WO2024058817A1

WO2024058817A1 - Toner particles exhibiting gpc peak area ratio

Info

Publication number: WO2024058817A1
Application number: PCT/US2023/013656
Authority: WO
Inventors: Keiichi Ishikawa; Osamu Ieda; Akinori Terada; Takahiro DANNO
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2022-09-16
Filing date: 2023-02-22
Publication date: 2024-03-21

Abstract

Toner particles can contain a binder resin, a colorant, and a release agent. The toner particles can exhibit a peak area ratio of 5/95 to 21/79 in a molecular weight distribution measured by gel permeation chromatography (GPC). The peak area ratio can represent a peak area at a molecular weight of 20,000 or more, relative to a peak area at a molecular weight of less than 20,000. The toner particles can exhibit no peak between 100 °C and 140 °C during a second temperature increase by modulated differential scanning calorimetry (MDSC).

Description

TONER PARTICLES EXHIBITING GPC PEAK AREA RATIO

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

[0001] This application claims priority to Japanese Patent Application Serial No. 2022- 148501, entitled “Toner Particles Exhibiting GPC Peak Area Ratio,” filed September 16, 2022, the contents of such application being hereby incorporated by reference in its entirety and for all purposes as if completely and fully set forth herein.

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, and subsequently, an electrostatically- charged image is formed on this 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. Then, this toner image is transferred and fixed onto the surface of a recording medium. Thereby, an image is formed. As the developer to be used herein, a two-component developer is composed of toner particles and a carrier, and a one- component developer uses a magnetic toner or a non-magnetic toner alone.

DETAILED DESCRIPTION

10003] Hereinafter, an embodiment of the toner particle will be described. The toner particle according to an embodiment contain a binder resin, a colorant, and a release agent.

[0004] The toner particles can have a GPC peak area ratio of 5/95 to 21/79. In the molecular weight distribution of the toner particles measured by gel permeation chromatography (GPC), the GPC peak area ratio can be a peak area ratio AH/ AL of a peak area AH at a molecular weight of 20,000 or more to a peak area AL at a molecular weight of less than 20,000. The GPC peak area ratio AH/ AL can represent the ratio of the amount of a high molecular weight component to the amount of a low molecular weight component when the molecular weight is 20,000 as a reference. The GPC peak area ratio AH/ AL can be measured by the method described by way of example herein. [00051 The lower limit of the GPC peak area ratio AH/ AL may be 8/92, 10/90, 12/88, or 14/86.

The upper limit of the GPC peak area ratio AH/ AL may be 20/80, 18/82, or 16/84.

[0006] The toner particles can exhibit no peak between 100 °C and 140 °C during the second temperature increase by modulated differential scanning calorimetry (MDSC). This peak can appear when toner particles have crystallinity. The toner particle can, for example, lack crystallinity. For example, crystallinity can be derived from a raw material of the binder resin. For example, the raw material or the binder resin can include a polyethylene terephthalate. Modulated differential scanning calorimetry (MDSC) can be performed as described in the examples herein.

[0007] The binder resin may contain a polyester resin. The binder resin may contain a first polyester resin having a softening point of 120 °C or more and a second polyester resin having a softening point of less than 120 °C (a polyester resin having a lower softening point). For example, the polyester resin having the softening point of 120 °C or more can correspond to a polyester resin having a higher softening point. For example, the second polyester resin having the softening point of less than 120 °C can correspond to a polyester resin having a lower softening point.

[0008] For example, a softening point can be defined as Tl/2 based on the flow curve of the resin measured using a flow tester (for example, “Flow Tester Model CFT-500” manufactured by Shimadzu Corporation). The softening point (Tl/2) can, for example, be measured by the method described in examples herein.

[0009] The softening point of the first polyester resin may be 123 °C or higher, 125 °C or higher, or 130 °C or higher, and may be 160 °C or lower, 155 °C or lower, 150 °C or lower, or 145 °C or lower. From the viewpoint of further improving low-temperature fixability, offset resistance, and heat-resistant storability, the softening point may be preferably 140 °C or lower, or 135 °C or lower.

[0010] The softening point of the second polyester resin may be 118 °C or lower, 115 °C or lower, or 110 °C or lower, or may be 80 °C or higher, and may be preferably 85 °C or higher or 90 °C or higher from the viewpoint of further excellent low-temperature fixability and heat-resistant storability. [00111 The first polyester resin may include one or more of a poly condensate of a polyethylene terephthalate, a carboxylic acid, and a diol. The first polyester resin can be obtained by subjecting one or more of a polyethylene terephthalate, a carboxylic acid, and a diol (hereinafter collectively referred to as a “first polycondensation component”) to an esterification reaction. For example, the first polyester resin can be obtained by causing an ester exchange reaction between ethylene glycol contained as a monomer unit in the polyethylene terephthalate and the diol, and causing polycondensation of the carboxylic acid.

