Toner for developing electrostatic images

Abstract

This invention relates to a core-shell type electrostatic image developing toner with excellent durability and a method for manufacturing the same. [Solution] A toner for electrostatic image development, which is a core-shell type toner in which core particles containing a crystalline vinyl resin C, an amorphous resin A, and a release agent are coated with a shell layer, and a method for manufacturing a toner for electrostatic image development, which is a core-shell type toner in which core particles containing a crystalline vinyl resin C, an amorphous resin A, and a release agent are coated with a shell layer, by suspension polymerization.

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, and a method for manufacturing the same. [Background technology]

[0002] Crystalline resins have been investigated as binder resins that provide good low-temperature fixation for toner. For example, Patent Document 1 discloses a toner that uses both crystalline vinyl resin and amorphous resin as a toner that provides good low-temperature fixation, high gloss, and good solid images with fewer white spots in an even faster electrophotographic image forming apparatus.

[0003] Furthermore, as a toner shape, there is a core-shell type toner in which core particles are coated with a shell layer. For example, Patent Document 2 discloses a capsule toner that exhibits good fixability at low temperatures and / or low pressures, and good storage properties at high temperatures. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2024-73163 [Patent Document 2] Japanese Patent Application Publication No. 3-68961 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] While core-shell type toners are effective in improving durability, constructing a shell layer that uniformly coats the core particles is not easy. In particular, if components that do not disperse well in the toner particles, such as release agents, are present near the core surface, it becomes difficult to coat the core with the resin that forms the shell layer, hindering the improvement of durability.

[0006] The present invention relates to a core-shell type electrostatic image developing toner with excellent durability and a method for manufacturing the same. [Means for solving the problem]

[0007] The present invention [1] A core-shell type toner in which core particles containing crystalline vinyl resin C, amorphous resin A, and a mold release agent are coated with a shell layer, and a toner for developing electrostatic images, and [2] A method for manufacturing electrostatic image developing toner, comprising manufacturing a core-shell type toner by suspension polymerization, in which core particles containing crystalline vinyl resin C, amorphous resin A, and a mold release agent are coated with a shell layer. Regarding. [Effects of the Invention]

[0008] The electrostatic image developing toner of the present invention exhibits excellent durability. [Modes for carrying out the invention]

[0009] The electrostatic image developing toner of the present invention is a core-shell type toner in which core particles are coated with a shell layer, and is characterized in that the core particles, which contain amorphous resin and a release agent, further contain crystalline vinyl resin. The reason why the effects of the present invention are achieved is not clear, but it is presumed to be as follows. Because crystalline vinyl resin is hydrophobic, using it in combination with a similarly hydrophobic release agent improves the dispersibility of the release agent in the amorphous resin. As a result, the amount of release agent near the surface of the core particles is reduced, which is thought to improve the uniformity of the shell layer coating and thus the durability of the toner. However, the above mechanism is a hypothesis and is not limited to this.

[0010] 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.

[0011] As described above, the toner of the present invention is a core-shell type toner in which core particles containing a crystalline vinyl resin C, an amorphous resin A, and a mold release agent are coated with a shell layer.

[0012] From the viewpoint of enhancing crystallinity, the crystalline vinyl resin C is preferably an addition polymer of raw material monomers containing a long-chain alkyl group (meth)acrylate alkyl ester L. In this specification, "(meth)acrylate alkyl ester" means alkyl acrylate and / or alkyl methacrylate.

[0013] The number of carbon atoms in the long-chain alkyl group of (meth)acrylate alkyl ester L is preferably 10 or more, more preferably 12 or more, and from the viewpoint of high-speed low-temperature fixation, it is preferably 36 or less, more preferably 30 or less. Note that the number of carbon atoms in the alkyl ester refers to the number of carbon atoms derived from the alcohol component constituting the ester.

[0014] Examples of the (meth)acrylic acid alkyl ester L include (iso)decyl (meth)acrylate, (iso)stearyl (meth)acrylate, (iso)behenyl (meth)acrylate, etc. In this specification, “(iso)” means including both the case where this group is present and the case where it is not present, and when these groups are not present, it means normal.

[0015] The content of the (meth)acrylic acid alkyl ester L in the raw material monomers is preferably 10 mol% or more, more preferably 25 mol% or more, still more preferably 35 mol% or more, and still more preferably 45 mol% or more, and is preferably 80 mol% or less, more preferably 70 mol% or less, still more preferably 60 mol% or less.

[0016] From the viewpoint of chargeability, the raw material monomers of the crystalline vinyl resin C preferably further contain a styrene compound and / or (meth)acrylic acid. In this specification, “(meth)acrylic acid” means acrylic acid and / or methacrylic acid.

[0017] Examples of the styrene compound include styrene and styrene derivatives such as α-methylstyrene and vinyltoluene. Among these, styrene is preferred.

[0018] The content of the styrene compound in the raw material monomers is preferably 1 mol% or more, more preferably 3 mol% or more, still more preferably 5 mol% or more, and is preferably 60 mol% or less, more preferably 50 mol% or less, still more preferably 40 mol% or less.

[0019] The content of (meth)acrylic acid in the raw material monomers is preferably 1 mol% or more, more preferably 3 mol% or more, still more preferably 5 mol% or more, and is preferably 60 mol% or less, more preferably 50 mol% or less, still more preferably 30 mol% or less, and still more preferably 20 mol% or less.

[0020] The raw material monomers may include alkyl (meth)acrylates with an alkyl group having 9 or fewer carbon atoms; nitrile group-containing monomers such as acrylonitrile, methacrylonitrile, and methacrylonitrile in which the methyl group is replaced by an alkyl group having 2 to 16 carbon atoms; ethylenically unsaturated monoolefins such as ethylene and propylene; diolefins such as butadiene; halovinyls such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; ethylenically monocarboxylic acid esters such as dimethylaminoethyl (meth)acrylate; vinyl ethers such as methyl vinyl ether; vinylidene halides such as vinylidene chloride; and N-vinyl compounds such as N-vinylpyrrolidone.

