Toner for developing electrostatic image

Abstract

To provide a toner for electrostatic charge image development excellent in suppression of photoreceptor fog under high temperature and high humidity.SOLUTION: An electrostatic charge image developing toner containing toner base particles and an external additive, wherein the toner base particles contain a polyester resin and a polymethyl methacrylate-based resin, the polyester resin contains an aromatic moiety and / or an unsaturated double bond, and a content of the polymethyl methacrylate-based resin is 5 parts by mass or more and 45 parts by mass or less with respect to 100 parts by mass of the polyester resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a toner for developing electrostatic images used in developing latent images formed in electrophotography, electrostatic recording, electrostatic printing, and the like. [Background technology]

[0002] Patent Document 1 discloses a toner comprising colored resin particles and resin microparticles attached to the surfaces of the colored resin particles and having a volume particle diameter smaller than that of the colored resin particles, wherein R0 / r is 150 or less, where R0 (μm) is the volume average particle diameter of the colored resin particles and r (μm) is the volume average particle diameter of the resin microparticles, and polymethyl methacrylate resin is used as the resin microparticles.

[0003] Patent Document 2 discloses an electrophotographic toner containing polylactic acid and polymethyl methacrylate having a molecular weight of 5,000 to 50,000 as binder resins, wherein the blending amount of the polymethyl methacrylate is 5 to 45% by mass relative to the amount of the toner.

[0004] Patent Document 3 discloses a toner for developing electrostatic images, which is characterized in that the toner is composed of at least a binder resin, a colorant, and a release agent, and the release agent contains fine particles capable of absorbing oil from the release agent, and polymethyl methacrylate resin is used as the fine particles capable of absorbing oil from the release agent. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-68331 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-175724 [Patent Document 3] Japanese Patent Application Publication No. 11-72950 Summary of the Invention [Problem to be solved by the invention]

[0006] Polymethyl methacrylate resins have the property of easily becoming positively charged due to friction with developing rollers, etc., but they are unable to retain the generated charge and tend to leak, resulting in significant degradation of image quality due to photoreceptor fogging under high temperature and humidity conditions.

[0007] The present invention relates to a toner for developing electrostatic images that is excellent in suppressing photoreceptor fogging under high temperature and high humidity conditions. [Means for solving the problem]

[0008] The present invention relates to a toner for developing electrostatic images, which contains toner base particles and an external additive, wherein the toner base particles contain a polyester resin and a polymethyl methacrylate resin, the polyester resin contains an aromatic moiety and / or an unsaturated double bond, and the content of the polymethyl methacrylate resin is 5 parts by mass or more and 45 parts by mass or less per 100 parts by mass of the polyester resin. [Effects of the Invention]

[0009] The toner for developing electrostatic images of the present invention is highly effective in suppressing photoreceptor fogging under high temperature and high humidity conditions. DETAILED DESCRIPTION OF THE INVENTION

[0010] The electrostatic image developing toner of the present invention contains toner base particles and external additives, and has a major feature in that the toner base particles contain a polyester resin containing an aromatic moiety and / or an unsaturated double bond and a predetermined amount of a polymethyl methacrylate resin. The reason why the electrostatic image developing toner of the present invention can suppress the occurrence of photoreceptor fogging under high temperature and high humidity conditions is not clear, but is presumed as follows. Note that the following mechanism is presumed and is not limited thereto.

[0011] Polymethyl methacrylate resins have the property of being easily positively charged by friction with a developing roller or the like, but have the drawback of being unable to retain the generated charge and prone to leaking. However, in the present invention, we have discovered that by combining a polyester resin having an aromatic moiety and / or an unsaturated double bond in its molecular skeleton with a polymethyl methacrylate resin, we can obtain a toner that exhibits excellent charge stability and suppresses photoreceptor fogging even in high-temperature, high-humidity environments. By incorporating a polyester resin having an aromatic moiety and / or an unsaturated double bond and a polymethyl methacrylate resin in toner particles (toner mother particles), the polymethyl methacrylate resin, which serves as a charge generating site, is dispersed throughout the toner particles, increasing its contact area with the polyester resin and reducing its contact area with the air. Therefore, while suppressing charge leakage via moisture in the air, the aromatic moiety and / or unsaturated double bond in the surrounding polyester resin traps and retains the charge generated in the polymethyl methacrylate resin. This is believed to maintain stable chargeability and suppress photoreceptor fogging even in high-temperature, high-humidity environments where charge stabilization is difficult.

