning calorimetry (MDSC). The crystalline polyester resin may contain an alcohol and a carboxylic acid as monomer units.

[0021] In various examples, the alcohol may be a polyhydric alcohol and the polyhydric alcohol may be a diol. The diol may be an aliphatic diol. In various examples, the number of carbon atoms of the alcohol may be 2 or more, 4 or more, 6 or more, 9 or more, 12 or less, 10 or less, or 9 or less. Examples of the alcohol include ethylene glycol, 1 ,6-hexanediol, 1 ,9-nonanediol, and 1 ,10- decanediol.

[0022] The alcohol may include an aliphatic diol having 4 or more carbon atoms in an amount of 90% by mole or more or 95% by mole or more based on the total amount of the alcohol. The alcohol may include the aliphatic alcohol having 4 or more carbon atoms.

[0023] In various examples, the carboxylic acid may be a polycarboxylic acid and the polycarboxylic acid may be a dicarboxylic acid. The dicarboxylic acid may be an aliphatic dicarboxylic acid. In various examples, the number of carbon atoms of the polycarboxylic acid (the number of carbon atoms other than carbon atoms constituting the carboxyl group) may be 8 or more, 9 or more, 10 or more, or 12 or less. Examples of the polycarboxylic acid include 1 ,10-decanedioic acid (sebacic acid) and 1 ,12-dodecanedioic acid.

[0024] The carboxylic acid may include an aliphatic dicarboxylic acid having 10 or more carbon atoms in an amount of 90% by mole or more or 95% by mole or more based on the total amount of the carboxylic acid. The carboxylic acid may include the aliphatic dicarboxylic acid having 10 or more carbon atoms. [0025] In various examples, the weight average molecular weight (Mw) of the crystalline polyester resin may be 4000 or more, 5000 or more, 5500 or more, 13,000 or less, 10,000 or less, or 7000 or less. The weight average molecular weight (Mw) of the crystalline polyester resin may be measured by example methods as described herein.

[0026] The acid value of the amorphous polyester resin may be 5 mgKOH/g or more and may be 20 mgKOH/g or less.

[0027] In various examples, the content of the crystalline polyester resin may be 2 parts by mass or more, 4 parts by mass or more, 5 parts by mass or more, 20 parts by mass or less, 15 parts by mass or less, or 10 parts by mass or less. In various examples, the content of the crystalline polyester resin may be 3% by mass or more, 5% by mass or more, 7% by mass or more, 20% by mass or less, 15% by mass or less, or 13% by mass or less, based on the total amount of the toner particle. [0028] In various examples, the mass ratio of the total content of terephthalic acid and ethylene glycol in the binder resin to the content of the crystalline polyester resin may be 3.5 to 12.0, the lower limit thereof may be 4.0, 4.5, or 5.0, and the upper limit thereof may be 11.0, 10.0, or 9.5. Accordingly, the toner particle may be a toner particle having low-temperature fixability and heat- resistant storage stability.

[0029] The content C (% by mass) of the crystalline polyester based on the total content of the amorphous polyester resin and the crystalline polyester resin may be 3.0% by mass or more, and satisfies Equation (1 ):

C < 33.3 x H + 7.0 (1 )

... Equation (1 ) [0030] wherein H (W/g) represents the height of an endothermic peak based on the toner particle being subjected to differential scanning calorimetry measurement.

[0031] The height H of the endothermic peak based on the toner particle being subjected to differential scanning calorimetry measurement may be measured by example methods described below in Examples.

[0032] In various examples, the content C of the crystalline polyester resin may be 3.5% by mass or more, 4.0% by mass or more, 5.0% by mass or more, 6.0% by mass or more, 7.0% by mass or more, 8.0% by mass or more, 9.0% by mass or more, 20.0% by mass or less, 18.0% by mass or less, or 15.0% by mass or less.

[0033] In various examples, the total content of terephthalic acid and ethylene glycol derived from the polyethylene terephthalate in the amorphous polyester resin may be 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 70% by mass or less, 65% by mass or less, or 60% by mass or less, based on the content of the binder resin.