[0021] The addition polymerization reaction of the raw material monomers for crystalline vinyl resin C can be carried out by conventional methods such as radical polymerization, anionic polymerization, and cationic polymerization, for example, in the presence of polymerization initiators, chain transfer agents, crosslinking agents, etc., in the presence of organic solvents, or in the absence of solvents.

[0022] Examples of polymerization initiators include organic peroxides such as dibutyl peroxide, dicumyl peroxide, and di-tert-butyl peroxide, and azo compounds such as 2,2'-azobis(2,3-dimethylvaleronitrile) and azobisisobutyronitrile.

[0023] The amount of polymerization initiator used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, per 100 parts by mass of raw material monomer.

[0024] As organic solvents, xylene, toluene, methyl ethyl ketone, acetone, tetrahydrofuran, etc., can be used.

[0025] Furthermore, if the alkyl (meth)acrylate L is a solid at room temperature, such as behenyl acrylate or stearyl acrylate, it is preferable to heat it in an organic solvent beforehand to dissolve it before using it in the addition polymerization reaction. The organic solvent is not particularly limited as long as it can dissolve the alkyl (meth)acrylate L, but examples include tetrahydrofuran, xylene, and toluene.

[0026] The amount of organic solvent used is preferably 10 parts by mass or more and 400 parts by mass or less per 100 parts by mass of raw material monomer.

[0027] The reaction temperature cannot be determined definitively as it varies depending on the type of starting monomer, polymerization initiator, and organic solvent. However, it is generally preferably 110°C or higher, more preferably 140°C or higher, and more preferably 200°C or lower, and more preferably 170°C or lower. However, when dissolving the alkyl (meth)acrylate L in an organic solvent, if a solvent with a boiling point below the above temperature, such as tetrahydrofuran or toluene, is used, it is preferable to carry out the reaction at a temperature below the boiling point of the solvent.

[0028] The softening point of the crystalline vinyl resin C is preferably 55°C or higher, more preferably 58°C or higher, and even more preferably 63°C or higher, from the viewpoint of high-speed low-temperature fixing, and is preferably 105°C or lower, more preferably 100°C or lower, and even more preferably 90°C or lower.

[0029] The melting point of the crystalline vinyl resin C is preferably 50°C or higher, more preferably 55°C or higher, and even more preferably 60°C or higher, from the viewpoint of high-speed low-temperature fixing, and preferably 100°C or lower, more preferably 90°C or lower, and even more preferably 80°C or lower.

[0030] The ratio of the softening point to the melting point (softening point / melting point) of the crystalline vinyl resin C is preferably 0.7 or higher, more preferably 0.9 or higher, and preferably 1.3 or lower, more preferably 1.2 or lower.

[0031] The content of crystalline vinyl resin C 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 25% by mass or less, and even more preferably 20% by mass or less, from the viewpoint of high-speed low-temperature fixing properties, in the total amount of crystalline vinyl resin C and amorphous resin A.

[0032] Examples of amorphous resin A include amorphous vinyl resin, amorphous polyester resin, amorphous epoxy resin, amorphous polycarbonate, amorphous polyurethane, and composite resins containing two or more of these resins. Among these, from the viewpoint of low-temperature fixation, amorphous vinyl resin, amorphous polyester resin, and composite resins of amorphous polyester resin and amorphous vinyl resin are preferred, with amorphous vinyl resin being more preferred.

[0033] As for amorphous vinyl resins, from the viewpoint of enhancing amorphousness, styrene-based resins, which are addition polymers of raw material monomers containing styrene compounds, are preferred, and styrene-acrylic resins, which are addition polymers of raw material monomers containing styrene compounds and (meth)acrylate alkyl ester S having a short-chain alkyl group, are more preferred.

[0034] The styrene compound is the same as the styrene compound in crystalline vinyl resin C.

[0035] The styrene compound content is preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 75 mol% or more, and preferably 95 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less, in the raw material monomer.

[0036] The number of carbon atoms in the short-chain alkyl group of (meth)acrylate alkyl ester S is 1 or more, preferably 2 or more, more preferably 3 or more, and from the viewpoint of preservation, it is preferably 10 or less, more preferably 7 or less.

[0037] Examples of alkyl methacrylate S include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, isohexyl methacrylate, 2-ethylhexyl methacrylate, and isooctyl methacrylate.

[0038] The content of (meth)acrylate alkyl ester S is preferably 5 mol% or more, more preferably 10 mol% or more, even more preferably 15 mol% or more, and preferably 40 mol% or less, more preferably 30 mol% or less, and even more preferably 25 mol% or less, in the raw material monomer.

[0039] The raw material monomers may include (meth)acrylate alkyl esters other than (meth)acrylate alkyl ester S; nitrile group-containing monomers such as acrylonitrile, methacrylonitrile, and methacrylonitrile in which the methyl group is replaced by an alkyl group having 2 to 16 carbon atoms; ethylenically unsaturated monoolefins such as ethylene and propylene; diolefins such as butadiene; halovinyls such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; ethylenically monocarboxylic acid esters such as (meth)acrylate dimethylaminoethyl; vinyl ethers such as methyl vinyl ether; vinylidene halides such as vinylidene chloride; and N-vinyl compounds such as N-vinylpyrrolidone.

[0040] Furthermore, the raw material monomers may include crosslinkable polymerizable monomers from the viewpoint of adjusting the softening point.

[0041] Preferred crosslinkable polymerizable monomers include divinyl monomers, such as aromatic divinyl compounds like divinylbenzene, divinylnaphthalene, and their derivatives; di(meth)acrylic acid esters like ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; and other divinyl compounds like N,N-divinylaniline and divinyl ether.

[0042] Amorphous vinyl resins, like crystalline vinyl resin C, are obtained by addition polymerization of raw material monomers.

[0043] The softening point of amorphous resin A is preferably 70°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher, from the viewpoint of electrostatic stability, and preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 155°C or lower, from the viewpoint of low-temperature fixation.

[0044] The glass transition temperature of amorphous resin A is preferably 40°C or higher, more preferably 45°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 fixing properties.

