JP2002244340A - Electrostatic latent image developing toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic latent image developing toner having high print density and high resolution in various environments, particularly at high temperature and high humidity and capable of providing a fog-free image even after the increase of the number of prints. SOLUTION: The electrostatic latent image developing toner contains colored particles and an external additive and this additive is fine silica particles (A) made hydrophobic by treatment with a cyclic silazane or the cyclic silazane and a silane coupling agent and having 5-30 nm number average particle diameter of primary particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image developing toner for developing an electrostatic latent image formed by an electrophotographic method, an electrostatic recording method, or the like. The present invention relates to a toner for developing an electrostatic latent image which does not cause a reduction in print density and no fogging.

[0002]

2. Description of the Related Art Conventionally, an electrostatic latent image formed in an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus is first developed with toner, and then the formed toner image is used as required. After being transferred onto a transfer material such as paper, it is fixed by various methods such as heating, pressing, and solvent vapor.
As a toner, generally, a colorant, a charge control agent, a release agent, and the like are melt-mixed and uniformly dispersed in a thermoplastic resin serving as a binder resin component to form a composition, and then the composition is pulverized. ,
A pulverized toner that obtains colored particles by classification, a colorant, a charge control agent, and a release agent are dissolved or dispersed in a polymerizable monomer that is a binder resin raw material, and after adding a polymerization initiator,
Suspension polymerized toner obtained by suspending in an aqueous dispersion medium containing a dispersion stabilizer, heating to a predetermined temperature to initiate polymerization, and filtering, washing, dehydrating and drying after polymerization to obtain colored particles, emulsification Particles of a binder resin containing a polar group obtained by polymerization, and particles containing a colorant and a charge control agent are stirred at a temperature higher than the glass transition temperature of the binder resin to associate the particles. Emulsion polymerization toners that obtain colored particles by filtration, drying and drying are used.

In recent years, there has been a growing demand for higher image quality, such as higher image quality, and stable image quality even in poor environments such as high temperature, high humidity, and low temperature, low humidity. ing. In response to such demands, it has been proposed to design binder resins and to include functional components such as charge control agents and release agents.
There is also a proposal to improve the image quality of the toner by adding an external additive such as organic or inorganic fine particles to the obtained colored particles.
Among the above-mentioned inorganic fine particles, silica fine particles, particularly silica fine particles whose particle surfaces have been subjected to a hydrophobic treatment, are widely used from the viewpoint of cost and effects on toner physical properties.

For example, Japanese Patent Application Laid-Open No. Sho 46-5782 discloses
Has an organic group having 1 to 3 carbon atoms (specifically,
Silica fine particles (treated with tildichlorosilane, etc.)
JP-A-55-120041 discloses that trimethylsilo is used.
Silica fine particles treated with a xyl group are disclosed in
Japanese Patent No. 32,575 discloses that a saturated metal having 5 or more carbon atoms is used.
Or unsaturated aliphatic organic groups or at least one hydrocarbon
Having an organic group having an elementary ring and having 8 or more carbon atoms (component
Physically, it was treated with dihexyldichlorosilane etc.)
Silica fine particles are disclosed in JP-A-4-231318.
Treated with fluorine-containing silane coupling agent (specific
Typically, CHF₂-CF₂-O- (CH) ₂-Si-
(OCH₃)₃Etc.) Silica fine particles are disclosed. I
However, these silica fine particles are added to the toner as an external additive.
Even if it is added by adding, there is a lot of fog, especially printing under high temperature and high humidity
If the number of images increases, sufficient images cannot be obtained
Was.

On the other hand, JP-A-59-45457 discloses that after treatment with a silane coupling agent (specifically, γ-aminopropyltriethoxysilane), a silicone oil (specifically, dimethyl silicone) is added. Oil) treated with silica fine particles described in JP-A-61-2779.
No. 64 discloses a hydrophobicity of 90% treated with a silicone oil (specifically, dimethyl silicone oil or the like).
The above silica fine particles are disclosed. However,
Although a certain improvement effect on fog can be seen, as the number of printed sheets increases, the effect of suppressing the occurrence of fog decreases, and the image quality deteriorates.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a toner which is free from fog and can provide a high print density image in various environments, especially under high temperature and high humidity. Is to do.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve this object, and as a result, they have a particle size in a specific range, and are hydrophobized with a cyclic silazane or a cyclic silazane and a silane coupling agent. It has been found that the above object can be achieved by incorporating the treated silica fine particles into an external additive, and the present invention has been completed based on this finding.