[0012] Properties of the polyethylene terephthalate can vary. For example, the number average molecular weight (Mn) of the polyethylene terephthalate may be 5,000 or more, 10,000 or more, or 15,000 or more, and may be 60,000 or less, 55,000 or less, 50,000 or less, or 45,000 or less. The polyethylene terephthalate may include a recycled polyethylene terephthalate. For example, environmentally-friendly toner particles can be provided.

[00131 The amount (charge amount) of the polyethylene terephthalate may be 5% by mass or more, 10% by mass or more, or 20% by mass or more, and may be 85% by mass or less, 80% by mass or less, or 70% by mass or less, based on the total amount of the first polycondensation component.

[0014] The carboxylic acid may be a polycarboxylic acid or an anhydride thereof. The polycarboxylic acid may contain a dicarboxylic acid or an anhydride thereof. Examples of the dicarboxylic acid include but are not limited to a dicarboxylic acid having a pendant group and a dicarboxylic acid having no pendant group.

[0015] The dicarboxylic acid having a pendant group has a chain (pendant group) which can be branched from a main chain having two carboxyl groups. The pendant group may include a chain hydrocarbon group, and may include an alkyl group or an alkenyl group. The carbon number of the pendant group may be 3 or more, 4 or more, 6 or more, 8 or more, 10 or more, or 12 or more, and may be 30 or less, 28 or less, 26 or less, 24 or less, 22 or less, 20 or less, 18 or less, 16 or less, 14 or less, or 12 or less.

[0016] Examples of the dicarboxylic acid having a pendant group include but are not limited to succinic acid having an alkyl group having 3 or more carbon atoms, succinic acid having an alkenyl group having 3 or more carbon atoms, alkylbissuccinic acid having an alkyl group having 3 or more carbon atoms, and alkenylbissuccinic acid having an alkenyl group having 3 or more carbon atoms. Specific examples of the dicarboxylic acid include, for example, octyl succinic acid, decyl succinic acid, dodecyl succinic acid, tetradecyl succinic acid, hexadecylsuccinic acid, octadecylsuccinic acid, isooctadecyl succinic acid, hexenyl succinic acid, octenylsuccinic acid, decenylsuccinic acid, dodecenylsuccinic acid, tetrapropenylsuccinic acid, tetradecenylsuccinic acid, hexadecenylsuccinic acid, isooctadecenylsuccinic acid, octadecenyl succinic acid, and nonenylsuccinic acid.

[0017] Examples of the dicarboxylic acid having no pendant group include, for example, 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, naphthal ene-l,4-dicarboxylic acid, naphthalene-l,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracenedicarboxylic acid, and cyclohexanedicarboxylic acid.

|0018] The carboxylic acid may contain a tricarboxylic acid or an anhydride thereof. Examples of the tricarboxylic acid include trimellitic acid, naphthalenetricarboxylic acid, and pyrenetricarboxylic acid.

[0019 [ The carboxylic acid may contain at least one selected from the group of a dicarboxylic acid or an anhydride thereof, and a tricarboxylic acid or an anhydride thereof, and can preferably contain at least one selected from the group of a dicarboxylic acid or an anhydride thereof having a pendant group, and a tricarboxylic acid or an anhydride thereof from the viewpoint of more easily obtaining toner particles that exhibit no peak of the MDSC described above.

[0020 [ The amount (charge amount) of the carboxylic acid may be 5% by mass or more, 10% by mass or more, or 15% by mass or more, and may be 65% by mass or less, 60% by mass or less, or 55% by mass or less, based on the total amount of the first polycondensation component.

[0021] Examples of the diol include, for example, 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 ethylene oxide adducts of bisphenol A and propylene oxide adducts of bisphenol A. These polyhydric alcohols may be used alone or in combination of two or more. The diol can contain an aromatic diol, and can consist of an aromatic diol (does not contain any diol other than the aromatic diol) from the viewpoint of further excellent offset resistance and heat-resistant storability.

[00221 The content of the diol may be 10% by mass or more, 15% by mass or more, or 20% by mass or more, and may be 70% by mass or less, 65% by mass or less, or 60% by mass or less, based on the total amount of the first polycondensation component.