[0034] The colorant can contain 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 may be used alone, or two or more kinds may be used as a mixture, in consideration of hue, chroma, brightness, weather-resistance, dispersibility in toner, and the like.

[0035] The black colorant may be carbon black, aniline black, and the like. The yellow colorant may be a condensed nitrogen compound, an isoindolinone compound, an anthraquine compound, an azo metal complex, an allylimide compound, and the like. Examples of the yellow colorant include C.l. Pigment Yellow 12, 13, 14, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111 , 128, 129, 147, 168, and 180.

[0036] 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, a perylene compound, and the like. Examples of the magenta colorant include C.l. 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.

[0037] The cyan colorant may be a copper phthalocyanine compound or a derivative thereof, an anthraquine compound, and the like. Examples of the cyan colorant include C.l. Pigment Blue 1 , 7, 15, 15: 1 , 15:2, 15:3, 15:4, 60, 62, and 66. [0038] The content of the colorant may be 1 % by mass or more, 2% by mass or more, 3% by mass or more, 10% by mass or less, 8% by mass or less, or 6% by mass or less, based on the total amount of the toner particle.

[0039] Examples of the release agent include a wax. The wax may be a natural wax or a synthetic wax. Examples of the wax include a polyethylene wax, a polypropylene wax, a silicon wax, a paraffin wax, an ester wax, a carnauba wax, a beeswax, a metallocene wax, and the like. The wax may be an ester wax.

[0040] The ester wax may be, for example, an ester of a fatty acid having 15 to 30 carbon atoms and a monohydric alcohol having 10 to 30 carbon atoms, or may be an ester of a fatty acid having 15 to 30 carbon atoms and a polyhydric alcohol having 3 to 30 carbon atoms. Examples of the ester wax include behenyl behenate, stearyl stearate, stearic acid ester of pentaerythritol, montanic acid glyceride, and the like.

[0041] The melting point of the wax may be 60°C or higher, 70°C or higher, 100°C or lower, or 90°C or lower.

[0042] The content of the wax may be 1 % by mass or more, 2% by mass or more, 3% by mass or more, 15% by mass or less, 10% by mass or less, or 8% by mass or less, based on the total amount of the toner particle.

[0043] In various examples, the toner particles may further contain a charge control agent. The charge control agent may be a negative-type charge control agent or a positive-type charge control agent.

[0044] In various examples, the toner particle may further include inorganic fine particles. Examples of the inorganic fine particles include silica fine particles, titanium oxide fine particles, aluminum oxide fine particles, and the like.

[0045] In various examples, an average particle diameter of the toner particles may be, for example, 3 pm or more, 5 pm or more, 10 pm or less, or 8 pm or less. The average particle diameter of the toner particles refers to a volumemedian particle diameter D50 that may be measured by example methods described below in Examples.

[0046] In various examples, the toner particles may be contained in a toner cartridge. The toner particles may be contained within a container in a toner cartridge. For example, the toner cartridge may contain a container to contain the toner particles.

[0047] Example methods for producing the above-described example toner particle will be described. An example method for producing an example toner particle includes an operation (also referred to as operation A) of reacting a polyethylene terephthalate, a carboxylic acid other than terephthalic acid, and an alcohol other than ethylene glycol to obtain an amorphous polyester resin, and a operation (also referred to as operation B) of forming a toner particle from raw materials containing the amorphous polyester resin, a crystalline polyester resin, a colorant, and a release agent.

[0048] An example method for obtaining the amorphous polyester resin in operation A may be a method in which polycondensation components containing a polyethylene terephthalate, an esterification catalyst, and the like are collectively placed into a reaction vessel, and the amorphous polyester resin is obtained by a known esterification reaction. The polycondensation components may further contain a carboxylic acid and may further contain an alcohol.