[0012] As described above, the toner base particles contain a polyester resin and a polymethyl methacrylate resin.

[0013] The polyester resin contains an aromatic moiety and / or an unsaturated double bond, and is preferably a polycondensation product of raw material monomers containing an aromatic moiety and / or an unsaturated double bond.

[0014] The raw material monomer preferably contains an alcohol component and a carboxylic acid component, and the alcohol component having an aromatic moiety is preferably a compound represented by the formula (I):

[0015] [ka]

[0016] (wherein OR and RO are oxyalkylene groups, R is an ethylene group and / or a propylene group, x and y are the average number of moles of alkylene oxide added and are each a positive number, and the sum of x and y is 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less.) Examples of the alkylene oxide adduct of bisphenol A represented by the formula:

[0017] An example of the alcohol component containing an unsaturated double bond is 1,4-dihydroxy-2-butene.

[0018] Examples of other alcohol components include saturated aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, neopentyl glycol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol; alicyclic diols such as cyclohexanediol; and trihydric or higher saturated aliphatic alcohols such as sorbitol, pentaerythritol, glycerin, and trimethylolpropane.

[0019] Examples of the carboxylic acid component having an aromatic moiety include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and phthalic acid, trivalent or higher aromatic carboxylic acids such as trimellitic acid and pyromellitic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

[0020] Examples of the carboxylic acid component containing an unsaturated double bond include unsaturated dicarboxylic acids such as fumaric acid, maleic acid, succinic acid derivatives substituted with an alkenyl group having from 2 to 20 carbon atoms, and citraconic acid, anhydrides of these acids, and alkyl esters of these acids having from 1 to 3 carbon atoms.

[0021] Examples of other carboxylic acid components include succinic acid, succinic acid derivatives substituted with an alkyl group, saturated dicarboxylic acids such as glutaric acid, adipic acid, and sebacic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

[0022] The alcohol component may appropriately contain a monohydric alcohol, and the carboxylic acid component may appropriately contain a monocarboxylic acid compound, and these may be monomers having an aromatic moiety and / or an unsaturated double bond.

[0023] The content of raw material monomers (alcohol components and / or carboxylic acid components) having an aromatic moiety and / or an unsaturated double bond in the raw material monomers is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more, but 100 mol% or less.

[0024] In this specification, macromonomers and hydroxycarboxylic acids such as lactic acid are not included in the alcohol component and carboxylic acid component.

[0025] The equivalent ratio of the carboxyl groups of the carboxylic acid component to the hydroxyl groups of the alcohol component (COOH groups / OH groups) is preferably 0.6 or more, more preferably 0.7 or more, even more preferably 0.8 or more, and is preferably 1.3 or less, more preferably 1.2 or less.

[0026] The polyester resin can be produced, for example, by polycondensing an alcohol component and a carboxylic acid component in an inert gas atmosphere, preferably in the presence of an esterification catalyst, and optionally in the presence of a co-catalyst, a polymerization inhibitor, etc., at a temperature of preferably 160°C or higher, more preferably 200°C or higher, and preferably 250°C or lower, more preferably 240°C or lower.

[0027] Examples of the esterification catalyst include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropoxybis(triethanolaminate). The amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1.5 parts by mass or less, more preferably 1 part by mass or less, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Examples of the co-catalyst for the esterification catalyst include gallic acid. The amount of the co-catalyst used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, more preferably 0.1 parts by mass or less, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Examples of the polymerization inhibitor include tert-butylcatechol. The amount of the polymerization inhibitor used is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, and preferably 0.5 part by mass or less, more preferably 0.1 part by mass or less, relative to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

[0028] In the present invention, the polyester resin may be modified to such an extent that its properties are not substantially impaired. Examples of modified polyester resins include polyester resins grafted or blocked with phenol, urethane, epoxy, or the like, by the methods described in JP-A Nos. 11-133668, 10-239903, and 8-20636. Among the modified polyester resins, urethane-modified polyester resins in which polyester resins are urethane-extended with a polyisocyanate compound are preferred.