[0023] The second polyester resin may be a polycondensate of a carboxylic acid and a diol. For example, the second polyester resin can be obtained by subjecting a carboxylic acid and a diol (hereinafter, collectively referred to as “second polycondensation component”) to an esterification reaction. The second polycondensation component may further contain a polyethylene terephthalate. Details of the carboxylic acid, the diol, and the polyethylene terephthalate can be the same as those described for the first polyester resin.

10024] The weight average molecular weight of the first polyester resin can be larger than the weight average molecular weight of the second polyester resin. The weight average molecular weight of the first polyester resin may be 20,000 or more, 30,000 or more, or 40,000 or more, and may be 80,000 or less, 75,000 or less, or 70,000 or less. The weight average molecular weight of the second polyester resin may be 5,000 or more, 6,000 or more, or 7,000 or more, and may be 30,000 or less, 20,000 or less, or 15,000 or less. The weight average molecular weights of the first and second polyester resins can be measured by the method described by example herein.

[00251 The content of the first polyester resin may be 2% by mass or more, 10% by mass or more, or 20% by mass or more, and may be 50% by mass or less, 45% by mass or less, or 40% by mass or less, based on the total amount of the binder resin. The content of the second polyester resin may be 50% by mass or more, 55% by mass or more, or 60% by mass or more, and or less, 90% by mass or less, or 80% by mass or less, based on the total amount of the binder resin. [0026 ] The content of the binder resin in the toner particles may be 40% by mass or more, 45% by mass or more, or 50% by mass or more, and may be 90% by mass or less, 85% by mass or less, or 75% by mass or less, based on the total amount of the toner particles.

[0027] 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 can be used alone, for example. Two or more kinds can be used as a mixture, for example, in consideration of hue, chroma, brightness, weather-resistance, dispersibility in toner, and the like.

[0028] 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.

[0029] 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.

[0030[ 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.

[0031] The content of the colorant may be 1% by mass or more, 2% by mass or more, or 3% by mass or more, and may be preferably 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.

[0032] Examples of the release agent include a wax. The wax may include 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, and a metallocene wax. The wax may preferably be an ester wax. [00331 The ester wax may include, 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 include 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, and montanic acid glyceride.

[0034] The melting point of the wax may be 60 °C or higher or 70 °C or higher, and may be 100 °C or lower or 90 °C or lower.

[0035] The content of the wax may be 1% by mass or more, 2% by mass or more, or 3% by mass or more, and 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.

(0036] The toner particles may further include a charge control agent. The charge control agent may include a negative-type charge control agent or a positive-type charge control agent.

[0037] The toner particle may contain inorganic fine particles. Examples of the inorganic fine particles include silica fine particles, titanium oxide fine particles, and aluminum oxide fine particles.

[0038] The toner particles may be contained in a toner cartridge, for example. A toner cartridge can contain the toner particles described herein. The toner particles may be contained within a container in a toner cartridge. For example, the toner cartridge may contain a container that contains the toner particles.

[0039] The toner particles can be used, for example, in an image forming apparatus. An image forming apparatus can contain the toner particles. The image forming apparatus may contain, for example, a photoreceptor, a charging device, an exposure device that forms an electrostatic latent image on the photoreceptor, a developing device that applies a developer to the electrostatic latent image and develops the electrostatic latent image, and a transfer device that transfers a toner image on the photoreceptor to a transfer material.

[0040] Examples [0041 [ Hereinafter, the toner particles will be described in more detail with reference to examples, but the toner particles are not limited to the examples. First, a method of measuring each characteristic measured in the examples will be described.

[0042] (MDSC measurement of toner particles)

[0043] For example, 0.01±0.005 g of the toner particles can be weighed in an aluminum pan and heated from 30 °C to 200 °C at a heating rate of 20 °C/min using a modulated differential scanning calorimeter Q2000 (manufactured by TA Instruments Inc.). Subsequently, the temperature can be lowered to 0 °C at a temperature lowering rate of 20 °C/min. Thereafter, the temperature can be raised again from 25 °C to 200 °C at a rate of temperature rise of 0.5 °C/min and modulation of 1 °C for 60 seconds, and the heat flow rate during this second temperature rise can be measured. In an example heat flow rate curve, there is no peak between 100 °C and 140 °C when the difference between the baseline and the maximum value of the heat flow rate is less than 1 J/g at 100 °C to 140 °C. For example, there is no temperature at which the difference between the baseline and the maximum value of the heat flow rate is 1 J/g or more at 100 °C to 140 °C.

|0 44] Measurement of molecular weight distribution of toner particles can be performed. For example, the molecular weight distribution of the toner particles can be measured by gel permeation chromatography (GPC) in the following manner.