[0045] The content of amorphous resin A is preferably 70% by mass or more, more preferably 75% by mass or more, even more preferably 80% by mass or more, and preferably 97% by mass or less, more preferably 95% by mass or less, and even more preferably 93% by mass or less, from the viewpoint of high-speed low-temperature fixing properties, in the total amount of crystalline vinyl resin C and amorphous resin A.

[0046] The mass ratio of crystalline vinyl resin C to amorphous resin A (crystalline vinyl resin C / amorphous resin A) is preferably 3 / 97 or higher, more preferably 5 / 95 or higher, even more preferably 7 / 93 or higher, and preferably 30 / 70 or lower, more preferably 25 / 75 or lower, and even more preferably 20 / 80 or lower, from the viewpoint of high-speed low-temperature fixing performance.

[0047] In the core particles, crystalline vinyl resin C and amorphous resin A are included as binder resins (binding agents).

[0048] The total content of crystalline vinyl resin C and amorphous resin A in the binder resin is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, and 100% by mass or less.

[0049] The binder resin content is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and preferably 97% by mass or less, more preferably 95% by mass or less, and even more preferably 93% by mass or less, in the core particles.

[0050] Examples of release agents include hydrocarbon waxes, ester waxes, silicone waxes, and fatty acid amide waxes. Examples of hydrocarbon waxes include mineral or petroleum-based hydrocarbon waxes such as paraffin wax and Fischer-Tropsch wax; and synthetic hydrocarbon waxes such as polyethylene wax, polypropylene wax, ethylene-propylene copolymer wax, and polyolefin wax such as polybutene wax. Examples of ester waxes include mineral or petroleum-based ester waxes such as montan wax; plant-based ester waxes such as carnauba wax, rice wax, and candelilla wax; animal-based ester waxes such as beeswax; and synthetic ester waxes obtained by condensing carboxylic acids such as fatty acids with alcohols such as aliphatic alcohols. Examples of fatty acid amide waxes include oleic acid amide and stearic acid amide. Among these, hydrocarbon waxes or ester waxes are preferred from the viewpoint of toner release properties, and ester waxes are more preferred.

[0051] Suitable ester waxes include pentaerythritol-based ester waxes, dipentaerythritol-based ester waxes, and aliphatic monoalcohol-based ester waxes.

[0052] Preferably, the pentaerythritol-based ester wax is an ester of pentaerythritol and an aliphatic monocarboxylic acid, the dipentaerythritol-based ester wax is an ester of dipentaerythritol and an aliphatic monocarboxylic acid, and the aliphatic monoalcohol-based ester wax is an ester of an aliphatic monoalcohol and an aliphatic monocarboxylic acid.

[0053] Examples of aliphatic monocarboxylic acids include stearic acid, behenic acid, caprylic acid, lauric acid, myristic acid, isostearic acid, palmitic acid, oleic acid, condensed ricinoleic acid, and 12-hydroxystearic acid.

[0054] The number of carbon atoms in the aliphatic monocarboxylic acid is preferably 10 or more, more preferably 12 or more, even more preferably 14 or more, and preferably 30 or less, more preferably 28 or less, and even more preferably 26 or less.

[0055] Examples of aliphatic monoalcohols include behenyl alcohol, stearyl alcohol, caprylic alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, oleyl alcohol, aragisyl alcohol, and ceryl alcohol.

[0056] The number of carbon atoms in the aliphatic monoalcohol is preferably 10 or more, more preferably 12 or more, even more preferably 14 or more, and preferably 30 or less, more preferably 28 or less, and even more preferably 26 or less.

[0057] Specific examples of pentaerythritol-based ester waxes include pentaerythritol tetrabehenate, pentaerythritol tetrastearate, and pentaerythritol tetrapalmitate.

[0058] Specific examples of dipentaerythritol-based ester waxes include dipentaerythritol hexastearate, dipentaerythritol hexabéhenate, and dipentaerythritol stearate.

[0059] Specific examples of aliphatic monoalcohol ester waxes include behenyl behenate, behenyl stearate, stearyl stearate, and stearyl behenate.

[0060] The melting point of the release agent is preferably 60°C or higher, more preferably 65°C or higher, and even more preferably 70°C or higher, from the viewpoint of toner release properties, and preferably 100°C or lower, more preferably 90°C or lower, even more preferably 85°C or lower, and even more preferably 80°C or lower, from the viewpoint of improving the low-temperature fixability of the toner.

[0061] The release agent content is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 7 parts by mass or more, and preferably 15 parts by mass or less, more preferably 13 parts by mass or less, and even more preferably 11 parts by mass or less, per 100 parts by mass of the binder resin.

[0062] The core particles may contain additives other than the binder resin and release agent, such as colorants, charge control agents, magnetic powders, flow improvers, conductivity modifiers, reinforcing fillers such as fibrous materials, antioxidants, and cleaning properties improvers.

[0063] 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.

[0064] 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.

[0065] The charge control agent may contain either a positively charged charge control agent or a negatively charged charge control agent.

[0066] 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," and "Bontron N-11" (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-161P, FCA-201-PS, and FCA-701PT (manufactured by Fujikura Chemicals, Ltd.).

[0067] Examples of negatively charged charge control agents include 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.

[0068] 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. If the charge control agent is a resin (polymer type), it is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, per 100 parts by mass of the binder resin.

[0069] The method for producing the toner of the present invention is not particularly limited as long as it is a method that can produce a core-shell type toner in which core particles are coated with a shell layer. However, from the viewpoint of durability, the toner of the present invention is preferably obtained by a suspension polymerization method, an emulsification agglutination method, etc., and more preferably by a suspension polymerization method.

[0070] When obtaining toner by suspension polymerization, for example, a polymerizable monomer composition containing amorphous vinyl resin raw material monomers, crystalline vinyl resin C, and a mold release agent, and optionally a colorant, charge control agent, etc., is suspended polymerized in an aqueous medium in the presence of a polymerization initiator to obtain toner. Specifically, it is preferable to granulate the polymerizable monomer composition in an aqueous medium in the presence of a polymerization initiator, and then perform suspension polymerization.

