Toner

Abstract

The present invention relates to a toner. A toner includes toner particles and silica particles on the surface of the toner particles, wherein there are a surface formed of a polyester resin and a surface formed of a styrene-acrylic resin on the surface of the toner particles; the number average particle size of the silica particles is 15 to 60 nm; the average pore diameter of the silica particles is 5.0 to 20.0 nm; and the total pore volume of the silica particles is 0.20 to 1.50 cm<supgt;3< / supgt> / g.

Description

Technical Field

[0001] The present disclosure relates to a toner for developing an electrostatic latent image formed by a method such as electrophotography, electrostatic recording, and toner jet system recording method to form a toner image. Background Art

[0002] With the increasing widespread use of receiving devices such as copiers, printers, and fax machines, for example, the electrophotographic technology used in these devices has also been subject to increasingly stringent requirements from users year by year. Due to the expansion of the usage environment caused by the market expansion, in recent years, there has been a strong demand for either obtaining stable image quality regardless of the environment or the ability to perform long-term printing while using a compact design.

[0003] To meet these requirements, at the level of the electrophotographic process, it is necessary that (1) the developability does not change during durable use, and (2) the latent image is transferred to the recording medium without disturbance. Thus, at the toner level, the charge amount must not change during durable use, and a large number of improvements have been implemented to solve this problem.

[0004] From the viewpoint of maintaining the physical property values of the toner, a technique is known in which relatively large external additives at the 100 nm level are added to the toner to suppress deterioration during durable use via a spacer effect.

[0005] For example, Japanese Patent Application Laid-Open No. 2013-003367 discloses a technique for further enhancing durability. In this technique, monodisperse spherical particles of 50 nm to 150 nm are externally added to base particles having a styrene-acrylic modified polyester resin provided in a shell layer, and separation is suppressed by providing a uniform adhesive force between the externally added particles and the surface of the smoothed base particles. Summary of the Invention

[0006] However, although it has been clearly confirmed that the use of this toner improves durability, it has been found that the embedding and detachment of external additive particles during the final stage of durable use, and the reduction of external additive particles acting on the toner particle surface are inevitable, and thus problems such as charge amount variation and reduction of developability and transferability occur. Especially during use in a harsh environment, that is, a high temperature and high humidity environment and a low temperature and low humidity environment, this problem is observed to a large extent.

[0007] It has also been found that when the amount of the toner external additive temporarily increases in the developing device, for example, during continuous output of high print rate images, charge amount variation also occurs, and then problems such as reduced image density stability and fogging occur.

[0008] That is, these problems can be attributed to the fact that there is no technology for maintaining the charge amount under the condition that the amount of the external additive of the toner in the developing device varies due to durable use or due to the use conditions. In order to provide the image quality stability required by the market, it is still desired that the toner can maintain a certain or constant charge amount.

[0009] The present disclosure provides a toner that suppresses charge amount variations related to durable use regardless of the use environment, exhibits suppression of fogging, excellent density stability, and excellent halftone quality, and does so even during long-term printing.

[0010] A toner comprising

[0011] toner particles, and

[0012] silica particles on the surface of the toner particles, wherein

[0013] there are a surface formed of a polyester resin and a surface formed of a styrene-acrylic resin on the surface of the toner particles;

[0014] the number average particle diameter of the silica particles is 15 to 60 nm;

[0015] the average pore diameter of the silica particles is 5.0 to 20.0 nm; and

[0016] the total pore volume of the silica particles is 0.20 to 1.50 cm 3 / g.

[0017] The present disclosure can provide a toner that suppresses charge amount variations related to durable use regardless of the use environment, exhibits suppression of fogging, excellent density stability, and excellent halftone quality, and does so even during long-term printing.

[0018] With reference to the accompanying drawings, further features of the present invention will become apparent from the following description of exemplary embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of an instrument for measuring the charge amount. DETAILED DESCRIPTION

[0020] Unless otherwise specifically stated, the expressions "from XX to YY" and "XX to YY" indicating a numerical range in the present disclosure mean a numerical range including the lower limit and the upper limit as endpoints. When numerical ranges are provided in stages, the upper and lower limits of a single numerical range can be combined in any combination.

[0021] The present disclosure is specifically described below.

[0022] The present disclosure relates to a toner, which comprises

[0023] toner particles and

[0024] silica particles on the surface of the toner particles, wherein

[0025] there are a surface formed of a polyester resin and a surface formed of a styrene-acrylic resin on the surface of the toner particles;

[0026] the number average particle diameter of the silica particles is 15 to 60 nm;

[0027] the average pore diameter of the silica particles is 5.0 to 20.0 nm; and

[0028] the total pore volume of the silica particles is 0.20 to 1.50 cm 3 / g.

[0029] The silica particles are porous silica particles having a specific average pore diameter and a specific total pore volume. The silica particles have unique properties such that depending on whether the surface of the toner particles is a polyester resin or a styrene-acrylic resin, the change in the charge amount with respect to the addition amount of the silica particles shows an opposite tendency. When the surface of the toner particles is a polyester resin, when the addition amount of the silica particles increases, the absolute value of the charge amount shows a tendency to decrease; in contrast, when the surface of the toner particles is a styrene-acrylic resin, the absolute value of the charge amount shows a tendency to increase.

[0030] As a result of in-depth research to utilize this property, when the silica particles are added to toner particles having a surface formed of a polyester resin and a surface formed of a styrene-acrylic resin on the surface, it was found that a charging buffering effect is exhibited, whereby the charge amount can be maintained substantially constant during durable use.

[0031] Regarding the operation of the charging buffering effect, the following mechanism is assumed.

[0032] For porous silica particles having a specific pore diameter, when silanol groups remain in the pores, due to the action of capillary action and the action of the remaining silanol groups, water has a tendency to be retained in the pores regardless of the environment. In addition, the polyester resin shows a higher water absorption rate than the styrene-acrylic resin.

[0033] Considering the case where friction occurs on the surface of the toner particles when the silica particles are in contact with the polyester resin, due to the high affinity between the polyester resin and the water retained in the pores of the silica particles, there is a tendency for the charge generated by triboelectric charging to leak through the retained water.

[0034] On the other hand, considering the case where frictional force occurs on the surface of the toner particles due to the contact between the silica particles and the styrene-acrylic resin, since the styrene-acrylic resin exhibits hydrophobicity, it hinders the movement of the water retained in the pores and the accumulation effect of the triboelectric charge amount comes into play.

[0035] It is assumed that when resin segments having a charging tendency diametrically opposite to that of the silica particles coexist on the surface of the toner particles, regardless of whether the amount of the silica particles present on the surface of the toner particles increases or decreases, the total charge amount converges and is maintained at a substantially constant value, and as a result, the charge amount buffering effect comes into play.

[0036] Therefore, it is considered that even when the amount of the silica particles present on the surface of the toner in the developing device varies during repeated printing in a copying machine or a printer, a constant charge amount will be maintained, and as a result, stable developability and stable transferability can be achieved during durable use, and a long life with high-quality image output can be achieved.

[0037] The silica particles are porous silica particles containing pores with an average pore diameter of 5.0 nm to 20.0 nm and a total pore volume of 0.20 cm 3 / g to 1.50 cm 3 / g.

[0038] The average pore diameter and the total pore volume are values determined by the BJH method.

[0039] The total pore volume here is the total pore volume measured by the BJH method in the pore diameter range of 1.7 nm to 300.0 nm.

[0040] By making the average pore diameter of the silica particles 5.0 nm or more, the water retained in the pores can be easily adsorbed and desorbed, and during the contact and friction on the surface of the toner particles, the functions of charge accumulation and leakage can be exhibited according to the resin type.

[0041] By making the average pore diameter 20.0 nm or less, the water retained in the pores will be retained even in a low-temperature and low-humidity environment.

[0042] The average pore diameter of the silica particles is preferably 7.0 nm to 15.0 nm.

[0043] The total pore volume of the silica particles is 0.20 cm 3 / g or more, enabling excellent performance of the charge amount buffering function due to the water retained in the pores of the silica particles.

[0044] Making the total pore volume 1.50 cm 3Below / g, even in a high-temperature and high-humidity environment, it prevents the water held by the silica particles from showing an excessive level, can prevent the charge amount from decreasing, and enables a stable charge amount to be maintained.

[0045] The total pore volume of the silica particles is preferably 0.40 cm 3 / g to 1.20 cm 3 / g.

[0046] The number-average particle diameter of the silica particles is 15 nm to 60 nm, preferably 15 nm to 49 nm, and more preferably 15 nm to 40 nm.

[0047] Making the number-average particle diameter of the silica particles 15 nm or more is used to suppress the embedding of the silica particles caused by the stress exerted by the toner in the developing device, and can maintain environmental characteristics and durability characteristics.

[0048] Making the number-average particle diameter of the silica particles 60 nm or less can prevent damage to the triboelectric charging characteristics of the silica particles, can suppress the decrease in the charge amount during durable use, and can maintain a constant charge amount.

[0049] The average pore diameter of the silica particles can be controlled using the temperature and pH during the reaction in the wet method for producing silica.

[0050] The total pore volume of the silica particles can be controlled using the pH and additives (such as catalysts like dimethylformamide and formaldehyde) during the reaction in the wet method for producing silica, and can also be controlled using the aging and drying conditions.

[0051] The content of the silica particles is preferably 0.1 part by mass to 10 parts by mass, more preferably 0.2 part by mass to 5.0 parts by mass, and still more preferably 0.5 part by mass to 3.0 parts by mass with respect to 100 parts by mass of the toner particles.

[0052] The silica particles can be exemplified as silica particles obtained by a wet method such as silica particles provided by a sol-gel method and silica particles provided by a gel method, and silica particles obtained by a gas-phase method such as fumed silica particles, fused silica particles, and deflagration silica particles.

[0053] From the viewpoint of being rich in residual silanol groups and showing particularly good adsorption / desorption characteristics of held water, among the foregoing, silica particles such as silica particles provided by a sol-gel method and silica particles provided by a gel method, i.e., wet silica, are preferred.

[0054] The hydrophobicity of the silica particles is preferably from 40% to 75%, more preferably from 43% to 70%, and still more preferably from 45% to 60%. When within this range, the water retained in the pores of the silica particles exhibits excellent adsorption / desorption characteristics, and the charge amount can be maintained at an appropriate level even in a harsh environment, and development characteristics such as transferability, fogging suppression, and environmental stability are excellent.

[0055] The hydrophobicity of the silica particles can be adjusted by subjecting the surface of the silica particles to a hydrophobization treatment.

[0056] There is no particular limitation on the treatment agent used in the hydrophobization treatment, and known silane and silazane compounds can be used. Specific examples are as follows:

[0057] Dimethyldichlorosilane, hexamethyldisilazane, methyltrimethoxysilane, octyltrimethoxysilane, isobutyltrimethoxysilane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilyl mercaptan, trimethylsilyl mercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, 1-hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and dimethylpolysiloxane having 2 to 12 siloxane units in each molecule and one hydroxyl group on each Si in the terminal units.