[0045 [ Preparation of sample solution. 20 mg of the toner particles can be weighed into a 20 cc screw tube, 10 mL of THF can be placed therein, and the mixture can be stirred for 4 hours with an AS ONE Mix Rotor Variable 1-1186-12. The solutions can be filtered through a fluororesin filter having a pore size of 0.2 pm “DISMIC-25JP” (manufactured by ADVANTEC) to remove insoluble components, and the resulting filtrates can be used as sample solutions.

[00461 Molecular weight measurement can be performed. The method can be implemented, for example, by a Waters e2695 (manufactured by Nihon Waters K.K.) was used as measuring apparatus, a cartridge guard column E (4.0x 10 mm x 2), manufactured by GL Science Corporation was used as a holder, and a KF-805L x 2 + KF-800D manufactured by Showa Denko K.K. was used as a column. THF can be flowed as an eluent at a flow rate of 1 mL/min., and the column can be stabilized in a constant temperature bath of 40 °C. Subsequently, 20 pL of the sample solutions can be injected, and measurement can be performed under conditions of 40 °C and a flow rate of 1.0 mL/min.

[0047] The molecular weight of the toner particles can be calculated based on a calibration curve prepared in advance. As the calibration curve, a calibration curve of a third order equation 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-l (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 can be used.

[0048] Measurement of weight-average molecular weight Mw of polyester resin can be performed. The molecular weight distribution of the polyester resin can be measured in the same manner as in the measurement of the molecular weight distribution of the toner particles described herein, and the weight average molecular weight Mw of the polyester resin can be calculated from the obtained molecular weight distribution.

10049] Measurement of softening point of polyester resin can be performed. The softening point of each polyester resin can be measured using a flow tester, for example, a constant test force extrusion type capillary rheometer “Flow Tester CFT-500 type”, manufactured by Shimadzu Corporation). Specifically, 1.0 g of each polyester resin can be pressure-molded and placed in a heating cylinder equipped with a nozzle having a diameter of 1 mm (length of 1 mm), and then a piston can be placed thereon to apply a 98 N (10 kgf) test load. While the resin is heated at a temperature rising rate of 3.0 °C/min, the resin can be extruded from the nozzle, and a piston lowering amount as a function of a melt outflow amount of the resin can be recorded to obtain a flow curve of the resin by a temperature rising method. In the flow curve, a piston lowering amount Smin at an inflection point A at which the piston starts to lower again after an inflection point (a point at which the piston turns from lowering to slightly raising due to thermal expansion of the resin) can first appear. In the flow curve, a piston lowering amount Smax at an end point B of resin outflow can be present. The piston lowering amount S 1/2 at an intermediate point C between the inflection point A and the end point B can be calculated by the following formula:

Sl/2 = Smim + (Smax - Smin) / 2 Eqn. (1)

[0050 | The temperature corresponding to the calculated piston lowering amount Sl/2 can be defined as the softening point Tl/2.

[0051] Next, methods for producing the polyester resin and the toner particles will be described.

| 052] Production of first polyester resins RH1 to RH4 and second polyester resins RL3 can be performed. Alcohols and a polyethylene terephthalate in example amounts shown in Table 1, and 0.1 to 0.2% by weight of an organic titanium such as dibutyltin oxide or titanium lactate as an esterification catalyst based on the total amount of the alcohols and the polyethylene terephthalate can be placed in a 1 -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, heated to 215 °C in a mantle heater in a nitrogen atmosphere, and allowed to react at normal pressure for 2 hours. When the temperature reaches 240 °C, water in the resins can be distilled off under a reduced pressure of 8 to 100 kPa to perform an esterifying reaction. After that, the acid value can be measured, and when the target is reached, the vacuum can be released and the temperature can be lowered to 200 °C. When the temperature reaches 200 °C, TMA can be added so as to achieve the target temperature, and acid-addition reaction can be performed for 1 hour to obtain first polyester resins RH1 to RH4, which can include polyester resins each having a higher softening point, and second polyester resins RL3, which can include a polyester resin having a lower softening point.