[0071] In the suspension polymerization method, the raw material monomers for amorphous vinyl resins are preferably mainly composed of monovinyl monomers.

[0072] Examples of monovinyl monomers include styrene compounds such as styrene, vinyltoluene, and styrene derivatives such as α-methylstyrene; (meth)acrylic acid; alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and dimethylaminoethyl (meth)acrylate; derivatives of (meth)acrylic acid such as (meth)acrylonitrile and (meth)acrylamide; olefins such as ethylene, propylene, and butylene; vinyl halides and vinylidene halides such as vinyl chloride, vinylidene chloride, and vinyl fluoride; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; vinyl ketones such as methyl vinyl ketone and methyl isopropenyl ketone; and nitrogen-containing vinyl compounds such as 2-vinylpyridine, 4-vinylpyridine, and N-vinylpyrrolidone. These monovinyl monomers may be used individually or in combination. Among these monovinyl monomers, styrene compounds and alkyl (meth)acrylates are preferred, and styrene compounds and the alkyl (meth)acrylate S are more preferred.

[0073] The styrene compound content is preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 75 mol% or more, and preferably 95 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less, in the monovinyl monomer.

[0074] The content of (meth)acrylate alkyl ester S is preferably 5 mol% or more, more preferably 10 mol% or more, even more preferably 15 mol% or more, and preferably 40 mol% or less, more preferably 30 mol% or less, and even more preferably 25 mol% or less, in the monovinyl monomer.

[0075] The monovinyl monomer content is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and 100% by mass or less, preferably 99.5% by mass or less, in the polymerizable monomer.

[0076] Furthermore, the content of monovinyl monomer in the polymerizable monomer composition is preferably 50% by mass or more, more preferably 65% ​​by mass or more, even more preferably 70% by mass or more, and preferably 97% by mass or less, more preferably 90% by mass or less.

[0077] From the viewpoint of resistance to hot offsetting, it is preferable that the polymerizable monomer includes a crosslinkable polymerizable monomer together with the monovinyl monomer. A crosslinkable polymerizable monomer is a monomer having two or more polymerizable functional groups. Divinyl monomers are preferred as crosslinkable polymerizable monomers, and examples include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and their derivatives; di(meth)acrylic acid esters such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; and other divinyl compounds such as N,N-divinylaniline and divinyl ether. These crosslinkable polymerizable monomers can be used individually or in combination of two or more. The content of the crosslinkable polymerizable monomer is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and preferably 5 parts by mass or less, more preferably 2 parts by mass or less, per 100 parts by mass of monovinyl monomer.

[0078] Furthermore, in the present invention, from the viewpoint of preservation and low-temperature fixation, it is preferable that the polymerizable monomer further includes a macromonomer. A macromonomer is a reactive oligomer or reactive polymer having polymerizable carbon-carbon unsaturated double bonds at the ends of its molecular chains.

[0079] The number-average molecular weight of the macromonomer is preferably 1,000 or more, more preferably 3,000 or more, and preferably 30,000 or less, more preferably 20,000 or less, and even more preferably 10,000 or less.

[0080] The macromonomer content is preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, even more preferably 0.05 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of monovinyl monomer.

[0081] The polymerizable monomer composition may further contain chain transfer agents, silica, aluminum oxide, titanium oxide, zinc oxide, tin oxide, and other inorganic fine particles.

[0082] Examples of chain transfer agents include mercaptans such as tert-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, and 2,2,4,6,6-pentamethylheptan-4-thiol. Chain transfer agents can be added before polymerization begins or during polymerization.

[0083] The content of the chain transfer agent is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, per 100 parts by mass of polymerizable monomer.

[0084] A polymerizable monomer composition is obtained by mixing amorphous vinyl resin raw material monomers, crystalline vinyl resin C, a mold release agent, and other additives as needed, and dissolving each component.

[0085] As the aqueous medium, one mainly composed of water is preferred. The water content in the aqueous medium is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more, and 100% by mass or less. Deionized water or distilled water is preferred as the water.

[0086] Other components that may be included in an aqueous medium include, for example, alkyl alcohols having 1 to 5 carbon atoms; dialkyl ketones having 3 to 5 carbon atoms such as acetone and methyl ethyl ketone; and water-soluble organic solvents such as cyclic ethers such as tetrahydrofuran.

[0087] The aqueous medium preferably contains a dispersion stabilizer.

[0088] Examples of dispersion stabilizers include sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate, and magnesium carbonate; phosphates such as calcium phosphate; metal oxides such as aluminum oxide and titanium oxide; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, and ferric hydroxide; water-soluble polymers such as polyvinyl alcohol, methylcellulose, and gelatin; anionic surfactants; nonionic surfactants; and organic polymer compounds such as amphoteric surfactants. Dispersion stabilizers can be used individually or in combination of two or more.

[0089] Among dispersion stabilizers, those containing metal compounds, particularly colloids of poorly water-soluble metal hydroxides, are preferable because they can narrow the particle size distribution of the resulting polymer particles, reduce the amount of residual dispersion stabilizer after washing, allow for clear image reproduction, and do not worsen environmental stability.

[0090] The content of the dispersion stabilizer is preferably 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of polymerizable monomer.

[0091] Polymerization initiators used in the polymerization of polymerizable monomer compositions include persulfates such as potassium persulfate and ammonium persulfate; azo compounds such as 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis(2-amidinopropane)dihydrochloride, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobisisobutyronitrile; and di-te Examples of peroxides include rt-butyl peroxide, benzoyl peroxide, tert-butyl peroxy-2-ethyl butanoate, tert-butyl peroxy-2-ethyl hexanoate, tert-hexyl peroxy-2-ethyl hexanoate, tert-butyl peroxypivalate, diisopropyl peroxydicarbonate, di-tert-butyl peroxyisophthalate, and tert-butyl peroxyisobutyrate. Alternatively, a redox initiator combining the above polymerization initiator and a reducing agent may be used.

[0092] The amount of polymerization initiator is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, even more preferably 0.5 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of polymerizable monomer.