[0058] Examples of silane compounds showing positive chargeability include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, and 3-(2-aminoethylamino)propyltriethoxysilane.

[0059] The aforementioned single kind can be used, or a mixture of two or more kinds can be used.

[0060] Among the above, hexamethyldisilazane is preferred. It is preferred to subject the silica particles to surface treatment with hexamethyldisilazane. Silica particles that have been hydrophobized by a wet method using hexamethyldisilazane are more preferred because the treatment is carried out very uniformly and the environmental stability is excellent.

[0061] It is also possible to use, in particular, silicone oil as a hydrophobizing agent in addition to the aforementioned ones, and the treatment with silicone oil can be carried out together with the above-mentioned silane or silazane compounds. Examples of silicone oil include dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene-modified silicone oil, chlorophenyl silicone oil, and fluorine-modified silicone oil.

[0062] The following methods are examples of methods for carrying out the treatment with silicone oil: directly mixing silicone oil with silica particles or silica particles that have been treated with a silane coupling agent using a mixer such as a Henschel mixer; spraying silicone oil onto silica particles as a substrate. In a preferred method, silicone oil is dissolved or dispersed in a suitable solvent, then silica particles are added and mixed, and the solvent is removed.

[0063] The hydrophobizing agent can be specifically exemplified as follows: for example, chlorosilanes such as methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tert-butyldimethylchlorosilane, and vinyltrichlorosilane; for example, alkoxysilanes such as tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltriethoxysilane, decyltriethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, and γ-(2-aminoethyl)aminopropylmethyldimethoxysilane; for example, silazanes such as hexamethyldisilazane, hexaethyldisilazane, hexapropyldisilazane, hexabutyldisilazane, hexapentyldisilazane, hexahyldisilazane, hexacyclohexyldisilazane, hexaphenyldisilazane, divinyltetramethyldisilazane, and dimethyltetravinyldisilazane; for example, silicones such as dimethyl silicone oil, methylhydrogen silicone oil, methylphenyl silicone oil, alkyl-modified silicone oil, chloroalkyl-modified silicone oil, chlorophenyl-modified silicone oil, fatty acid-modified silicone oil, polyether-modified silicone oil, alkoxy-modified silicone oil, methanol-modified silicone oil, amino-modified silicone oil, fluorine-modified silicone oil, and terminal-reactive silicone oil; for example, siloxanes such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldisiloxane, and octamethyltrisiloxane; and for example, long-chain fatty acids such as undecanoic acid, lauric acid, tridecanoic acid, dodecanoic acid, myristic acid, palmitic acid, pentadecanoic acid, stearic acid, heptadecanoic acid, arachidic acid, montanic acid, oleic acid, linoleic acid, and arachidonic acid, and salts of these fatty acids with metals such as zinc, iron, magnesium, aluminum, calcium, sodium, and lithium, etc. as fatty acids and their metal salts.

[0064] Among the above, hydrophobization treatment is easily carried out with alkoxysilanes, silazanes, and linear silicone oils, and thus their use is preferred. These hydrophobizing agents can be used alone, or two or more of them can be used in combination.

[0065] Although there are surfaces formed of a polyester resin and surfaces formed of a styrene-acrylic resin on the surface of the toner particles, the toner according to the present disclosure can exhibit a charge amount buffering effect by triboelectric charging with silica particles having a specific average pore diameter and total pore volume.

[0066] There is no particular limitation on the polyester resin present on the surface of the toner particles, and known polyester resins can be used.

[0067] The polyester resin is preferably a condensate between one or more polyols and one or more polycarboxylic acids.

[0068] For example, the following diols (more specifically, glycols or bisphenols) or trihydric or higher alcohols can be suitably used as the alcohols for synthesizing the polyester resin. For example, the following dicarboxylic acids or trihydric or higher carboxylic acids, or their acid anhydrides or lower alkyl esters can be suitably used as the carboxylic acids for synthesizing the polyester resin. The polyester resin is more preferably a condensate of a diol with a dicarboxylic acid and a trihydric carboxylic acid (its acid anhydride or lower alkyl ester).

[0069] Advantageous examples of glycols are ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-butene-1,4-diol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polybutylene glycol.

[0070] Advantageous examples of bisphenols are bisphenol A, hydrogenated bisphenol A, bisphenol A / ethylene oxide adduct, and bisphenol A / propylene oxide adduct. The addition mole number of the bisphenol A / ethylene oxide adduct and the bisphenol A / propylene oxide adduct is preferably from 1.0 mole to 10.0 moles and more preferably from 1.0 mole to 4.0 moles.

[0071] Advantageous examples of trihydric or higher alcohols are sorbitol, 1,2,3,6-hexanetetraol, 1,4-anhydrosorbitol, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

[0072] Preferred examples of the dibasic acid are maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, succinic acid, alkyl succinic acids (and more specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid, and isododecyl succinic acid, etc.), and alkenyl succinic acids (more specifically, n-butene succinic acid, isobutene succinic acid, n-octyl succinic acid, dodecene succinic acid, and isododecene succinic acid).

[0073] Tricarboxylic acids and higher, their acid anhydrides and lower alkyl esters may be exemplified by 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxy-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetrakis(methylenecarboxy)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and Empol trimer acid, as well as the acid anhydrides and lower alkyl esters of the foregoing.

[0074] The diol preferably contains bisphenol.

[0075] The acid value of the polyester resin is preferably from 0.5 mgKOH / g to 20.0 mgKOH / g, and more preferably from 1.0 mgKOH / g to 10.0 mgKOH / g.

[0076] The glass transition temperature Tg of the polyester resin is preferably from 50 °C to 70 °C.

[0077] There is no particular limitation on the styrene-acrylic resin present on the surface of the toner particles, and known styrene-acrylic resins can be used.

[0078] The styrene-acrylic resin is a copolymer of one or more styrene monomers and one or more acrylic monomers. For example, the following styrene monomers and acrylic monomers can be suitably used to synthesize the styrene-acrylic resin.

[0079] Preferred examples of the styrene monomer are styrene, alkylstyrenes (e.g., α-methylstyrene, p-ethylstyrene, and 4-tert-butylstyrene), p-hydroxystyrene, m-hydroxystyrene, vinyltoluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene.

[0080] Preferred examples of the acrylic monomer are (meth)acrylic acid, (meth)acrylic acid alkyl esters, and (meth)acrylic acid hydroxyalkyl esters.

[0081] Preferred examples of the (meth)acrylic acid alkyl ester are methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0082] Preferred examples of the hydroxyalkyl (meth)acrylate are 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0083] The styrene-acrylic resin is preferably a copolymer of a monomer containing styrene and a (meth)acrylic acid alkyl ester.

[0084] The percentage of the total surface area of the surface formed of the styrene-acrylic resin and the surface formed of the polyester resin with respect to the total surface area of the toner particles (St-Ac + PES surface area percentage) is preferably 90 area% or more of the toner particles, and more preferably 95 area% or more. The upper limit is preferably 100 area% or less.

[0085] In addition, on the surface of the toner particles, the percentage of the surface area of the surface formed of the styrene-acrylic resin with respect to the total surface area of the surface formed of the styrene-acrylic resin and the surface formed of the polyester resin (St-Ac surface area percentage) is preferably 40 area% to 80 area%, and more preferably 45 area% to 75 area%.

[0086] A surface formed of a component other than the styrene-acrylic resin and the polyester resin may also be present on the surface of the toner particles. There is no particular limitation on the surface formed of this other component; however, by making this area 10 area% or less of the total surface area of the toner particles, the charge amount buffering effect can be better exhibited.

[0087] Making the St-Ac surface area percentage 40 area% to 80 area% enables the charge amount to be further stabilized during durable use regardless of the environment.

[0088] Under normal printing use conditions, for the toner in the developing device, as the durable use progresses, the silica particles present on the surface of the toner particles become buried in the toner particles or detached from the toner particles due to the stress received from the friction member, and there is a tendency to show a decrease in the amount of silica particles acting on the surface of the toner particles.

[0089] Even if the amount of silica particles acting on the surface of the toner particles decreases, making the St-Ac surface area percentage 40 area% or more provides an excellent effect in suppressing overcharge even in a low-temperature and low-humidity environment through the charge buffering action.

[0090] In addition, by making the St-Ac surface area percentage 80 area% or less, the charge buffering effect works and a decrease in the charge amount in a high-temperature and high-humidity environment can be suppressed.

[0091] On the other hand, when continuously outputting high-print-percentage images, the silica particles are temporarily accumulated in the developing device, and there is a tendency for an increase in the amount of silica particles present on the surface of the toner particles to be visible.

[0092] Even if the amount of silica particles acting on the surface of the toner particles increases, making the St-Ac surface area percentage 40 area% or more can suppress a decrease in the charge amount, and making the St-Ac surface area percentage 80 area% or less can also suppress overcharging.

[0093] The St-Ac surface area percentage can be controlled by the particle size and addition amount of the resin fine particles attached to the surface of the toner particles by means of a wet method or external addition.

[0094] The percentage (PES surface area percentage) of the surface area formed by the polyester resin with respect to the total surface area occupied by the surface formed by the styrene-acrylic resin and the surface formed by the polyester resin is preferably 20 area% to 60 area%, and more preferably 25 area% to 55 area%.

[0095] Due to the difference in triboelectric charging characteristics, which is a characteristic of the function of retaining water in the pores between the porous silica particles and the polyester resin and the styrene-acrylic resin on the surface of the toner particles respectively, the toner according to the present disclosure exhibits a charge buffering effect. The toner can be a negatively charged toner or a positively charged toner.

[0096] The adjustment of positive or negative charging can be achieved by controlling the resin composition on the surface of the toner particles, the addition of a charge control agent, and the surface treatment agent for the external additive.

[0097] The surface formed by the polyester resin and the surface formed by the styrene-acrylic resin must each exist on the surface of the toner particles in a clearly independent manner.

[0098] The following method is a preferred embodiment: The toner particles have a core-shell structure, the core composition and the shell composition are each selected from a styrene-acrylic resin and a polyester resin, complete coating of the shell is not achieved, and the presence of the two surfaces is brought about by the exposure of a part of the core.

[0099] Specifically, the following can be suitably used, for example: a method in which shell is formed by adding resin fine particles having a composition different from that of the core particles to the core particles, and / or a method in which the added resin fine particles are fixed by additionally applying mechanical impact, and / or a method in which the added resin fine particles are transformed into a film by heat treatment, for example.

[0100] Among the foregoing, a structure in which the resin particles forming the shell exist in a state of being fused and adhered to each other and to the core particles is preferred because it provides an excellent charge amount buffering effect due to the stable maintenance of the contact opportunity between the silica particles and the toner particle surface.

