JP2017003881A - Toner for electrostatic latent image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means that suppresses a reduction in image quality and a reduction in transferability of a toner for electrostatic latent image development in a high-temperature and high-humidity environment to enable stable image formation.SOLUTION: A toner for electrostatic latent image development comprises toner base particles including an amorphous resin and external additive particles, and uses, as the external additive particles, vinyl crosslinked resin particles having a number average particle diameter of 50 to 300 nm and a ratio of a sulfur element measured by X-ray photoelectron spectroscopy of 0.10 to 0.50 atom%.SELECTED DRAWING: None

Description

  The present invention relates to an electrostatic latent image developing toner used for electrophotographic image formation.

  With the spread of digital printing, higher image quality and higher stability are increasingly required. In the field of electrostatic latent image developing toner (hereinafter also simply referred to as “toner”), from the viewpoint of energy saving, the melting temperature and melt viscosity of the binder resin contained in the toner are lowered to reduce the energy required for fixing. A method for reducing the amount of toner on paper and a method for reducing energy required for fixing have been considered.

  In recent years, as the speed of image forming apparatuses increases, the strength of stirring in the developing device increases, and the stress due to stirring received by the developer has increased. As a result, the deterioration of the toner is promoted, and there is a problem that the charge amount and the external additive are buried due to the crushing of the toner.

  Here, for the purpose of preventing the deterioration of the toner due to the burying of the external additive, a large-diameter external additive has been conventionally used. This is because by using a large-diameter external additive, the contact between the toner particles and the external additive particles is reduced, making it difficult for the external additive to be buried (spacer effect). Conventionally, large-diameter silica has been used as such a large-diameter external additive. However, large-diameter silica has a problem that the charge amount decreases.

  On the other hand, it has been proposed to use organic fine particles as an external additive instead of inorganic particles such as large-diameter silica. Here, there is a problem that the non-crosslinked organic fine particles are easily crushed because of low strength, and the spacer effect cannot be sufficiently exhibited. On the other hand, the technique which suppresses the burying of an external additive by ensuring the spacer effect by using the crosslinked organic fine particle as an external additive is proposed (for example, refer patent document 1).

JP 2008-15136 A

  As described above, by using the organic fine particles as the external additive, it is possible to prevent the deterioration of the toner due to the external additive being buried and the deterioration of the image quality resulting therefrom. However, according to the study by the present inventors, when organic fine particles as described in Patent Document 1 are used as an external additive, the image quality deteriorates or the transferability deteriorates in a high temperature and high humidity environment. It has been found that there is a problem that stable image formation is difficult.

  The present invention has been made in consideration of the above circumstances, and in an electrostatic latent image developing toner, it is possible to suppress deterioration in image quality and transferability in a high-temperature and high-humidity environment, thereby stabilizing the image. The object is to provide means that can be formed.

  The present inventors have conducted intensive studies in view of the above problems. As a result, the toner base particles are combined with vinyl cross-linked resin particles having a predetermined particle size as external additive particles to constitute a toner, and the amount of sulfur element present in the cross-linked resin particles is within a predetermined range. It has been found that the above problem can be solved by controlling the value within the range, and the present invention has been completed.

  That is, according to one aspect of the present invention, there is provided a toner for developing an electrostatic latent image including toner base particles containing an amorphous resin and external additive particles. In the toner according to this embodiment, the external additive particles include vinyl crosslinked resin particles having a number average particle diameter of 50 to 300 nm, and the vinyl crosslinked resin is measured by X-ray photoelectron spectroscopy. It is characterized in that the sulfur element ratio in the particles is 0.10 to 0.50 atomic%.

  ADVANTAGE OF THE INVENTION According to this invention, in the electrostatic latent image developing toner, there is provided a technique that enables stable image formation by suppressing deterioration in image quality and transferability under a high temperature and high humidity environment.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

<Toner>
The toner according to an embodiment of the present invention includes toner base particles and external additive particles. The external additive particles include vinyl-based crosslinked resin particles having a number average particle diameter of 50 to 300 nm. And the sulfur element ratio in the said vinyl type crosslinked resin particle measured by a X ray photoelectron spectroscopy is controlled in the range of 0.10-0.50 atomic%. According to the toner according to the present invention having such a configuration, it is possible to suppress a decrease in image quality and a decrease in transferability under a high temperature and high humidity environment, thereby enabling stable image formation. Although the mechanism by which such an effect is manifested is not completely clear, it is estimated as follows.

  First, when conventional inorganic particles such as large-diameter silica are used as external additive particles, it is considered that the image quality deteriorates as a result of a decrease in charge amount in a high temperature and high humidity environment. In addition, when non-crosslinked organic fine particles are used as external additive particles, as described above, they are easily crushed due to low strength, and as a result, the spacer effect cannot be fully exhibited, resulting in deterioration in image quality and transferability. Can not be sufficiently prevented. Further, even when organic fine particles such as crosslinked vinyl-based crosslinked resin particles are used as external additive particles, if the amount of sulfur element in the crosslinked resin particles is too large, the external additive particles are converted into a high-temperature and high-humidity environment. Adsorption of moisture tends to occur. As a result, it is considered that the chargeability is lowered and the image quality is lowered, and the adhesiveness of the toner is increased and the transferability is lowered as the liquid crosslinking power is increased. On the other hand, if the amount of elemental sulfur in the vinyl-based crosslinked resin particles is too small, sufficient chargeability cannot be obtained, and it is considered that the image quality is deteriorated. Further, regarding the particle size of the vinyl resin crosslinked particles, if the particle size is too large or too small, the adhesion to the toner is lowered and the spacer effect cannot be sufficiently exhibited, and the chargeability is also reduced. It cannot be improved, and it is considered that deterioration in image quality and transferability in a high temperature and high humidity environment cannot be prevented. On the other hand, by adopting the configuration according to the present invention, the spacer effect can be sufficiently exerted as the external additive particles, and sufficient chargeability can be secured, and further to the external additive particles. As a result of the suppression of moisture adsorption, it is presumed that deterioration in image quality and transferability are suppressed and stable image formation becomes possible.

  Hereinafter, the components of the toner according to the present invention will be described in detail.

(Toner base particles)
The toner base particles according to the present invention contain at least an amorphous resin as a binder resin as a constituent component, and if necessary, a crystalline resin, a colorant, a magnetic powder, a release agent, a charge control agent, and the like. Other toner components may be contained. The toner base particles according to the present invention are obtained by, for example, a wet manufacturing method (for example, an emulsion aggregation method) prepared in an aqueous medium. Here, from the viewpoint of excellent fixability, the toner base particles according to the present invention have a domain matrix structure in which a domain phase containing a crystalline resin is dispersed in a matrix phase containing an amorphous resin. It is preferable. Hereinafter, a case where the toner base particles have a domain matrix structure will be described as an example, but the technical scope of the present invention is not limited to such a form.

  First, the “domain matrix structure” refers to a structure in which a domain phase having a closed interface (boundary between phases) exists in a continuous matrix phase. In other words, in the toner base particles, it means a state in which the crystalline resin is introduced incompatible with the amorphous resin. In addition, this structure can observe the cross section of the toner base particle dye | stained by the osmium by a usual method using a transmission electron microscope. In the case of cutting a section with an ultramicrotome, the thickness of the section is set to 100 nm. In addition to the crystalline resin, wax or the like may be added in the domain.

-Amorphous resin There is no particular limitation on the amorphous resin constituting the matrix phase in the domain matrix structure, and conventionally known amorphous resin in this technical field can be used. It is preferable to contain a functional vinyl resin. When the amorphous resin contains the vinyl resin, interaction with the vinyl-based crosslinked resin particles added as the external additive particles occurs, and the binder resin (non-crystalline resin) and the external additive particles are between. As a result of the further improvement in the adhesiveness, the effects of the present invention can be more remarkably exhibited. The “vinyl resin” is a resin obtained by polymerization using at least a vinyl monomer. Specific examples of the amorphous vinyl resin include an acrylic resin and a styrene acrylic copolymer resin. Among these, as the amorphous vinyl resin, a styrene acrylic copolymer resin formed using a styrene monomer and a (meth) acrylic acid ester monomer is preferable.