[0049] Based on the polycondensation components containing a carboxylic acid and an alcohol other than ethylene glycol, in the esterification reaction, an ester exchange reaction occurs between ethylene glycol contained as a monomer unit in the polyethylene terephthalate and the alcohol, and polycondensation of the carboxylic acid also occurs, whereby the amorphous polyester resin is produced. In this case, the example method of operation A may be a method in which the polyethylene terephthalate, the alcohol, the esterification catalyst, and the like are placed into a reaction vessel in advance, the ester exchange reaction is allowed to sufficiently proceed, the carboxylic acid is placed into the reaction vessel, and the esterification reaction is allowed to proceed to obtain the amorphous polyester resin.

[0050] In the example method using the ester exchange reaction as described above, a part of ethylene glycol contained as a monomer unit in the polyethylene terephthalate remains as a monomer unit in the obtained amorphous polyester resin. The content of ethylene glycol contained as a monomer unit in the amorphous polyester resin (EG residual ratio) may be 40 to 95% by mass, the lower limit may be 45%, 50%, 60%, 65%, or 70% by mass, and the upper limit may be 90%, 85%, 80%, 75%, or 70% by mass, based on the content of ethylene glycol contained as a monomer unit in the polyethylene terephthalate.

[0051] Physical properties of the polyethylene terephthalate are not limited, but as an example, a number average molecular weight (Mn) of the polyethylene terephthalate may be 5000 or more, 10,000 or more, 15,000 or more, 60,000 or less, 55,000 or less, 50,000 or less, or 45,000 or less. The number average molecular weight (Mn) of polyethylene terephthalate may be measured by example methods described below in Examples. The polyethylene terephthalate may be a recycled polyethylene terephthalate. In this case, environmentally- friendly toner particles can be provided.

[0052] The amount of the polyethylene terephthalate may be 20% by mole or more, 30% by mole or more, 35% by mole or more, 85% by mole or less, 70% by mole or less, or 60% by mole or less, based on the total amount of the polycondensation components. Here, the amount of the polyethylene terephthalate is a value obtained by converting a molecular weight (= 192 = 62 + 166 - (18 x 2)) of a structure corresponding to one constituent unit of polyethylene terephthalate (e.g., a unit formed by esterification of one ethylene glycol molecule and one terephthalic acid molecule) into a molar mass of the polyethylene terephthalate. That is, the amount of the polyethylene terephthalate may be a value converted on the assumption that the molar amount of the polyethylene terephthalate is 192 g/mol.

[0053] The carboxylic acid may contain a carboxylic acid other than terephthalic acid. Examples of the carboxylic acid other than terephthalic acid are as described above. The amount of the carboxylic acid other than terephthalic acid may be 0% by mole or more, 0.5% by mole or more, 1 % by mole or more, 45% by mole or less, 40% by mole or less, or 35% by mole or less, based on the total amount of the polycondensation components.

[0054] The carboxylic acid may contain terephthalic acid. The amount of terephthalic acid may be 0.3% by mole or more, 0.6% by mole or more, 1 .0% by mole or more, 10% by mole or less, 7% by mole or less, or 5% by mole or less, based on the total amount of the polycondensation components.

[0055] Examples of the alcohol other than ethylene glycol are as described above. The amount of the alcohol other than ethylene glycol may be 2% by mole or more, 5% by mole or more, 10% by mole or more, 80% by mole or less, 75% by mole or less, or 70% by mole or less, based on the total amount of the polycondensation components.

[0056] Examples of the esterification catalyst include antimony-based, tin- based, titanium-based, and aluminum-based catalysts. The esterification catalyst may be, for example, an organic metal such as dibutyltin dilaurate or dibutyltin oxide, or a metal alkoxide such as tetrabutyl titanate. The amount of the esterification catalyst may be, for example, 0.05 parts by mass or more, 0.2 parts by mass or more, 1 part by mass or less, or 0.7 parts by mass or less, with respect to 100 parts by mass of the total amount of the polycondensation components.