[0101] The core component of the core-shell structure can be a polyester resin or a styrene-acrylic resin, and as long as there is an exposed portion of the core, a charge amount buffering effect provided by friction with the silica particles can be obtained.

[0102] The toner particles preferably have a core-shell structure having core particles and a shell formed on the surface of the core particles.

[0103] In a preferred embodiment, the core particles contain a polyester resin, the shell contains a styrene-acrylic resin, and since a part of the polyester resin contained in the core particles is exposed on the toner particle surface, a surface formed of the polyester resin exists on the toner particle surface. More preferably, the resin component contained in the core particles is a polyester resin, and the resin component contained in the shell is a styrene-acrylic resin. Even more preferably, the resin component of the shell consists only of a styrene-acrylic resin.

[0104] In another preferred embodiment, the core particles contain a styrene-acrylic resin, the shell contains a polyester resin, and since a part of the styrene-acrylic resin contained in the core particles is exposed on the toner particle surface, a surface formed of the styrene-acrylic resin exists on the toner particle surface. More preferably, the resin component contained in the core particles is a styrene-acrylic resin, and the resin component contained in the shell is a polyester resin. Even more preferably, the resin component of the shell consists only of a polyester resin.

[0105] A structure in which the core particles contain a polyester resin and the shell contains a styrene-acrylic resin can maintain a high absolute value of the charge amount and support a tendency for further improvement in environmental stability, and is thus preferred.

[0106] Particles prepared by a pulverization method, a suspension polymerization method, a dissolution suspension method, or an emulsion polymerization and aggregation method can be used as the core particles.

[0107] Among the above, it is preferable to use the particles obtained by the pulverization method for exposing the core resin during the core-promoting shell formation step and being able to form a surface where the core resin clearly exists, and thus.

[0108] The number-average primary particle diameter of the resin particles forming the shell is preferably from 10 nm to 500 nm, and more preferably from 20 nm to 200 nm. Resin particles having a number-average particle diameter of 10 nm or more are likely to form a uniform and stable surface on the surface of the core particles. In addition, resin particles having a number-average particle diameter of 500 nm or less enable the layer thickness of the portion formed by the resin particles to be controlled to be constant without unevenness.

[0109] The amount of the shell, expressed per 100 parts by mass of the core particles, is preferably from 0.20 part by mass to 7.00 parts by mass, and more preferably from 0.50 part by mass to 2.00 parts by mass.

[0110] The constituent components of the toner particles are described below.

[0111] [Binder resin]

[0112] The toner particles contain a binder resin.

[0113] Since a surface formed of a styrene-acrylic resin and a surface formed of a polyester resin are present on the surface of the toner particles, the toner particles preferably have a styrene-acrylic resin and / or a polystyrene resin as the binder resin. The toner particles may contain a resin other than the above as the binder resin.

[0114] There is no particular limitation on the other binder resin, and known binder resins such as vinyl resins, olefin resins, polyurethane resins, and polyamide resins can be used.

[0115] [Crosslinking agent]

[0116] A crosslinking agent can be added to the polymerization of the polymerizable monomer in order to control the molecular weight of the binder resin.

[0117] In the case of vinyl resins, examples are aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; carboxylate esters having two double bonds such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, and 1,6-hexanediol diacrylate; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide, and divinyl sulfone; and compounds having three or more vinyl groups.

[0118] In the case of polyester resins, a polycarboxylic acid having three or more carboxylic acid groups or a polyol having three or more hydroxyl groups can be added.

[0119] Polycarboxylic acids having three or more carboxyl groups may be exemplified by trimellitic acid, pyromellitic acid, cyclohexane tricarboxylic acid, 2,5,7-naphthalene tricarboxylic acid, 1,2,4-naphthalene tricarboxylic acid, 1,2,4-butane tricarboxylic acid, 1,2,5-hexane tricarboxylic acid, 1,3-dicarboxy-2-methylenecarboxypropane, 1,3-dicarboxy-2-methylmethylenecarboxypropane, tetra(methylenecarboxy)methane, 1,2,7,8-octane tetracarboxylic acid, and acid anhydrides of the foregoing acids.

[0120] Alcohols having three or more hydroxyl groups may be exemplified by sorbitol, 1,2,3,6-hexanetetraol, 1,4-anhydrosorbitol, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose, 1,2,4-butanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-tris(hydroxymethyl)benzene.

[0121] The addition amount of the crosslinking agent is preferably 0.001 part by mass to 10.000 parts by mass with respect to 100 parts by mass of the polymerizable monomer.

[0122] [Wax]

[0123] The toner particles may include wax.

[0124] Examples of the wax include petroleum waxes such as paraffin wax, microcrystalline wax, and petrolatum and their derivatives, montan wax and its derivatives, hydrocarbon waxes obtained by the Fischer-Tropsch method and their derivatives, polyolefin waxes such as polyethylene and polypropylene and their derivatives, natural waxes such as carnauba wax and candelilla wax and their derivatives, higher fatty alcohols, fatty acids such as stearic acid and palmitic acid and their amides, esters, and ketones, hydrogenated castor oil and its derivatives, plant waxes, animal waxes, and silicone resins. Hydrocarbon waxes and ester waxes are preferred.

[0125] Incidentally, the derivatives include oxides, block copolymers with vinyl monomers, and graft-modified products. The amount of the wax is preferably 2.0 parts by mass to 20.0 parts by mass with respect to 100 parts by mass of the binder resin or the polymerizable monomer that forms the binder resin.

[0126] [Colorant]

[0127] The toner may include a colorant. There is no particular limitation on the colorant, and known colorants can be used.

[0128] Examples of the yellow pigment include yellow iron oxide, and condensed azo compounds such as navel orange yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methylene compounds, and allylamide compounds. Specific examples are shown below.

[0129] C.I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 155, 168, 180, 185, 193.

[0130] Examples of orange pigments are shown below.

[0131] Permanent Orange GTR, Pyrazolone Orange, Vulcan Orange, Benzidine Orange G, Indanthrene Brilliant Orange RK, and Indanthrene Brilliant Orange GK.

[0132] Examples of red pigments include Indian Red such as Permanent Red 4R, Lithol Red, Pyrazolone Red, Watching Red calcium salt, Lake Red C, Lake Red D, Brilliant Carmine 6B, Brilliant Carmine 3B, Eosine Lake, Rhodamine Lake B, and Alizarin Lake, etc., condensation azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, perylene compounds. Specific examples are shown below.

[0133] C.I. Pigment Red 2, 3, 5, 6, 7, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 122, 144, 146, 150, 166, 169, 177, 184, 185, 202, 206, 220, 221, 254.

[0134] Examples of blue pigments include, for example, basic blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, fast sky blue, and Indanthrene Blue BG, etc., copper phthalocyanine compounds and their derivatives, anthraquinone compounds, and basic dye lake compounds, etc. Specific examples are shown below.

[0135] C.I. Pigment Blue 1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, 66.

[0136] Examples of purple pigments include Fast Purple B and Methyl Violet Lake.

[0137] Examples of green pigments include Pigment Green B, Malachite Green Lake, and Final Yellow Green G. Examples of white pigments include zinc white, titanium oxide, antimony white, and zinc sulfide.

[0138] Examples of black pigments include carbon black, aniline black, non-magnetic ferrite, magnetite, and those colored black by using the above yellow-based colorants, red-based colorants, and blue-based colorants. These colorants can be used alone or in mixtures, or in the form of solid solutions.

[0139] The amount of the colorant is preferably 3.0 to 15.0 parts by mass with respect to 100.0 parts by mass of the binder resin or the polymerizable monomer that forms the binder resin.

[0140] [Magnetic body]

[0141] The toner can also be used in the form of a magnetic toner. In this case, magnetic bodies such as the following examples are used:

[0142] For example, iron oxides such as magnetite, maghemite, and ferrite, and iron oxides containing other metal oxides; metals such as Fe, Co, and Ni, and alloys of these metals with metals such as Al, Co, Cu, Pb, Mg, Ni, Sn, Zn, Sb, Ca, Mn, Se, and Ti; and mixtures of the foregoing.

[0143] More specific examples are iron tetroxide (Fe3O4), iron sesquioxide (γ-Fe2O3), zinc ferrite (ZnFe2O4), copper ferrite (CuFe2O4), neodymium ferrite (NdFe2O3), barium ferrite (BaFe 12 O 19 ), magnesium ferrite (MgFe2O4), and manganese ferrite (MnFe2O4). One of these magnetic materials can be used alone, or a mixture of two or more can be used. Fine powders of iron tetroxide and fine powders of γ-iron sesquioxide are particularly advantageous magnetic materials.

[0144] The number average particle diameter of these magnetic bodies is preferably 0.1 μm to 2 μm, and more preferably 0.1 μm to 0.3 μm. The magnetic properties under an applied magnetic field of 795.8 kA / m (10 kOe) are as follows: the coercive force (Hc) is 1.6 kA / m to 12 kA / m (20 Oe to 150 Oe), and the saturation magnetization (σs) is 5 Am 2 / kg to 200 Am 2 / kg and preferably 50 Am 2 / kg to 100 Am 2 / kg. The remanent magnetization (σr) is preferably 2 Am 2 / kg to 20 Am 2 / kg.

[0145] The content of the magnetic body is preferably 10 to 200 parts by mass per 100 parts by mass of the binder resin, and more preferably 20 to 150 parts by mass.

[0146] [Charge control agent]

[0147] Toner particles may contain a charge control agent. Known charge control agents can be used as the charge control agent. In particular, a charge control agent that provides a rapid rise in charge amount supports excellent charge amount maintenance characteristics for a suitable charge amount, and is thus preferred.

[0148] The following are examples of charge control agents for controlling toner particles to be negatively charged:

[0149] For example, metal compounds of aromatic carboxylic acids such as salicylic acid, alkylsalicylic acid, dialkylsalicylic acid, naphthoic acid, and dicarboxylic acid, and polymers and copolymers containing such metal compounds of aromatic carboxylic acids;

[0150] Polymers and copolymers containing a sulfonic acid group, a sulfonate group, or a sulfonate ester group;

[0151] Metal salts and metal complexes of azo dyes and azo pigments; and

[0152] Boron compounds, silicon compounds, and calixarenes.

[0153] Polymers and copolymers having a sulfonate group or a sulfonate ester group can be exemplified as follows:

[0154] For example, homopolymers of vinyl-based monomers containing a sulfonic acid group such as styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, and methacrylsulfonic acid, and copolymers of these vinyl-based monomers containing a sulfonic acid group and vinyl-based monomers as described in the binder resin item.

[0155] The following are examples of charge control agents for controlling toner particles to be positively charged:

[0156] Quaternary ammonium salts and high molecular weight compounds having a quaternary ammonium salt in the chain position; guanidine compounds; anilide-based compounds; and imidazole compounds.

[0157] Resin-based charge control agents can be exemplified as melamine resins, guanamine resins, aniline resins, urea-formaldehyde resins, polyurethane resins, sulfonamide resins, polyimide resins, and derivatives of these resins.