As the vinyl monomer that forms the amorphous vinyl resin, one or more selected from the following may be used.
(1) Styrene monomer styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, α-methyl styrene, p-phenyl styrene, p-ethyl styrene, 2,4-dimethyl styrene, p-tert -Butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, and derivatives thereof.
(2) (meth) acrylic acid ester monomer (meth) methyl acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isopropyl (meth) acrylate, isobutyl (meth) acrylate, T-butyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, phenyl (meth) acrylate, (meth ) Diethylaminoethyl acrylate, dimethylaminoethyl (meth) acrylate, and derivatives thereof.
(3) Vinyl esters Vinyl propionate, vinyl acetate, vinyl benzoate and the like.
(4) Vinyl ethers such as vinyl methyl ether and vinyl ethyl ether.
(5) Vinyl ketones Vinyl methyl ketone, vinyl ethyl ketone, vinyl hexyl ketone and the like.
(6) N-vinyl compounds N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidone and the like.
(7) Other vinyl compounds such as vinyl naphthalene and vinyl pyridine, acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide.

  Moreover, as a vinyl-type monomer, it is preferable to use the monomer which has ionic dissociation groups, such as a carboxy group, a sulfonic acid group, and a phosphoric acid group, for example. Specific examples include the following: monomers having a carboxy group include acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl Examples include esters. Examples of the monomer having a sulfonic acid group include styrene sulfonic acid, allyl sulfosuccinic acid, and 2-acrylamido-2-methylpropane sulfonic acid. Furthermore, examples of the monomer having a phosphate group include acid phosphooxyethyl methacrylate.

  Furthermore, polyfunctional vinyls can be used as the vinyl monomer, and the amorphous vinyl resin can have a crosslinked structure. Polyfunctional vinyls include divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol Examples include diacrylate.

  As described above, the vinyl resin has been described in detail as a preferred form of the amorphous resin, but an amorphous polyester resin or the like may be used as the amorphous resin.

  The glass transition point (Tg) of the amorphous resin is preferably 25 to 60 ° C, more preferably 35 to 55 ° C. When the glass transition point of the amorphous resin is in the above range, sufficient low-temperature fixability and heat-resistant storage stability can be obtained at the same time. The glass transition point (Tg) of the amorphous resin is a value measured using “diamond DSC” (manufactured by PerkinElmer). As a measurement procedure, 3.0 mg of a measurement sample (amorphous resin) is sealed in an aluminum pan and set in a holder. The reference used an empty aluminum pan. The measurement conditions were a measurement temperature of 0 ° C. to 200 ° C., a temperature increase rate of 10 ° C./min, a temperature decrease rate of 10 ° C./min, and heat-cool-heat temperature control. Perform analysis based on the data in Heat, draw a baseline extension before the rise of the first endothermic peak, and a tangent line indicating the maximum slope between the rise of the first peak and the peak apex, Let the intersection be the glass transition point.

  Moreover, it is preferable that the molecular weight measured by gel permeation chromatography (GPC) of an amorphous resin is 10,000-100,000 in a weight average molecular weight (Mw). In this invention, the molecular weight by GPC of an amorphous resin is a value measured as follows. That is, using an apparatus “HLC-8120GPC” (manufactured by Tosoh Corporation) and a column “TSKguardcolumn + TSKgelSuperHZ-M3 series” (manufactured by Tosoh Corporation), while maintaining the column temperature at 40 ° C., tetrahydrofuran (THF) was used as a carrier solvent at a flow rate of 0. The sample (non-crystalline resin) was flowed at 2 ml / min, dissolved in tetrahydrofuran to a concentration of 1 mg / ml under a dissolution condition in which the treatment was performed for 5 minutes using an ultrasonic disperser at room temperature, A sample solution is obtained by processing with a 2 μm membrane filter, and 10 μL of this sample solution is injected into the apparatus together with the carrier solvent, detected using a refractive index detector (RI detector), and the molecular weight distribution of the measurement sample. Using a calibration curve measured using monodisperse polystyrene standard particles Calculated. Ten polystyrenes are used for calibration curve measurement.

-Crystalline resin There is no particular limitation on the crystalline resin that constitutes the domain phase in the domain matrix structure, and a conventionally known crystalline resin in this technical field can be used. It is preferable to include. “Crystalline polyester resin” means a differential scanning among known polyester resins obtained by polycondensation reaction of divalent or higher carboxylic acid (polyvalent carboxylic acid) and divalent or higher alcohol (polyhydric alcohol). In calorimetry (DSC), it refers to a resin having a clear endothermic peak rather than a stepwise endothermic change. The clear endothermic peak specifically means a peak in which the half-value width of the endothermic peak is within 15 ° C. when measured at a rate of temperature increase of 10 ° C./min in differential scanning calorimetry (DSC). To do.

  The polyvalent carboxylic acid is a compound containing two or more carboxy groups in one molecule. Specifically, for example, oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, n-dodecyl succinic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, tetradacandiol Saturated aliphatic dicarboxylic acids such as cycloaliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid; trivalent or higher polyvalent carboxylic acids such as trimellitic acid and pyromellitic acid Acid; and anhydrides of these carboxylic acid compounds or alkyl esters having 1 to 3 carbon atoms. These may be used individually by 1 type and may be used in combination of 2 or more type.

  A polyhydric alcohol is a compound containing two or more hydroxyl groups in one molecule. Specifically, for example, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol , 1,8-octanediol, 1,9-nonanediol, dodecanediol, neopentylglycol, 1,4-butenediol and other aliphatic diols; glycerin, pentaerythritol, trimethylolpropane, sorbitol A polyhydric alcohol etc. are mentioned. These may be used individually by 1 type and may be used in combination of 2 or more type.

  The melting point (Tm) of the crystalline polyester resin is preferably 50 to 95 ° C, more preferably 55 to 85 ° C. When the melting point of the crystalline polyester resin is in the above range, sufficient low-temperature fixability and excellent hot offset resistance can be obtained. The melting point of the crystalline polyester resin can be controlled by the resin composition.

  In the present invention, the melting point of the crystalline polyester resin is a value measured as follows. That is, using a differential scanning calorimeter “Diamond DSC” (manufactured by PerkinElmer Co., Ltd.), a first temperature raising process in which the temperature is raised from 0 ° C. to 200 ° C. at an elevation rate of 10 ° C./min, and a cooling rate of 10 ° C./min is 200 ° C. It is measured by the measurement conditions (temperature rise / cooling conditions) that pass through the cooling process for cooling from 0 to 0 ° C. and the second temperature raising process for raising the temperature from 0 ° C. to 200 ° C. at a raising / lowering rate of 10 ° C./min. The endothermic peak top temperature derived from the crystalline polyester resin in the first temperature raising process is defined as the melting point (Tm) based on the DSC curve obtained by this measurement. As a measurement procedure, 3.0 mg of a measurement sample (crystalline polyester resin) is sealed in an aluminum pan and set in a diamond DSC sample holder. The reference uses an empty aluminum pan.

  The molecular weight of the crystalline polyester resin measured by gel permeation chromatography (GPC) is 5,000 to 50,000 in terms of weight average molecular weight (Mw) and 1,500 to 25 in terms of number average molecular weight (Mn). , 000 is preferable. The molecular weight measured by GPC of the crystalline polyester resin is measured in the same manner as described above except that the crystalline polyester resin is used as a measurement sample.

  The mass ratio of the amorphous resin to the crystalline resin (amorphous resin / crystalline resin) is preferably 97/3 to 70/30, and more preferably 95/5 to 75/25. When the mass ratio (amorphous resin / crystalline resin) is in the above range, the crystalline resin constituting the domain phase is not exposed to the surface of the toner particles to be formed or is exposed even if it is exposed. An amount of crystalline resin that is extremely small and that can achieve low-temperature fixability can be introduced into the toner particles.

  The crystalline resin forming the domain preferably includes a crystalline resin formed by chemically bonding a vinyl polymer segment and a polyester polymer segment (hereinafter also simply referred to as “hybrid resin”). At this time, the vinyl polymer segment and the polyester polymer segment are preferably a crystalline resin bonded via both reactive monomers. In addition, the said polyester polymerization segment is comprised from crystalline polyester resin. When the crystalline resin contains the hybrid resin, an interaction with the vinyl-based crosslinked resin particles added as the external additive particles occurs, and the adhesion between the binder resin and the external additive particles is further improved. As a result, the operational effects of the present invention can be expressed more remarkably.