[0057] In operation B, a binder resin containing the amorphous polyester resin obtained in operation A and a crystalline polyester resin, a colorant, a release agent, and other components used are premixed using, for example, a mixer, and kneaded using, for example, a twin-screw kneader. The kneaded mixture may be finely pulverized and classified to obtain toner particles having a desired particle diameter. The toner particles may be further mixed with, for example, inorganic fine particles to obtain toner particles containing the inorganic fine particles attached to the surfaces thereof.

Examples

[0058] Hereinafter, examples of the toner particles will be described in more detail. However, the toner particles are not limited to the examples. First, an example method of measuring each characteristic measured in the examples will be described.

(Endothermic peak temperature of crystalline polyester resin)

[0059] 0.01 to 0.02 g of crystalline polyester resin was weighed in an aluminum pan, heated from room temperature to 140°C at a heating rate of 20°C/min using a modulated differential scanning calorimeter Q2000 (manufactured by TA Instruments Inc.), and held still for 1 minute. Thereafter, the sample was cooled to 0°C at a cooling rate of 20°C/min, held still for 1 minute, heated again to 140°C at a heating rate of 10°C/min, and the heat flow rate was measured. Among the endothermic peaks observed, the temperature corresponding to the top of the peak having the largest heat flow rate was taken as the endothermic peak temperature.

(Glass transition temperature of amorphous polyester resin)

[0060] 0.01 to 0.02 g of amorphous polyester resin was weighed in an aluminum pan, heated from room temperature to 140°C at a heating rate of 20°C/min using a modulated differential scanning calorimeter Q2000 (manufactured by TA Instruments Inc.), and left to stand for 1 minute. Thereafter, the sample was cooled to 0°C at a cooling rate of 20°C/min, held still for 1 minute, heated again to 140°C at a heating rate of 10°C/min, and the heat flow rate was measured. The glass transition temperature was defined as the temperature at the intersection of an extension line of the base line at a temperature equal to or lower than the endothermic peak temperature and a tangent line indicating the maximum slope from the rising portion of the endothermic peak to the top of the peak.

(Height of endothermic peak (H) of toner particles)

[0061] 0.01 to 0.02g of toner particles was weighed in an aluminum pan, and the temperature was heated from room temperature to 140°C at a heating rate of 20°C/min using a modulated differential scanning calorimeter Q2000 (manufactured by TA Instruments Inc.), and was held still for 1 minute. Thereafter, the sample was cooled to 0°C at a cooling rate of 20°C/min, held still for 1 minute, and heated again to 140°C for the second time at a temperature increasing rate of 10°C/min. The height of the endothermic peak H of the toner particles was calculated using Equation (2):

Height of endothermic peak H (W/g) = H1 - H2

... Equation (2) [0062] wherein H1 is the heat-flow rate (W/g) per unit mass (1 g of the toner particles) of the endothermic peak of the crystalline polyester resin observed during the second heating, and H2 is the heat-flow rate (W/g) per unit mass (1 g of the toner particles) of the baseline at a temperature equal to or higher than the endothermic peak temperature.

(Acid value of amorphous polyester resin and crystalline polyester resin)

[0063] The acid value was measured based on the method of JIS K0070. However, the measurement solvents were changed from the mixed solvents of ethanol and ether specified in JIS K0070 to mixed solvents of tetrahydrofuran and toluene (tetrahydrofuran : toluene = 1 : 1 (volume ratio)).

(Number average molecular weight (Mn) of polyethylene terephthalate)

[0064] The molecular weight distribution of the polyethylene terephthalate was measured by a gel permeation chromatography (GPC) method in the following manner, and the number average molecular weight was obtained.

(1 ) Preparation of sample solutions

[0065] The polyethylene terephthalate was dissolved in chloroform at 40°C so that the concentration is 0.5g/100ml. The solutions were filtered using a fluororesin filter "DISMIC 25JP" (manufactured by ADVANTEC) having a pore size of 0.2 pm to remove insoluble components, thereby obtaining sample solutions.