[0029] The softening point of the polyester resin is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher, from the viewpoint of charging stability, and is preferably 175°C or lower, more preferably 165°C or lower, and even more preferably 160°C or lower, from the viewpoint of low-temperature fixability.

[0030] The glass transition temperature of the polyester resin is preferably 40° C. or higher, more preferably 50° C. or higher, from the viewpoint of storage stability, and is preferably 80° C. or lower, more preferably 70° C. or lower, from the viewpoint of low-temperature fixability.

[0031] The acid value of the polyester resin is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, from the viewpoint of low-temperature fixability, and is preferably 50 mgKOH / g or less, more preferably 40 mgKOH / g or less, from the viewpoint of charging stability.

[0032] The polyester resin preferably contains an amorphous polyester resin from the viewpoint of achieving both low-temperature fixability and hot offset resistance.

[0033] The crystallinity of a resin is expressed by the ratio of the softening point to the maximum endothermic peak temperature measured by a differential scanning calorimeter, that is, the crystallinity index defined as the value of [softening point / maximum endothermic peak temperature]. An amorphous resin is a resin in which no endothermic peak is observed, or if an endothermic peak is observed, the resin has a crystallinity index of more than 1.4, preferably more than 1.5, more preferably 1.6 or more, or less than 0.6, preferably 0.5 or less. On the other hand, the crystalline resin is a resin having a crystallinity index of 0.6 or more, preferably 0.7 or more, more preferably 0.9 or more, and 1.4 or less, preferably 1.2 or less, more preferably 1.1 or less. The crystallinity of a resin can be adjusted by the types and ratios of raw material monomers, and production conditions (e.g., reaction temperature, reaction time, cooling rate), etc. The maximum endothermic peak temperature refers to the temperature of the peak with the largest peak area among the observed endothermic peaks. For crystalline resins, the maximum endothermic peak temperature is the melting point.

[0034] The content of the amorphous polyester resin in the polyester resin is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, and 100% by mass or less.

[0035] The polyester resin is contained in the toner base particles as a binder resin. The binder resin may contain resins other than the polyester resin within a range that does not impair the effects of the present invention. Examples of other resins include vinyl resins such as styrene-acrylic resins, polyamide resins, epoxy resins, polycarbonate resins, polyurethane resins, and composite resins containing two or more of these resins.

[0036] The content of the polyester resin in the binder resin is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, and 100% by mass or less.

[0037] The content of the polyester resin in the toner is preferably 55% by mass or more, more preferably 70% by mass or more, even more preferably 75% by mass or more, and is preferably 95% by mass or less, more preferably 93% by mass or less, even more preferably 90% by mass or less.

[0038] Examples of polymethyl methacrylate resins include polymers of methyl methacrylate and copolymers of methyl methacrylate with other monomers. Examples of other monomers include styrene and butyl acrylate. The content of methyl methacrylate units in the polymethyl methacrylate resins is preferably 60 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more, and 100 mol% or less, of the monomer units.

[0039] The content of the polymethyl methacrylate resin is 5 parts by mass or more, preferably 7 parts by mass or more, more preferably 9 parts by mass or more, and 45 parts by mass or less, preferably 35 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 15 parts by mass or less, relative to 100 parts by mass of the polyester resin.

[0040] Furthermore, the content of polymethyl methacrylate resin in the toner is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, even more preferably 10% by mass or less.

[0041] The toner for developing electrostatic images of the present invention may contain additives such as a colorant, a release agent, a charge control agent, a magnetic powder, a flowability improver, a conductivity adjuster, a reinforcing filler such as a fibrous substance, an antioxidant, and a cleaning property improver, in addition to the polyester resin and the polymethyl methacrylate resin.