Thus, according to the present invention, there is provided (1) colored particles and an external additive, wherein the external additive has a number average particle diameter of primary particles of 5 to 30 nm, and comprises a cyclic silazane or a cyclic silazane. An electrostatic latent image developing toner containing silica fine particles (A) hydrophobized with a silane coupling agent; (2) containing colored particles and an external additive, wherein the external additive is a primary particle (A) having a number average particle diameter of 5 to 30 nm, and having been subjected to a hydrophobic treatment with a cyclic silazane or a cyclic silazane and a silane coupling agent (A); A toner for developing an electrostatic latent image, comprising: (3) colored particles and an external additive, wherein the external additive has a number average particle diameter of primary particles of 5 to 30 nm, and a cyclic silazane. Or cyclic silazane and silane coupling agent Toner for developing an electrostatic latent image, which contains silica fine particles (A) hydrophobized with an agent and conductive metal oxide particles (D) having a number average primary particle diameter of 0.1 to 1 μm. (4) silica containing colored particles and an external additive, wherein the external additive has a number average particle diameter of primary particles of 5 to 30 nm and is subjected to a hydrophobizing treatment with a cyclic silazane or a cyclic silazane and a silane coupling agent; Fine particles (A), silica fine particles (B) having a number average primary particle size of 30 to 100 nm, and conductive metal oxide particles (D) having a number average primary particle size of 0.1 to 1 μm. (5) A toner as described in (1) to (4) is adhered to the surface of the photoreceptor on which the electrostatic latent image has been recorded to form a visible image. An image forming method for transferring to a transfer material.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The toner for developing an electrostatic latent image of the present invention contains colored particles and an external additive. The colored particles used in the present invention contain a colorant and a binder resin.

As the binder resin, resins that have been widely used in toners are used. For example, polystyrene, poly p-chlorostyrene, a polymer of styrene such as polyvinyltoluene and a substituted product thereof; styrene-p-
Chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-acryl Butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate Copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer Coalescence, styrene-acryloni Styrene copolymers such as ril-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, Polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin,
Examples thereof include phenol resins, aliphatic or alicyclic hydrocarbon resins, and aromatic petroleum resins, which can be used alone or in combination.

As the colorant contained in the colored particles, any pigment and / or dye other than carbon black and titanium white can be used. As the black carbon black, those having a primary particle size of 20 to 40 nm are suitably used. If it is less than 20 nm, dispersion of carbon black cannot be obtained, and the toner may have a high fog. On the other hand, if it is larger than 40 nm, the amount of the polyvalent aromatic hydrocarbon compound becomes large, and an environmental safety problem may occur.

When a full-color toner is obtained, a yellow colorant, a magenta colorant and a cyan colorant are usually used. Compounds such as azo pigments and condensed polycyclic pigments are used as the yellow colorant. Specifically, C.I. I. Pigment Yellow 3, 12, 13, 14, 15, 17,
62, 65, 73, 83, 90, 93, 97, 120,
138, 155, 180 and 181.
As the magenta colorant, compounds such as azo pigments and condensed polycyclic pigments are used. Specifically, C.I. I. Pigment Red 48, 57, 58, 60, 63, 64, 68,
81, 83, 87, 88, 89, 90, 112, 11
4, 122, 123, 144, 146, 149, 16
3, 170, 184, 185, 187, 202, 20
6, 207, 209, 251, C.I. I. Pigment Violet 19 and the like. As the cyan colorant,
Copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds and the like can be used. Specifically, C.I. I. Pigment Blue 2, 3, 6, 15, 15: 1, 15: 2, 1
5: 3, 15: 4, 16, 17, and 60, and the like. The amount of the colorant used is 1 to 10 parts by weight based on 100 parts by weight of the binder resin or the polymerizable monomer.

The coloring particles may contain a releasing agent, a charge controlling agent, and the like in order to improve the performance of the toner. As the release agent, for example, low molecular weight polyethylene,
Low molecular weight polypropylene, low molecular weight polyolefin wax such as low molecular weight polybutylene, low molecular weight oxidized polypropylene with low molecular weight, low molecular weight terminal modified polypropylene with molecular terminal substituted by epoxy group, block polymer of these and low molecular weight polyethylene, low molecular weight oxidized low molecular weight End-modified polyolefin waxes such as polyethylene, low molecular weight polyethylene having a molecular terminal substituted by an epoxy group and block polymers of these and low molecular weight polypropylene; natural plant waxes such as candelilla, carnauba, rice, wood wax, jojoba; paraffin, micron Petroleum waxes such as crystallin and petrolactam and modified waxes; mineral waxes such as montan, ceresin, ozokerite, etc .; Fischer-Tropsch wax and the like Forming waxes; pentaerythritol myristate, pentaerythritol monopalmitate, such as a polyfunctional ester compounds such as dipentaerythritol hexa myristate and the like. These can be used alone or in combination of two or more.