[0053] Production of second polyester resins RL1 and RL2 can be performed. Alcohols and carboxylic acids in example amounts shown in Table 1 and an esterifying catalyst can be placed in a 1 -liter four flask equipped with a nitrogen-introducing tube, a dewatering tube, a stirrer, and a thermocouple, and reacted at 260 °C under a nitrogen atmosphere to obtain second polyester resins RL1, RL2, and RL4, which can include polyester resins each having a lower softening point. [00541 The weight-average molecular weight Mw and the softening point Tl/2 of each of the obtained polyester resins can be measured by the methods described herein, according to examples shown in Table 1.

Table 1

[0055] The abbreviations in Table 1 have the following meanings.

BPA-2PO: polyoxypropylene-2,2-bis (4-hydroxyphenyl) propane (average number of moles added of propylene oxide = 2.2)

BPA-2EO: polyoxyethylene-2, 2-bis (4-hydroxyphenyl) propane (average number of moles of ethylene 2EO added = 2)

NPG: neopentyl glycol i-PhA: isophthalic acid

AdiA: adipic acid

DDSA: dodecenyl succinic anhydride

DimerAcid: dimer acid

TMA: trimellitic acid PET : polyethylene terephthalate (number average molecular weight Mn: 24000)

[0056] (Production of toner particles)

[0057] 100 parts by mass of each of the binder resins having compositions shown in Tables 2 and 3, 10 parts by mass of carbon black “MA-100” (manufactured by Mitsubishi Chemical Corporation) as a colorant, and 7 parts by mass of release agent “WEP-5” (manufactured by NOF Corporation, melting point: 83 °C) can be premixed using a Henschel mixer, and then kneaded using a twin-screw kneader (PCM-30 manufactured by Ikegai Corporation). Subsequently, the resultant can be finely pulverized using a supersonic jet pulverizer Labojet (manufactured by Nippon Pneumatic Mfg. Co., Ltd.), and then classified using an air classifier (MDS-I manufactured by Nippon Pneumatic Mfg. Co., Ltd.) to obtain a powder of toner particles having a volume-median particle diameter (D50) of 6.8 pm.

10058] The molecular weight distribution of each of the obtained toner particles of Examples and Comparative Examples can be measured by the example methods herein, and the peak area ratio AH/ AL of the peak area AH in the higher molecular weight region having a molecular weight of 20,000 or more to the peak area AL in the lower molecular weight region having a molecular weight of less than 20,000 can be calculated from the obtained molecular weight distribution. In addition, the obtained toner particles of Examples and Comparative Examples can be subjected to the MDSC measurement by the example methods herein, and the presence or absence of a peak between 100 °C and 140 °C during the second temperature increase can be determined. Furthermore, evaluations can be performed on the obtained toner particles of Examples and Comparative Examples. The results are shown according to Tables 2 and 3.

10059] Evaluation of minimum fixing temperature (MFT)) can be performed. Using a belttype 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 can be 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 can be 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 can be measured. Thereafter, a 3M 810 tape can be attached to the image site, the weight of the 500 g can be reciprocated five times, and then the tape can be removed. Thereafter, the optical density after tape removal can be measured. The lowest temperature at which the fixability (%) can be obtained by the following formula:

Fixability (%) = (initial optical density / optical density after tape removal) x 100 Eqn. (2)

[0060] can be 90% or more can be defined as the minimum fixing temperature (MFT, unit: °C). The lower MFT is, the more excellent the low-temperature fixability is.

[0061] Evaluation of offset temperature can be performed. Using a belt-type fixing device (manufactured by Samsung Electronics Co., Ltd., Color Laser 660 model), an unfixed test image having a 100% solid pattern can be 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 can be fixed at each temperature at intervals of 1 °C in the range of 150 °C to 220 °C. The presence or absence of offset can be visually confirmed. The lowest temperature at which offset occurred can be taken as the offset temperature (°C). The higher the offset temperature is, the more excellent the offset resistance is.

|0062] Heat-resistant storability can be measured. The degree of aggregation after leaving the toner particles to stand for 100 hours in an environment at a temperature of 50 °C / a humidity of 80 RH% can be measured. For the measurement of the degree of aggregation, a POWDER TESTER (manufactured by HOSOKAWA MICRON CORPORATION, sieves 53, 45, and 38 pm) can be used. When the sieves can be mounted to be overlapped in the order of 53 pm, 45 pm, and 38 pm from the top, 2 g of the toner particles can be loaded on the sieve at the top, and the sieves can be vibrated, the mass of toner particles remaining on each of the sieves can be measured (amplitude 1 mm, vibration time for 40 seconds), and the degree of aggregation can be calculated according to the following formula:

Degree of aggregation = (MT/2 + Mc/2 x (3/5) + MB/2 X (1/5)) / 100 Eqn. (4)

[0063] wherein MT represents mass of toner particles remaining on the sieve in the upper row; Me represents mass of toner particles remaining on the sieve in the middle row; and MB represents mass of toner particles remaining on the sieve in the lower row. According to the calculated degree of aggregation, the heat-resistant storability can be evaluated based on criteria including a degree of aggregation less than 20% (S); a degree of aggregation 20% or more and less than 25% (A); a degree of aggregation 25% or more and less than 30% (B); or a degree of aggregation 30% or more (C).

