Toner for developing electrostatic images

Abstract

This relates to a toner for electrostatic image development that offers excellent resistance to cold offsets even during high-speed printing, and also excellent resistance to hot offsets. [Solution] A toner for electrostatic image development containing toner matrix particles containing a binder resin and an external additive containing inorganic particles A, wherein the solubility parameter of the binder resin is 11.0 (cal / cm²). 3 ) 1 / 2 More than 12.5(cal / cm 3 ) 1 / 2 The following is true: The amount of water vapor adsorbed by the inorganic particle A is 10 cm 3 / g or more 250cm 3 A toner for developing electrostatic images, wherein the particle size is less than or equal to / g, and the coverage rate by the inorganic particles A is 150% to 800%.

Description

[Technical Field]

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

[0002] While external additives are usually added to the surface of toner for electrostatic image development for reasons of fluidity, it is known that the degree to which the filler effect of the external additive is exerted on the surface of the toner particles can be adjusted by changing the amount added and the mixing time of the external additive (see Patent Document 1).

[0003] Furthermore, regarding external additives, the combined use of two types of external additives is also being considered from the viewpoint of electrostatic properties and fixation properties (see Patent Documents 2 and 3). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-96339 [Patent Document 2] Japanese Patent Publication No. 2018-72534 [Patent Document 3] Japanese Patent Publication No. 2011-154277 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In recent years, with the growth of the print-on-demand market, the demand for faster electrophotographic technology has been increasing. However, as speed increases, the amount of energy supplied to the toner per unit time tends to decrease. To address these challenges, increasing the SP value of the toner binder resin, that is, making it hydrophilic, improves adhesion to paper, which also has hydrophilic properties, allowing it to be fixed to the paper even with low energy.

[0006] However, in order to meet the requirement of further high-speed printing with a linear speed of 100 to 200 mm / sec, when using a binder resin with an even higher SP value, while the adhesion between the toner and the paper is improved, the hydrogen bonds between the binder resins also increase, making it difficult for the toners to melt together. When the poorly melted toner adheres to the fixing roller, it will fix and stain outside the desired location of the next conveyed recording medium, resulting in a problem of cold offset phenomenon. To solve this problem, it is necessary to further reduce the molecular weight and viscosity of the binder resin. In that case, however, the toner will have an excessive low viscosity at high temperatures, resulting in a decrease in internal cohesive force, and the toner will be torn towards the fixing roller side. When it adheres to the fixing roller, it will fix and stain outside the desired location of the next conveyed recording medium, causing hot offset. Therefore, it is difficult to achieve both cold offset resistance and hot offset resistance by increasing the SP value and reducing the molecular weight of the binder resin.

[0007] The present invention relates to an electrostatic charge image developing toner that is excellent in cold offset resistance even during high-speed printing and is further excellent in hot offset resistance.

Means for Solving the Problems

[0008] The present invention is an electrostatic charge image developing toner containing toner mother particles containing a binder resin and an external additive containing inorganic particles A, wherein the solubility parameter of the binder resin is 11.0 (cal / cm 3 ) 1 / 2 or more and 12.5 (cal / cm 3 ) 1 / 2 or less, the water vapor adsorption amount of the inorganic particles A is 10 cm 3 / g or more and 250 cm 3 / g or less, and the coating rate by the inorganic particles A is 150% or more and 800% or less.

Effects of the Invention

[0009] The toner for electrostatic charge image development of the present invention exhibits an excellent effect in achieving both cold offset resistance and hot offset resistance.

Mode for Carrying Out the Invention

[0010] The toner for electrostatic charge image development of the present invention contains toner mother particles and an external additive. The toner mother particles contain a binder resin having a relatively high solubility parameter (SP value), and are externally added at a high coverage rate with inorganic particles (inorganic particles A) having high surface hydrophilicity. It has a major feature in that respect. Although the reason for the effect of the present invention is not clear, it is presumed as follows. Note that the following mechanism is an estimate and is not limited thereto.

[0011] When the present inventors investigated in detail the cause of cold offset occurrence in high-speed printing, it was confirmed that peeling occurred at the toner particle interface during fixing to paper and offset occurred. As a reason for this, it is considered that the melting of toner particles is insufficient during fixing at low energy such as high-speed printing. Therefore, as a result of intensive studies to improve cold offset resistance, it was found that by externally adding inorganic particles having high surface hydrophilicity to toner mother particles at a high coverage rate, peeling at the toner particle interface and thus cold offset can be suppressed. Although the reason for this is not clear, inorganic particles having high surface hydrophilicity have a high affinity with the high SP value, that is, the highly hydrophilic binder resin on the toner surface, and thus exhibit a filler effect during fixing and function as an adhesion aid between toner particles, It is considered that it suppresses the peeling of the toner fixed to the paper and prevents adhesion to the fixing roller. Therefore, it is presumed that by increasing the coverage rate by inorganic particles, the filler effect is surely exhibited between toner particles, and as a result, the cold offset resistance is improved. Furthermore, it was found that these inorganic particles penetrate into the toner when the temperature is high, that is, when the toner is sufficiently melted, and thus contribute to improving the internal cohesive force of the toner and improving the hot offset resistance. Therefore, by coating the toner surface with high SP value and high hydrophilicity with inorganic particles having high affinity with such a toner surface, in addition to improving the adhesion to paper by the binder resin with high SP value, both cold offset resistance and hot offset resistance can be achieved.