-Vinyl-type polymer segment The vinyl-type polymer segment which comprises a hybrid resin is comprised from resin obtained by superposing | polymerizing a vinyl-type monomer. Here, as the vinyl monomer, those described above as the monomers constituting the vinyl resin can be used in the same manner, and thus detailed description thereof is omitted here. In addition, it is preferable that content of the vinyl-type polymerization segment in a hybrid resin exists in the range of 5-30 mass%. Within this range, a good domain matrix structure can be obtained and the strength of the toner image can be increased.

-Polyester polymerization segment The polyester polymerization segment which comprises a hybrid resin is comprised from the crystalline polyester resin manufactured by performing polycondensation reaction in the presence of a catalyst with polyhydric carboxylic acid and polyhydric alcohol. Here, specific types of the polyvalent carboxylic acid and the polyhydric alcohol are as described above, and thus detailed description thereof is omitted here.

・ Amotropic monomer "Amotropic monomer" is a monomer that binds a polyester polymer segment and a vinyl polymer segment. In the molecule, a hydroxy group or a carboxy group that forms a polyester polymer segment. , A monomer having both a group selected from an epoxy group, a primary amino group and a secondary amino group and an ethylenically unsaturated group forming a vinyl polymerized segment. Both reactive monomers are preferably monomers having a hydroxy group or a carboxy group and an ethylenically unsaturated group. More preferably, it is a monomer having a carboxy group and an ethylenically unsaturated group. That is, it is preferably a vinyl carboxylic acid.

  Specific examples of the both reactive monomers include, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid, and the like, and these hydroxyalkyl (1 to 3 carbon atoms) esters. However, acrylic acid, methacrylic acid or fumaric acid is preferable from the viewpoint of reactivity. The polyester polymer segment and the vinyl polymer segment are bonded through the both reactive monomers.

  From the viewpoint of improving the low-temperature fixability, high-temperature offset resistance and durability of the toner, the amount of both reactive monomers used is based on 100 parts by mass of the total amount of vinyl monomers constituting the vinyl polymer segment. 1-10 mass parts is preferable and 4-8 mass parts is more preferable.

-Manufacturing method of hybrid resin As a method of manufacturing hybrid resin, the existing general scheme can be used. The following three methods are listed as typical methods.
(1) A polyester polymerization segment is preliminarily polymerized, and the polyester polymerization segment is reacted with an amphoteric monomer, and further, an aromatic vinyl monomer and (meth) for forming a vinyl polymerization segment A method of forming a hybrid resin by reacting an acrylate monomer.
(2) A vinyl polymer segment is polymerized in advance, the vinyl polymer segment is reacted with an amphoteric monomer, and a polyvalent carboxylic acid and a polyhydric alcohol for forming a polyester polymer segment are further reacted. A method for forming a polyester polymer segment by causing the polyester polymer segment to form.
(3) A method in which a polyester polymer segment and a vinyl polymer segment are polymerized in advance, and then both reactive monomers are reacted with each other to bond them together.

  In the present invention, any of the above production methods can be used, but the method of the above item (2) is preferred. Specifically, a polyvalent carboxylic acid and a polyhydric alcohol that form a polyester polymer segment, a vinyl monomer that forms a vinyl polymer segment, and both reactive monomers are mixed, and a polymerization initiator is added. It is preferable to carry out a polycondensation reaction by adding an esterification catalyst after addition polymerization of a vinyl monomer and an amphoteric monomer to form a vinyl polymer segment.

  Here, as a catalyst for synthesizing the polyester polymerization segment, various conventionally known catalysts can be used. In addition, examples of the esterification catalyst include tin compounds such as dibutyltin oxide and tin (II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropylate bistriethanolamate. An acid etc. are mentioned.

<Colorant>
In the toner according to the present invention, when the toner base particles are configured to contain a colorant, the colorant may be contained in either the matrix phase or the domain phase. From the viewpoint, it is particularly preferable that it is contained in the matrix phase.

  Examples of carbon black include channel black, furnace black, acetylene black, thermal black, and lamp black. Examples of black iron oxide include magnetite, hematite, and iron iron trioxide.

  Examples of the dye include C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95 and the like.

  Examples of the pigment include C.I. I. Pigment Red 5, 48: 1, 48: 3, 53: 1, 57: 1, 81: 4, 122, 139, 144, 149, 150, 166, 177, 178, 222, 238, 269, C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment yellow 14, 17, 74, 93, 94, 138, 155, 156, 158, 180, 185, C.I. I. Pigment green 7, C.I. I. Pigment Blue 15: 3, 60, and the like.

  The colorant for obtaining the toner of each color can be used singly or in combination of two or more for each color. The content of the colorant is preferably 1 to 10% by mass in the toner base particles, and more preferably 2 to 8% by mass.

<Release agent (offset prevention agent)>
In the toner according to the present invention, in the case where the toner base particles are configured to contain a release agent, the release agent may be contained in either the matrix phase or the domain phase. From the viewpoint of exudation of the surface of the mold, it is particularly preferable that it is contained in the matrix phase.

  As the wax, polyolefin waxes such as low molecular weight polypropylene, polyethylene, or oxidized polypropylene, polyethylene, and ester waxes such as behenate behenate can be preferably used.

  Specifically, polyolefin waxes such as polyethylene wax and polypropylene wax; branched hydrocarbon waxes such as microcrystalline wax; long-chain hydrocarbon waxes such as paraffin wax and sazol wax; dialkyls such as distearyl ketone Ketone wax; carnauba wax, montan wax, behenate behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol di Ester wax such as stearate, trimellitic trimellitic acid, distearyl maleate; ethylenediamine behenylamide, trimellitic acid tristearylamide Such as amide waxes.

  Among these, from the viewpoint of releasability during low-temperature fixing, it is preferable to use those having a low melting point, specifically, those having a melting point of 40 to 90 ° C. The content ratio of the release agent is preferably 1 to 20% by mass in the toner base particles, and more preferably 5 to 20% by mass.

<Charge control agent>
In the toner according to the present invention, when the toner base particles are configured to contain a charge control agent, the charge control agent may be contained in either the matrix phase or the domain phase. From the viewpoint of dispersibility, it is particularly preferred that it is contained in the matrix phase.

  The content ratio of the charge control agent is usually 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the finally obtained binder resin.

(External additive particles)
The toner according to the present invention includes external additive particles in addition to the toner base particles. The external additive particles essentially contain vinyl-based crosslinked resin particles having a number average particle diameter of 50 to 300 nm.

  The vinyl-based crosslinked resin particles according to the present invention are not particularly limited, but specifically, particles composed of a crosslinked resin containing a structural unit derived from a crosslinkable vinyl monomer are preferable.

  As described above, the vinyl-based cross-linked resin particles according to the present invention are preferably particles composed of a resin containing a structural unit derived from a cross-linkable vinyl monomer capable of radical polymerization. Crosslinking by a radically polymerizable unsaturated group that is not involved in the polymerization among a plurality of radically polymerizable unsaturated groups or other reactive functional groups may be used without any particular limitation. The crosslinkable vinyl monomer is not particularly limited. Among them, as the crosslinkable vinyl monomer having a plurality of radically polymerizable unsaturated groups, for example, divinylbenzene, 1,4-divinyloxybutane, Vinyl compounds such as divinyl sulfone; diallyl phthalate and its isomers, triallyl isocyanurate and derivatives thereof, allyl compounds such as triallyl trimethate; ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, etc. (Poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate and other (poly) oxyalkylene glycol di (meth) acrylate; pentaerythritol tetra (me ) Acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, glycerol tri (meth) ) Acrylate, glycerol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, tetramethylol methane tri (meth) acrylate, tetramethylolpropane tetra (meth) acrylate, etc. (Meth) acrylic compounds; and the like. “(Meth) acrylate” means “acrylate” or “methacrylate”.

  Similarly, among the crosslinkable vinyl monomers, examples of the crosslinkable vinyl monomer having a reactive functional group other than a radically polymerizable unsaturated group include an epoxy group as a reactive functional group. , A radical polymerizable vinyl monomer having an amino group, a carboxyl group, a hydroxyl group, a thiohydroxyl group (—SH group), and the like. Specifically, hydroxyethyl (meth) acrylate, dimethylaminoethyl ( Preferable examples include (meth) acrylate, glycidyl (meth) acrylate, (meth) acrylic acid, (meth) acrylamide and the like. These crosslinkable vinyl monomers may be used alone or in combination of two or more.