Table 2

Table 3

|(1064] As described above, the toner particles can include toner particles having excellent low-temperature fixability. The toner particles can include toner particles having excellent offset resistance. The toner particles can include toner particles having excellent heat- resistant storability.

[00651 various examples of the toner particles, toner cartridge, and image forming apparatus have been described; however, various modifications and alterations can be made in the scope and the spirit described herein. That is, all alterations are intended to be included to the extent that is maintained in the scope and the spirit described herein.

Claims

WHAT IS CLAIMED IS:

1. Toner particles comprising: a binder resin; a colorant; and a release agent, wherein the toner particles exhibit a peak area ratio of 5/95 to 21/79 in a molecular weight distribution measured by gel permeation chromatography (GPC), wherein the peak area ratio represents a peak area at a molecular weight of 20,000 or more, relative to a peak area at a molecular weight of less than 20,000, and wherein the toner particles exhibit no peak between 100 °C and 140 °C during a second temperature increase by modulated differential scanning calorimetry (MDSC).

2. The toner particles according to claim 1, wherein the binder resin comprises a first polyester resin having a softening point of 120 °C or more and a second polyester resin having a softening point of less than 120 °C.

3. The toner particles according to claim 2, wherein the first polyester resin is a polycondensate of a polyethylene terephthalate, a carboxylic acid, and a diol.

4. The toner particles according to claim 3, wherein the diol consists of an aromatic diol.

5. The toner particles according to claim 3, wherein the carboxylic acid comprises at least one selected from the group consisting of a dicarboxylic acid having a pendant group or an anhydride thereof, and a tricarboxylic acid having a pendant group or an anhydride thereof.

6. A toner cartridge comprising toner particles, wherein the toner particles exhibit a peak area ratio of 5/95 to 21/79 in a molecular weight distribution measured by gel permeation chromatography (GPC), wherein the peak area ratio represents a peak area at a molecular weight of 20,000 or more, relative to a peak area at a molecular weight of less than 20,000, and wherein the toner particles exhibit no peak between 100 °C and 140 °C during a second temperature increase by modulated differential scanning calorimetry (MDSC).

7. The toner cartridge according to claim 6, wherein the toner particles comprise a first polyester resin having a softening point of 120 °C or more and a second polyester resin having a softening point of less than 120 °C.

8. The toner cartridge according to claim 7, wherein the first polyester resin is a polycondensate of a polyethylene terephthalate, a carboxylic acid, and a diol.

9. The toner cartridge according to claim 8, wherein the diol consists of an aromatic diol.

10. The toner cartridge according to claim 8, wherein the carboxylic acid comprises at least one selected from the group consisting of a dicarboxylic acid having a pendant group or an anhydride thereof, and a tricarboxylic acid having a pendant group or an anhydride thereof.

11. An image forming apparatus comprising toner particles, wherein the toner particles exhibit a peak area ratio of 5/95 to 21/79 in a molecular weight distribution measured by gel permeation chromatography (GPC), wherein the peak area ratio represents a peak area at a molecular weight of 20,000 or more, relative to a peak area at a molecular weight of less than 20,000, and wherein the toner particles exhibit no peak between 100 °C and 140 °C during a second temperature increase by modulated differential scanning calorimetry (MDSC).

12. The image forming apparatus according to claim 11, wherein the toner particles comprise a first polyester resin having a softening point of 120 °C or more and a second polyester resin having a softening point of less than 120 °C.

13. The image forming apparatus according to claim 12, wherein the first polyester resin is a poly condensate of a polyethylene terephthalate, a carboxylic acid, and a diol.

14. The image forming apparatus of claim 13, wherein the diol consists of an aromatic diol.

15. The image forming apparatus according to claim 13, wherein the carboxylic acid comprises at least one selected from the group consisting of a dicarboxylic acid having a pendant group or an anhydride thereof, and a tricarboxylic acid or an anhydride thereof.