[0012] As described above, the toner for electrostatic charge image development of the present invention contains toner base particles containing a binder resin and an external additive containing inorganic particles A.

[0013] The solubility parameter (SP value) of the binder resin is 11.0 (cal / cm 3 ) 1 / 2 or more, preferably 11.1 (cal / cm 3 ) 1 / 2 or more, and 12.5 (cal / cm 3 ) 1 / 2 or less, preferably 12.3 (cal / cm 3 ) 1 / 2 or less, more preferably 12.0 (cal / cm 3 ) 1 / 2 or less. When the binder resin is composed of two or more resins, the SP value calculated by weighted averaging the SP values of each resin is taken as the SP value of the binder resin.

[0014] In the present invention, the SP value means the solubility parameter by the Fedors method, and is the value δ obtained based on the following formula described in [Robert F. Fedors, Polymer Engineering and Science, 14, 147-154 (1974)]. Fedors' formula: δ = (ΣΔei / ΣΔvi) 1 / 2 [Unit: (cal / cm 3 ) 1 / 2 [Here, Δei: evaporation energy of atoms and atomic groups (cal / mol), Δvi: molar volume (cm 3 / mol).]

[0015] ​As the binder resin, an amorphous polyester resin, which is a polycondensate of an alcohol component and a carboxylic acid component, is preferred.

[0016] The crystalline or amorphous nature of a resin is determined by its crystallinity index. The crystallinity index is defined as the ratio of the resin's softening point to its maximum endothermic peak temperature (softening point (°C) / maximum endothermic peak temperature (°C)) in the measurement method described in the examples below. A crystalline resin is one in which the crystallinity index is between 0.6 and 1.4. An amorphous resin is one in which no endothermic peak is observed, or if observed, the crystallinity index is less than 0.6 or greater than 1.4. The crystallinity of a resin can be adjusted by the type and ratio of raw material monomers, as well as the manufacturing conditions (e.g., reaction temperature, reaction time, cooling rate). The maximum endothermic peak temperature refers to the temperature of the peak with the largest peak area among the observed endothermic peaks. In crystalline resins, the maximum endothermic peak temperature is defined as the melting point.

[0017] The alcohol component is given by formula (I):

[0018] [ka]

[0019] (In the formula, OR and RO are oxyalkylene groups, R is an ethylene group and / or a propylene group, x and y represent the average number of moles of alkylene oxide added, each being a positive number, and the sum of x and y is 1 or greater, preferably 1.5 or greater, and 16 or less, preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less.) Examples include alkylene oxide adducts of bisphenol A, aromatic diols such as bisphenol A, aliphatic diols, hydrogenated bisphenol A, sorbitol, pentaerythritol, glycerin, trivalent or higher alcohols such as trimethylolpropane, and others.

[0020] As for the alcohol component, alkylene oxide adducts of bisphenol A are preferred from the viewpoint of cold offset resistance, and aliphatic diols are preferred from the viewpoint of hot offset resistance.

[0021] From the viewpoint of resistance to cold offset, the content of the bisphenol A alkylene oxide adduct is preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and 100 mol% or less, in the alcohol component.

[0022] Examples of aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 2,3-pentanediol, 2,4-pentanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 1,6-hexanediol, 2,3-hexanediol, 3,4-hexanediol, 2,4-hexanediol, 2,5-hexanediol, 1,4-butenediol, 1,3-butanediol, neopentyl glycol, and others.

[0023] From the viewpoint of hygroscopicity, the carbon number of the aliphatic diol is preferably 2 or more, more preferably 3 or more, and from the viewpoint of heat-resistant storage, it is preferably 6 or less, more preferably 5 or less, and even more preferably 3 or less.

[0024] Furthermore, among aliphatic diols, those having a hydroxyl group bonded to a secondary carbon atom are preferred.

[0025] The aliphatic diol having a hydroxyl group bonded to a secondary carbon atom preferably has 3 or more carbon atoms, preferably 6 or less, and more preferably 4 or less.