[0042] As the colorant, dyes, pigments, magnetic materials, etc. used as toner colorants can be used. Examples include carbon black, phthalocyanine blue, permanent brown FG, brilliant fast scarlet, pigment red 122, pigment green B, rhodamine-B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, isoindoline, disazo yellow, etc. In the present invention, the toner may be either a black toner or a color toner.

[0043] From the viewpoint of improving the image density and low-temperature fixability of the toner, the content of the colorant is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 40 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0044] Examples of the release agent include hydrocarbon waxes such as polypropylene wax, polyethylene wax, ethylene-propylene copolymer wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax, and oxides thereof; ester waxes such as carnauba wax, montan wax, and deacidified waxes thereof, and fatty acid ester wax; fatty acid amides, fatty acids, higher alcohols, and fatty acid metal salts, and these may be used alone or in combination of two or more.

[0045] The melting point of the release agent is preferably 60°C or higher, more preferably 70°C or higher, from the viewpoint of charge stability, and is preferably 160°C or lower, more preferably 140°C or lower, even more preferably 120°C or lower, and even more preferably 110°C or lower, from the viewpoint of low-temperature fixability.

[0046] From the viewpoint of the charge stability of the toner and the dispersibility in the binder resin, the content of the release agent is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, relative to 100 parts by mass of the binder resin, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less.

[0047] The charge control agent is not particularly limited, and may contain either a positively chargeable charge control agent or a negatively chargeable charge control agent. However, from the viewpoint of effectively utilizing the positive chargeability of the polymethyl methacrylate resin, the toner of the present invention is preferably a positively chargeable toner, and therefore preferably contains a positively chargeable charge control agent.

[0048] Examples of positively chargeable charge control agents include nigrosine dyes such as "Nigrosine Base EX," "Oil Black BS," "Oil Black SO," "Bontron N-01," "Bontron N-04," "Bontron N-07," "Bontron N-09," "Bontron N-11," and "Bontron N-79" (all manufactured by Orient Chemical Industries Co., Ltd.); triphenylmethane dyes containing a tertiary amine as a side chain; quaternary ammonium salt compounds such as "Bontron P-51" (manufactured by Orient Chemical Industries Co., Ltd.), cetyltrimethylammonium bromide, and "COPY CHARGE PX Examples of suitable resins include polyamine resins such as "AFP-B" (manufactured by Orient Chemical Industries Co., Ltd.); imidazole derivatives such as "PLZ-2001" and "PLZ-8001" (both manufactured by Shikoku Chemical Industry Co., Ltd.); and styrene-acrylic resins such as "FCA-701PT" and "FCA-201-PS" (manufactured by Fujikura Chemical Industries Co., Ltd.).

[0049] Examples of negatively chargeable charge control agents include metal-containing azo dyes such as "Balifast Black 3804," "Bontron S-31," "Bontron S-32," "Bontron S-34," and "Bontron S-36" (all manufactured by Orient Chemical Industries, Ltd.), "Eisenspiron Black TRH," and "T-77" (manufactured by Hodogaya Chemical Co., Ltd.); metal compounds of benzilic acid compounds such as "LR-147" and "LR-297" (manufactured by Nippon Carlit Co., Ltd.); metal compounds of salicylic acid compounds such as "Bontron E-81," "Bontron E-84," "Bontron E-88," and "Bontron E-304" (all manufactured by Orient Chemical Industries, Ltd.), and "TN-105" (manufactured by Hodogaya Chemical Co., Ltd.); copper phthalocyanine dyes; and quaternary ammonium salts such as "COPY CHARGE NX VP434 (manufactured by Clariant), nitroimidazole derivatives, etc.; organometallic compounds, etc.