  In the vinyl-based crosslinked resin particles according to the present invention, the content of the structural unit derived from the crosslinkable vinyl monomer is not particularly limited, but is 0.5% with respect to 100% by mass of the non-crosslinkable vinyl monomer. It is preferable that it is -100 mass%, More preferably, it is 3-50 mass%, More preferably, it is 5-30 mass%. If this content is 0.5% by mass or more, the strength becomes high, and a spacer effect over a long period of time can be obtained. On the other hand, when the content is 100% by mass or less, there is an advantage that control to a desired particle size is easy.

  In the vinyl-based cross-linked resin particles according to the present invention, in addition to the structural unit derived from the cross-linkable vinyl monomer, a structural unit derived from a non-cross-linkable vinyl monomer capable of radical polymerization, and other radical polymerizable units. A structural unit derived from a monomer may be contained.

  Although it does not specifically limit as said non-crosslinkable vinyl monomer, For example, styrene, p- (m-) methylstyrene, p- (m-) ethylstyrene, p- (m-) chlorostyrene, p- ( m-) styrene-based monomers such as chloromethylstyrene, styrenesulfonic acid, p- (m-) t-butoxystyrene, α-methyl-pt-amyloxystyrene, pt-amyloxystyrene; Methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylamino Ethyl (meth) acrylate, hydroxyethyl (meth) acrylate, diethylene glycol mono (meth) acrylate (Meth) acrylic acid ester monomers such as glycerol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, butanediol mono (meth) acrylate; unsaturated carboxylic acids such as (meth) acrylic acid and maleic acid Monomers; alkyl vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; vinyl ester monomers such as vinyl acetate and vinyl butyrate; (meth) acrylonitrile, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide; and the like. These may be used alone or in combination of two or more.

  Although it does not specifically limit as said other radically polymerizable monomer, For example, Polyethylene glycol components, such as monomers having hydroxy groups, such as hydroxyethyl (meth) acrylate; And the like. These may be used alone or in combination of two or more. Also, trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, pentanefluoropropyl (meth) acrylate, octafluoroamyl (meth) acrylate, heptadecafluorodecyl (meth) acrylate, perfluorobutylethyl (meth) Fluorine atom-containing (meth) acrylates such as acrylate; These may be used alone or in combination of two or more.

  In the vinyl-based crosslinked resin particles according to the present invention, the structural unit derived from the non-crosslinkable vinyl monomer and the structural unit derived from another radical polymerizable monomer are structural units derived from the crosslinkable vinyl monomer. It may be included outside the range of the content ratio.

  The number average particle diameter of the vinyl-based crosslinked resin particles according to the present invention is essential to be 50 to 300 nm, and preferably 70 to 200 nm. If the average particle size is less than 50 nm or exceeds 300 nm, it is impossible to prevent deterioration in image quality and transferability under a high temperature and high humidity environment. This is presumably because the adhesion to the toner is lowered and the spacer effect cannot be sufficiently exhibited. In this specification, the number average particle diameter of the vinyl-based cross-linked resin particles is determined by using a scanning electron microscope (SEM) “JEM-7401F” (manufactured by JEOL Ltd.) and a toner (development) of 30,000 times. In the case of the toner in the agent flow, the organic fine particles may be crushed. Therefore, the SEM photograph of the toner in the bottle is taken in with a scanner, and the SEM photograph is taken with an image processing analysis apparatus “LUZEX AP” (manufactured by Nireco). The vinyl cross-linked resin particles in the image are binarized, the horizontal ferret diameter for 100 vinyl cross-linked resin particles is calculated, and the average value is taken as the number average particle diameter. At this time, it is necessary to distinguish from inorganic particles by EDS.

Here, as a method of controlling the particle size of the vinyl-based crosslinked resin particles to a value within the above-described range,
(1) controlling the surfactant concentration in the aqueous medium;
(2) controlling the amount of polymerization initiator used;
(3) controlling the polymerization temperature;
By combining these conditions as appropriate, vinyl-based crosslinked resin particles having a desired number average particle diameter can be produced.

  Further, in the present invention, the amount of sulfur element present on the surface of the vinyl-based crosslinked resin particles is controlled to a value within a predetermined range that is relatively less than that in the past. Specifically, the vinyl-based crosslinked resin particles according to the present invention have a sulfur element ratio (hereinafter, also referred to as “surface sulfur element ratio”) measured by X-ray photoelectron spectroscopy for the crosslinked resin particles of 0.10. The surface sulfur element ratio is preferably 0.15 to 0.40 atomic%. When the surface sulfur element ratio exceeds 0.50 atomic%, there is a problem that deterioration in image quality under a high temperature and high humidity environment cannot be suppressed. This is because if too much sulfur element is present on the surface of the vinyl-based crosslinked resin particles, the adsorption of moisture to the external additive particles tends to occur in a high-temperature and high-humidity environment, resulting in a decrease in chargeability. Conceivable. In addition, if there is too much sulfur element present on the surface of the vinyl-based crosslinked resin particles, the transferability also deteriorates. This is because when the moisture adsorbs easily on the external additive particles, the liquid crosslinking force increases. This is thought to be due to the increased adhesion of the toner. On the other hand, if the surface sulfur element ratio is less than 0.10 atomic%, it is still impossible to suppress the deterioration of the image quality in a high temperature and high humidity environment. This is thought to be due to the lack of

  In addition, although the predetermined amount of sulfur atom exists in the surface of the vinyl type crosslinked resin particle concerning this invention, the presence form of this sulfur atom is not specifically limited. However, from the viewpoint of improving the chargeability, the sulfur atom present on the surface of the vinyl-based crosslinked resin particles is preferably in the form of sulfate ions (sulfate radicals) represented by the following formula.

  Further, the amount of the precipitate generated when vacuum-dried, measured by the following measuring method, is preferably 20% by mass or less, and preferably 5% by mass or less with respect to the total amount of vinyl-based crosslinked resin particles. Is more preferable.

(Measurement method of amount of sediment)
About 0.3 g of the dried vinyl-based crosslinked resin particles are weighed as a sample, put into 30 g of tetrahydrofuran, and stirred for 60 minutes. Next, the centrifuge “H-900” (manufactured by Kokusan Co., Ltd.) is centrifuged at 20000 rpm for 5 minutes. Then, after drying a deposit with a vacuum dryer, the mass is measured.

  The method for producing vinyl-based crosslinked resin particles according to the present invention includes, for example, a step of radical polymerization of a radical polymerizable monomer containing a crosslinkable vinyl monomer.

  The vinyl-based crosslinked resin particles are particles obtained by radical polymerization of a radically polymerizable monomer containing a crosslinkable vinyl monomer, and the crosslinkable vinyl monomer is as described above. Moreover, although the crosslinked resin particle can be obtained by using a crosslinkable vinyl monomer, the crosslinked form is not particularly limited, and a desired crosslinked form depends on the kind of the crosslinkable vinyl monomer to be used. It can be. For example, among other radical polymerizable unsaturated groups, there may be crosslinking by radical polymerizable unsaturated groups that did not participate in polymerization, for example, crosslinking by dehydration condensation of hydroxy groups and crosslinking by reaction of epoxy groups and amino groups, etc. And cross-linking with a functional group having the following reactivity.

  Although there is no restriction | limiting in particular about the manufacturing method of the said vinyl type crosslinked resin particle, For example, an emulsion polymerization method (a soap free is also included) is mentioned. Specifically, the emulsion polymerization method is a mixture of a medium such as water, a monomer that is hardly soluble in the medium, and an emulsifier (surfactant), and a polymerization initiator (usually a radical generator) that can be dissolved in the medium. ).

  Here, as a polymerization initiator used in the present invention, persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate are preferable from the viewpoint of charging. By producing vinyl-based crosslinked resin particles by polymerization using these polymerization initiators, the above-described sulfur atoms (sulfate radicals) in the form of sulfate ions can be present on the surface of the particles. A polymerization initiator may be used individually by 1 type, and may use 2 or more types together. The amount of the polymerization initiator used is not particularly limited, but a preferred range is 0.1 to 5% by mass, and a more preferred range is 0.3 to 3% by mass with respect to 100% by mass of the vinyl monomer. It is. However, it is necessary to keep the surface sulfur element ratio of the vinyl-based crosslinked resin particles in the above range in combination with the surfactant. For this reason, it is preferable not to control the particle size of the vinyl-based crosslinked resin particles depending on the amount of the polymerization initiator. In this case, by controlling the particle size based on the use amount of the surfactant described later, the surface sulfur element ratio can be set to a value within a predetermined range while achieving a desired particle size.