[0026] Aliphatic diols having a hydroxyl group bonded to a secondary carbon atom with 3 to 6 carbon atoms include 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 2,3-pentanediol, and 2,4-pentanediol.

[0027] From the viewpoint of resistance to hot offsetting, the content of aliphatic diols, preferably aliphatic diols having a hydroxyl group bonded to a secondary carbon atom, is preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and 100 mol% or less in the alcohol component.

[0028] From the viewpoint of preservation, it is preferable that the carboxylic acid component contains an aromatic dicarboxylic acid compound.

[0029] Examples of aromatic dicarboxylic acid compounds include phthalic acid, isophthalic acid, terephthalic acid, anhydrides of these acids, and alkyl esters of these acids with 1 to 3 carbon atoms.

[0030] The content of aromatic dicarboxylic acid compounds is preferably 60 mol% or more, more preferably 65 mol% or more, even more preferably 70 mol% or more, and 100 mol% or less, in the carboxylic acid component.

[0031] Other carboxylic acid components include adipic acid (6 carbon atoms), suberic acid (8 carbon atoms), azelaic acid (9 carbon atoms), sebacic acid (10 carbon atoms), dodecanediic acid (12 carbon atoms), tetradecanediic acid (14 carbon atoms), hexadecanedioic acid (16 carbon atoms), aliphatic dicarboxylic acids such as succinic acid having an alkyl or alkenyl group in the side chain, trivalent or higher carboxylic acids such as trimellitic acid and pyromellitic acid, anhydrides of these acids, and alkyl esters of these acids with 1 to 3 carbon atoms.

[0032] The alcohol component may contain a monohydric alcohol, and the carboxylic acid component may contain a monohydric carboxylic acid compound, as appropriate.

[0033] In this specification, macromonomers and hydroxycarboxylic acids such as lactic acid are not included in the alcohol and carboxylic acid components.

[0034] The equivalent ratio (COOH group / OH group) of the carboxyl group of the carboxylic acid component to the hydroxyl group of the alcohol component is preferably 0.6 or higher, more preferably 0.7 or higher, even more preferably 0.8 or higher, and preferably 1.3 or lower, more preferably 1.2 or lower.

[0035] Amorphous polyester resins can be produced, for example, by polycondensing an alcohol component and a carboxylic acid component in an inert gas atmosphere, and optionally in the presence of an esterification catalyst, co-catalyst, polymerization inhibitor, etc., at a temperature preferably 160°C or higher, more preferably 200°C or higher, and preferably 250°C or lower, more preferably 240°C or lower.

[0036] Examples of esterification catalysts include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropoxybis(triethanolamine) and titanium dihydroxybis(triethanolamine). The amount of 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, and more preferably 1 part by mass or less, per 100 parts by mass of the total amount of alcohol and carboxylic acid components. Examples of co-catalysts for the esterification catalyst include gallic acid. The amount of 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, and more preferably 0.1 parts by mass or less, per 100 parts by mass of the total amount of alcohol and carboxylic acid components. Examples of polymerization inhibitors include tert-butylcatechol. The amount of polymerization inhibitor 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, and more preferably 0.1 parts by mass or less, based on 100 parts by mass of the total amount of alcohol and carboxylic acid components.

[0037] In this invention, the polyester resin may be a polyester resin that has been modified to such an extent that its properties are not substantially impaired. Examples of modified polyester resins include polyester resins that have been grafted or blocked with phenol, urethane, epoxy, etc., by methods described in Japanese Patent Publication No. 11-133668, Japanese Patent Publication No. 10-239903, Japanese Patent Publication No. 8-20636, etc. Among modified polyester resins, urethane-modified polyester resins obtained by urethane elongation of polyester resin with a polyisocyanate compound are preferred.

[0038] The softening point of amorphous 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 electrostatic stability, and 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.

[0039] The glass transition temperature of amorphous polyester resin is preferably 40°C or higher, more preferably 50°C or higher, from the viewpoint of storage properties, and preferably 80°C or lower, more preferably 70°C or lower, from the viewpoint of low-temperature fixation properties.

[0040] The content of amorphous polyester resin is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and 100% by mass or less, in the binder resin.

[0041] The binder resin may contain resins other than amorphous polyester resin, as long as they do not impair the effects of the present invention. Examples of other resins include crystalline polyester resin, vinyl resins such as styrene-acrylic resin, polyamide resin, epoxy resin, polycarbonate resin, polyurethane resin, and composite resins containing two or more of these resins.

[0042] The binder resin content 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 preferably 99% by mass or less, more preferably 95% by mass or less, and even more preferably 93% by mass or less.

[0043] The electrostatic image developing toner of the present invention may contain additives other than a binder resin (binder), such as a colorant, release agent, charge control agent, magnetic powder, flowability improver, conductivity modifier, reinforcing filler such as a fibrous material, antioxidant, and cleaning performance improver.