[0050] From the viewpoint of the charge stability of the toner, the content of the charge control agent is preferably 0.01 parts by mass or more, more preferably 0.2 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less, relative to 100 parts by mass of the binder resin. When the charge control agent is a resin (polymer type), the content is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0051] The toner base particles may be particles obtained by any conventionally known method such as a melt-kneading method, an emulsion aggregation method, or a suspension polymerization method, but from the viewpoint of charge stability, pulverized particles obtained by a melt-kneading method, i.e., pulverized particles obtained by a method including a step of melt-kneading raw materials containing a polyester resin and a polymethyl methacrylate resin and a step of pulverizing the resulting kneaded mixture, are preferred. Specifically, for example, the toner base particles can be produced by uniformly mixing raw materials such as a polyester resin and a polymethyl methacrylate resin, and, if necessary, a colorant, a release agent, and a charge control agent, in a mixer such as a Henschel mixer, melt-kneading the mixture in an internal kneader, a single-screw or twin-screw extruder, an open-roll kneader, or the like, followed by cooling, pulverization, and classification.

[0052] The volume median particle size of the toner base particles (D 50 ) is preferably 3 μm or more, more preferably 4 μm or more, and is preferably 15 μm or less, more preferably 10 μm or less. 50 ) means the particle size at which the cumulative volume frequency calculated by volume fraction is 50% calculated from the smallest particle size.

[0053] Examples of the external additive include inorganic fine particles such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide, and organic fine particles such as melamine-based resin fine particles and polytetrafluoroethylene resin fine particles, and two or more of these may be used in combination. Among these, silica is preferred, and from the viewpoint of toner transferability, hydrophobic silica that has been subjected to a hydrophobic treatment is more preferred.

[0054] Examples of hydrophobic treatment agents for hydrophobizing the surfaces of silica particles include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), cyclic silazanes, silicone oils, aminosilanes, octyltriethoxysilane (OTES), and methyltriethoxysilane.

[0055] From the viewpoint of the chargeability, fluidity, and transferability of the toner, the average particle diameter of the external additive is preferably 10 nm or more, more preferably 15 nm or more, and is preferably 250 nm or less, more preferably 200 nm or less, and even more preferably 90 nm or less.

[0056] The external addition treatment by mixing the toner base particles with the external additives can be carried out in accordance with a conventional method, and a mixer such as a Henschel mixer can be used.

[0057] From the viewpoint of the chargeability, fluidity, and transferability of the toner, the content of the external additive is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.3 parts by mass or more, relative to 100 parts by mass of the toner base particles before treatment with the external additive, and is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less.

[0058] The toner of the present invention can be used as a toner for one-component development as it is, or as a toner for two-component development mixed with a carrier, in an image forming apparatus of a one-component development system or a two-component development system, respectively. [Example]

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Physical properties of resins and the like can be measured by the following methods.

[0060] [Softening point of resin] Using a flow tester "CFT-500D" (Shimadzu Corporation), 1 g of sample is heated at a temperature increase rate of 6°C / min while applying a load of 1.96 MPa with the plunger, and extruding it from a nozzle 1 mm in diameter and 1 mm in length. The plunger depression distance of the flow tester is plotted against the temperature, and the temperature at which half of the sample flows out is taken as the softening point.

[0061] [Maximum endothermic peak temperature of resin] Using a differential scanning calorimeter "Q-100" (TA Instruments Japan Co., Ltd.), weigh 0.01-0.02 g of sample into an aluminum pan, cool from room temperature (25°C) to 0°C at a rate of 10°C / min, and maintain at 0°C for 1 minute. Then, measure at a rate of 10°C / min. The temperature of the peak with the largest peak area among the observed endothermic peaks is taken as the maximum endothermic peak temperature. For crystalline resins, the maximum endothermic peak temperature is taken as the melting point.

[0062] [Glass transition temperature of resin] Using a differential scanning calorimeter "Q-100" (TA Instruments Japan), 0.01-0.02 g of sample is weighed into an aluminum pan, heated to 200°C, and cooled to 0°C at a rate of 10°C / min. The sample is then heated at a rate of 10°C / min, and the endothermic peak is measured. The glass transition temperature is the temperature at the intersection of an extension of the baseline below the maximum endothermic peak temperature and a tangent line showing the maximum slope from the rising part of the peak to the peak apex.