Among these, synthetic waxes (particularly Fischer-Tropsch wax), terminal-modified polyolefin waxes, petroleum waxes, and polyfunctional ester compounds are preferred. Among the polyfunctional ester compounds, in a DSC curve measured by a differential scanning calorimeter, the endothermic peak temperature at the time of temperature rise is 30 to 200 ° C, preferably 40 to 200 ° C.
Polyester compounds such as pentaerythritol ester having a temperature in the range of 160 ° C., more preferably in the range of 50 to 120 ° C., and dipentaerythritol ester having the endothermic peak temperature in the range of 50 to 80 ° C., are fixed and peeled as toner. It is particularly preferable from the viewpoint of the balance of properties. Among them, it has a molecular weight of 1,000 or more, dissolves at least 5 parts by weight at 25 ° C with respect to 100 parts by weight of styrene, and has an acid value of 10 mg / KO.
Those having H or less are more preferable because they have a remarkable effect on lowering the fixing temperature. The endothermic peak temperature is ASTM D3418.
This is the value measured by -82. The release agent is used in an amount of usually 0.5 to 50 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the binder resin or the polymerizable monomer used to obtain the binder resin.

As the charge control agent, various charge control agents can be used. For example, Bontron N01 (manufactured by Orient Chemical), Nigrosine Base EX (manufactured by Orient Chemical), Spiron Black TRH (manufactured by Hodogaya Chemical), T-77 (manufactured by Hodogaya Chemical), Bontron S-
34 (manufactured by Orient Chemical), Bontron E-81 (manufactured by Orient Chemical), Bontron E-84 (manufactured by Orient Chemical), Bontron E-89 (manufactured by Orient Chemical), Bontron F-21 (manufactured by Orient Chemical) ), C
OPY CHRGE NX (Clariant), CO
PY CHRGENEG (Clariant), TN
Charge control agents such as S-4-1 (manufactured by Hodogaya Chemical Co., Ltd.), TNS-4-2 (manufactured by Hodogaya Chemical Co., Ltd.), LR-147 (manufactured by Nippon Carlit Co., Ltd.), JP-A-11-15192,
JP-A-3-175456, JP-A-3-24395
4, quaternary ammonium (salt) group-containing copolymers described in JP-A-3-243954, JP-A-3-242954, and the like.
A charge control agent (charge control resin) such as a sulfonic acid (salt) group-containing copolymer described in JP-A-17464 and JP-A-3-15858 can be used. Among these, it is preferable to use a charge control agent that can be controlled to have positive chargeability. The resin is preferable because it has high compatibility with the binder resin, is colorless, and can provide a toner having stable chargeability even in high-speed color continuous printing. The charge control agent is used in an amount of usually 0.01 to 20 parts by weight, preferably 0.1 to 1 part by weight, per 100 parts by weight of the binder resin or the polymerizable monomer.
It is used in a proportion of 0 parts by weight.

[0016] The colored particles may contain a magnetic material. The materials used in this case are magnetite, γ
Iron oxides such as iron oxides, ferrites, and iron-rich ferrites; metals such as iron, cobalt, and nickel, or aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth,
Cadmium, calcium, manganese, selenium, titanium,
Alloys with metals such as tungsten and vanadium, and mixtures thereof, and the like can be given.

The particle diameter of the colored particles is defined as a volume average particle diameter (dv)
Is 3 to 12 μm, preferably 4 to 10 μm, and the ratio (dv / dn) of the volume average particle diameter to the number average particle diameter (dn) is desirably in the range of 1 to 1.3.

The colored particles may be so-called core-shell type (also called capsule type) particles obtained by combining two different polymers inside (core layer) and outside (shell layer) of the particles. In the core-shell type particles, the balance between the lowering of the fixing temperature and the prevention of aggregation during storage can be achieved by encapsulating the material having a lower softening point inside (core layer) with a material having a higher softening point. It is preferred. The colored particles having a core-shell structure may be obtained by a pulverization method, or may be obtained by a polymerization method, an association method, or a phase inversion emulsification method.

In the case of core-shell type particles, the volume average particle diameter of the core particles is not particularly limited, but is usually 2 to 10 μm, preferably 2 to 9 μm, more preferably 3 to 8 μm. In addition, volume average particle diameter (dv) / number average particle diameter (d
Although p) is not particularly limited, it is usually 1.7 or less, preferably 1.5 or less, more preferably 1.3 or less.