[0093] A polymerizable monomer composition can be granulated in an aqueous medium in the presence of a polymerization initiator. The polymerization initiator may be added to the aqueous medium after the polymerizable monomer composition has been dispersed in the aqueous medium and before granulation, or it may be added to the polymerizable monomer composition beforehand before dispersion in the aqueous medium.

[0094] The granulation method is not particularly limited, but it is preferable to use equipment capable of strong stirring, such as an (in-line type) emulsifier / disperser (product name: Milder MDN303V (manufactured by Taiheiyo Kiko Co., Ltd.), product name "Ebara Milder" (manufactured by Ebara Corporation)), or a high-speed emulsifier / disperser (product name "TK Homomixer MARK II" (manufactured by Primix Co., Ltd.)).

[0095] After granulation, the aqueous medium in which the granulated polymerizable monomer composition is dispersed is heated to initiate polymerization.

[0096] The polymerization temperature of the polymerizable monomer composition is preferably 50°C or higher, more preferably 60°C or higher, and preferably 95°C or lower. The polymerization reaction time is preferably 1 hour or more, more preferably 2 hours or more, and preferably 20 hours or less, and more preferably 15 hours or less.

[0097] In this invention, polymer particles obtained by suspension polymerization, emulsification agglutination, etc., are used as core particles, and a shell layer is formed on the outside thereof to obtain a core-shell type toner (capsule toner).

[0098] There are no particular restrictions on the method for producing core-shell type toner using polymer particles as core particles, and it can be produced by conventionally known methods. In situ polymerization and phase separation methods are preferred from the viewpoint of production efficiency.

[0099] Core-shell type toners produced by in situ polymerization can be manufactured, for example, by the following method. A polymerizable monomer for forming the shell layer (shell resin), along with other shell additives as needed, is dissolved or dispersed in deionized water to obtain an aqueous dispersion of the polymerizable monomer. A polymerization initiator for polymerizing the polymerizable monomer is added to this aqueous dispersion of the polymerizable monomer, and the mixture is placed in an aqueous medium containing dispersed core particles. Polymerization is then performed to obtain a core-shell type toner.

[0100] As the polymerizable monomer for the shell, the same polymerizable monomers as those mentioned above can be used, but from the viewpoint of durability, the shell layer preferably contains polymethyl methacrylate (PMMA). Therefore, methyl methacrylate is preferred as the polymerizable monomer for the shell.

[0101] The methyl methacrylate content is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and even more preferably 95 mol% or more, and 100 mol% or less in the polymerizable monomer for shells.

[0102] Other shell additives may include inorganic fine particles such as silica, aluminum oxide, titanium oxide, zinc oxide, and tin oxide, as well as crosslinkable polymers having two or more polymerizable functional groups, such as urethane acrylate polymers.

[0103] Polymerization initiators used for polymerizable monomers for shells include persulfate metal salts such as potassium persulfate and ammonium persulfate; and water-soluble polymerization initiators such as azo-based initiators like 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] and 2,2'-azobis[2-methyl-N-[1,1-bis(hydroxymethyl)2-hydroxyethyl]propionamide].

[0104] The amount of polymerization initiator is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, per 100 parts by mass of polymerizable monomer for the shell.

[0105] The polymerization temperature of the shell layer is preferably 50°C or higher, more preferably 60°C or higher, and preferably 95°C or lower. The polymerization reaction time is preferably 1 hour or more, more preferably 2 hours or more, and preferably 20 hours or less, and more preferably 15 hours or less.

[0106] After polymerization is complete, the core-shell toner can be separated from the aqueous dispersion of the core-shell toner by washing, dehydrating, and drying operations in accordance with conventional methods, including filtration and removal of dispersion stabilizers. It is preferable to repeat the filtration, washing, dehydrating, and drying operations several times as needed.

[0107] As for the cleaning method, when an inorganic compound such as an inorganic hydroxide is used as a dispersion stabilizer, it is preferable to dissolve and remove the dispersion stabilizer in water by adding an acid or alkali to the aqueous dispersion of toner particles. When a colloid of poorly water-soluble inorganic hydroxide is used as a dispersion stabilizer, it is preferable to add an acid to adjust the pH of the aqueous dispersion of toner particles to 6.5 or below. As the acid to be added, inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, or organic acids such as formic acid and acetic acid can be used, but sulfuric acid is preferred because of its high removal efficiency and low burden on manufacturing equipment.

[0108] The dehydration and filtration methods are not particularly limited and can be any of the known methods. Examples include centrifugal filtration, vacuum filtration, and pressure filtration.

[0109] The circularity of the toner particles obtained by the suspension polymerization method is preferably 0.975 or higher, more preferably 0.978 or higher, even more preferably 0.980 or higher, and preferably 0.995 or lower, more preferably 0.992 or lower, and even more preferably 0.990 or lower.

[0110] The toner of the present invention preferably contains external additives to improve transferability. Examples of external additives include inorganic fine particles such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide, and organic fine particles such as melamine resin fine particles and polytetrafluoroethylene resin fine particles, and two or more may be used in combination. Among these, silica is preferred, and from the viewpoint of toner transferability, hydrophobic silica that has been hydrophobicized is more preferred.

[0111] Examples of hydrophobic agents used to hydrophobize the surface of silica particles include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), cyclic silazane, silicone oil, aminosilane, octyltriethoxysilane (OTES), and methyltriethoxysilane.

[0112] The average particle size of the external additive is preferably 5 nm or larger, more preferably 250 nm or smaller, more preferably 200 nm or smaller, and even more preferably 90 nm or smaller, from the viewpoint of the toner's chargeability, fluidity, and transferability.

[0113] External additive treatment, which involves mixing toner particles with external additives, can be carried out according to conventional methods, and a mixer such as a Henschel mixer can be used.

[0114] From the viewpoint of the toner's electrostatic properties, fluidity, and transferability, the content of the external additive is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.3 parts by mass or more, and preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of toner particles before treatment with the external additive.