  Although it does not specifically limit as surfactant, The following ionic surfactant can be mentioned as an example of a suitable surfactant.

  Examples of the ionic surfactant include sodium dodecylbenzenesulfonate, sodium arylalkylpolyethersulfonate, sodium 3,3-disulfonediphenylurea-4,4-diazo-bis-amino-8-naphthol-6-sulfonate. Sulfonates such as o-carboxybenzene-azo-dimethylaniline, 2,2,5,5-tetramethyl-triphenylmethane-4,4-diazo-bis-β-naphthol-6-sulfonate, lauryl Sulfate esters such as sodium sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, sodium caprate, sodium caprylate, sodium caproate, potassium stearate, olei Fatty acid salts such as calcium and the like. Especially, the sulfur atom (sulfate radical) of the form of the above-mentioned sulfate ion can be made to exist in the surface of a vinyl type crosslinked resin particle by using the ionic surfactant which has the form of a sulfate ester salt.

  Nonionic surfactants can also be used. For example, polyethylene oxide, polypropylene oxide, combination of polypropylene oxide and polyethylene oxide, ester of polyethylene glycol and higher fatty acid, alkylphenol polyethylene oxide, ester of higher fatty acid and polyethylene glycol, ester of higher fatty acid and polypropylene oxide, sorbitan ester Etc. However, in the same manner as described above, it is necessary to keep the surface sulfur element ratio in the vinyl-based crosslinked resin particles within a predetermined range in combination with the polymerization initiator, and if necessary, the surface of the crosslinked resin particles by dialysis or the like The surface sulfur element ratio can be controlled by performing an operation of removing the surfactant remaining on the surface of the crosslinked resin particles. In addition, if the vinyl resin crosslinked particles have a relatively small particle size, the amount of the remaining surfactant is relatively large, so that dialysis treatment is often required.

  The amount of the vinyl-based crosslinked resin particles added is not particularly limited, but is preferably 0.05 to 3.0% by mass, more preferably 0.2 to 1.5% with respect to 100% by mass of the toner base particles. % By mass. If it is 0.05% by mass or more, the effect of addition can be sufficiently exhibited, while if it is 3.0% by mass or less, carrier contamination by excessively added vinyl-based crosslinked resin particles is suppressed. Therefore, it is preferable because a decrease in the charge amount after durability can be prevented.

  In addition to the vinyl-based crosslinked resin particles described above, other conventionally known external additive particles may be added. Examples of such external additive particles include inorganic oxide fine particles such as silica fine particles, alumina fine particles, and titania fine particles, inorganic stearate compound fine particles such as aluminum stearate fine particles and zinc stearate fine particles, or titanic acid. Examples thereof include fine particles of inorganic titanate compounds such as strontium and zinc titanate. These inorganic fine particles are preferably subjected to a gloss treatment with a silane coupling agent, a titanium coupling agent, a higher fatty acid, a silicone oil or the like in order to improve heat-resistant storage stability and environmental stability. In addition, organic fine particles other than the predetermined vinyl-based crosslinked resin particles according to the present invention may also be used in combination as external additive particles. These can be used individually by 1 type or in combination of 2 or more types.

  The addition amount of the external additive particles in the toner is not particularly limited, but is preferably 0.1 to 10.0% by mass, more preferably 1.0 to 3.0% with respect to 100% by mass of the toner. % By mass.

(Toner glass transition point)
The glass transition point (Tg) of the toner according to the present invention is preferably 25 to 65 ° C, more preferably 35 to 55 ° C. When the glass transition point of the toner of the present invention is in the above range, sufficient low-temperature fixing property and heat-resistant storage property can be obtained at the same time. The glass transition point of the toner is measured in the same manner as described above except that the toner is used as a measurement sample.

(Toner particle size)
The average particle diameter of the toner according to the present invention is preferably 3 to 8 μm, and more preferably 5 to 8 μm, for example, on a volume basis median diameter. This average particle size can be controlled by the concentration of the flocculant used during production, the amount of organic solvent added, the fusing time, the composition of the binder resin, and the like. When the volume-based median diameter is in the above range, a very small dot image of 1200 dpi level can be faithfully reproduced. The volume-based median diameter of the toner is measured and calculated using a measuring device in which a computer system equipped with data processing software “Software V3.51” is connected to “Multisizer 3” (manufactured by Beckman Coulter). It is. Specifically, 0.02 g of a measurement sample (toner) was added to 20 mL of a surfactant solution (for example, a surfactant obtained by diluting a neutral detergent containing a surfactant component 10 times with pure water for the purpose of dispersing toner particles). Solution) and ultrasonically dispersed for 1 minute to prepare a toner dispersion, and this toner dispersion is a beaker containing “ISOTON II” (manufactured by Beckman Coulter) in a sample stand. Then, inject with a pipette until the displayed concentration of the measuring device is 8%. Here, a reproducible measurement value can be obtained by setting the concentration range. In the measuring apparatus, the measurement particle count number is 25000, the aperture diameter is 100 μm, and the frequency value is calculated by dividing the range of 2 to 60 μm, which is the measurement range, into 256 parts. % Particle diameter is defined as the volume-based median diameter.

(Average circularity of toner)
In the toner according to the present invention, the individual toner particles constituting the toner preferably have an average circularity of 0.930 to 1.000 from the viewpoint of stability of charging characteristics and low-temperature fixability. More preferably, it is from 950 to 0.995. When the average circularity is within the above range, the individual toner particles are less likely to be crushed, the contamination of the frictional charge imparting member is suppressed, the toner chargeability is stabilized, and the image quality of the formed image is high. It will be a thing. The average circularity of the toner is a value measured using “FPIA-2100” (manufactured by Sysmex). Specifically, the measurement sample (toner) was blended with an aqueous solution containing a surfactant, dispersed by performing ultrasonic dispersion for 1 minute, and then subjected to measurement conditions HPF by “FPIA-2100” (manufactured by Sysmex). In the (high magnification imaging) mode, images are taken at an appropriate density of 3,000 to 10,000 HPF detections, and the circularity of each toner particle is calculated according to the following formula, and the circularity of each toner particle is added. And a value calculated by dividing by the total number of toner particles. If the number of HPF detections is in the above range, reproducibility can be obtained.

Circularity = (perimeter of a circle having the same projection area as the particle image) / (perimeter of the particle projection image)
<Toner production method>
<Method for producing toner base particles>
The toner base particles according to the present invention can be produced by an emulsion aggregation method. That is, for example, an aqueous dispersion of amorphous resin fine particles composed of a vinyl resin, an aqueous dispersion of crystalline resin fine particles composed of, for example, a hybrid resin, and an aqueous dispersion of colorant fine particles are mixed, Toner base particles having a domain matrix structure can be obtained by aggregating and then fusing the respective fine particles. The aqueous dispersion of resin fine particles is preferably prepared by multistage polymerization by a miniemulsion polymerization method.

  Further, the toner base particles having a core-shell structure can be obtained by using the toner base particles as a core and providing a shell layer on the surface thereof. By adopting a core-shell structure, heat-resistant storage properties and low-temperature fixability can be further improved. In the case of the core-shell type, it is preferable that a domain matrix structure exists in the core.

When the toner base particles according to the present invention are manufactured by the emulsion aggregation method, a production example of toner base particles containing a colorant is specifically shown.
(1) A step of preparing a dispersion of amorphous resin fine particles in an aqueous medium, that is, in the aqueous medium, amorphous resin fine particles composed of, for example, a vinyl resin are formed by polymerization, and the amorphous Step of preparing an aqueous dispersion of amorphous resin fine particles in which crystalline resin fine particles are dispersed (2) Step of preparing a dispersion of crystalline resin fine particles composed of, for example, a hybrid resin in an aqueous medium (3) Water based Step (4) of preparing a dispersion of colorant fine particles in a medium, mixing the dispersion of amorphous resin fine particles, the dispersion of crystalline resin fine particles, and the dispersion of colorant fine particles, Step of aggregating the amorphous resin fine particles, the crystalline resin fine particles, and the colorant fine particles and then fusing (5) Washing and drying the particles obtained by the agglomeration and fusing, toner base particles Can form Kill.

<Method for producing toner particles>
(External additive addition process)
The external additive adding step is a step of preparing toner particles by adding and mixing the external additive particles to the dried toner base particles. Examples of the method for adding the external additive include a dry method in which the external additive is added in powder form to the dried toner base particles. Examples of the mixing device include mechanical mixing devices such as a Henschel mixer and a coffee mill. It is done.