[0044] As colorants, dyes, pigments, magnetic materials, etc., used as colorants for toners can be used. Examples include carbon black, phthalocyanine blue, permanent brown FG, brilliant first scarlet, pigment green B, rhodamine-B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, isoindoline, disazo yellow, etc. In this invention, the toner may be either black toner or color toner.

[0045] From the viewpoint of improving the image density of the toner and its low-temperature fixability, the amount of 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, per 100 parts by mass of the binder resin.

[0046] Examples of mold release agents include hydrocarbon waxes and their oxides, such as polypropylene wax, polyethylene wax, ethylene propylene copolymer wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax; ester waxes such as carnauba wax, montane wax and their deoxidizing waxes, and fatty acid ester waxes; and fatty acid amides, fatty acids, higher alcohols, fatty acid metal salts, etc., which can be used individually or in combination of two or more.

[0047] The melting point of the release agent is preferably 60°C or higher, more preferably 70°C or higher, from the viewpoint of electrostatic stability, and 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 fixation.

[0048] The release agent content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 1.5 parts by mass or more, and 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, per 100 parts by mass of binder resin, from the viewpoint of the electrostatic stability of the toner and its dispersibility in the binder resin.

[0049] The charge control agent is not particularly limited and may contain either a positively charged charge control agent or a negatively charged charge control agent.

[0050] Positively charged 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, Ltd.); triphenylmethane-based dyes containing tertiary amines as side chains; quaternary ammonium salt compounds, such as "Bontron P-51" (manufactured by Orient Chemical Industries, Ltd.), cetyltrimethylammonium bromide, and "COPY CHARGE PX." Examples include VP435 (manufactured by Clariant), polyamine resins such as AFP-B (manufactured by Orient Chemical Industries, Ltd.), imidazole derivatives such as PLZ-2001 and PLZ-8001 (both manufactured by Shikoku Chemicals, Ltd.), and styrene-acrylic resins such as FCA-701PT and FCA-201-PS (manufactured by Fujikura Chemicals, Ltd.).

[0051] Furthermore, as negative charge control agents, metal-containing azo dyes, such as "Barifast 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 benzyl acid compounds, such as "LR-147" and "LR-297" (both 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" Examples include VP434 (manufactured by Clariant), nitroimidazole derivatives, organometallic compounds, etc.

[0052] 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, per 100 parts by mass of the binder resin.

[0053] Volume median particle size of toner matrix particles (D 50 The volume median particle size (D) is preferably 3 μm or more, more preferably 4 μm or more, and preferably 15 μm or less, more preferably 10 μm or less. 50 ) refers to the particle size at which the cumulative volume frequency, calculated using volume fractions, accounts for 50% of the total volume frequency, starting from the smallest particle size.

[0054] The external additive contains inorganic particles A having a predetermined amount of water vapor adsorption.

[0055] The amount of water vapor adsorbed by inorganic particle A is determined to be 10 cm from the perspective of affinity with the binder resin. 3 / g or more, preferably 50cm 3 / g or more, preferably 100cm 3 / g or more, more preferably 200cm 3 It is more than / g, and from the standpoint of hygroscopicity, 250cm 3 It is less than or equal to / g, preferably 240cm 3 / g or less, more preferably 230cm 3 Less than or equal to / g, more preferably 225cm² 3 It is less than / g.

[0056] Examples of inorganic particles A include silica, alumina, titania, zirconia, tin oxide, and zinc oxide, and among these, silica is preferred from the viewpoint of electrostatic chargeability.

[0057] Inorganic particles A may be surface-treated with a hydrophobic treatment agent or the like, as long as they have a predetermined amount of water vapor adsorption capacity; however, from the viewpoint of low-temperature fixation, unsurface-treated inorganic particles are preferred.

[0058] Examples of hydrophobic treatment agents include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), cyclic silazane, silicone oil, aminosilane, octyltriethoxysilane (OTES), methyltriethoxysilane, and trimethylsilyl.

[0059] The number-average particle diameter of inorganic particles A is preferably 5 nm or larger, more preferably 50 nm or smaller, more preferably 20 nm or smaller, and even more preferably 10 nm or smaller, from the viewpoint of durability.

[0060] The coverage rate by inorganic particles A (also called the coverage rate of inorganic particles A) is 150% or more, preferably 200% or more, and more preferably 300% or more, from the viewpoint of cold offset resistance, and 800% or less, preferably 600% or less, and more preferably 400% or less, from the viewpoint of thermal conductivity.

[0061] The content of inorganic particles A is preferably 0.5 parts by mass or more, more preferably 1.2 parts by mass or more, even more preferably 2.0 parts by mass or more, even more preferably 2.2 parts by mass or more, and preferably 8 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 4 parts by mass or less, per 100 parts by mass of toner matrix particles.