[0115] The volume-intermediate particle size (D) of the toner of the present invention 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. Furthermore, if the toner is treated with an external additive, the volume median particle size of the toner particles before treatment with the external additive is considered the volume median particle size of the toner.

[0116] The toner obtained by the method of the present invention can be used as a one-component developing toner, or mixed with a carrier to form a two-component developing agent. [Examples]

[0117] 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 the resin and the like were measured by the following methods.

[0118] [Number-average molecular weight of macromonomers] The number-average molecular weight is determined by gel permeation chromatography (GPC) using the following method. (1) Preparation of Sample Solution Dissolve the resin in tetrahydrofuran so that the concentration becomes 0.5 g / 100 mL. Then, filter this solution using a fluororesin filter with a pore size of 2 μm (manufactured by Sumitomo Electric Industries, Ltd., product name: FP-200) to remove insoluble components and obtain a sample solution. (2) Molecular Weight Measurement Using the following measuring device and analytical column, flow tetrahydrofuran as an eluent at a flow rate of 1 mL per minute and stabilize the column in a thermostat at 40°C. Inject 100 μL of the sample solution there and perform the measurement. The molecular weight of the sample is calculated based on a calibration curve prepared in advance. For the calibration curve at this time, several monodisperse polystyrenes with known molecular weights (manufactured by Tosoh Corporation; 2.63×10 3 , 2.06×10 4 , 1.02×10 5 , manufactured by GL Sciences Inc.; 2.10×10 3 , 7.00×10 3 , 5.04×10 4 ) are used as standard samples to create it. Measuring device: CO-8010 (product name, manufactured by Tosoh Corporation) Analytical column: GMH XL +G3000H XL (Both are product names, manufactured by Tosoh Corporation)

[0119] 〔Softening Point of Resin〕 Using a flow tester "CFT-500D" (manufactured by Shimadzu Corporation), while heating 1 g of the sample at a heating rate of 6°C / min, apply a load of 1.96 MPa with a plunger and extrude it from a nozzle with a diameter of 1 mm and a length of 1 mm. Plot the plunger drop amount of the flow tester against the temperature, and the temperature at which half of the sample flows out is defined as the softening point.

[0120] 〔Maximum Peak Temperature of Heat Absorption of 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 while raising the temperature to 180°C 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.

[0121] [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.

[0122] [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 at a heating rate of 10°C / min, and then cooled from 200°C to 0°C at a cooling rate of 10°C / min. Next, the sample is heated again at a heating 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.

[0123] [Average particle size of external additives] The average particle diameter refers to the number-average particle diameter, which is calculated by measuring the particle size (average of the major and minor axes) of 500 particles (primary particles) from scanning electron microscope (SEM) images and using the number-average value of these measurements.

[0124] [Toner volume medium particle size (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 )

[0125] [Circularity of toner particles] The circularity of the toner particles will be measured under the following conditions. • Measurement device: Flow-type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation) • Dispersion: Prepared by dissolving polyoxyethylene lauryl ether "Emulgen (registered trademark) 109P" [manufactured by Kao Corporation, HLB (Griffin) = 13.6] in deionized water to a concentration of 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 deionized water and disperse for another minute using the ultrasonic disperser to prepare the sample dispersion. • Measurement mode: HPF measurement mode

[0126] Resin manufacturing example 1 400g of tetrahydrofuran (THF) was placed in a 3-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, fall-flow condenser, dropping funnel, and nitrogen inlet tube. In a separate container, 350g of THF, the raw material monomers for vinyl resins shown in Table 1, and polymerization initiators were added. The mixture was stirred and prepared at 40°C and then added to the dropping funnel. Under a nitrogen atmosphere, the THF was heated to 60°C while stirring, and the mixture in the dropping funnel was added dropwise over 1 hour. The temperature was then raised to 65°C and held at 65°C for 2 hours. After that, the pressure in the flask was further reduced and held at 8kPa for 1 hour, and the THF was removed at 65°C to obtain crystalline vinyl resins (resins C1-C3).

[0127] Resin manufacturing example 2 400 g of xylene was placed in a 3-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, fall-flow condenser, dropping funnel, and nitrogen inlet tube. In a separate container, 350 g of xylene, the raw material monomers for vinyl resin shown in Table 1, and polymerization initiators were added. The mixture was stirred and adjusted at 40°C and then added to the dropping funnel. Under a nitrogen atmosphere, the xylene was heated to 130°C while stirring, and the mixture in the dropping funnel was added dropwise over 1 hour. The temperature was then raised to 140°C and held at that temperature for 2 hours. After that, the pressure in the flask was further reduced and held at 8 kPa for 1 hour, and the xylene was removed at 200°C to obtain crystalline vinyl resin (resin C4).

[0128] Resin manufacturing example 3 400g of toluene was placed in a 3-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, fall-flow condenser, dropping funnel, and nitrogen inlet tube. In a separate container, 350g of toluene, the raw material monomers for vinyl resin shown in Table 1, and polymerization initiators were added. The mixture was stirred and mixed at 40°C and then added to the dropping funnel. Under a nitrogen atmosphere, the toluene was heated to 80°C while stirring, and the mixture in the dropping funnel was added dropwise over 1 hour. The temperature was then raised to 85°C and held at 85°C for 2 hours. After that, the pressure in the flask was further reduced and held at 8kPa for 1 hour, and the toluene was removed at 130°C to obtain crystalline vinyl resin (resin C5).

[0129] [Table 1]

[0130] Example 1 (1) Preparation of polymerizable monomer composition for core A polymerizable monomer mixture was obtained by dispersing 72 parts by mass of styrene and 18 parts by mass of n-butyl acrylate as polymerizable monomers, and 5 parts by mass of CI Pigment Blue 15 (manufactured by DIC Corporation, trade name "Fastogen Blue GCTF") as a coloring agent using a media-type emulsifying disperser. To the obtained polymerizable monomer mixture, 10 parts by mass of resin C1, 0.75 parts by mass of a polymeric positive charge control agent (manufactured by Fujikura Chemicals Co., Ltd., trade name: Acrybase FCA-161P, quaternary ammonium salt-containing resin, softening point: 110°C, glass transition temperature: 60°C), 8 parts by mass of ester wax "WEP-4" (manufactured by NOF Corporation, pentaerythritol tetrapalmitate, melting point: 71°C) as a mold release agent, 0.3 parts by mass of polymethacrylate ester macromonomer (manufactured by Toagosei Co., Ltd., trade name: AA6, number average molecular weight: 6,000) as a macromonomer, 0.6 parts by mass of divinylbenzene as a crosslinkable polymerizable monomer, and 1.6 parts by mass of tert-dodecyl mercaptan as a chain transfer agent were added, and then the mixture was mixed and dissolved to prepare a polymerizable monomer composition.