The weight ratio between the core layer and the shell layer of the core-shell type particles is not particularly limited, but is usually 80/20 to 9/9.
Used at 9.9 / 0.1. When the ratio of the shell layer is smaller than the above ratio, the storage stability is deteriorated. On the other hand, when the ratio is larger than the above ratio, fixing at a low temperature may be difficult.

The average thickness of the shell layer of the core-shell type particles is usually 0.001 to 1.0 μm, preferably 0.001 to 1.0 μm.
3 to 0.5 μm, more preferably 0.005 to 0.2 μm
m. When the thickness is large, the fixability is reduced, and when the thickness is small, the storability may be reduced. Note that the core particles forming the core-shell type colored particles need not be entirely covered with the shell layer, and may be such that only a part of the surface of the core particles is covered with the shell layer. When the core particle diameter of the core-shell type particles and the thickness of the shell layer can be observed by an electron microscope, it can be measured by directly measuring the size and the shell thickness of the particles randomly selected from the observation photograph, When it is difficult to observe the core layer and the shell layer with a microscope, it can be calculated from the particle size of the core particles and the amount of the monomer forming the shell layer used in the production of the colored particles.

The colored particles used in the present invention are not limited by the production method. For example, in a thermoplastic resin serving as a binder resin component, after a colorant, a charge control agent, a release agent, and the like are melt-mixed and uniformly dispersed to form a composition, the composition is pulverized and classified. Crushing method to obtain colored particles by
Dissolve or disperse the colorant, charge control agent, release agent, etc. in the polymerizable monomer which is the binder resin raw material, add the polymerization initiator, and suspend in the aqueous dispersion medium containing the dispersion stabilizer. Then, the polymerization is started by heating to a predetermined temperature, and after the polymerization is completed, filtration, washing, dehydration, a polymerization method of obtaining colored particles by drying, particles of a binder resin obtained by emulsion polymerization or suspension polymerization, An association method of obtaining colored particles by filtering and drying particles obtained by stirring and associating particles containing a colorant and a charge controlling agent at a temperature higher than the glass transition temperature of the binder resin, and hydrophilicity. A group-containing resin is used as a binder resin, and after adding a coloring agent or the like thereto and dissolving it in an organic solvent, the resin is neutralized and phase-inverted, and then dried by phase-inversion emulsification to obtain colored particles. It can be manufactured, but the image quality with good dot reproducibility From the viewpoint of obtaining an electrostatic latent image developing toner to obtain, it is preferable to use an electrostatic latent image developing toner obtained by a polymerization method.

When the colored particles contained in the toner for developing an electrostatic latent image of the present invention are produced by a polymerization method, a known suspension polymerization method, emulsion polymerization method, dispersion polymerization method and the like can be applied. Among these, a suspension polymerization method that can uniformly incorporate a colorant, a release agent, and the like into particles without using an emulsifier that affects control of chargeability, and can obtain a target particle size in one step. preferable. Hereinafter, a method for producing colored particles will be described using a suspension polymerization method as an example.

The colored particles used in the present invention are obtained by suspending a monomer composition obtained by adding at least a polymerizable monomer and a coloring agent to a dispersion medium containing a dispersion stabilizer. Thereafter, it can be produced by polymerization.

As a preferred polymerizable monomer used for producing the binder resin contained in the colored particles, a monovinyl monomer can be used. Specifically, aromatic vinyl monomers such as styrene, vinyltoluene and α-methylstyrene; acrylic acid, methacrylic acid; methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, Cyclohexyl acrylate, isobonyl acrylate, cyclohexyl methacrylate, isobonyl methacrylate, dimethylaminoethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, dimethylaminoethyl methacrylate, Derivatives of acrylic acid or methacrylic acid such as acrylamide and methacrylamide; monoolefin monomers such as ethylene, propylene and butylene; vinyl esters such as vinyl acetate and vinyl propionate Vinyl methyl ether, vinyl ethers such as vinyl ethyl ether, vinyl methyl ketone, vinyl ketones such as methyl isopropenyl ketone; 2-vinylpyridine,
Monovinyl monomers such as nitrogen-containing vinyl compounds such as 4-vinylpyridine and N-vinylpyrrolidone; The monovinyl monomer may be used alone, or a plurality of monomers may be used in combination. Of these monovinyl monomers, an aromatic vinyl monomer, or a combination of an aromatic vinyl monomer and a derivative of acrylic acid or methacrylic acid is preferably used.