<Developer for developing electrostatic latent image>
The toner according to the present invention can be used as a magnetic or non-magnetic one-component developer, but may be used as a two-component developer by mixing with carrier particles. When the toner is used as a two-component developer, the carrier particles are made of a magnetic material, but the resin-coated carrier particles in which the surface of the core particles made of the magnetic material is coated with a resin, or the resin It can also be composed of resin-dispersed carrier particles in which magnetic fine powder is dispersed. The carrier particles may contain an internal additive such as a resistance adjuster as necessary. Among these, from the viewpoint of realizing good chargeability and developability, a two-component developer using resin-coated carrier particles is preferable. Therefore, in a preferred embodiment of the present invention, the static according to the present invention described above is used. There is provided a two-component developer for developing an electrostatic latent image comprising a toner for developing an electrostatic latent image and carrier particles obtained by coating the surface of core material particles with a coating resin.

The core particles constituting the carrier particles are made of various ferrites in addition to metal powders such as iron powders, for example. Among these, ferrite is preferable. As the ferrite, ferrite containing heavy metals such as copper, zinc, nickel and manganese and light metal ferrite containing alkali metals or alkaline earth metals are preferable. Ferrite is a compound represented by the formula: (MO) _x (Fe ₂ O ₃ ) _y , and the molar ratio y of Fe ₂ O ₃ constituting the ferrite is preferably 30 to 95 mol%. Ferrite having a composition ratio y in the above range is easy to obtain a desired magnetization, and thus has an advantage that carrier particles that hardly cause carrier adhesion can be produced. M in the formula is manganese (Mn), magnesium (Mg), strontium (Sr), calcium (Ca), titanium (Ti), copper (Cu), zinc (Zn), nickel (Ni), aluminum (Al) , Silicon (Si), zirconium (Zr), bismuth (Bi), cobalt (Co), lithium (Li) and the like, which can be used alone or in combination.

  By using a highly hydrophobic alicyclic methacrylate compound as a monomer for obtaining a coating resin (that is, the coating resin includes a structural unit derived from an alicyclic methacrylate compound), the carrier The amount of moisture adsorbed by the particles is reduced, the difference in charging environment is reduced, and the decrease in the charging amount is suppressed particularly in a high temperature and high humidity environment. In addition, a resin obtained by polymerizing a monomer containing an alicyclic methacrylic acid ester compound has an appropriate mechanical strength, and the surface of the carrier particles is refreshed by appropriate film abrasion as a coating material. The

  As the alicyclic methacrylic acid ester compound, those having a cycloalkyl group having 5 to 8 carbon atoms are preferable, and specific examples include cyclopentyl methacrylate, cyclohexyl methacrylate, cycloheptyl methacrylate, cyclooctyl methacrylate and the like. It is done. Of these, cyclohexyl methacrylate is particularly preferred from the viewpoint of mechanical strength and environmental stability of the charge amount.

  The average film thickness of the coating agent in the carrier particles is preferably in the range of 0.05 to 4.0 μm, more preferably in the range of 0.05 to 4.0 μm from the viewpoint of achieving both durability of the carrier particles and low electrical resistance. It is in the range of 3.0 μm. When the average film thickness of the coating material is within the above range, the chargeability and durability can be set within preferable ranges.

As for the magnetization of the carrier particles, it is preferable that the saturation magnetization is in the range of 30 to 80 Am ² / kg and the residual magnetization is 5.0 Am ² / kg or less. By using carrier particles having such magnetic properties, the carrier particles are prevented from partially agglomerating, and the two-component developer is uniformly dispersed on the surface of the developer conveying member, so that there is no unevenness in density and uniformity. Thus, a high-definition toner image can be formed.

  The volume-based median diameter of the carrier is preferably 20 to 100 μm, more preferably 25 to 80 μm. The volume-based median diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

  The “toner” according to the present invention contains “toner base particles” as described above. The “toner base particles” are referred to as “toner particles” by adding an external additive. The “toner” refers to an aggregate of “toner particles”.

<Electrophotographic image forming method>
The developer for developing an electrostatic latent image according to the present invention can be used in various known electrophotographic image forming methods. For example, it can be used in a monochrome image forming method or a full color image forming method. In the full-color image forming method, four types of color developing devices for yellow, magenta, cyan, and black, and one electrostatic latent image carrier (also referred to as “electrophotographic photosensitive member” or simply “photosensitive member”). 4 cycle type image forming method, and a color developing device for each color and an image forming unit having an electrostatic latent image carrier for each color, An image forming method can also be used.

  As an electrophotographic image forming method, specifically, using the developer for developing an electrostatic latent image according to the present invention, for example, charging on an electrostatic latent image carrier with a charging device (charging process), By developing an electrostatic latent image (exposure process) electrostatically formed by image exposure by charging toner with a carrier in the developer for developing an electrostatic latent image according to the present invention in a developing device. A toner image is obtained by developing the image (development process). Then, the toner image is transferred to a sheet (transfer process), and then the toner image transferred onto the sheet is fixed on the sheet (fixing process) by a contact heating type fixing process to obtain a visible image.

  The effects of the present invention will be described using the following examples and comparative examples. In the following examples, “parts” and “%” mean “parts by mass” and “mass%”, respectively, unless otherwise specified, and each operation is performed at room temperature (25 ° C.). In addition, this invention is not limited to an Example below.

≪Preparation of vinyl resin particles≫
(Preparation of vinyl resin particles 1)
A glass reactor equipped with a thermometer, a reflux condenser, a nitrogen gas inlet tube, and a stirrer was charged with 500 parts of deionized water and 2 parts of sodium lauryl sulfate as a surfactant, and 80 to 85 while ventilating nitrogen gas. The mixture is heated to 0 ° C., 7 parts of potassium persulfate as a polymerization initiator is added with stirring, 450 parts of styrene and 450 parts of methyl methacrylate as non-crosslinkable monomers, and a crosslinkable monomer A monomer mixture consisting of 100 parts of divinylbenzene was added dropwise over 1 hour, and stirring was continued for 1 hour. The emulsion thus obtained was dried by spray drying to obtain vinyl resin particles 1 having a number average particle diameter of 100 nm. In addition, the surface sulfur element ratio in the vinyl resin particle 1 was 0.30 atomic%. Further, the vinyl resin particles 1 did not dissolve at all in tetrahydrofuran (THF). In addition, the measurement of the surface sulfur element ratio was performed by the following method.

[Measurement method of surface sulfur element ratio]
Using an X-ray photoelectron spectroscopy analyzer “K-Alpha” (manufactured by Thermo Fisher Scientific), sulfur element, carbon element, silicon element, nitrogen element, titanium element, oxygen element, calcium element, Quantitative analysis of zinc element and sodium element was performed, and the sulfur element ratio was calculated from each atomic peak area using a relative sensitivity factor:
X-ray: Al monochromatic radiation source Acceleration: 12 kV, 6 mA
Beam system: 400 μm
Pass energy: 50eV
Step size: 0.1 eV.

(Preparation of vinyl resin particles 2)
The mass ratio of the surfactant (sodium lauryl sulfate) and the polymerization initiator (potassium persulfate) was changed as shown in Table 1 below, and the resulting emulsion was subjected to dialysis treatment, Vinyl resin particles 2 were prepared in the same manner as the adjustment of vinyl resin particles 1 described above. Here, the dialysis treatment was carried out for 3 days against deionized water while transferring the obtained emulsion to a dialysis tube (Spectra / Por dialysis membrane, MWCO 6000-8000) and exchanging water three times a day. . In addition, the surface sulfur element ratio in the vinyl resin particle 2 was 0.10 atomic%.

(Preparation of vinyl resin particles 3-11)
Except that the types and mass ratios of the non-crosslinkable monomer, the crosslinkable monomer, the surfactant and the polymerization initiator were changed as shown in Table 1 below, the same as the preparation of the vinyl resin particles 1 described above. Thus, vinyl resin particles 3 to 11 were prepared. Here, when the vinyl resin particles 6 and 7 were prepared, the dialysis treatment performed at the time of preparing the vinyl resin particles 2 was performed in the same manner. The number average particle diameter and surface sulfur element ratio of the obtained vinyl resin particles are shown in Table 1 below.