[0158] One of these charge control agents can be introduced, or a combination of two or more can be introduced. The addition amount of the charge control agent is preferably 0.01 parts by mass to 10.0 parts by mass with respect to 100 parts by mass of the binder resin.

[0159] However, when satisfactory chargeability of the toner can be ensured, it is not necessary to introduce a charge control agent.

[0160] [External Additives]

[0161] In addition to the above-mentioned silica particles, the toner may further contain, for example, a fluidizing agent, a cleaning aid, etc. as so-called external additives in order to provide satisfactory fluidity, cleanability, etc.

[0162] As the external additives, those known heretofore can be used without particular limitation. Specific examples are, for example, inorganic fine particles such as silica particles and metal oxides (more specifically, alumina, titanium oxide, magnesia, zinc oxide, zinc stearate, strontium titanate, calcium titanate, barium titanate, and hydrotalcite, etc.); for example, organic fine particles such as vinyl-based resins, silicone resins, and melamine resins; and organic-inorganic composite fine particles.

[0163] One of these can be used alone or a combination of two or more can be used.

[0164] In addition, the external additives can be surface-treated. As the surface treatment agents, for example, higher fatty acids, silicone varnishes, various modified silicone varnishes, unmodified silicone oils, various modified silicone oils, silane compounds, silane coupling agents, other organosilicon compounds, and organotitanium compounds, etc. can be used alone or in combination.

[0165] [Production method of toner particles]

[0166] Hereinafter, a preferred embodiment in which a surface formed of a styrene-acrylic resin and a surface formed of a polyester resin exist on the surface of the toner particles will be described as an example to describe a method for producing toner particles having a core-shell structure.

[0167] [Preparation of core particles]

[0168] Known processes can be used for the production method of the core particles of the toner, and the core particles can be produced by suspension polymerization, solution suspension method, emulsion polymerization and aggregation method, or pulverization method.

[0169] When the core particles are obtained by suspension polymerization, first, a polymerizable monomer composition is prepared by mixing a polymerizable monomer constituting the binder resin and, optionally, for example, wax and a colorant.

[0170] Then, an aqueous medium containing a dispersion stabilizer is prepared, and the aqueous medium is put into a stirring container provided with a stirrer capable of generating a high shear force. The polymerizable monomer composition is added to the aqueous medium, and the polymerizable monomer composition is dispersed by stirring to form droplets of the polymerizable monomer composition. Then, the polymerizable monomer in the droplets of the polymerizable monomer composition is polymerized to obtain core particles in which a binder resin is formed.

[0171] When obtaining core particles by the dissolution suspension method, a resin solution is prepared by dissolving or dispersing the following materials uniformly in an organic solvent: a binder resin and other optional materials such as wax, polar resin, colorant, and charge control agent. The resulting resin solution is granulated by dispersing it in an aqueous medium, and the organic solvent present in the particles provided by granulation is removed to obtain core particles having a desired particle size.

[0172] To obtain core particles using the emulsion aggregation method, first, fine particles of a binder resin and fine particles of materials such as a colorant are dispersed and mixed in an aqueous medium containing a dispersion stabilizer. A surfactant can also be added to the aqueous medium. Subsequently, aggregation is achieved to a desired core particle size by adding an aggregating agent and by performing fusion adhesion between the resin fine particles after or during aggregation. Shape adjustment by heating can be optionally performed to obtain core particles.

[0173] To obtain core particles by the pulverization method, a binder resin is mixed with optional components such as a colorant, a release agent, and a charge control agent. Then the obtained mixture is melt-kneaded. Subsequently, the resulting melt-kneaded material is pulverized, and the obtained pulverized product is classified. This results in the production of core particles having a desired particle size.

[0174] (Formation of the shell)

[0175] Then, a shell is formed on the surface of the obtained core particles. Preferred examples of the shell formation method are described below.

[0176] A dispersion of core particles and fine particles of the resin that will form the shell is added to an aqueous medium whose pH has been adjusted.

[0177] The resin fine particles adhere to the surface of the core particles in the aqueous medium. To make the resin fine particles adhere uniformly to the surface of the core particles, it is preferred that the core particles be highly dispersed in the aqueous medium containing the resin fine particles. For this purpose, the addition of a surfactant and the strengthening of the stirring force are effective.

[0178] Surfactants can be exemplified by anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants.

[0179] Specific examples here are anionic surfactants such as alkylbenzene sulfonates, α-olefin sulfonates, and phosphate esters; for example, amine salt types such as alkylamine salts, amino alcohol / fatty acid derivatives, polyamine / fatty acid derivatives, and imidazolines, and quaternary ammonium salt types such as alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, pyridinium salts, alkylisoquinolinium salts, and benzethonium chloride, etc. cationic surfactants; for example, nonionic surfactants such as fatty acid amide derivatives and polyol derivatives; and zwitterionic surfactants such as alanine, dodecylbis(aminoethyl)glycine, bis(octylaminoethyl)glycine, and N-alkyl-N,N-dimethylammonium betaine.

[0180] One surfactant can be used alone or two or more can be used in combination.

[0181] The addition amount of the resin fine particles forming the shell is an appropriately adjusted amount so as to provide a desired coating rate with the core particles exposed.

[0182] Then, while stirring the aqueous medium containing the core particles and the resin fine particles, the temperature is raised to a temperature of 50°C to 85°C at a rate of 0.1°C / minute to 3°C / minute.

[0183] In order to fully achieve shell formation, a holding time of 30 minutes to 8 hours is preferably set.

[0184] During the interval when the temperature of the aqueous medium is maintained at a high temperature, immobilization of the resin fine particles on the surface of the core particles is carried out, or they are transformed into a film by melting.

[0185] Any of the following can be used for shell formation: a structure in which the resin fine particles have a granular property and are two-dimensionally connected; a film structure provided by melting. Any of the following can be used for the adhesion state of the resin fine particles: adhesion by melting the core particles; adhesion by melting the resin fine particles.

[0186] Then the dispersion of the core-shell particles is neutralized and subsequently cooled to room temperature.

[0187] The cooled core-shell particle dispersion is filtered and washed and then dried to obtain toner particles having a core-shell structure with the core particles partially exposed.

[0188] For the shell formation method, additional examples by the dry method will now be described.

[0189] A shell is formed by mixing core particles and resin fine particles using a mixer (for example, an FM mixer (Nippon Coke & Engineering Co., Ltd.)) so that the resin fine particles adhere to the surface of the toner core particles.

[0190] For surface treatment of the shell, it is also possible to use, for example, a hybrid system (Nara Machinery Co., Ltd.), a mechanical fusion system (Hosokawa Micron Corporation), a Faculty (Hosokawa Micron Corporation), or a MeteoRainbow MR Type (Nippon Pneumatic Mfg. Co., Ltd.) optionally.

[0191] [Method for producing toner]

[0192] The toner can be obtained by adding the above-mentioned silica particles and optionally other external additives to the toner particles.

[0193] The following are examples of devices that can be used for external addition: double cone blender, V-type blender, drum blender, Super Blender (Kawata Mfg. Co., Ltd.), FM Blender (Nippon Coke & Engineering Co., Ltd.), Nobilta (Hosokawa Micron Corporation), Hybridizer (Nara Machinery Co., Ltd.), Nauta blender, and Mechano Hybrid.

[0194] The toner can be used as a one-component developer, but it can also be mixed with a carrier and used as a two-component developer.

[0195] As the carrier, it is possible to use magnetic particles composed of generally known materials such as metals such as iron, ferrite, magnetite, etc., and alloys of these metals with metals such as aluminum and lead. Among them, ferrite particles are preferred. In addition, a coated carrier obtained by coating the surface of magnetic particles with a coating agent such as resin, or a resin-dispersed carrier obtained by dispersing magnetic fine powder in a binder resin can be used as the carrier.

[0196] The volume average particle diameter of the carrier is preferably from 15 μm to 100 μm, and more preferably from 25 μm to 80 μm.

[0197] The measurement methods of various physical properties will be described below.

[0198] In order to measure the properties of the silica particles and the toner particles from the toner to which silica particles have been externally added, the silica particles and other external additives are separated from the toner, and then measurement can be carried out.

[0199] The silica particles and other external additives are separated by subjecting the toner to ultrasonic dispersion in methanol and allowing it to stand for 24 hours. The toner particles can be separated by separating the sedimented toner particles from the silica particles and other external additives dispersed in the supernatant, followed by recovery, thorough washing, and drying. The silica particles and other external additives can be separated by repeatedly centrifuging the supernatant using a centrifugation step.

[0200] <Number average primary particle size of silica particles>

[0201] The number average primary particle size of the silica particles is measured using a "JEM-2800" transmission electron microscope (JEOL Ltd.). The toner to which fine silica particles have been externally added is observed, and the number average particle size is determined by measuring the major axis of 100 randomly selected primary particles in a field of view magnified up to 200,000 times. The observation magnification is appropriately adjusted according to the size of the silica particles.

[0202] The silica particles can be distinguished among the external additives of the toner by STEM-EDS measurement. The measurement conditions are as follows.

[0203] JEM2800 type transmission electron microscope: 200 kV acceleration voltage

[0204] EDS detector: JED-2300T (JEOL Ltd., element area 100 mm 2 )

[0205] EDS analyzer: Noran System 7 (Thermo Fisher Scientific K.K.)

[0206] X-ray storage rate: 10,000 to 15,000 cps

[0207] Dead time: Adjust the electron dose to provide 20% to 30%, and perform EDS analysis (number of scans = 100 or measurement time = 5 minutes).

[0208] <Hydrophobicity of silica particles>

[0209] The hydrophobicity of the silica particles is measured using a "WET-100P" powder wettability tester from Rhesca Co., Ltd.

[0210] A fluororesin-coated spindle-shaped stir bar with a length of 25 mm and a maximum diameter of 8 mm was introduced into a cylindrical glass container with a thickness of 1.75 mm and a diameter of 5 cm. 70 mL of water-containing methanol composed of 50 vol% methanol and 50 vol% water was introduced into the cylindrical glass container, and then 0.5 g of silica particles was added and placed in a powder wettability tester.

[0211] While stirring at a rotational speed of 3.3 revolutions per second using a magnetic stirrer, methanol was added to the liquid at a rate of 0.8 mL / minute through the powder wettability tester. The transmittance of light with a wavelength of 780 nm was measured, and the hydrophobicity was taken as the value expressed by the volume percentage of methanol (= (volume of methanol / volume of the mixture) × 100) when the transmittance reached 50%. The initial volume ratio of methanol and water was appropriately adjusted corresponding to the hydrophobicity of the sample.

[0212] <Average pore diameter and total pore volume of silica particles>

[0213] Using a Tristar 3000 (Shimadzu Corporation) pore size distribution analyzer, the average pore diameter and total pore volume of the silica particles were measured by the gas adsorption method of adsorbing nitrogen to the surface of the sample. The measurement method followed the operation manual issued by Shimadzu Corporation.