[0062] From the viewpoint of hygroscopicity, it is preferable that the external additive further contains inorganic particle B, which has a smaller water vapor adsorption capacity than inorganic particle A.

[0063] The amount of water vapor adsorbed by inorganic particle B is preferably 10 cm³. 3 Less than / g, more preferably 5cm 3 / g or less, more preferably 1cm 3 It is less than / g.

[0064] Examples of inorganic particles B include silica, alumina, titania, zirconia, tin oxide, and zinc oxide, and among these, silica is preferred from the viewpoint of electrostatic chargeability.

[0065] From the viewpoint of hygroscopicity, inorganic particles B are preferably surface-treated with a hydrophobic treatment agent or the like. Examples of hydrophobic treatment agents include those similar to those used for inorganic particles A.

[0066] The number-average particle diameter of inorganic particles B is preferably 10 nm or more, more preferably 20 nm or more, and preferably 100 nm or less, and more preferably 50 nm or less, from the viewpoint of durability and fluidity.

[0067] The content of inorganic particles B is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, even more preferably 1.5 parts by mass or more, and preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less, per 100 parts by mass of toner matrix particles.

[0068] The mass ratio of inorganic particle A to inorganic particle B (inorganic particle A / inorganic particle B) is preferably 20 / 80 or more, more preferably 40 / 60 or more, even more preferably 60 / 40 or more, and preferably 90 / 10 or less, more preferably 80 / 20 or less, and even more preferably 70 / 30 or less.

[0069] The toner of the present invention may contain external additives other than inorganic particles A and B, such as organic fine particles like melamine resin fine particles and polytetrafluoroethylene resin fine particles, as long as the effects of the present invention are not impaired. However, the total amount of inorganic particles A and B in the external additive is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, and 100 mol% or less.

[0070] The toner of the present invention may be obtained by any of the conventionally known methods, such as the melt-kneading method, the emulsification-coagulation method, or the suspension polymerization method, but pulverized toner is preferred, and from the viewpoint of the miscibility of the toner raw materials, pulverized toner obtained by the melt-kneading method, that is, toner obtained by a method including the steps of melt-kneading the raw materials, pulverizing the resulting mixture to obtain toner mother particles, and mixing the toner mother particles with an external additive is more preferred. Specifically, for example, raw materials such as a binder resin and, if necessary, a colorant, release agent, charge control agent, etc., can be uniformly mixed in a mixer such as a Henschel mixer, then melt-kneaded in a closed-type kneader, a single-screw or twin-screw extruder, an open-roll type kneader, etc., cooled, pulverized, and classified, and the obtained toner mother particles can be mixed with an external additive to produce the toner.

[0071] External additive treatment by mixing toner base particles with an external additive can be carried out according to conventional methods, and a mixer such as a Henschel mixer can be used. Inorganic particles A and B may be mixed with the toner base particles at once or separately, but in the present invention, from the viewpoint of toner fluidity, it is preferable that inorganic particles A and B exist on the surface of the toner base particles in a manner in which inorganic particles A and inorganic particles B are stacked in that order from the toner base particle side. Therefore, it is preferable to mix the toner base particles and inorganic particles A to coat the surface of the toner base particles with inorganic particles A, and then add and mix inorganic particles B.

[0072] From the viewpoint of the toner's electrostatic properties, fluidity, and transferability, the content of the external additive is preferably 1.0 part by mass or more, more preferably 2.2 parts by mass or more, even more preferably 3.5 parts by mass or more, even more preferably 3.7 parts by mass or more, and preferably 9.5 parts by mass or less, more preferably 6.5 parts by mass or less, and even more preferably 5.5 parts by mass or less, per 100 parts by mass of toner mother particles.

[0073] The toner of the present invention can be used as is as a one-component developing toner, or as a two-component developing toner used in combination with a carrier, in image forming apparatuses using either a one-component developing method or a two-component developing method, respectively. [Examples]

[0074] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way by these examples. The physical properties of resins, etc., can be measured by the following methods.

[0075] [Softening point of resin] Using a flow tester "CFT-500D" (manufactured by Shimadzu Corporation), 1 g of sample is heated at a heating rate of 6°C / min while a load of 1.96 MPa is applied by a plunger, and the sample is extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. The amount of plunger descent of the flow tester is plotted against temperature, and the temperature at which half of the sample has flowed out is defined as the softening point.