<Preparation of dispersion>
(Preparation of amorphous resin fine particle dispersion 1)
First stage polymerization A reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube and a nitrogen introduction device was charged with a solution obtained by dissolving 4 parts of polyoxyethylene (2) sodium dodecyl ether sulfate in 3000 parts of ion-exchanged water, The internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream. After raising the temperature, 10 parts of potassium persulfate dissolved in 200 parts of ion-exchanged water was added to obtain a liquid temperature of 75 ° C.
-After dropping a monomer mixture consisting of 584 parts by mass of styrene, 160 parts by mass of n-butyl acrylate, and 56 parts by mass of methacrylic acid over 1 hour, polymerization is performed while heating and stirring at 75 ° C for 2 hours. Thus, a dispersion of resin fine particles [b1] was prepared.

Second stage polymerization A reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube and a nitrogen introduction device was charged with a solution obtained by dissolving 2 parts of polyoxyethylene (2) sodium dodecyl ether sulfate in 3000 parts of ion-exchanged water, The internal temperature was raised to 80 ° C. Next, 42 parts (in terms of solid content) of the dispersion of resin fine particles [b1] obtained above and 70 parts of microcrystalline wax “HNP-0190” (manufactured by Nippon Seiwa Co., Ltd.)
・ Styrene 239 parts by mass ・ n-butyl acrylate 111 parts by mass ・ methacrylic acid 26 parts by mass ・ n-octyl mercaptan 3 parts by mass A dispersion containing emulsified particles (oil droplets) was prepared by mixing and dispersing for 1 hour using a mechanical disperser “CLEARMIX” (manufactured by M Technique Co., Ltd.).

  Next, an initiator solution in which 5 parts of potassium persulfate is dissolved in 100 parts of ion-exchanged water is added to this dispersion, and this system is heated and stirred at 80 ° C. for 1 hour to perform polymerization. A dispersion of fine particles [b2] was prepared.

Third stage polymerization A solution prepared by dissolving 10 parts of potassium persulfate in 200 parts of ion-exchanged water was added to the dispersion of resin fine particles [b2] obtained above.
-A monomer mixture consisting of 380 parts by mass of styrene, 132 parts by mass of n-butyl acrylate, 39 parts by mass of methacrylic acid, and 6 parts by mass of n-octyl mercaptan was added dropwise over 1 hour. After completion of the dropwise addition, polymerization was carried out by heating and stirring for 2 hours, and then cooled to 28 ° C. to prepare amorphous resin fine particle dispersion 1.

(Preparation of amorphous resin fine particle dispersion 2)
In a 10-liter four-necked flask equipped with a nitrogen inlet tube, a dehydrating tube, a stirrer and a thermocouple, 500 parts of bisphenol A propylene oxide 2-mol adduct, 117 parts of terephthalic acid, 82 parts of fumaric acid and an esterification catalyst ( 2 parts of tin octylate) was added, subjected to a condensation polymerization reaction at 230 ° C. for 8 hours, further reacted at 2 kPa for 2 hours, and cooled to 160 ° C. to obtain an amorphous resin made of a polyester resin.

  93 parts of the amorphous resin obtained above and 7 parts of microcrystalline wax “HNP-0190” (manufactured by Nippon Seiwa Co., Ltd.) were dissolved in 400 parts of ethyl acetate. Next, 25 parts of a 5.0% aqueous sodium hydroxide solution was added to prepare an amorphous resin solution. While stirring this amorphous resin solution into a container having a stirring device, 638 parts of a 0.26% aqueous sodium lauryl sulfate solution was added dropwise and mixed over 30 minutes. During the dropwise addition of the aqueous sodium lauryl sulfate solution, the liquid in the reaction vessel became cloudy, and after adding the entire amount of the aqueous sodium lauryl sulfate solution, an emulsion in which amorphous resin fine particles were uniformly dispersed was obtained. Next, this emulsion was heated to 40 ° C., and ethyl acetate was distilled off under reduced pressure of 150 hPa using a diaphragm vacuum pump “V-700” (manufactured by BUCHI), thereby forming an amorphous resin comprising a polyester resin. Amorphous resin fine particle dispersion 2 in which the fine resin fine particles were dispersed was obtained.

(Preparation of crystalline resin fine particle dispersion 1)
A nitrogen-introducing tube contains 220 parts of sebacic acid (molecular weight 202.25) as a polyvalent carboxylic acid compound and 298 parts of 1,12-dodecanediol (molecular weight 202.33) as a polyhydric alcohol compound. In a reaction vessel equipped with a dehydration tube, a stirrer and a thermocouple, the mixture was heated to 160 ° C. and dissolved. On the other hand, a solution of 46 parts of styrene, 12 parts of n-butyl acrylate, 4 parts of dicumyl peroxide, and 3 parts of acrylic acid as a bireactive monomer, which is a premixed vinyl polymer segment material, is added by a dropping funnel. The solution was added dropwise over 1 hour. Stirring was continued for 1 hour while maintaining the reaction system at 170 ° C., and after polymerizing styrene, n-butyl acrylate and acrylic acid, 2.5 parts of tin (II) 2-ethylhexanoate and 0.2 g of gallic acid were added. The temperature of the reaction system was raised to 210 ° C. and the reaction was carried out for 8 hours after the temperature was raised. Furthermore, reaction was performed at 8.3 kPa for 1 hour, and the crystalline resin which consists of hybrid resin was obtained.

  100 parts of the crystalline resin obtained above was dissolved in 400 parts of ethyl acetate. Next, 25 parts of 5.0% aqueous sodium hydroxide solution was added and heated to prepare an amorphous resin solution. While stirring this amorphous resin solution into a container having a stirring device, 638 parts of a 0.26% aqueous sodium lauryl sulfate solution was added dropwise and mixed over 30 minutes. During the dropwise addition of the aqueous sodium lauryl sulfate solution, the liquid in the reaction vessel became cloudy, and after adding the entire amount of the aqueous sodium lauryl sulfate solution, an emulsion in which amorphous resin fine particles were uniformly dispersed was obtained. Next, this emulsion was heated to 40 ° C., and ethyl acetate was distilled off under a reduced pressure of 150 hPa using a diaphragm vacuum pump “V-700” (manufactured by BUCHI), whereby crystallinity comprising a hybrid resin was obtained. A crystalline resin fine particle dispersion 1 in which resin fine particles are dispersed was obtained.

(Preparation of colorant fine particle dispersion [Bk])
90 parts of polyoxyethylene-2-dodecyl ether sodium sulfate was stirred and dissolved in 1510 parts of ion-exchanged water. While stirring this solution, 400 parts of carbon black “Regal 330” (Cabot Corp.) is gradually added, and then dispersed by using a stirring device “Claremix” (M Technique Corp.). A colorant fine particle dispersion [Bk] was prepared.

<< Production of toner >>
(Preparation of Toner 1)
<Aggregation / fusion process>
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe and a nitrogen introducing device, 360 parts of amorphous resin fine particle dispersion 1 (in terms of solid content), 1100 parts of ion-exchanged water, and colorant fine particle dispersion [Bk] After charging 40 parts (in terms of solid content) and adjusting the liquid temperature to 30 ° C., the pH was adjusted to 10 by adding a 5N aqueous sodium hydroxide solution. Next, an aqueous solution obtained by dissolving 60 parts of magnesium chloride in 60 parts of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. The temperature was raised after holding for 3 minutes, and the temperature of the system was raised to 85 ° C. over 60 minutes, agglomerating while maintaining 85 ° C., and the particle growth reaction was continued. In this state, the particle size of the aggregated particles was measured with “Coulter Multisizer 3” (manufactured by Beckman Coulter), and when the volume-based median diameter reached 6 μm, 40 parts of sodium chloride was added to ion-exchanged water 160 The aqueous solution dissolved in the part is added to stop the particle growth, and further, as a ripening step, the mixture is heated and stirred at a liquid temperature of 80 ° C. for 1 hour to promote fusion between the particles. A dispersion was prepared.

<Washing and drying process>
The dispersion of toner base particles 1 prepared as described above was subjected to solid-liquid separation with a basket-type centrifuge “MARK III model number 60 × 40 + M” (manufactured by Matsumoto Kikai Co., Ltd.) to form a wet cake of toner base particles. The wet cake was washed with ion exchange water at 40 ° C. using the basket type centrifuge until the electric conductivity of the filtrate reached 5 μS / cm, and then the “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.). The toner base particles 1 were prepared by transferring and drying until the water content became 0.5%.