[0214] First, approximately 0.5 g of the sample was introduced into the sample tube and evacuated at 100 °C for 24 hours. After the evacuation was completed, the sample mass was accurately weighed to obtain the sample. The total pore volume and average pore diameter in the range of 1.7 nm to 300.0 nm could be determined by the BJH method using the obtained sample and the aforementioned pore size distribution analyzer. The true density value measured using an AccuPyc 1330 dry pycnometer (Shimadzu Corporation) was used for the density measurement required.

[0215] <Identification of the surface formed by the polyester resin and the surface formed by the styrene-acrylic resin, and the percentage of the total surface area of the surface formed by the styrene-acrylic resin and the surface formed by the polyester resin relative to the total surface area of the toner particles>

[0216] The St-Ac+PES surface area percentage could be determined using a scanning electron microscope by staining the toner particles with ruthenium and analyzing the observed images of the stained toner particles.

[0217] A "JSM-7800F" scanning electron microscope (JEOL Ltd.) was used and the backscattered electron images of the stained toner particles were analyzed.

[0218] The ease of ruthenium staining varies depending on the type of resin. For example, the rate of ruthenium staining differs significantly between polyester resins and styrene-acrylic resins. Thus, in the backscattered electron image of the surface of the resulting toner particles, a brightness difference occurs between the surface formed by the polyester resin and the surface formed by the styrene-acrylic resin, and thereby the surface formed by the polyester resin and the surface formed by the styrene-acrylic resin can be distinguished.

[0219] For image analysis, a binary image is obtained by binarization processing based on the brightness of each pixel using image analysis software (“WinROOF”, Mitani Corporation). The following are calculated using the obtained binary image: the total surface area on the surface of the toner particles attributable to the styrene-acrylic resin (hereinafter designated as the St-Ac surface area) and the total surface area on the surface of the toner particles attributable to the polyester resin (hereinafter designated as the PES surface area).

[0220] Except for the surface formed by the styrene-acrylic resin and the surface formed by the polystyrene resin, when a surface formed by another resin exists on the surface of the toner particles, the surface formed by the other resin can be distinguished by the brightness difference.

[0221] In this case, the percentage of the surface area occupied by the surface formed by the other resin relative to the total surface area of the toner particles can be calculated by setting a threshold value for the brightness value attributable to the other resin.

[0222] The percentage of the total surface area of the surface formed by the styrene-acrylic resin and the surface formed by the polyester resin relative to the total surface area of the toner particles is determined using the formula given below.

[0223] The surface area percentage is calculated for each of 100 toner particles, and the average value thereof is used.

[0224] The surface area percentage (%) of the total surface area of the surface formed by the styrene-acrylic resin and the surface formed by the polyester resin relative to the total surface area of the toner particle surface = “St-Ac surface area + PES surface area” / “total surface area of the toner particle surface” × 100

[0225] When the resin present on the surface of the toner particles consists only of the styrene-acrylic resin and the polyester resin, the surface area percentage of the sum of the surface formed by the styrene-acrylic resin and the surface formed by the polyester resin relative to the total surface area of the toner particle surface becomes 100%.

[0226] <Percentage of the surface area of the surface formed by the styrene-acrylic resin relative to the total surface area of the surface formed by the styrene-acrylic resin and the surface formed by the polyester resin>

[0227] The ruthenium staining of the toner particles and the image analysis of the surface of the stained toner particles are carried out as described above, and the St-Ac surface area percentage is calculated using the formula given below.

[0228] The surface area percentage is calculated for each of 100 toner particles, and the average value thereof is used.

[0229] The surface area percentage (%) of the surface formed of the styrene-acrylic resin with respect to the total surface area of the surface formed of the styrene-acrylic resin and the surface formed of the polyester resin = "St-Ac surface area" / "St-Ac surface area + PES surface area" × 100

[0230] <Measurement of the particle size of the toner particles>

[0231] The particle size of the toner particles can be measured by the pore resistance method. For example, "Coulter Counter Multisizer 3" and dedicated software "Beckman Coulter Multisizer 3 Version 3.51" (manufactured by Beckman Coulter, Inc.) can be used for measurement and calculation.

[0232] A precision particle size distribution measuring device based on the pore resistance method (trade name: "Coulter Counter Multisizer 3", manufactured by Beckman Coulter, Inc.) and dedicated software "Beckman Coulter Multisizer 3 Version 3.51" (manufactured by Beckman Coulter, Inc.) are used. Measurement is carried out with a 100 μm aperture with 25,000 effective measurement channels, and the measurement data is analyzed and calculated.

[0233] A solution prepared by dissolving special grade sodium chloride in ion-exchanged water to a concentration of about 1 mass%, for example, "ISOTON II" (trade name) manufactured by Beckman Coulter, Inc. can be used as the aqueous electrolyte solution to be used for measurement.

[0234] The dedicated software is set in the following manner before measurement and analysis.

[0235] Set the total count in the control mode on the "Change Standard Measurement Method (SOM) Screen" of the dedicated software to 50,000 particles, set the measurement count to 1, and set the value obtained using "Standard Particle 10.0μm" (manufactured by Beckman Coulter, Inc.) as the Kd value. Automatically set the threshold and noise level by pressing the threshold / noise level button. In addition, set the current to 1600 μA, set the gain to 2, set the electrolyte solution to ISOTON II (trade name), and check the "Rinse the mouthpiece tube after measurement".

[0236] In the "Pulse to Particle Size Conversion Setting Screen" of the dedicated software, set the element interval to for particle size, set the particle size element to 256 - particle size element, and set the particle size range to 2 μm to 60 μm.

[0237] The specific measurement method is described below.

[0238] (1) Introduce approximately 200 mL of electrolyte aqueous solution into a 250 m round - bottom glass beaker dedicated to Multisizer 3, place the beaker on the sample stage, and stir it counter - clockwise at 24 rpm with a stir bar. Remove dirt and bubbles in the mouthpiece tube through the "Mouthpiece tube rinse" function of the dedicated software.

[0239] (2) Introduce approximately 30 mL of electrolyte aqueous solution into a 100 mL flat - bottom glass beaker. Then, add approximately 0.3 mL of the dilution obtained by diluting "CONTAMINON N" (trade name) (10 mass% aqueous solution of a neutral detergent for washing precision measuring instruments, manufactured by Wako Pure Chemical Industries, Ltd.) by 3 times the mass with ion - exchange water.

[0240] (3) Put a predetermined amount of ion - exchange water into the water tank of the ultrasonic disperser "Ultrasonic Dispersion System Tetora150" (manufactured by Nikkaki Bios Co., Ltd.) with an electrical output of 120 W and two oscillators with an oscillation frequency of 50 kHz and a 180 - degree phase shift built - in, and add approximately 2 mL of CONTAMINON N (trade name) to the water tank.

[0241] (4) Set the beaker in (2) above in the beaker fixing hole of the ultrasonic disperser and start the ultrasonic disperser. Then, adjust the height position of the beaker so that the resonance state of the liquid level of the electrolyte aqueous solution in the beaker is maximized.

[0242] (5) While irradiating the electrolyte aqueous solution in the beaker in (4) above with ultrasonic waves, gradually add about 10 mg of toner (particles) to the electrolyte aqueous solution and disperse it therein. Then, further continue the ultrasonic dispersion treatment for 60 seconds. During the ultrasonic dispersion, appropriately adjust the water temperature in the water tank to a temperature of 10 °C to 40 °C.

[0243] (6) Use a pipette to drop the electrolyte aqueous solution in which the toner (particles) is dispersed in (5) above into the round-bottom beaker placed on the sample stage in (1) above, and adjust the measurement concentration to about 5%. Then, perform the measurement until the number of measured particles reaches 50,000.

[0244] (7) Analyze the measurement data using the dedicated software set in the device and calculate the weight-average particle diameter (D4). When the dedicated software is set to Chart / Volume%, the "Average Diameter" on the "Analysis / Volume Statistical Value (Arithmetic Mean)" screen is the weight-average particle diameter (D4). When the dedicated software is set to Chart / Number%, the "Average Diameter" on the "Analysis / Number Statistical Value (Arithmetic Mean)" screen is the number-average particle diameter (D1).

[0245] <Method for Measuring Acid Value of Resin>

[0246] The acid value of resin etc. is measured as follows. The acid value is the number of milligrams of potassium hydroxide required to neutralize the acid present in 1 g of the sample. Measure the acid value of the binder resin according to JIS K 0070-1992, and use the following procedure to specifically measure it.

[0247] (1) Preparation of Reagents

[0248] Obtain a phenolphthalein solution by dissolving 1.0 g of phenolphthalein in 90 mL of ethanol (95 vol%) and making it 100 mL by adding deionized water.

[0249] Dissolve 7 g of special grade potassium hydroxide in 5 mL of water, and make it 1 L by adding ethanol (95 vol%). Introduce it into an alkali-resistant container, avoid contact with, for example, carbon dioxide, and let it stand for 3 days. After that time, filter it to obtain a potassium hydroxide solution. Store the obtained potassium hydroxide solution in an alkali-resistant container. When 25 mL of 0.1 mol / L hydrochloric acid is introduced into a conical flask, add a few drops of phenolphthalein solution, and when titrating with the potassium hydroxide solution, determine the factor of the potassium hydroxide solution from the amount of the potassium hydroxide solution required for neutralization. Prepare the 0.1 mol / L hydrochloric acid used according to JIS K 8001-1998.

[0250] (2) Operation

[0251] (A) Main Test

[0252] Accurately weigh 2.0 g of the crushed sample into a 200 mL conical flask, add 100 mL of a toluene / ethanol (2:1) mixed solution, and dissolve it within 5 hours. Add a few drops of phenolphthalein solution as an indicator and titrate with potassium hydroxide solution. Take the titration endpoint as the light red color of the indicator persisting for about 30 seconds.

[0253] (B) Blank test

[0254] Perform the same titration as in the above operation, except that no sample is used (i.e., only the toluene / ethanol (2:1) mixed solution is used).

[0255] (3) Calculate the acid value by substituting the obtained results into the following formula.

[0256] A = [(C – B) × f × 5.61] / S

[0257] Here, A: acid value (mg KOH / g); B: amount of potassium hydroxide solution in the blank test (mL); C: amount of potassium hydroxide solution added in the main test (mL); f: factor of the potassium hydroxide solution; and S: mass of the sample (g).

[0258] (Measurement of the glass transition temperature (Tg) of resins, etc.)

[0259] Measure the glass transition temperature and melting peak temperature according to ASTM D3418 - 82 using a differential scanning calorimeter "Q2000" (manufactured by TA Instruments).

[0260] Use the melting points of indium and zinc for temperature calibration of the device detection part, and use the heat of fusion of indium for heat calibration.