[0063] [Acid value of resin] Measurement is performed based on the method of JIS K 0070:1992, except that the measurement solvent is changed from the ethanol and ether mixture specified in JIS K 0070 to a mixture of acetone and toluene (acetone:toluene = 1:1 (volume ratio)).

[0064] [Melting point of release agent] Using a differential scanning calorimeter "Q-100" (TA Instruments Japan), 0.02 g of sample is weighed into an aluminum pan, heated to 200°C, and then cooled from 200°C to 0°C at a rate of 10°C / min. The sample is then heated at a rate of 10°C / min, the calorific value is measured, and the maximum endothermic peak temperature is taken as the melting point.

[0065] [Volume median particle size of toner base particles (D 50 ) Measuring instrument: "Coulter Multisizer (registered trademark) III" (manufactured by Beckman Coulter, Inc.) Aperture diameter: 50 μm Analysis software: "Multisizer (registered trademark) III Version 3.51" (Beckman Coulter, Inc.) Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.) Dispersion: Polyoxyethylene lauryl ether "Emulgen (registered trademark) 109P" (manufactured by Kao Corporation, HLB (Griffin) = 13.6) dissolved in the electrolyte to adjust the concentration to 5% by mass Dispersion conditions: 10 mg of the measurement sample was added to 5 mL of the dispersion, and the mixture was dispersed for 1 minute using an ultrasonic disperser (machine name: US-1 manufactured by SND Corporation, output: 80 W). 25 mL of electrolyte was then added, and the mixture was further dispersed for 1 minute using the ultrasonic disperser to prepare a sample dispersion. Measurement conditions: The sample dispersion was added to 100 mL of the electrolyte to adjust the concentration so that the particle size of 30,000 particles could be measured in 20 seconds. Then, 30,000 particles were measured, and the volume median particle size (D 50 ) is found.

[0066] [Average particle size of external additives] The average particle size refers to the number-average particle size, and is calculated by measuring the particle sizes (average values ​​of major and minor axes) of 500 particles in a scanning electron microscope (SEM) photograph and averaging these values ​​by number.

[0067] Preparation Example 1 of Alkenyl Succinic Anhydride (1) Propylene tetramer (manufactured by Nippon Oil Corporation, trade name: "Light Tetramer") was fractionally distilled at a heating condition of 183 to 208°C to obtain an alkylene compound (a). The obtained alkylene compound (a) had 40 peaks in gas chromatography mass spectrometry, which will be described later. The distribution of the alkylene compound was measured according to the analysis of alkylene compound A by mass spectrometry gas chromatography in JP 2014-013384 A, and the C9H 18 :0.5% by mass, C 10 H 20 :4% by mass, C 11 H 22 :20% by mass, C 12 H 24 :66% by mass, C 13 H 26 :9% by mass, C 14 H 28 : 0.5% by mass (6 peaks corresponding to alkylene compounds having 9 to 14 carbon atoms).

[0068] (2) A 1-liter autoclave manufactured by Nitto Koatsu Co., Ltd. was charged with 542.4 g of alkylene compound (a), 157.2 g of maleic anhydride, 0.4 g of the antioxidant "Cherex-O" (triisooctyl phosphite manufactured by SC Organic Chemical Co., Ltd.), and 0.1 g of butylhydroquinone as a polymerization inhibitor. Pressure and nitrogen substitution (0.2 MPaG) were repeated three times. After stirring was started at 60°C, the temperature was raised to 230°C over 1 hour, and the reaction was carried out for 6 hours. The pressure when the reaction temperature was reached was 0.3 MPaG. After the reaction was completed, the mixture was cooled to 80°C, returned to atmospheric pressure (101.3 kPa), and transferred to a 1-liter four-neck flask. The temperature was raised to 180°C with stirring, and the remaining alkylene compound was distilled off at 1.3 kPa over 1 hour. Subsequently, the mixture was cooled to room temperature (25°C) and then returned to normal pressure (101.3 kPa) to obtain 406.1 g of the target product, alkenyl succinic anhydride A. The average molecular weight of alkenyl succinic anhydride A calculated from the acid value was 268.