In producing a binder resin, the use of a crosslinkable compound such as a crosslinkable monomer or a crosslinkable polymer together with a polymerizable monomer is effective for improving hot offset.
The crosslinkable monomer is a monomer having two or more polymerizable carbon-carbon unsaturated double bonds. Specifically, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene and derivatives thereof; diethylenically unsaturated carboxylic esters such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; N, N-divinylaniline, divinyl ether and the like And other divinyl compounds having two vinyl groups; pentaerythritol triallyl ether, trimethylolpropane triacrylate, and other compounds having three or more vinyl groups. The crosslinkable polymer is a polymer having two or more vinyl groups in the polymer, and specifically, a polymer having two or more hydroxyl groups in a molecule (a hydroxyl group-containing polyethylene, a hydroxyl group-containing polypropylene, Polyethylene glycol, polypropylene glycol, etc.)
And an ethylenically unsaturated carboxylic acid (eg, acrylic acid or methacrylic acid). These crosslinkable monomers and crosslinkable polymers can be used alone or in combination of two or more. The amount used is usually 10 parts by weight or less, preferably 0.1 to 2 parts by weight, per 100 parts by weight of the polymerizable monomer. Such a polymerizable monomer or a crosslinkable compound is polymerized to form a binder resin.

Examples of the dispersion stabilizer include sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate and magnesium carbonate; phosphates such as calcium phosphate; and metal oxides such as aluminum oxide and titanium oxide. Products; metal compounds such as aluminum hydroxide, magnesium hydroxide, and ferric hydroxide; water-soluble polymers such as polyvinyl alcohol, methyl cellulose, and gelatin; anionic surfactants and nonionic surfactants Agents, amphoteric surfactants and the like. Among these, the dispersion stabilizer containing a metal compound, particularly a colloid of a poorly water-soluble metal hydroxide, can narrow the particle size distribution of the polymer particles, and the residual amount of the dispersion stabilizer after washing. This is preferable since the influence on the image is small.

The dispersion stabilizer containing a colloid of a poorly water-soluble metal hydroxide is not limited by its production method, but the poorly water-soluble polyhydric metal compound obtained by adjusting the pH of an aqueous solution of a polyvalent metal compound to 7 or more can be used. Metal hydroxide colloid,
In particular, it is preferable to use a colloid of a poorly water-soluble metal hydroxide formed by a reaction of a water-soluble polyvalent metal compound and an alkali metal hydroxide in an aqueous phase. The reaction ratio between the water-soluble polyvalent metal salt and the alkali metal hydroxide is such that the chemical equivalent ratio A of the alkali metal hydroxide to the water-soluble polyvalent metal salt is in the range of 0.4 ≦ A ≦ 1.0.

The colloid of the poorly water-soluble metal compound has a number particle size distribution D50 (50% cumulative value of the number particle size distribution) of 0.5.
It is preferable that D90 (90% cumulative value of the number particle size distribution) be 1 μm or less. When the particle size of the colloid is large, the stability of polymerization is lost, and the storage stability of the toner is reduced.

The dispersion stabilizer is usually used in a proportion of 0.1 to 20 parts by weight based on 100 parts by weight of the polymerizable monomer. If this ratio is too low, agglomerates of polymer particles are likely to be formed, while if this ratio is too high, the distribution of toner particle diameters becomes wide, so that classification is required and the yield decreases. I do.

Examples of the polymerization initiator that can be used in the polymerization include persulfates such as potassium persulfate and ammonium persulfate;
4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis-2-methyl-N-1,1′-bis (hydroxymethyl ) -2-Hydroxyethylpropioamide, 2,
2′-azobis (2,4-dimethylvaleronitrile),
Azo compounds such as 2,2'-azobisisobutyronitrile and 1,1'-azobis (1-cyclohexanecarbonitrile); methyl ethyl ketone peroxide, di-t-butyl peroxide, acetylacetone peroxide, dicumyl peroxide , Lauroyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperbutyl neodecanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxypiate Valate, t-hexylperoxypivalate, di-isopropylperoxydicarbonate, bis (t-butylperoxy) isophthalate, 1,1 ′, 3,3′-tetramethylbutylperoxy-2-ethylhexano Peracids such as ate and t-butylperoxyisobutyrate And the like. Further, a redox initiator obtained by combining these polymerization initiators and a reducing agent can be exemplified.

Among these, it is particularly preferable to select an oil-soluble polymerization initiator soluble in the polymerizable monomer to be used, and if necessary, a water-soluble polymerization initiator can be used in combination therewith. . The polymerization initiator comprises a polymerizable monomer 10
0.1 to 20 parts by weight, preferably 0.3 to 15 parts by weight, more preferably 0.5 to 10 parts by weight, based on 0 parts by weight.