(2) Molecular weight measurement

[0066] A Waters e2695 (manufactured by Nippon Waters Co., Ltd.) was used as a measurement device, Inertsil CN-3 25cm two series (manufactured by GL Sciences Inc.) was used as an analysis column, chloroform was allowed to flow as an eluent at a flow rate of 1 ml per minute, and the column was stabilized in a thermostatic bath at 40°C. The measurement was performed by injecting 100 pl of the sample solution thereto. The molecular weight of the polyethylene terephthalate was calculated based on a calibration curve prepared in advance. The calibration curve was prepared using several types of monodisperse polystyrenes (A-500 (5.0 x 102), A-1000 (1.01 x 103), A-2500 (2.63 x 103), A- 5000 (5.97 x 103), F-1 (1 .02 x 104), F-2 (1.81 x 104), F-4 (3.97 x 104), F-10 (9.64 x 104), F-20 (1.90 x 105), F-40 (4.27 x 105), F-80 (7.06 x 105), and F-128 (1.09 x 106) manufactured by Tosoh Corporation) as standard samples.

(Weight average molecular weight (Mw) of amorphous polyester resin and crystalline polyester resin)

[0067] The weight average molecular weight (Mw) was measured by a gel permeation chromatography (GPC) method of tetrahydrofuran (THF) soluble component. A Waters e2695 (manufactured by Nippon Waters Co., Ltd.) was used as a measuring device, and Inertsil CN-3 25cm two series (manufactured by GL Sciences Inc.) was used as a column. 10mg of the amorphous polyester resin was put into 10mL of tetrahydrofuran (THF) (containing a stabilizer, manufactured by Wako Pure Chemical Industries, Ltd.), stirred for 1 hour, and filtered with a 0.2 pm filter to obtain a filtered liquid, which was used as a sample. The tetrahydrofuran (THF) sample solutions (20 pL) were injected into the measurement apparatus, and measurement was performed under conditions of 40°C and a flow rate of 1 .0 mL/min.

(Volume-median particle diameter (D50) of toner particles)

[0068] The volume-median particle diameter (D50) of the toner particles was measured by a pore electric resistance method. The measurement was performed using a Coulter Counter (manufactured by Beckman Coulter, Inc.) as a measurement device, using ISOTON II (manufactured by Beckman Coulter, Inc.) as an electrolytic solution, and using an aperture tube having an aperture diameter of 100 pm under the condition of the number of measurement particles of 30,000. Based on the measured diameter distribution of the toner particles, the volumes occupied by the particles included in the divided diameter ranges were accumulated from the small particle diameter side, and the diameter at which the accumulation was 50% was taken as the volume-median particle diameter D50. [0069] Example methods for producing the amorphous polyester resins, the crystalline polyester resins, and the toner particles used in Examples will be described below.

(Production of amorphous polyester resins (resins 1 to 7))

[0070] An alcohol and polyethylene terephthalate (PET) shown in Table 1 and 1 wt% of dibutyltin oxide as an esterification catalyst based on the total amount of the alcohol and PET were placed in a 10-liter four flask equipped with a thermometer, a stainless-steel stirring rod, a fractionating column, a dehydration tube, a cooling tube, and a nitrogen inlet tube. The temperature was raised to 235°C in a mantle heater in a nitrogen atmosphere, and the reaction was carried out at normal pressure for 3 hours. Thereafter, an ester exchange reaction was performed by distilling off a desired amount of ethylene glycol under reduced pressure of 8 to 100 kPa. Subsequently, the mixture was cooled to 210°C, the carboxylic acid shown in Table 1 was added thereto, the temperature was raised to 235°C, and the reaction was carried out at normal pressure for 3 hours. Thereafter, the reaction was carried out in 8 kPa until a desired acid value was reached, thereby obtaining resins 1 to 7 which were amorphous polyester resins. [Table 1]

[Table 1] (continuation)

[0071] In Table 1 , "BPA-PO" represents polyoxypropylene-2,2-bis(4- hydroxyphenyl) propane (average number of moles added of propylene oxide = 2), and "BPA-EO" represents polyoxyethylene-2, 2-bis(4-hydroxyphenyl) propane (average number of moles added of ethylene oxide = 2).