[0069] Resin manufacturing example 1 The alcohol component, carboxylic acid component other than trimellitic anhydride, esterification catalyst, and co-catalyst shown in Table 1 were placed in a 10-liter four-neck flask equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and the mixture was heated to 235°C under a nitrogen atmosphere and then polycondensed at 235°C for 6 hours. The temperature was then lowered to 210°C, trimellitic anhydride was added, and the mixture was reacted at 210°C for 1 hour. The reaction was then continued at 210°C under a reduced pressure of 10 kPa until the softening point shown in Table 1 was reached, yielding an amorphous polyester resin (Resin A1). The physical properties are shown in Table 1.

[0070] Resin manufacturing example 2 The alcohol components, fumaric acid, and polymerization inhibitor shown in Table 1 were placed in a 10-liter four-neck flask equipped with a dehydration tube with a nitrogen inlet tube, a stirrer, and a thermocouple, and the temperature was raised to 230°C in a mantle heater under a nitrogen atmosphere, and polycondensation was carried out for 7 hours. The temperature was then lowered to 200°C, and trimellitic anhydride shown in Table 1 was added, after which the temperature was raised to 210°C and polycondensation reaction was carried out until the softening point reached the temperature shown in Table 1, yielding an amorphous polyester resin (Resin A2). The physical properties are shown in Table 1.

[0071] Resin manufacturing example 3 The alcohol component, carboxylic acid component, esterification catalyst, and cocatalyst shown in Table 1 were placed in a 10-liter four-neck flask equipped with a nitrogen inlet tube, a dehydration tube fitted with a fractionating column through which hot water at 98°C had passed, a stirrer, and a thermocouple. The flask was heated to 180°C under a nitrogen atmosphere and held there for 1 hour. The temperature was then increased from 180°C to 230°C at a rate of 10°C / h, followed by a polycondensation reaction at 230°C for 6 hours. The reaction was then continued at 230°C under a reduced pressure of 8 kPa until the softening point shown in Table 1 was reached, yielding an amorphous polyester resin (Resin A3). The physical properties are shown in Table 1.

[0072] [Table 1]

[0073] Examples 1 to 7 and Comparative Examples 1 and 3 100 parts by mass of the polyester resin and polymethyl methacrylate resin shown in Table 2, 2.0 parts by mass of a release agent "WE-14" (manufactured by NOF Corporation, ester wax, melting point: 79°C), 10 parts by mass of a polymer-type positively charged charge control agent "FCA-201-PS" (manufactured by Fujikura Chemical Industries, Ltd., softening point: 119°C, glass transition temperature: 65°C), 1 part by mass of a positively charged charge control agent "Bontron N-79" (manufactured by Orient Chemical Industries Co., Ltd.), and 6 parts by mass of a colorant "REGAL 330" (manufactured by Cabot Corporation) were mixed for 1 minute using a Henschel mixer and then melt-kneaded under the conditions shown below.

[0074] Co-rotating twin-screw extruder "PCM-30" (manufactured by Ikegai Corporation, shaft diameter 2.9 cm, shaft cross-sectional area 7.06 cm 2 The operating conditions were a barrel temperature of 100°C, a shaft rotation speed of 200 r / min (circumferential speed of shaft rotation: 0.30 m / sec), a mixture supply rate of 10 kg / h (amount of mixture supplied per unit cross-sectional area of ​​the shaft: 1.42 kg / h cm 2 ) was.

[0075] The obtained kneaded product was cooled and coarsely pulverized using a pulverizer "Rotoplex" (manufactured by Hosokawa Micron Corporation), and a coarsely pulverized product having a volume median particle diameter of 2 mm or less was obtained using a sieve with a mesh size of 2 mm. The obtained coarsely pulverized product was classified into a volume median particle diameter (D 50 The resulting finely pulverized product was classified using a DSX2 air classifier (manufactured by Nippon Pneumatic Mfg. Co., Ltd.) by adjusting the static pressure (internal pressure) so that the volume median particle size was 7.5 μm, thereby obtaining toner base particles.