[0261] Specifically, accurately weigh 3 mg of a sample such as resin, place the sample in an aluminum pan, and use an empty aluminum pan as a reference to perform the measurement under the following conditions.

[0262] Heating rate: 10 °C / min

[0263] Measurement start temperature: 30 °C

[0264] Measurement final temperature: 180 °C

[0265] Perform the measurement at a heating rate of 10 °C / min in the measurement range of 30 °C to 100 °C. Heat up to 180 °C and hold for 10 minutes, then cool down to 30 °C, and then heat up again. During the second heating process, obtain the change in specific heat in the temperature range of 30 °C to 100 °C. Take the intersection of the line at the midpoint between the baselines before and after the change in specific heat at this time and the differential thermal curve as the glass transition temperature (Tg).

[0266] Embodiment

[0267] The present invention will be described more specifically using examples. The present invention is not limited by the following examples. Unless otherwise specifically stated, in all cases, the parts in the following formulations are by mass.

[0268] <Production Example of Silica Particles 1>

[0269] A catalyst solution was obtained by adding a mixture of 500 parts of methanol and 70 parts of water adjusted to pH 8.3 with 10% by mass ammonia water to a 1.5 L glass reactor equipped with a stirrer, a dropping nozzle, and a thermometer.

[0270] After adjusting the alkaline catalyst solution to 40°C, while stirring, 100 parts of tetramethoxysilane (TMOS) and 20 parts of 1.0% by mass ammonia water were simultaneously added dropwise within 60 minutes to obtain a hydrophilic silica particle dispersion.

[0271] Then, the obtained silica particle dispersion was concentrated to a solid content concentration of 40% by mass using an R-Fine rotary filter (Kotobuki Industrial Co., Ltd.) to obtain a concentrated silica particle dispersion.

[0272] 40 parts of hexamethyldisilazane (HMDS) was added as a hydrophobizing agent to 250 parts of the concentrated silica particle dispersion, and the reaction was carried out at 130°C for 2 hours, followed by cooling and drying by spray drying to obtain silica particles 1. The properties of the obtained silica particles 1 are shown in Table 1.

[0273] <Production Example of Silica Particles 2>

[0274] Except that the pH of the alkaline aqueous solution added to the catalyst solution was changed to 5.6, the temperature of the catalyst solution was adjusted to 30°C, and in addition to the TMOS and 1.0% by mass ammonia water added dropwise, 20 parts of dimethylformamide (DMF) was simultaneously added dropwise within 100 minutes, silica particles 2 were obtained by performing the same steps as in the production example of silica particles 1. The properties of the obtained silica particles 2 are shown in Table 1.

[0275] <Production Examples of Silica Particles 3 to 9>

[0276] Silica particles 3 to 9 were produced in the same manner as silica particles 1, except that some of the production conditions of silica particles 1 were changed to the conditions shown in Table 1 (produced as in the case of silica particles 2 in the example using DMF). The properties are shown in Table 1. 10% by mass ammonia water or 10% by mass hydrochloric acid was used to adjust the pH of the water added to the catalyst solution.

[0277] <Production Example of Silica Particles 10>

[0278] Silica particles 10 were obtained by performing the same steps as in the production example of silica particles 1, except that hexamethyldisilazane (HMDS) added as a hydrophobizing agent was changed to 3-aminopropyltrimethoxysilane (APTMS). The properties of the obtained silica particles 10 are given in Table 1.

[0279] <Production Examples of Silica Particles 11 and 12>

[0280] Silica particles 11 and 12 were produced as in silica particles 1, except that some of the production conditions of silica particles 1 were changed to the conditions given in Table 1 (production of silica particles 11 using DMF as in silica particles 2). The properties are given in Table 1. 10 mass% ammonia water or 10 mass% hydrochloric acid was used to adjust the pH of the water added to the catalyst solution.

[0281] <Production Example of Silica Particles 13>

[0282] 100 parts of untreated fumed silica with an average particle size of 12 nm were introduced into a reactor; operated under a nitrogen atmosphere, 2 parts of water were added and 20 parts of 3-aminopropyltrimethoxysilane (APTMS) were added; and heating and stirring were carried out at 200 °C for 1 hour, and methanol was removed and then cooled. Then, a crushing treatment was performed using an impact crusher to provide silica particles 13. The properties of the obtained silica particles 13 are given in Table 1.

[0283] <Production Example of Silica Particles 14>

[0284] Silica particles 14 were obtained by performing the same steps as in the production example of silica particles 1, except that the pH of the alkaline aqueous solution added to the catalyst solution was changed to 6.6, the adjustment temperature of the catalyst solution was changed to 30 °C, 30 parts of formaldehyde were simultaneously added within 30 minutes except for the dropwise addition of TMOS and 1.0 mass% ammonia water, and the hexamethyldisilazane (HMDS) hydrophobizing agent was changed to 3-aminopropyltrimethoxysilane (APTMS). The properties of the obtained silica particles 14 are given in Table 1.

[0285] [Table 1]

[0286]

[0287] The abbreviations used in the table are as follows.

[0288] HMDS: Hexamethyldisilazane

[0289] APTMS: 3-aminopropyltrimethoxysilane

[0290] <Production of Polyester Resin 1>

[0291] 47 mol parts of terephthalic acid, 35 mol parts of fumaric acid, 15 mol parts of dodecenyl succinic acid, 60 mol parts of a 2-mol addition product of bisphenol A and propylene oxide, and 40 mol parts of a 2-mol addition product of bisphenol A and ethylene oxide were introduced into a reactor equipped with a nitrogen inlet tube, a water separation tube, a stirrer, and a thermocouple. Subsequently, 0.5 part of dibutyltin oxide was added as a catalyst relative to 100 parts of the total monomer amount. Then, under a nitrogen atmosphere at atmospheric pressure, polycondensation was carried out by rapidly raising the temperature to 180 °C and then distilling off water while heating from 180 °C to 210 °C at a rate of 10 °C / hour.

[0292] When 210 °C was reached, 1 mol part of trimellitic anhydride was added, the inside of the reactor was depressurized to below 5 kPa, and polycondensation was carried out under the conditions of 210 °C and below 5 kPa to obtain Polyester Resin 1. The properties of the obtained Polyester Resin 1 are given in Table 2.

[0293] <Production of Polyester Resins 2 and 3>

[0294] Except that the monomer composition described in the production example of Polyester Resin 1 was changed to the monomer composition described in Table 2, Polyester Resins 2 and 3 were obtained similarly. The properties are given in Table 2.

[0295] <Production of Styrene-Acrylic Resin 1>

[0296] 100.0 parts of xylene, 80.0 parts of styrene, 20.0 parts of n-butyl acrylate, 0.3 part of hexanediol diacrylate, and 2.0 parts of Perbutyl O (half-life temperature of 10 hours: 72.1 °C (NOF Corporation)) were added to a reactor equipped with a reflux condenser, a stirrer, a thermometer, and a nitrogen inlet tube, and heating was carried out to 80 °C and stirring was carried out for 6 hours.

[0297] The solvent was distilled off for 6 hours while heating to 100 °C to obtain Styrene-Acrylic Resin 1 to be used as a core resin. The glass transition point Tg of the obtained Styrene-Acrylic Resin 1 was 60 °C.

[0298] <Production of Styrene-Acrylic-Modified Polyester Resin 1>

[0299] · 2-mol addition product of bisphenol A and propylene oxide: 500 parts

[0300] · Terephthalic acid: 154 parts

[0301] · Fumaric acid: 45 parts

[0302] · Dibutyltin oxide: 3 parts

[0303] These materials are charged into a reactor equipped with a reflux condenser, a stirrer, a thermometer, and a nitrogen inlet tube, and a polycondensation reaction is carried out at a temperature of 230 °C for 8 hours. The polycondensation reaction is continued for 1 hour at 8 kPa, and then cooled to 160 °C.

[0304] Then, 10 parts of acrylic acid are charged at 160 °C, and then maintained for 20 minutes under mixing, and then a mixture of the following compounds is added dropwise from a dropping funnel within 1 hour.

[0305] · Styrene: 315 parts

[0306] · n-Butyl acrylate: 65 parts

[0307] · Polymerization initiator (di-tert-butyl peroxide): 9 parts

[0308] An addition polymerization reaction is carried out for 1 hour while maintaining the temperature at 160 °C. Subsequently, the temperature is raised to 200 °C and maintained for 1 hour at 10 kPa to produce Styrene-Acrylic-Modified Polyester Resin 1 with a content of styrene-acrylic copolymer molecular chains of 35% by mass.

[0309] The obtained Styrene-Acrylic-Modified Polyester Resin 1 has a glass transition point Tg of 60 °C.

[0310] [Table 2]

[0311]

[0312] The abbreviations used in the table are as follows.

[0313] BPA-PO: 2-mole adduct of propylene oxide with bisphenol A

[0314] BPA-EO: 2-mole adduct of ethylene oxide with bisphenol A

[0315] <Production of Core Particle 1>

[0316] Using an FM mixer (Nippon Coke & Engineering Co., Ltd.), 100 parts of Polyester Resin 1, 5 parts of HNP-9 hydrocarbon wax (NOF Corporation, melting point = 74 °C), and 5 parts of colorant (C.I. Pigment Blue 15:3) are mixed at a rotational speed of 2500 rpm.

[0317] Then, the obtained mixture was melt-kneaded using a twin-screw extruder (“PCM-30”, Ikegai Corporation). Then, the obtained kneaded material was cooled. Subsequently, the cooled kneaded material was pulverized using a turbo mill (Freund-Turbo Corporation). The obtained pulverized material was classified using a classifier (“Elbow Jet EJ-LABO”, Nittetsu Mining Co., Ltd.). As a result, core particles 1 with a weight-average particle diameter (D4) of 6 μm were obtained.

[0318] <Production of core particles 2>

[0319] Except that the added polyester resin 1 was changed to polyester resin 2, core particles 2 with a weight-average particle diameter (D4) of 6 μm were obtained as in the production of core particles 1.

[0320] <Production of core particles 3>

[0321] Except that the added polyester resin 1 was changed to polyester resin 3, core particles 3 with a weight-average particle diameter (D4) of 6 μm were obtained as in the production of core particles 1.

[0322] <Production of core particles 4>

[0323] Except that the added polyester resin 1 was changed to styrene-acrylic resin 1, core particles 4 with a weight-average particle diameter (D4) of 6 μm were obtained as in the production of core particles 1.

[0324] <Production of core particles 5>

[0325] A dispersion of core particles 5 was prepared using emulsion polymerization or aggregation method.

[0326] (Preparation of polyester particle dispersion)

[0327] · Polyester resin 1 200.0 parts

[0328] · Deionized water 500.0 parts

[0329] These materials were introduced into a stainless-steel container; heated to 95 °C on a hot bath and melted; and, while stirring thoroughly at 7800 rpm using a homogenizer (Ultra-Turrax T50, IKA), the pH was made greater than 7.0 by adding 0.1 mol / L sodium bicarbonate. Then, a polyester particle dispersion was obtained by gradually dropping a mixed solution of 3.0 parts of sodium dodecylbenzenesulfonate and 297.0 parts of deionized water while emulsifying and dispersing.