[0076] [Maximum peak temperature of endothermic resin] Using a differential scanning calorimeter "Q-100" (manufactured by T.A. Instruments Japan Co., Ltd.), 0.01 to 0.02 g of the sample is weighed into an aluminum pan and cooled from room temperature (25°C) to 0°C at a rate of 10°C / min, and maintained at 0°C for 1 minute. Then, measurements are taken at a rate of 10°C / min. Among the observed endothermic peaks, the temperature of the peak with the largest peak area is defined as the maximum endothermic peak temperature. For crystalline resins, the maximum endothermic peak temperature is defined as the melting point.

[0077] [Glass transition temperature of resins] Using a differential scanning calorimeter "Q-100" (manufactured by T.A. Instruments Japan Co., Ltd.), 0.01 to 0.02 g of the sample is weighed into an aluminum pan, heated to 200°C, and then cooled to 0°C at a rate of 10°C / min. Next, the sample is heated again at a rate of 10°C / min, and the endothermic peak is measured. The temperature at the intersection of the baseline extension below the maximum endothermic peak temperature and the tangent line showing the maximum slope from the rise of the peak to the peak apex is defined as the glass transition temperature.

[0078] [Acid value of resins] The measurement will be performed according to the method of JIS K 0070:1992. However, the measurement solvent will be changed from the mixed solvent of ethanol and ether specified in JIS K 0070 to a mixed solvent of chloroform and dimethylformamide (chloroform:dimethylformamide = 7:3 (volume ratio)).

[0079] [Melting point of release agent] Using a differential scanning calorimeter "Q-100" (manufactured by T.A. Instruments Japan Co., Ltd.), 0.02 g of the 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. Next, the sample is heated again at a rate of 10°C / min, the amount of heat is measured, and the maximum peak temperature of endothermic heating is defined as the melting point.

[0080] [Medium volume particle size of toner matrix 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" (manufactured by Beckman Coulter, Inc.) • Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.) • Dispersion: Prepared by dissolving polyoxyethylene lauryl ether "Emulgen (registered trademark) 109P" [manufactured by Kao Corporation, HLB (Griffin) = 13.6] in the electrolyte to adjust the concentration to 5% by mass. • Dispersion conditions: Add 10 mg of the sample to 5 mL of the dispersion and disperse for 1 minute using an ultrasonic disperser (machine name: US-1 manufactured by SND Corporation, output: 80W). Then, add 25 mL of electrolyte and disperse for another minute using the ultrasonic disperser to prepare the sample dispersion. • Measurement conditions: The sample dispersion is added to 100 mL of the electrolyte to adjust the concentration so that the particle size of 30,000 particles can be measured in 20 seconds. Then, the 30,000 particles are measured, and the volume median particle size (D) is determined from the particle size distribution. 50 )

[0081] [Amount of water vapor adsorption by external additives] Water vapor adsorption amount (cm³) measured with a gas adsorption measuring device 3 This represents the amount of water vapor adsorbed at an equilibrium relative pressure of 0.85 (per g). Specifically, the analysis will be performed under the following measurement conditions. Measurement device: Multi-sample high-performance specific surface area / pore distribution analyzer 3Flex-3MP (manufactured by micromeritics) Dispersed adsorbent: Ion-exchanged water Pretreatment: 40°C for 4 hours or more Equilibrium relative pressure: 0.04~0.90 [0.04~0.10 (in increments of 0.01), 0.10~0.90 (in increments of 0.25)] Equilibrium interval: 20 seconds Measurement temperature: 30℃

[0082] [Average particle size of external additives] The particle size (average of the major and minor axes) of 500 particles (primary particles) is measured from scanning electron microscope (SEM) images, and the average of these values ​​is defined as the number-average particle size.

[0083] [Coverage rate of external additives] It is calculated using the following formula. Coverage rate (%)=√3 / 2π×(D·ρt) / (d·ρs)×C×100 (In the formula, D is the volume median particle size of the toner matrix particles (D 50 (μm), where d is the number-average particle size of the external additive (μm), ρt is the specific gravity of the toner particles, ρs is the specific gravity of the external additive, and C is the mass ratio of toner particles to external additive (external additive / toner particles). The total coverage rate of the external additives shall be the sum of the coverage rates calculated for each external additive. In all examples and comparative examples, the specific gravity of the toner matrix particles shall be 1.2, the specific gravity of silica shall be 2.2, and the specific gravity of alumina shall be 3.4.

[0084] Resin manufacturing example 1 A 10-liter four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. The alcohol component, terephthalic acid, and esterification catalyst shown in Table 1 were added. Under a nitrogen atmosphere, the mixture was heated to 235°C while stirring and held at 235°C for 6 hours. After that, the pressure inside the flask was reduced and held at 8 kPa for 1 hour. After returning to atmospheric pressure, the mixture was cooled to 220°C, trimellitic anhydride was added, and the reaction was carried out at 220°C for 0.5 hours. Then, the pressure inside the flask was reduced and the reaction was carried out at 20 kPa until the softening point shown in Table 1 was reached to obtain an amorphous polyester resin (resin X1). The physical properties are shown in Table 1.