Upon polymerization, a molecular weight modifier and the like may be further added. Examples of the molecular weight modifier include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, and n-octyl mercaptan;
Halogenated hydrocarbons such as carbon tetrachloride and carbon tetrabromide; and the like. These molecular weight regulators can be added before the start of polymerization or during the polymerization.
The molecular weight modifier is usually added to 100 parts by weight of the monomer.
It is used in a proportion of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight.

For the purpose of, for example, uniformly dispersing the colorant in the binder resin, a lubricant such as oleic acid or stearic acid; a dispersing aid such as a silane-based or titanium-based coupling agent; Good. Such a lubricant or dispersant is generally used at a ratio of about 1/1000 to 1/1 based on the weight of the colorant.

Methods for producing core-shell type colored particles include spray drying, interfacial reaction, and in situ method.
A method such as a u polymerization method and a phase separation method can be employed. In particular, an in situ polymerization method or a phase separation method is preferable from the viewpoint of production efficiency.

A method for producing core-shell type colored particles by an in situ polymerization method will be described below. In an aqueous dispersion medium containing a dispersion stabilizer, a polymerizable monomer composition (core monomer composition) containing at least a polymerizable monomer (core polymerizable monomer) and a colorant is prepared. By suspending and polymerizing using a polymerization initiator, core particles are produced. Further, a polymerizable monomer (monomer for shell) for forming a shell and a polymerization initiator are added, and polymerization is performed. Can be manufactured. The core particles can be obtained in the same manner as the toner obtained by the above-mentioned suspension polymerization method.

As the core monomer, the same as the above-mentioned polymerizable monomers can be exemplified. Among them, the glass transition temperature is usually 0 to 80 ° C, preferably 40 to 60 ° C.
Those which can form a polymer at ℃ are suitable as the core monomer. If the glass transition temperature is too high, the fixing temperature increases, and if the glass transition temperature is too low, the storage stability decreases. Usually, the core monomer is often used alone or in combination of two or more.

The monomer for shell desirably provides a polymer having a glass transition temperature higher than the glass transition temperature of the polymer constituting the core particles. As monomers constituting the shell monomer, styrene, acrylonitrile, methyl methacrylate and the like have a glass transition temperature of 8
Monomers that form polymers having a temperature exceeding 0 ° C. can be used alone or in combination of two or more.

The glass transition temperature of the polymer obtained from the monomer for shell needs to be set at least higher than the glass transition temperature of the polymer obtained from the monomer for core particles. The glass transition temperature of the polymer obtained from the monomer for shell is usually 50 to 130 ° C., preferably 60 to 120 ° C. in order to improve the storage stability of the polymerized toner.
° C, more preferably 80 to 110 ° C. The difference in glass transition temperature between the polymer obtained from the monomer for core particles and the polymer obtained from the monomer for shell is usually 10 ° C. or higher, preferably 20 ° C. or higher, more preferably 30 ° C. or higher. It is.

As a method for forming the shell layer, a method in which a monomer for shell is added to the reaction system of the polymerization reaction for obtaining the core particles to continuously polymerize, or a method obtained by another reaction system is used. A method in which core particles are charged, a monomer for shell is added thereto, and polymerization is carried out stepwise can be exemplified.
The shell monomer can be added at once to the reaction system, or can be added continuously or intermittently using a pump such as a plunger pump.

When the shell monomer is added, it is preferable to add a water-soluble radical initiator in order to easily obtain core-shell type colored particles. When the water-soluble radical initiator is added during the addition of the shell monomer, the water-soluble radical initiator enters near the outer surface of the core particle to which the shell monomer has migrated, and the polymer ( It is considered that this is because a shell is easily formed.

Examples of the water-soluble radical initiator include persulfates such as potassium persulfate and ammonium persulfate;
Azobis (4-cyanovaleric acid), 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis-2-methyl-N-1,1′-bis (hydroxymethyl) -2 Azo initiators such as -hydroxyethylpropioamide; and the like. The amount of the water-soluble radical initiator is usually 0.001 to 1% by weight based on the aqueous medium.

The external additive used in the present invention has a number average particle diameter of primary particles of 5 to 30 nm, and is composed of cyclic silazane or silica fine particles (A) which has been subjected to a hydrophobic treatment with a cyclic silazane and a silane coupling agent. contains.

Cyclic silazane or silica fine particles hydrophobically treated with a cyclic silazane and a silane coupling agent (A)
The number average particle size of the primary particles is preferably 5 to 25 n.
m, more preferably 5 to 20 nm. If the number average particle size of the primary particles is small, the fluidity becomes too good, and fogging is likely to occur. Conversely, if the number average particle size is large, the fluidity is deteriorated and fuzziness is liable to occur.