[0330] When measuring the particle size distribution of the polyester particle dispersion using a particle size distribution analyzer (LA-920, Horiba, Ltd.), the number average particle size of the contained polyester particles was 0.25 μm and no coarse particles exceeding 1 μm were observed.

[0331] (Preparation of wax particle dispersion)

[0332] · 500.0 parts of deionized water

[0333] · Fischer-Tropsch wax (C105, Sasol Limited, melting point: 80 °C) 250.0 parts

[0334] These materials were introduced into a stainless steel container; heated to 95 °C on a hot bath and melted; and while stirring thoroughly at 7800 rpm using a homogenizer (Ultra-Turrax T50, IKA), the pH was made greater than 7.0 by adding 0.1 N sodium bicarbonate. Subsequently, while emulsifying and dispersing, a mixed solution of 5.0 parts by mass of sodium dodecylbenzenesulfonate and 245.0 parts by mass of deionized water was gradually added dropwise. When measuring the particle size distribution of the wax particles in the wax particle dispersion using a particle size distribution analyzer (LA-920, Horiba, Ltd.), the number average particle size of the contained wax particles was 0.35 μm and no coarse particles exceeding 1 μm were observed.

[0335] (Preparation of colorant particle dispersion)

[0336] · 100.0 parts of C.I. Pigment Blue 15:3

[0337] · 5.0 parts of sodium dodecylbenzenesulfonate

[0338] · 400.0 parts of deionized water

[0339] The foregoing was mixed and dispersed using a sand mill. When measuring the particle size distribution of the colorant particles contained in the colorant particle dispersion using a particle size distribution analyzer (LA-920, Horiba, Ltd.), the number average particle size of the contained colorant particles was 0.2 μm and no coarse particles exceeding 1 μm were observed.

[0340] (Production of core particle dispersion)

[0341]

[0342] The polyester resin particle dispersion 1, the wax particle dispersion, and sodium dodecylbenzenesulfonate were introduced into a reactor (a 1-liter flask equipped with a baffle and an anchor blade) and mixed until homogeneous. The colorant particle dispersion was separately mixed until homogeneous in a 500 mL beaker and gradually added to the reactor while stirring to provide a mixed dispersion. While stirring the obtained mixed dispersion, an aqueous solution of aluminum sulfate in an amount of 0.5 part by solid content was added dropwise to form aggregated particles.

[0343] After the addition was completed, the inside of the system was purged with nitrogen and held at 50 °C for 1 hour and then at 55 °C for another 1 hour.

[0344] Then it was heated at 90 °C and held for 30 minutes. Subsequently, it was cooled to 63 °C and then held for 3 hours to form coalesced particles. After a predetermined time, it was cooled to 40 °C at a cooling rate of 0.5 °C per minute to obtain a dispersion of core particles 5 with a weight average particle diameter (D4) of 6 μm.

[0345] <Production of Core Particles 6>

[0346] A dispersion of core particles 6 was prepared using the dissolution-suspension method.

[0347]

[0348] These materials were dispersed for 3 hours using a grinder (Mitsui Mining & Smelting Co., Ltd.) to obtain a colorant dispersion.

[0349] In addition, an aqueous medium was prepared by adding 1.8 parts of tricalcium phosphate to 300.0 parts of deionized water heated to a temperature of 60 °C and stirring at a stirring speed of 10,000 rpm using a TK homomixer (Tokushu Kika Kogyo Co., Ltd.). The colorant dispersion was introduced into this aqueous medium, and colorant particle granulation was carried out by stirring at a stirring speed of 12,000 rpm for 15 minutes using a TK homomixer at a temperature of 65 °C and in an N2 atmosphere.

[0350] Then the TK homomixer was changed to an ordinary propeller stirrer. The stirring speed of the stirrer was maintained at 150 rpm; the internal temperature was raised to a temperature of 95 °C; and the solvent was removed from the dispersion by holding for 3 hours to prepare a dispersion of core particles 6 with a weight average particle diameter (D4) of 6 μm.

[0351] <Production of Core Particles 7>

[0352] Except for adding 0.7 part of BONTRON P-51 (Orient Chemical Industries Co., Ltd.) charge control agent in addition to the added wax and colorant, core particles 7 having a weight average particle diameter (D4) of 6 μm were obtained as in the production of core particles 1.

[0353] <Preparation of Shell Resin Particles 1>

[0354] A glass container equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube was placed on a water bath, and 500 parts of deionized water and 28.3 parts of Neogen RK anionic surfactant (Dai-ichi Kogyo Seiyaku Co., Ltd.) were introduced into the flask. Then the temperature in the flask was raised to 80°C. Subsequently, two different solutions (the first solution and the second solution) were each dropwise added to the contents of the flask at 80°C over 3 hours.

[0355] The first solution was a mixture of 84 parts of styrene and 16 parts of butyl acrylate. The second solution was a solution in which 1 part of potassium persulfate was dissolved in 50 parts of deionized water. Then the temperature in the flask was maintained at 80°C for an additional 2 hours to polymerize the contents of the flask. As a result, a dispersion containing shell resin particles 1 was obtained. The number average primary particle diameter of the obtained shell resin particles 1 was 50 nm and the Tg was 70°C.

[0356] <Preparation of Shell Resin Particles 2>

[0357] Except for changing the addition amount of Neogen RK anionic surfactant (Dai-ichi Kogyo Seiyaku Co., Ltd.) to 16.7 parts and changing the monomer composition added as the first solution to 73.5 parts of styrene, 24.5 parts of butyl acrylate, and 2 parts of acrylic acid, a dispersion containing shell resin particles 2 was obtained as in the preparation of shell resin particles 1. The number average primary particle diameter of the obtained shell resin particles 2 was 72 nm and the Tg was 61°C.

[0358] <Preparation of Shell Resin Particles 3 and 4>

[0359] Except for changing the addition amount of Neogen RK anionic surfactant (Dai-ichi Kogyo Seiyaku Co., Ltd.) and the monomer composition to the amounts given in Table 3, a dispersion containing shell resin particles 3 and 4 was obtained as in the preparation of shell resin particles 1. The properties of the dispersion containing shell resin particles 3 and 4 are given in Table 3.

[0360] <Preparation of Shell Resin Particles 5>

[0361] · 1,200 parts of polyester resin

[0362] · 500 parts of deionized water

[0363] Introduce these materials into a stainless-steel container; heat to 95 °C and melt on a hot bath; and, while stirring sufficiently at 7,800 rpm using a homogenizer (Ultra-Turrax T50, IKA), adjust the pH to greater than 7.0 by adding 0.1 mol / L sodium bicarbonate. Then, obtain a dispersion of polyester resin particles by gradually dropping a mixed solution of 3 parts of sodium dodecylbenzenesulfonate and 297 parts of deionized water while emulsifying and dispersing.

[0364] When measuring the particle size distribution of this dispersion of polyester resin particles using a particle size distribution analyzer (LA-920, Horiba, Ltd.), the number average particle size of the contained polyester resin particles is 240 nm and no coarse particles exceeding 1 μm are observed.

[0365] <Preparation of resin particles 6 for the shell>

[0366] Except for changing the added polyester resin 1 to styrene-acrylic-modified polyester resin 1, obtain a fine dispersion of shell resin particles 6 as in the preparation of resin particles 5 for the shell. The number average particle size of the obtained styrene-acrylic-modified polyester resin particles is 250 nm, and no coarse particles exceeding 1 μm are observed.

[0367] [Table 3]

[0368]

[0369] The abbreviations used in the table are as follows.

[0370] St: Styrene

[0371] BA: n-Butyl acrylate

[0372] MA: Methyl acrylate

[0373] AA: Acrylic acid

[0374] 2-HEMA: 2-Hydroxyethyl methacrylate

[0375] <Production of toner 1>

[0376] (Formation of core / shell particles)

[0377] Prepare a three-necked flask equipped with a thermometer and a stirring blade and place the flask on a water bath. Introduce 100 parts of deionized water into the flask and maintain the temperature in the flask at 30 °C using the water bath. Adjust the pH of the contents of the flask to 4 by adding 10 mass% hydrochloric acid to the flask.

[0378] The previously prepared dispersion containing 1.00 part by solid content of the resin particles for the shell was added to the flask. Then, 100 parts of the core particles 1 prepared by the previously described procedure were added to the flask, and the contents of the flask were thoroughly stirred. As a result, a dispersion of the core particles 1 and the resin particles for the shell was obtained in the flask.

[0379] Another 100 parts of deionized water were added to the flask, and while stirring at a rotational speed of 100 rpm, the contents of the flask were heated to 50 °C at a rate of 1.0 °C per minute.

[0380] At the point where the temperature in the flask reached 50 °C, 0.5 part of Neogen RK anionic surfactant (Dai-ichi Kogyo Seiyaku Co., Ltd.) was added, and then the pH was adjusted to 7 by adding sodium bicarbonate.

[0381] While stirring the contents of the flask at a rotational speed of 100 rpm, the contents of the flask were continuously heated to 85 °C at a rate of 1.0 °C per minute and held at 85 °C for 2 hours. Subsequently, the contents of the flask were cooled to room temperature to obtain a dispersion containing the toner particles 1.

[0382] The resulting dispersion containing the toner particles 1 was filtered (solid-liquid separation), and re-dispersed and filtered using deionized water for washing. Subsequently, it was dried using a flash dryer to obtain the toner particles 1.

[0383] The toner particles 1 have a core-shell structure in which a part of the core particles is exposed, and the toner particle surface is formed from the surface formed by the polyester resin and the surface formed by the styrene-acrylic resin.

[0384] The total surface area of the surface formed by the styrene-acrylic resin and the surface formed by the polyester resin is 100 (area %) with respect to the total surface area of the toner particle surface of the toner particles 1, and the surface area percentage of the surface formed by the styrene-acrylic resin with respect to the total surface area of the surface formed by the styrene-acrylic resin and the surface formed by the polyester resin is 60 (area %).

[0385] (External addition step)

[0386] Using a Henschel mixer (Model FM-10, Mitsui Miike Chemical Engineering Machinery Co., Ltd.), 100.0 parts of the resulting toner particles 1 were mixed with 1.0 part of the silica particles 1 to obtain the negatively charged toner 1. The properties are given in Table 4.

[0387] <Production of Toner 2>

[0388] A negatively charged toner 2 is produced as in the production of toner 1, except that the addition amount of the dispersion containing the shell resin particles 1 is changed to an amount providing 0.75 parts by solid content, and the silica particles 1 added in the (external addition step) are changed to silica particles 2. The St-Ac+PES surface area percentage of the toner particles 2 is 100 (area %), and the St-Ac surface area percentage is 50 (area %). The properties are given in Table 4.