[0085] Resin manufacturing example 2 A 10-liter four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. The alcohol component, terephthalic acid, and esterification catalyst shown in Table 1 were added. Under a nitrogen atmosphere, the reaction system was held at 180°C for 1 hour with stirring, then the temperature was increased from 180°C to 230°C at a rate of 10°C / h, and then held at 230°C for 5 hours. After that, it was cooled to 220°C, trimellitic anhydride was added, and the reaction was carried out at 220°C for 0.5 hours. Then, the pressure inside the flask was reduced, and the reaction was carried out at 20 kPa until the softening point shown in Table 1 was reached to obtain amorphous polyester resin (resin X2). The physical properties are shown in Table 1.

[0086] Resin manufacturing example 3 A 10-liter four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. The alcohol component, carboxylic acid components other than trimellitic anhydride, and esterification catalyst shown in Table 1 were added. Under a nitrogen atmosphere, the mixture was heated to 235°C while stirring and held at 235°C for 6 hours. After that, the pressure inside the flask was reduced and held at 8 kPa for 1 hour. After returning to atmospheric pressure, the mixture was cooled to 220°C, trimellitic anhydride was added, and the reaction was carried out at 220°C for 0.5 hours. After that, the pressure inside the flask was reduced and the reaction was carried out at 20 kPa until the softening point shown in Table 1 was reached to obtain an amorphous polyester resin (resin X3). The physical properties are shown in Table 1.

[0087] [Table 1]

[0088] Resin manufacturing example 4 A 10-liter four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. The alcohol and carboxylic acid components shown in Table 2 were added, and the mixture was heated to 140°C while stirring under a nitrogen atmosphere and held for 1 hour. Subsequently, the temperature was increased at 10°C / h until 200°C was reached, at which point the esterification catalyst was added and the mixture was held for 1 hour. After holding, the pressure inside the flask was reduced, and the reaction was carried out at 8 kPa until the softening point shown in Table 2 was reached, yielding a crystalline polyester resin (resin Y1). The physical properties are shown in Table 2.

[0089] [Table 2]

[0090] Examples 1-13 and Comparative Examples 1-4 100 parts by mass of the binder resin shown in Table 4, 0.2 parts by mass of the negative charge control agent "Bontron E-304" (manufactured by Orient Chemical Industry Co., Ltd.), 6 parts by mass of the coloring agent "ECB-301" (manufactured by Dainichi Seika Kogyo Co., Ltd., phthalocyanine blue), and 2 parts by mass of the release agent "HNP-9" (manufactured by Nippon Seiro Co., Ltd., paraffin wax, melting point: 75°C) were thoroughly pre-mixed in a Henschel mixer. Then, the mixture was melt-kneaded using a co-rotating twin-screw extruder at a roll rotation speed of 200 r / min (peripheral speed 0.3 m / min) and a heating temperature in the rolls of 100°C. After the obtained melt-kneaded material was cooled and coarsely ground, it was melt-kneaded again using a co-rotating twin-screw extruder with a total length of the kneading section of 1,560 mm, a screw diameter of 42 mm, and a barrel inner diameter of 43 mm. The screw rotation speed was 200 r / min (peripheral speed 0.3 m / min), the heating setting temperature inside the roll was 100°C, the temperature of the kneaded material was 160°C, the kneaded material supply rate was 10 kg / h, and the average residence time was approximately 18 seconds.

[0091] After cooling the kneaded mixture, it was coarsely ground to approximately 1 mm using a hammer mill (manufactured by Hosokawa Micron Corporation). The resulting coarsely ground material was then finely ground using an impact plate type jet mill IDS-2 (manufactured by Nippon Pneumatic Mfg. Co., Ltd.) at a feed rate of 4.0 kg / h to obtain the desired medium particle size (D 50 The particle size was set to 7.0 μm, and the grinding pressure was adjusted to obtain toner matrix particles.

[0092] To 100 parts by mass of the obtained toner matrix particles, the external additives (first stage) shown in Table 5 were added and mixed for 3 minutes at a peripheral speed of 32 m / s (rotation speed of 3000 r / min) using a Henschel mixer (manufactured by Nippon Coke Industries Co., Ltd., with a stirring blade diameter of 0.206 m). Next, the external additives (second stage) shown in Table 5 were added and mixed for 3 minutes at a peripheral speed of 32 m / s (rotation speed of 3000 r / min) using a Henschel mixer to obtain toner.

[0093] Example 14 Toner was obtained in the same manner as in Example 1, except that the second external additive step was omitted, and the external additives (first stage) shown in Table 5 were added to 100 parts by mass of toner mother particles, and the mixture was mixed for 3 minutes at a peripheral speed of 32 m / s (rotation speed of 3000 r / min) using a Henschel mixer (manufactured by Nippon Coke Industries Co., Ltd., with a stirring blade diameter of 0.206 m).