[0072] In Table 1 , "Ratio (mass ratio) of TPA + EG derived from PET in amorphous polyester resin" represents the ratio of the total amount of terephthalic acid and ethylene glycol derived from the polyethylene terephthalate in the amorphous polyester resin to the total amount of the amorphous polyester resin, and was calculated by (amount of PET - amount of ethylene glycol distilled off) I (total amount of polycondensation components - amount of ethylene glycol distilled off - amount of water produced by condensation).

[0073] In Table 1 , "Ratio (mass ratio) of TPA + EG in amorphous polyester resin" represents the ratio of the total amount of terephthalic acid and ethylene glycol in the amorphous polyester resin to the total amount of the amorphous polyester resin, and was calculated by (amount of PET + amount of terephthalic acid - amount of ethylene glycol distilled off) I (total amount of polycondensation component - amount of ethylene glycol distilled off -amount of water produced by condensation).

[0074] In Table 1 , "EG residual ratio (% by mass)" represents the content of ethylene glycol in the amorphous polyester resin based on the content of ethylene glycol in the polyethylene terephthalate, and was calculated by [1 - (amount of ethylene glycol distilled off I amount of PET * 60 / 192)] x 100.

[0075] In Table 1 , "EG in amorphous polyester resin I TPA in amorphous polyester resin (mass ratio)" represents the mass ratio of the content of ethylene glycol in the amorphous polyester resin to the content of terephthalic acid in the amorphous polyester resin, and was calculated by measuring the amorphous polyester resin by proton nuclear magnetic resonance spectroscopy (1 H-NMR method) under the following conditions:

Measurement apparatus: nuclear magnetic resonance apparatus JNM- 400A manufactured by JEOL Ltd.

Sample temperature: room temperature

Measurement solvent: deuterated chloroform Sample rotation rate: about 15Hz

Chemical shift criteria: 1 H [TMS, 0 ppm]

[0076] From the obtained 1 H-NMR chart, peaks independent of peaks attributed to constituent elements of other alcohols and other carboxylic acids were selected from peaks attributed to constituent elements of ethylene glycol and terephthalic acid, and integral values of the respective peaks were calculated. The molar ratio of ethylene glycol and terephthalic acid was calculated from the calculated integral value, and further converted into a mass ratio. The mass ratio was calculated by multiplying the molar ratio by 601 132.

(Production of crystalline polyester resins (resins 8 to 12))

[0077] An alcohol and a carboxylic acid shown in Table 2 and 1 wt% of dibutyltin oxide as an esterification catalyst based on the raw materials were placed in a 10-liter four flask equipped with a thermometer, a stainless-steel stirring rod, a fractionating column, a dehydration tube, a cooling tube, and a nitrogen inlet tube. The temperature was raised to 140°C in a mantle heater in a nitrogen atmosphere, and reaction was performed for 5 hours. Thereafter, the temperature was raised stepwise to 210°C at a temperature raising rate of 0.2°C/min. Subsequently, the reaction was carried out in 8 kPa until a desired acid value was reached, thereby obtaining resins 8 to 12 which were crystalline polyester resins.

[Table 2]

(Production of toner particles)

[0078] 100 parts by mass of a binder resin obtained by mixing the amorphous polyester resin and crystalline polyester resin shown in Tables 3 and 4, 6 parts by mass of carbon black "MA-100" (manufactured by Mitsubishi Chemical Corporation) as a colorant, 6 parts by mass of release agent "WEP-5" (manufactured by NOF Corporation, melting point: 83°C), and 1 part by mass of charge control agent "T-77" (manufactured by Hodogaya Chemical Co., Ltd.) were premixed using a Henschel mixer, and kneaded using a twin-screw kneader (PCM-30 manufactured by Ikegai Corporation). The resultant was finely pulverized using a supersonic jet pulverizer Labojet (manufactured by Nippon Pneumatic Mfg. Co., Ltd.), and classified using an air classifier (MDS-I manufactured by Nippon Pneumatic Mfg. Co., Ltd.) to obtain a powder of toner base particles having a volume-median particle diameter (D50) of 6.8 pm.