[0389] <Production of Toners 3 to 17 and 20 to 25>

[0390] Toners 3 to 17 and toners 20 to 25 are produced as in the production of toner 1, except that the types and addition amounts of the core particles and shell resin particles added and the silica particles added in the external addition step are changed as shown in Table 4. The properties are given in Table 4.

[0391] In the production of toner 15, the addition amount of the dispersion of the core particles 5 and in the production of toner 16, the addition amount of the dispersion of the core particles 6 are each an amount providing 100 parts by solid content.

[0392] <Production of Toner 18>

[0393] A positively charged toner 18 is produced as in the production of toner 1, except that when adding the dispersion containing the shell resin particles 1, 0.084 parts of an aqueous solution of hydroxymethyl melamine (Mirbane Resin SM-607, Showa Denko Kabushiki Kaisha) is further added.

[0394] The St-Ac+PES surface area percentage of the toner particles 18 is 90 (area %), and the St-Ac surface area percentage is 60 (area %). The properties are given in Table 4.

[0395] <Production of Toner 19>

[0396] A positively charged toner 19 is produced as in the production of toner 18, except that the addition amount of the aqueous solution of hydroxymethyl melamine (Mirbane Resin SM-607, Showa Denko Kabushiki Kaisha) is changed to 0.140 parts.

[0397] The St-Ac+PES surface area percentage of the toner particles 19 is 88 (area %), and the St-Ac surface area percentage is 60 (area %). The properties are given in Table 4.

[0398] [Table 4]

[0399]

[0400] In the table, PES refers to a polyester resin, St-Ac refers to a styrene-acrylic resin, and St-Ac-modified PES refers to a styrene-acrylic-modified polyester resin.

[0401] St-Ac + PES surface area percentage: The percentage of the total surface area of the surfaces formed by the styrene-acrylic resin and the surfaces formed by the polyester resin relative to the total surface area of the toner particles

[0402] St-Ac surface area percentage: On the surface of the toner particles, the surface area of the surfaces formed by the styrene-acrylic resin relative to the total surface area of the surfaces formed by the styrene-acrylic resin and the surfaces formed by the polyester resin

[0403] <Image evaluation>

[0404] A color laser beam printer (HP LaserJet Enterprise Color M652n) from Hewlett-Packard was used as the image forming device; it was modified so that the processing speed was 300 mm / second. A Genuine HP 656X LaserJet toner cartridge (cyan) was used for the cartridge. The product toner was taken out of the cartridge, then cleaned with a hair dryer, and filled with 300 g of the toner to be evaluated.

[0405] The refilled toner cartridge was installed in the cyan station; dummy cartridges were installed in the other stations; and the image output test was conducted as described below. The evaluation of the positively charged toners (toners 17 to 19, 24, and 25) was conducted in the same manner except that various potential settings were changed so that development could be carried out with the positively charged toner.

[0406] <Measurement of toner charge amount>

[0407] To clarify the relationship between the results of the image output test and the toner charge amount, the toner was taken out of the developer container before and after each of the durability tests described below, and the toner charge amount was measured using the following method.

[0408] Weigh 9.4 g of the carrier for charge measurement (F81-2535, Powdertech Co., Ltd.) into a 50 mL polyethylene container. Then weigh 0.6 g of the toner to be measured into the polyethylene container containing the carrier, and close the container with its lid. Subsequently, place the container in a shaker (Model YS-LD, YAYOI Co., Ltd.) and shake it for 2 minutes under the shaking condition of 150 times per minute.

[0409] Within 1 minute thereafter, introduce approximately 0.4 g of the shaken sample into the metal measurement container 2 having a 500-mesh sieve 3 at the bottom as shown in the attached figure, and cover it with the metal lid 4. Measure the mass of the entire measurement container 2 at this time, and designate this value as W1 (g). Designate the potential of the electrometer 9 at this time as 0 V (volt).

[0410] Then use the suction device 1 (the part in contact with the measurement container 2 is at least an insulator) to perform suction through the suction port 7, and adjust by using the air volume regulating valve 6 to make the pressure at the vacuum gauge 5 become 2.5 kPa (±0.1 kPa) within 10 seconds. Make the time from measuring W1 to starting suction within 30 seconds. Subsequently, perform suction for 3 minutes to suck out the toner particles. Designate the potential at the electrometer 9 at this time as V (volt). Here, 8 is the capacitance, and designate the capacitance as C (μF).

[0411] Measure the mass of the entire measurement container after suction, and designate the value at this time as W2 (g). Calculate the toner charge amount (mC / kg) of the sample using the following formula.

[0412] Charge amount (mC / kg) = (C × V) / (W1 - W2)

[0413] Measure the charge amount on the measurement samples provided by removing the toner from the developer container before and after the durability test. The durability test is carried out in the following low-temperature and low-humidity environment (temperature 15°C, humidity 10% RH: LL environment), high-temperature and high-humidity environment (temperature 30°C / humidity 80% RH: HH environment), and normal-temperature and normal-humidity environment (temperature 23°C, humidity 50% RH: NN environment).

[0414] In the evaluation of the positively charged toner, except for changing the carrier for charge measurement from (F81-2535, Powdertech Co., Ltd.) to (F-150, Powdertech Co., Ltd.), the measurement is carried out in the same manner.

[0415] [Halftone (HT) Image Reproducibility]

[0416] Operate in a low-temperature and low-humidity environment (temperature 15°C, humidity 10%RH). After each output of two images with a printing percentage of 1%, repeat the intermittent operation of temporarily stopping to conduct a total of 30,000 printing output tests.

[0417] After the printing output test is completed, output the original halftone images at 30h, 80h, and C0h, visually inspect each image, and evaluate the dot reproducibility using the criteria given below.

[0418] The 30h in the halftone image displays the values of 256 gray levels in hexadecimal and represents the controlled image. Thus, 00h is the first gray level (white background area) of the 256 gray levels, and FFh is the 256th gray level (solid area) of the 256 gray levels.

[0419] A: On the entire halftone image, the dots can be reproduced with good accuracy; this is the level where the image is uniform without unevenness.

[0420] B: Minor dot perturbations are observed in a part of the halftone image, but this is the level where the density non-uniformity is not a problem.

[0421] C: Dot perturbations are observed in a part of the halftone image, and density non-uniformity is seen; however, from the perspective of the actual image, this non-uniformity is not significant.

[0422] D: The dot reproducibility is poor on the entire halftone image; this is the level where roughness and / or non-uniformity are generated.

[0423] [Fogging evaluation]

[0424] Operate in a high-temperature and high-humidity environment (temperature 30°C / humidity 80%RH). After each output of two images with a printing percentage of 1%, repeat the intermittent operation of temporarily stopping to conduct a total of 30,000 printing output tests.

[0425] After the printing output test is completed, output a solid white image, and measure the reflectance (%) of this solid white image using "Reflectometer Model TC-6DS" (Tokyo Denshoku Co., Ltd.). Evaluate using the value (%) obtained by subtracting this reflectance from the reflectance (%) measured in the same way on the original printing output paper (standard glossy paper).

[0426] The smaller the value, the better the suppression of image fogging. Output a solid white image in glossy paper mode using glossy paper (HP Brochure Paper 200g, Glossy, 200g / m 2 , from Hewlett-Packard).

[0427] Evaluation Criteria

[0428] A: The difference is less than 0.5%.

[0429] B: The difference is 0.5% or more and less than 1.5%.

[0430] C: The difference is 1.5% or more and less than 3.0%.

[0431] D: The difference is 3.0% or more.

[0432] [Image density and image density stability]

[0433] Under normal temperature and humidity environment (temperature 23°C, humidity 50%RH), a total of 10,000 print output tests were conducted as follows: Continuously output 5,000 images with a print percentage of 1%, and then continuously output 5,000 high-print-percentage images with a print percentage of 25%.

[0434] Before and after the start and end of the output print test, sample images of solid black images with a side length of 20 mm printed at the four corners and the center of the paper surface were output on GF-C081 (81.4 g / m 2 , Canon Marketing Japan Inc.). The reflection density was measured using the X-Rit500 series (Videojet X-Rite K.K.), and the average value of the image density at five positions was calculated.

[0435] The evaluation criteria for image density are as follows.

[0436] A: Both the initial image density and the image density after the durability test are 1.40 ± (less than 0.10)

[0437] B: Both the initial image density and the image density after the durability test are 1.40 ± (0.10 or more and less than 0.15)

[0438] C: Both the initial image density and the image density after the durability test are 1.40 ± (0.15 or more and less than 0.20)

[0439] D: Both the initial image density and the image density after the durability test are 1.40 ± (0.20 or more)

[0440] The evaluation criteria for image density stability are as follows.

[0441] A: The absolute difference between the initial image density and the image density after the durability test is less than 0.10

[0442] B: The absolute difference between the starting image density and the image density after the durability test is 0.10 or more and less than 0.15

[0443] C: The absolute difference between the starting image density and the image density after the durability test is 0.15 or more and less than 0.20

[0444] D: The absolute difference between the starting image density and the image density after the durability test is 0.20 or more

[0445] [Examples 1 to 19]

[0446] In Examples 1 to 19, each of the toners 1 to 19 was used as the toner to conduct the evaluation shown above. The evaluation results are given in Table 5.

[0447] [Comparative Examples 1 to 6]

[0448] In Comparative Examples 1 to 6, each of the toners 20 to 25 was used as the toner to conduct the evaluation shown above. The evaluation results are given in Table 5.

[0449] [Table 5]

[0450]

[0451] Although the present invention has been described with reference to exemplary embodiments, it should be understood that the present invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be accorded the broadest interpretation so as to cover all such modifications as well as equivalent structures and functions.

Claims

1. A toner, comprising The toner particles have a core-shell structure including a core particle and a shell formed on the surface of the core particle, and Silica particles on the surface of the toner particles, characterized in that The core particle includes a polyester resin, and the shell includes a styrene-acrylic resin; On the surface of the toner particle, there are a surface formed by the polyester resin and a surface formed by the styrene-acrylic resin due to a part of the polyester resin contained in the core particle being exposed on the surface of the toner particle; The percentage of the total surface area of the surface formed by the styrene-acrylic resin and the surface formed by the polyester resin with respect to the total surface area of the toner particle is 95 area% or more; The percentage of the surface area of the surface formed by the styrene-acrylic resin with respect to the total surface area of the surface formed by the styrene-acrylic resin and the surface formed by the polyester resin is 45 to 75 area%; The number average particle diameter of the silica particles is 15 to 40 nm; The average pore diameter of the silica particles is 7.0 to 15.0 nm; and The total pore volume of the silica particles is 0.40 to 1.20 cm 3 / g.

2. The toner according to claim 1, wherein the silica particles are wet silica.

3. The toner according to claim 1, wherein the hydrophobicity of the silica particles is 40 to 75%.

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