[0131] (2) Preparation of aqueous dispersion medium A magnesium hydroxide colloidal dispersion was prepared by gradually adding an aqueous solution prepared by dissolving 10.4 parts by mass of magnesium chloride in 280 parts by mass of deionized water, to an aqueous solution prepared by dissolving 7.3 parts by mass of sodium hydroxide in 50 parts by mass of deionized water, while stirring.

[0132] (3) Preparation of polymerizable monomers for shells Two parts by mass of methyl methacrylate and 130 parts by mass of deionized water were subjected to fine dispersion treatment using an ultrasonic emulsifier to prepare an aqueous dispersion of polymerizable monomer for shells.

[0133] (4) Granulation process To the magnesium hydroxide colloidal dispersion obtained in (2), the polymerizable monomer composition obtained in (1) was added at room temperature, and the mixture was stirred further until the droplets stabilized. Then, 4.4 parts by mass of tert-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, trade name: Perbutyl O) was added as a polymerization initiator. The dispersion with the polymerization initiator added was stirred at a high shear speed of 15,000 r / min using an in-line emulsifying disperser (manufactured by Taiheiyo Kiko Co., Ltd., trade name: Milder MDN303V) to form droplets of the polymerizable monomer composition.

[0134] (5) Suspension polymerization process: A dispersion containing droplets of the polymerizable monomer composition obtained in (4) was placed in a reactor and heated to 90°C to carry out the polymerization reaction. After the polymerization conversion rate reached approximately 100%, 0.1 parts by mass of 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide] (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name: VA-086, water-soluble initiator) was dissolved in the aqueous dispersion of polymerizable monomer for shells obtained in (3) and added to the reactor. The polymerization was then continued by holding at 95°C for 4 hours, after which the reaction was stopped by water cooling to obtain an aqueous dispersion of toner particles.

[0135] (6) Post-processing steps (5) The aqueous dispersion of toner particles obtained in (5) was acid washed by adding sulfuric acid dropwise while stirring at room temperature until the pH was 6.0 or lower. Next, filtration separation was performed, and 500 parts by mass of deionized water was added to the obtained solid to form a slurry again, and the water washing treatment (washing, filtration, and dewatering) was repeated several times. Next, filtration separation was performed, and the obtained solid was placed in the container of a dryer and dried at 40°C for 24 hours to obtain the medium volume particle size (D 50 Toner particles with a diameter of 6.4 μm and a circularity of 0.985 were obtained.

[0136] (7) External addition process To 100 parts by mass of toner particles obtained in (6), 1 part by mass of hydrophobic silica (manufactured by Cabot, product name "TG820F", hydrophobic treatment agent: HMDS and cyclic silazane, average particle size: 8 nm) and 1 part by mass of hydrophobic silica (manufactured by Nippon Aerosil Co., Ltd., product name "NA50H", hydrophobic treatment agent: HMDS and aminosilane, average particle size: 30 nm) were added, and the mixture was mixed for 3 minutes at a rotation speed of 3000 r / min (peripheral speed 32 m / sec) using a Henschel mixer to obtain a core-shell type positively charged toner.

[0137] Furthermore, when a vinyl resin with the same monomer composition as the vinyl resin contained in the core particles (styrene / n-butyl acrylate = 80 / 20) was prepared by the following method, it was confirmed that the resulting resin was amorphous.

[0138] In a 3-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, fall-flow condenser, dropping funnel, and nitrogen inlet tube, 400 g of xylene was placed. In the dropping funnel, 880 g of styrene, 220 g of n-butyl acrylate, and 110 g of dibutyl peroxide as a radical polymerization initiator were placed. Under a nitrogen atmosphere, the xylene was heated to 130°C while stirring, and the mixture in the dropping funnel was added dropwise over 1 hour. The temperature was then raised to 140°C and held at that temperature for 2 hours. After that, the pressure in the flask was further reduced and held at 8 kPa for 1 hour, and the xylene was removed at 200°C to obtain vinyl resin. The obtained vinyl resin had a softening point of 104°C, a maximum endothermic peak temperature of 60°C, a crystallinity index of 1.7, and a glass transition temperature of 52°C, indicating that it was an amorphous vinyl resin.

[0139] Examples 2-4 Toner was obtained in the same manner as in Example 1, except that the amounts of styrene, n-butyl acrylate, and resin C1 used were changed to the quantities listed in Table 2.

[0140] Examples 5-8 Toner was obtained in the same manner as in Example 1, except that a crystalline vinyl resin listed in Table 2 was used instead of resin C1.

[0141] Examples 9-11 A toner was obtained in the same manner as in Example 1, except that the release agent listed in Table 2 was used instead of the ester wax "WEP-4".

[0142] Comparative Example 1 A toner was obtained in the same manner as in Example 1, except that 80 parts by mass of styrene and 20 parts by mass of n-butyl acrylate were used as polymerizable monomers, and crystalline vinyl resin was not used.