<External additive addition process>
To 100 parts of toner base particle 1, 1 part of hydrophobic silica (volume-based median diameter = 12 nm), 0.3 part of hydrophobic titania (volume-based median diameter = 20 nm) and 1 part of vinyl resin particle 1 are added. Toner 1 was prepared by mixing with a Henschel mixer.

(Preparation of Toner 2)
Toner 2 was prepared in the same manner as toner 1 described above except that vinyl resin particles 2 were used instead of vinyl resin particles 1.

(Preparation of Toner 3)
A toner 3 was prepared in the same manner as the preparation of the toner 1 except that the vinyl resin particles 4 were used instead of the vinyl resin particles 1.

(Preparation of Toner 4)
A toner 4 was prepared in the same manner as the toner 1 described above except that the vinyl resin particles 6 were used instead of the vinyl resin particles 1.

(Preparation of Toner 5)
A toner 5 was produced in the same manner as in the production of the toner 1 except that the vinyl resin particles 8 were used in place of the vinyl resin particles 1.

(Production of Toner 6)
A toner 6 was prepared in the same manner as the toner 1 described above except that the vinyl resin particles 10 were used instead of the vinyl resin particles 1.

(Preparation of Toner 7)
A toner 7 was prepared in the same manner as the toner 1 described above except that the amorphous resin fine particle dispersion 2 was used instead of the amorphous resin fine particle dispersion 1. (Preparation of toner 8)
Preparation of the toner 1 described above, except that 300 parts of the amorphous resin fine particle dispersion 1 (in terms of solid content) and 60 parts of the crystalline resin fine particle dispersion 1 were used instead of the amorphous resin fine particle dispersion 1. In the same manner, Toner 8 was produced.

(Preparation of Toner 9)
A toner 9 was produced in the same manner as in the production of the toner 1 except that the vinyl resin particles 3 were used instead of the vinyl resin particles 1.

(Production of Toner 10)
A toner 10 was prepared in the same manner as the toner 1 described above except that the vinyl resin particles 5 were used in place of the vinyl resin particles 1.

(Production of Toner 11)
A toner 11 was produced in the same manner as in the production of the toner 1 except that the vinyl resin particles 7 were used instead of the vinyl resin particles 1.

(Preparation of Toner 12)
A toner 12 was produced in the same manner as in the production of the toner 1 except that the vinyl resin particles 9 were used instead of the vinyl resin particles 1.

(Preparation of Toner 13)
A toner 13 was produced in the same manner as in the production of the toner 1 except that the vinyl resin particles 11 were used instead of the vinyl resin particles 1.

(Preparation of Toner 14)
Toner 14 was prepared in the same manner as toner 1 described above except that sol-gel silica (HMDS treatment, degree of hydrophobicity 72%, number average particle size 100 nm) was used instead of vinyl resin particles 1.

≪Creation of carrier≫
(Preparation of carrier 1)
MnO: 35 mol%, MgO: 14.5 _mol%, Fe ₂ O 3: 50 mol% and SrO: materials were weighed to 0.5 mole%, was mixed with water, with a wet media mill A slurry was obtained by grinding for 5 hours.

  The obtained slurry was dried with a spray dryer to obtain true spherical particles. After adjusting the particle size, the particles were heated at 950 ° C. for 2 hours to be pre-baked. After pulverizing with a wet ball mill for 1 hour using a stainless steel bead having a diameter of 0.3 cm, further pulverizing for 4 hours using a zirconia bead having a diameter of 0.5 cm. Polyvinyl alcohol (PVA) as a binder is added in an amount of 0.8% by mass based on 100% by mass of solid content, then granulated and dried by a spray dryer, and held in an electric furnace at a temperature of 1350 ° C. for 5 hours, followed by main firing. Went.

  Thereafter, the mixture was crushed, further classified to adjust the particle size, and then the low magnetic product was separated by magnetic separation, whereby carrier core particles 1 were obtained. The average particle diameter of the carrier core material particles 1 was 60 μm.

(Preparation of core coating resin 1)
To a 0.3% by mass sodium benzenesulfonate aqueous solution, cyclohexyl methacrylate and methyl methacrylate were added at a “mass ratio = 50: 50” (copolymerization ratio), and the total amount of the monomers was 0.1%. An amount of potassium persulfate corresponding to 5% by mass was added to carry out emulsion polymerization, followed by spray-drying to prepare a core material coating resin 1. The obtained core coating resin 1 had a weight average molecular weight of 500,000.

(Preparation of carrier 1)
100 parts by mass of the carrier core material particles 1 obtained above as core material particles and 4.5 parts by mass of the core material coating resin 1 prepared above were charged into a high-speed agitation mixer equipped with horizontal agitating blades. After mixing and stirring at 22 ° C. for 15 minutes under the condition that the peripheral speed of the rotor blade is 8 m / sec, the mixture is mixed at 120 ° C. for 50 minutes and applied to the surface of the core particles by the action of mechanical impact force (mechanochemical method). A carrier 1 was prepared by coating a coating resin.

(Production of carrier 2)
A carrier 2 was produced in the same manner as the carrier 1 described above except that styrene was used instead of cyclohexyl methacrylate as the monomer for producing the core coating resin.

≪Preparation of two-component developer≫
Any of the toners 1 to 14 prepared above and any of the carriers 1 to 2 prepared above are combined as shown in Table 2 below, and mixed so that the toner concentration is 6% by mass. Developers 1 to 15 were prepared. A V-type mixer was used for mixing the carrier and the toner, and the mixing time was 30 minutes.

≪Evaluation of two-component developer≫
A commercially available copier “bizhub c 454” (manufactured by Konica Minolta Co., Ltd.) was prepared as a two-component developer evaluation apparatus, and the two-component developer prepared above was sequentially loaded, and the following evaluation was performed. Each evaluation was performed using a new developer.

(Evaluation of image quality)
In a printing environment of high temperature and high humidity (30 ° C./80% RH), a gradation pattern having a gradation ratio of 32 steps was output, and the granularity of the gradation pattern was evaluated according to the following evaluation criteria. Here, the granularity of the gradation pattern is evaluated by performing a Fourier transform process in consideration of MTF (Modulation Transfer Function) correction on the reading value of the gradation pattern by the CCD, and obtaining a GI value (Graininess) that matches the human's relative visibility. Index) was measured to determine the maximum GI value. The GI value is a value published in Journal of the Imaging Society of Japan 39 (2), 84/93 (2000). Moreover, it means that evaluation is so favorable that the maximum GI value is small, and here, the maximum GI value was set to 0.20 or less. The results are shown in Table 3 below.

(Evaluation of transferability)
In a printing environment of high temperature and high humidity (30 ° C., 80% RH), the maximum image density was measured after 20000 copies of 2% character charts were copied. Here, the maximum image density is measured by printing a solid image on high-quality paper (65 g / m ² ) of A4 size, and using a densitometer “RD-918” (manufactured by Macbeth Co., Ltd.), with the blank paper density as a reference. This was done by measuring the relative reflection density. Here, the highest image density value is set to 1.2 or more. The results are shown in Table 3 below.

  From the results shown in Table 3, it can be seen that with the developer using the toner according to the present invention, deterioration of image quality and transferability under high temperature and high humidity environment are suppressed, and stable image formation is possible.

Claims (6)

Toner base particles containing an amorphous resin;
External additive particles;
An electrostatic latent image developing toner comprising:
The external additive particles include vinyl-based crosslinked resin particles having a number average particle diameter of 50 to 300 nm,
A toner for developing an electrostatic latent image, wherein a sulfur element ratio in the vinyl-based crosslinked resin particles measured by X-ray photoelectron spectroscopy is 0.10 to 0.50 atomic%.   The electrostatic latent image developing toner according to claim 1, wherein the amorphous resin includes a vinyl resin. The electrostatic latent image developing toner according to claim 1, wherein a sulfur atom in the form of a sulfate ion represented by the following formula is present on the surface of the vinyl-based crosslinked resin particles:
  The electrostatic latent image developing toner according to claim 1, which has a domain matrix structure in which a domain phase containing a crystalline resin is dispersed in a matrix phase containing the amorphous resin. The electrostatic latent image developing toner according to any one of claims 1 to 4,
Carrier particles formed by coating the core particle surface with a coating resin;
A two-component developer for developing an electrostatic latent image.   The two-component developer for developing an electrostatic latent image according to claim 5, wherein the coating resin contains a structural unit derived from an alicyclic methacrylate ester compound.