[0076] 100 parts by mass of the obtained toner base particles and 0.5 parts by mass of hydrophobic silica "R972" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: DMDS, average particle size: 16 nm) and 1 part by mass of hydrophobic silica "RY50" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: silicone oil, average particle size: 40 nm) as external additives were mixed in a Henschel mixer at 2100 r / min for 3 minutes to obtain a toner.

[0077] Comparative Example 2 Toner base particles were obtained in the same manner as in Example 1, except that no polymethyl methacrylate resin was used.

[0078] 100 parts by mass of the obtained toner base particles and 25 parts by mass of polymethyl methacrylate resin microparticles "MASD-23PP" (manufactured by Sekisui Chemical Co., Ltd., number average particle size 300 nm) were mixed in a Henschel mixer at 3000 r / min (circumferential speed 29 m / sec) for 30 minutes.

[0079] 100 parts by mass of the obtained mixture and 0.5 parts by mass of hydrophobic silica "R972" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: DMDS, average particle size: 16 nm) and 1 part by mass of hydrophobic silica "RY50" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: silicone oil, average particle size: 40 nm) as external additives were mixed in a Henschel mixer at 2100 r / min (circumferential speed: 29 m / sec) for 3 minutes to obtain a toner.

[0080] Test example [Photoreceptor fogging in a high temperature and humidity environment] The toner was loaded into an OKI MICROLINE 5400 non-magnetic single-component developing device (Oki Electric Industry Co., Ltd.), and 5,000 images with a 1% coverage were printed at a temperature of 32°C and a relative humidity of 80% with a 20-second break per page (one page was printed, followed by a 20-second break before printing the next page). Next, a solid white image (0% coverage) was printed, and the power was turned off midway through the printing process. The toner on the photoreceptor surface was then adhered using Scotch® Mending Tape 810 (3M Japan, Ltd., width: 18 mm). The color density was measured at five equally spaced locations using an X-Rite GRETAG SPM50 image densitometer. The difference from the color density of the tape itself before the toner was applied was calculated, and the average of the measurements was calculated. The results are shown in Table 2. A smaller value indicates better suppression of photoreceptor fogging.

[0081] [Table 2]

[0082] From the above results, it can be seen that the toners of Examples 1 to 7 suppress photoreceptor fogging under high temperature and high humidity conditions. In particular, a comparison between Example 1 and Example 6 reveals that the aromatic moiety is more effective in suppressing photoreceptor fogging than the unsaturated double bond. In contrast, photoreceptor fogging occurred in the toner of Comparative Example 1, which did not contain polymethyl methacrylate resin; the toner of Comparative Example 2, which contained polymethyl methacrylate resin as an external additive mixed with the toner base particles rather than as an internal additive added to the toner base particles; and the toner of Comparative Example 3, in which the polyester resin contained neither an aromatic moiety nor an unsaturated double bond. [Industrial Applicability]

[0083] The toner for developing electrostatic images of the present invention is suitably used for developing latent images formed in electrophotography, electrostatic recording, electrostatic printing and the like.

Claims

1. A toner for developing electrostatic images, comprising toner base particles and an external additive, wherein the toner base particles contain a polyester resin and a polymethyl methacrylate resin, the polyester resin contains an aromatic moiety and / or an unsaturated double bond, and the content of the polymethyl methacrylate resin is 5 parts by mass or more and 45 parts by mass or less per 100 parts by mass of the polyester resin.

2. 2. The toner for developing electrostatic images according to claim 1, wherein the polyester resin comprises an amorphous polyester resin.

3. 3. The toner for developing electrostatic images according to claim 1, wherein the polyester resin is a polycondensate of raw material monomers containing an aromatic moiety and / or an unsaturated double bond.

4. 3. The toner for developing electrostatic images according to claim 1, wherein the toner base particles are pulverized particles obtained by a method comprising the steps of melt-kneading raw materials containing a polyester resin and a polymethyl methacrylate resin and pulverizing the resulting kneaded mixture.

Images