[0079] To 100 parts by mass of the obtained powder, 1 .0 parts by mass of an external additive "Aerosil R-972" (hydrophobic silica, manufactured by Nippon Aerosil Co., Ltd., average particle diameter 16nm) was added and mixed with a Henschel mixer at 3600 r/min for 5 minutes to perform external additive treatment, thereby obtaining toner particles having a volume-median particle diameter (D50) of 6.8 pm. Each of the obtained toner particles was evaluated as follows. The results are shown in Tables 3 and 4.

(Minimum fixing temperature (MFT))

[0080] Using a belt-type fixing device (a fixing device of color laser 660 model (trade name) manufactured by Samsung Electronics Co., Ltd.), an unfixed test image having a 100% solid pattern was fixed on a test sheet of 60 g paper (X-9 (trade name) manufactured by Boise Co., Ltd.) under conditions of a fixing speed of 160 mm/second and a fixing time of 0.08 seconds. The test unfixed image was fixed at each temperature at intervals of 1 °C in the range of 110°C to 180°C. The initial optical density of the fused image was measured. Thereafter, a 3M 810 tape was attached to the image site, a weight of 500 g was reciprocated five times, and the tape was removed. Thereafter, the optical density after tape removal was measured. The lowest temperature at which the fixability (%) obtained by Equation (3) was 90% or more was defined as the minimum fixing temperature (MFT).

Fixability (%) = (initial optical density I optical density after tape removal) x 100 ... Equation (3) [0081] Based on MFT being 135°C or less, low-temperature fixability is excellent.

(Heat-resistant storabilitv)

[0082] The change in the degree of aggregation at the time of leaving the toner particles to stand for 100 hours in an environment at a temperature of 50°C I a humidity of 80 RH% was measured. For the degree of aggregation, a POWDER TESTER (manufactured by HOSOKAWA MICRON CORPORATION, sieves 53, 45, and 38 pm) was used. Based on the sieves being mounted to be overlapped in the order of 53 pm, 45 pm, and 38 pm from the top, 2 g of the toner particles were loaded on the sieve at the top, and the sieves were vibrated, the mass of toner particles remaining on each of the sieves was measured (amplitude 1 mm, vibration time for 40 seconds), and the degree of aggregation was calculated according to Equation (4):

Degree of aggregation = (T/2 + C/2 x (3/5) + B/2 x (1 /5))/100

... Equation (4) [0083] wherein T represents the mass of toner particles remaining on the sieve in the upper row, C represents the mass of toner particles remaining on the sieve in the middle row, and B represents the mass of toner particles remaining on the sieve in the lower row.

[0084] Based on the degree of aggregation after leaving for 100 hours being 30 or lower, the heat-resistant storability is excellent. [Table 3]

[Table 3] (continuation)

[Table 4]

[0085] In Tables 3 and 4, the "Content of TPA + EG derived from PET in binder resin (% by mass)" represents the total content of terephthalic acid and ethylene glycol derived from the polyethylene terephthalate based on the total amount of the binder resin, and was calculated by [(amount of PET - amount of distilled ethylene glycol) I (total amount of polycondensation components - amount of distilled ethylene glycol - amount of water produced by condensation)] x (mass of amorphous polyester resin).

[0086] In Tables 3 and 4, "TPA + EG amount I crystalline polyester resin amount (mass ratio) in binder resin" represents the mass ratio of the total amount of terephthalic and ethylene glycol in the binder resin to the content of crystalline polyester resin, and was calculated by [(ratio (mass ratio) of TPA + EG of amorphous polyester resin) x mass of amorphous polyester resin] I mass of crystalline polyester resin.

[0087] As described above, an example toner particle may be a toner particle having excellent low-temperature fixability and heat-resistant storage stability.

[0088] It should be understood that examples of the toner particle and toner cartridge described herein should be considered in a descriptive sense and not for purposes of limitation. Descriptions of features or aspects within each example should typically be considered as available for other similar features or aspects in other examples. While examples have been described, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.