[0094] Table 3 shows the details of the external additives used in the examples and comparative examples.

[0095] [Table 3]

[0096] Test Example 1 [Cold Offset Resistance] Using high-quality paper "J Paper A4 size" (manufactured by Fujifilm Business Innovation Co., Ltd.) and a commercially available printer "Microline® 5400" (manufactured by Oki Electric Industry Co., Ltd.), the amount of toner adhering to the paper was 0.60 ± 0.01 mg / cm². 2 The resulting solid image was printed on A4 paper, leaving a 5mm margin at the top edge, and extending to a length of 50mm without being fixed. Next, a modified version of the printer with a variable-temperature fuser was prepared. The fuser temperature was set to 140°C, and the print was fixed in the A4 portrait direction at a line speed of 200 mm / sec per sheet. The fuser temperature was then lowered by 5°C increments until the temperature at which a cold offset occurred was reached. The results are shown in Table 5. Cold offset refers to the phenomenon where, when the fuser temperature is low, the toner on the unfixed image does not melt sufficiently and adheres to the fuser roller. The occurrence of cold offset can be determined by whether or not toner adheres to the paper again after the fuser roller completes one rotation. In this test, cold offset was determined when peeling occurred in the solid image on the paper.

[0097] Test Example 2 [Toner's Hot Offset Resistance] Using high-quality paper "J Paper A4 size" (manufactured by Fujifilm Business Innovation Co., Ltd.) and a commercially available printer "Microline® 5400" (manufactured by Oki Electric Industry Co., Ltd.), the amount of toner adhering to the paper was 0.60 ± 0.01 mg / cm². 2 The resulting solid image was printed on A4 paper, leaving a 5mm margin at the top edge, and extending to a length of 50mm without being fixed. Next, a modified version of the printer with a variable-temperature fuser was prepared. The fuser temperature was set to 140°C, and the print was fixed in the A4 portrait direction at a line speed of 100 mm / sec per sheet. The fuser temperature was then increased by 5°C increments until a hot offset occurred at each 5°C fixing temperature. The results are shown in Table 5. Hot offset refers to the phenomenon where, when the fixing temperature is set to a high temperature, the viscoelasticity of the toner on the unfixed image decreases, or the release properties become poor at high temperatures, causing the toner to adhere to the fixing roller. The occurrence of hot offset can be determined by whether or not toner adheres to the paper again after the fixing roller has completed one rotation. In this test, hot offset was determined when peeling occurred in the solid image on the paper surface.

[0098] [Table 4]

[0099] [Table 5]

[0100] From the above results, it can be seen that the toners of Examples 1 to 14 have good resistance to both cold offset and hot offset. In contrast, Comparative Example 1, which has a low SP value for the binder resin, Comparative Examples 2 and 3, which have low water vapor adsorption amounts for the external additives, and Comparative Example 4, which has a low coating rate with external additives having a predetermined water vapor adsorption amount, show that even if their hot offset resistance is within the acceptable range, their cold offset resistance is insufficient. [Industrial applicability]

[0101] The electrostatic image developing toner 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 matrix particles containing a binder resin and an external additive containing inorganic particles A, wherein the solubility parameter of the binder resin is 11.0 (cal / cm²). ３ ) １／２ More than 12.5 (cal / cm ３ ) １／２ The following is true: The amount of water vapor adsorbed by the inorganic particle A is 10 cm ３ / g or more 250cm ３ A toner for developing electrostatic images, wherein the amount is less than or equal to / g, and the coverage rate by the inorganic particles A is 150% or more and 800% or less.

2. The electrostatic image developing toner according to claim 1, wherein the inorganic particle A is silica.

3. The electrostatic image developing toner according to claim 1 or 2, wherein the inorganic particles A are inorganic particles that have not undergone surface treatment.

4. The electrostatic image developing toner according to claim 1 or 2, wherein the number-average particle diameter of inorganic particles A is 5 nm or more and 50 nm or less.

5. The electrostatic image developing toner according to claim 1 or 2, wherein the content of inorganic particles A is 0.5 parts by mass or more and 8 parts by mass or less per 100 parts by mass of toner matrix particles.

6. Furthermore, the external additive has a water vapor adsorption capacity of 10 cm ３ The electrostatic image developing toner according to claim 1 or 2, which contains inorganic particles B of less than 1g.

7. The electrostatic image developing toner according to claim 6, wherein inorganic particles A and inorganic particles B are present on the surface of the toner matrix particle in a manner in which inorganic particles A and inorganic particles B are stacked on top of each other from the toner matrix particle side.

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