[0143] Comparative Example 2 (1) Preparation of polymerizable monomer composition A polymerizable monomer mixture was obtained by dispersing 72 parts by mass of styrene and 18 parts by mass of n-butyl acrylate as polymerizable monomers, and 5 parts by mass of CI Pigment Blue 15 (manufactured by DIC Corporation, trade name "Fastogen Blue GCTF") as a coloring agent using a media-type emulsifying disperser. To the obtained polymerizable monomer mixture, 10 parts by mass of resin C1, 0.75 parts by mass of a polymeric positive charge control agent (manufactured by Fujikura Chemicals Co., Ltd., trade name: Acrybase FCA-161P, quaternary ammonium salt-containing resin, softening point: 110°C, glass transition temperature: 60°C), 8 parts by mass of ester wax "WEP-4" (manufactured by NOF Corporation, pentaerythritol tetrapalmitate, melting point: 71°C) as a mold release agent, 0.3 parts by mass of polymethacrylate ester macromonomer (manufactured by Toagosei Co., Ltd., trade name: AA6, number average molecular weight: 6,000) as a macromonomer, 0.6 parts by mass of divinylbenzene as a crosslinkable polymerizable monomer, and 1.6 parts by mass of tert-dodecyl mercaptan as a chain transfer agent were added, and then the mixture was mixed and dissolved to prepare a polymerizable monomer composition.

[0144] (2) Preparation of aqueous dispersion medium A magnesium hydroxide colloidal dispersion was prepared by gradually adding an aqueous solution prepared by dissolving 10.4 parts by mass of magnesium chloride in 280 parts by mass of deionized water, to an aqueous solution prepared by dissolving 7.3 parts by mass of sodium hydroxide in 50 parts by mass of deionized water, while stirring.

[0145] (3) Granulation process To the magnesium hydroxide colloidal dispersion obtained in (2), the polymerizable monomer composition obtained in (1) was added at room temperature, and the mixture was stirred further until the droplets stabilized. Then, 4.4 parts by mass of tert-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, trade name: Perbutyl O) was added as a polymerization initiator. The dispersion with the polymerization initiator added was stirred at a high shear speed of 15,000 r / min using an in-line emulsifying disperser (manufactured by Taiheiyo Kiko Co., Ltd., trade name: Milder MDN303V) to form droplets of the polymerizable monomer composition.

[0146] (4) Suspension polymerization process The dispersion containing droplets of the polymerizable monomer composition obtained in (3) was placed in a reactor and heated to 90°C to carry out the polymerization reaction. The polymerization was then continued by maintaining the temperature at 95°C for 4 hours, after which the reaction was stopped by water cooling to obtain an aqueous dispersion of toner particles.

[0147] (5) Post-processing steps (4) The aqueous dispersion of toner particles obtained in (4) was acid washed by adding sulfuric acid dropwise while stirring at room temperature until the pH was 6.0 or lower. Next, filtration separation was performed, and 500 parts by mass of deionized water was added to the obtained solid to form a slurry again, and the water washing treatment (washing, filtration, and dewatering) was repeated several times. Next, filtration separation was performed, and the obtained solid was placed in the container of a dryer and dried at 40°C for 24 hours to obtain the medium volume particle size (D 50 Toner particles with a diameter of 6.2 μm and a circularity of 0.984 were obtained.

[0148] (6) External addition process To 100 parts by mass of toner particles obtained in (5), 1 part by mass of hydrophobic silica (manufactured by Cabot, product name "TG820F", hydrophobic treatment agent: HMDS and cyclic silazane, average particle size: 8 nm) and 1 part by mass of hydrophobic silica (manufactured by Nippon Aerosil Co., Ltd., product name "NA50H", hydrophobic treatment agent: HMDS and aminosilane, average particle size: 30 nm) were added, and the mixture was mixed for 3 minutes at a rotation speed of 3000 r / min (peripheral speed 32 m / sec) using a Henschel mixer to obtain positively charged toner.

[0149] Test example [Toner durability] A commercially available non-magnetic single-component color printer (Brother Industries, Ltd., HL-3240CDW) was loaded with toner, and a diagonal stripe pattern with a blackening rate of 5.5% was continuously printed under conditions of 32°C and 85% relative humidity. Every 500 sheets, a solid black image was printed to check for streaks. Printing was stopped when streaks appeared on the image, up to a maximum of 5000 sheets. The number of printed sheets up to the point where streaks were visually observed on the image was considered the number of sheets where streaks occurred due to toner fusion and adhesion to the developing roll, and durability was evaluated. The results are shown in Table 2. In the table, ">5000" means that no streaks appeared even at 5000 sheets. A higher number of sheets without streaks indicates higher toner durability.

[0150] [Table 2]

[0151] From these results, it can be seen that the core-shell type toners of Examples 1 to 11 have superior durability compared to the toner of Comparative Example 1, which does not use crystalline vinyl resin, and the toner of Comparative Example 2, which does not have a shell layer. [Industrial applicability]

[0152] The electrostatic image developing toner of the present invention is suitably used for developing latent images formed in electrostatic image developing methods, electrostatic recording methods, electrostatic printing methods, and the like.

Claims

1. A core-shell type toner for electrostatic image developing, comprising core particles containing crystalline vinyl resin C, amorphous resin A, and a mold release agent, coated with a shell layer.

2. The electrostatic image developing toner according to claim 1, wherein the content of crystalline vinyl resin C is 3% by mass or more and 30% by mass or less of the total amount of crystalline vinyl resin C and amorphous resin A.

3. The electrostatic image developing toner according to claim 1 or 2, wherein the crystalline vinyl resin C is an addition polymer of a raw material monomer containing an alkyl (meth)acrylate having an alkyl group having 10 to 36 carbon atoms.

4. The electrostatic image developing toner according to claim 1 or 2, wherein the melting point of the crystalline vinyl resin C is 50°C or higher and 100°C or lower.

5. The toner for developing electrostatic images according to claim 1 or 2, wherein the shell layer contains polymethyl methacrylate.

6. The toner for developing electrostatic images according to claim 1 or 2, wherein the release agent contains ester wax.

7. The toner for developing electrostatic images according to claim 1 or 2, which is obtained by suspension polymerization.

8. A method for producing electrostatic image developing toner, comprising manufacturing a core-shell type toner by suspension polymerization, in which core particles containing a crystalline vinyl resin C, an amorphous resin A, and a mold release agent are coated with a shell layer.

9. A method for producing a toner for electrostatic image development according to claim 8, wherein the shell layer contains polymethyl methacrylate.

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