The silica fine particles (A) have a degree of hydrophobicity of usually 30 to 90%, preferably 40 to 80%, as measured by a method called a methanol method. If the degree of hydrophobicity is small, the influence of the environment is great, and fogging may easily occur particularly under high temperature and high humidity conditions.

Examples of the cyclic silazane compound include compounds represented by the following formula (1).

Embedded image(Where R¹And R²Is hydrogen, halogen, alkyl,
Independent of the county consisting of alkoxy and aryloxy
Chosen, R³Is hydrogen, (CH₂)_nCH₃, C (O)
(CH₂)_nCH₃, C (O) NH₂, C (O) NH
(CH₂)_nCH₃, And C (O) N [(CH₂)_n
CH₃] (CH₂)_mCH₃(Where n and m are 0
-3), R⁴Is [(CH₂)_a(CH
X)_b(CHY) _cWherein X, Y and Z are water
Element, halogen, alkyl, alkoxy and arylo
Independently selected from the county consisting of Kishi, a, b and c are:
satisfying the condition that a + b + c is equal to an integer between 2 and 6
Which is an integer of 0 to 6)

Examples of the silane coupling agent include generally used compounds such as dimethyldichlorosilane, trimethylchlorosilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, and γ-glycidyloxypropyltrimethoxysilane. Among them, an aminosilane compound containing an amino group in the compound is preferable. Examples of the aminosilane compound include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N
-(Β-aminoethyl) -γ-aminopropyltrimethoxysilane, N, N-diethyl-γ-aminopropyltrimethoxysilane, p-aminophenyltrimethoxysilane, γ-anilinopropyltrimethoxysilane and the like. .

As the cyclic silazane used in the present invention, or silica fine particles (A) which have been subjected to a hydrophobizing treatment with a cyclic silazane and a silane coupling agent, commercially available ones can be used. For example, JP-A-10-330115 discloses After the silica gel was dried in hot air in an open vessel, the vessel was sealed and cooled to room temperature while purging with dry nitrogen. While stirring the inside of the closed container, cyclic silazane was added thereto, and the stirring was continued.
It is possible to leave it at room temperature and then heat it at a high temperature to produce it. As a method of performing a hydrophobic treatment with a cyclic silazane and a silane coupling agent, the silica fine particles obtained by performing the hydrophobic treatment with the cyclic silazane described above are further subjected to a hydrophobic treatment using a silane coupling agent. It is not clear why the use of the silica fine particles treated by this method as an external additive improves fog, but it is presumed that by reacting such a cyclic silazane compound,
The highly water-absorbing silanol groups present on the surface of the silica fine particles efficiently react with the silylating agent (chemically fixed), and the silazane groups are introduced to increase the hydrophobicity. ), It is estimated that fog can be improved.

The amount of the silica fine particles (A) to be added is generally 0.1 to 3.0 parts by weight, preferably 0.2 to 2.0 parts by weight, based on 100 parts by weight of the colored particles. If the addition amount is small, the fluidity is reduced, and scumming is likely to occur.

The external additive used in the present invention preferably contains silica fine particles (B) having a number average particle diameter of primary particles of 30 to 100 nm and / or conductive metal oxide particles.

The number average particle size of the primary particles of the silica fine particles (B) is usually 30 to 100 nm, preferably 30 to 60 nm.
nm, more preferably 30 to 50 nm. When the number average particle diameter of the primary particles is small, the polishing effect is reduced, and the occurrence of filming cannot be suppressed. Conversely, when the number average particle size is large, the fluidity is deteriorated and fuzz is likely to occur.

The silica fine particles (B), like the silica fine particles (A), have a degree of hydrophobicity measured by a methanol method of usually 30 to 90%, preferably 40 to 80%. If the degree of hydrophobicity is small, the influence of the environment is great, and fogging may easily occur particularly under high temperature and high humidity conditions. The silica fine particles (B) subjected to the hydrophobic treatment are not particularly limited, but it is preferable to use those treated with the above-mentioned cyclic silazane or an aminosilane compound and an amino-modified silicone oil.

The cyclic silazane and the aminosilane compound are as described above. Examples of the amino-modified silicone oil include KF393, KF857, KF860, and KF860.
F864 (all manufactured by Shin-Etsu Chemical Co., Ltd.) and SF8417 (manufactured by Toray Silicone Co., Ltd.).

The amount of the silica fine particles (B) to be added is usually 0.05 to 1.0 part by weight based on 100 parts by weight of the colored particles.
Preferably it is 0.1-0.5 weight part. If the amount is small, the polishing effect is small, and it is not possible to suppress the occurrence of filming. On the other hand, if the amount is large, the fluidity is deteriorated and fuzz is easily generated.

The number average particle size of the primary particles of the conductive metal oxide particles (D) is usually 0.1 to 1.0 μm, preferably 0.2 to 0.6 μm. If the number average particle size is small, filming may not be prevented, whereas if it is large, the fluidity may be reduced.

The conductive metal oxide particles (D) are not particularly limited, but those subjected to a surface treatment with tin or antimony are preferred. Specifically, as tin / antimony-doped titanium oxide, EC-300 (trade name; manufactured by Titanium Industry Co., Ltd.), ET-300, HJ-1, HI-2 (all trade names; manufactured by Ishihara Sangyo Co., Ltd.), W -P (trade name; manufactured by Mitsubishi Materials Corporation) and the like, and as antimony-doped tin oxide, SN-100P (trade name; manufactured by Ishihara Techno), T
-1 (trade name; manufactured by Mitsubishi Materials Corporation) and SH-S (trade name; manufactured by Nippon Chemical Industry Co., Ltd.).

The amount of the conductive metal oxide particles (D) is not particularly limited, but is usually 0.05 to 1 part by weight, preferably 0.1 to 0.5 part by weight, per 100 parts by weight of the colored particles. It is. If the amount is small, filming is likely to occur, and if the amount is large, the fluidity is deteriorated and the film is likely to be worn.

The toner for developing an electrostatic latent image of the present invention can be obtained by mixing the colored particles and the external additive with a high-speed stirrer such as a Henschel mixer.

According to the image forming method of the present invention, the toner is adhered to the surface of the photoreceptor on which the electrostatic latent image is recorded to form a visible image, and the visible image is transferred to a transfer material to form an image. can do.

Hereinafter, the image forming method will be described in detail with reference to the drawings. Although the following description is for a non-magnetic one-component developing system, the image forming method of the present invention is not limited to this, and a magnetic one-component developing system, a non-magnetic two-component developing system, and a magnetic two-component developing system can be used. A method may be used. As shown in FIG. 1, a photosensitive drum 1 as a photosensitive member is mounted on the image forming apparatus so as to be rotatable in the direction of arrow A. The photosensitive drum 1 has a photoconductive layer provided on the outer peripheral surface of a conductive support drum. The photoconductive layer is made of, for example, an organic photoconductor, a selenium photoconductor, a zinc oxide photoconductor, an amorphous silicon photoconductor, or the like.

Around the photosensitive drum 1, along a circumferential direction thereof, a charging roll 3 as a charging unit, a laser beam irradiation device 4 as a latent image forming unit, a developing roll 7 as a developing unit, and a transfer roll as a transferring unit. A transfer roll 5 and a cleaning device (not shown) are provided.

The charging roll is for uniformly charging the surface of the photosensitive drum positively or negatively. By applying a voltage to the charging roll and bringing the charging roll into contact with the photosensitive drum, the surface of the photosensitive drum is charged. Is charged. The charging roll 3 can be replaced by charging means using corona discharge.

The laser beam irradiation device 4 irradiates the surface of the photosensitive drum with light corresponding to the image signal, and irradiates the uniformly charged surface of the photosensitive drum with light in a predetermined pattern.
The purpose is to form an electrostatic latent image on a portion irradiated with light (in the case of reversal development) or to form an electrostatic latent image on a portion not irradiated with light (in the case of regular development). As another latent image forming unit, there is a unit formed of an LED array and an optical system.

The developing roll is for applying toner to the electrostatic latent image on the photosensitive drum 1 to form a visible image.
In reversal development, toner is adhered only to the light irradiation part,
In normal development, a bias voltage is applied between the developing roll and the photosensitive drum so that the toner adheres only to the light non-irradiated portion.

A developing roll 7 and a supply roll 9 are provided in a developing device 11 in which the toner 10 is stored.
The developing roll is arranged close to and in contact with the photosensitive drum, and rotates in a direction B opposite to the photosensitive drum. The supply roll 9 contacts the development roll 7 and rotates in the same direction C as the development roll to supply toner to the outer periphery of the development roll. Normally, a voltage is also applied to the supply roll so that the toner can be supplied smoothly.

At a position between the point of contact with the supply roll and the point of contact with the photosensitive drum around the developing roll,
A developing roll blade 8 as a layer thickness regulating means is provided. This blade 8 is made of conductive rubber or stainless steel, and performs charge injection into toner.
A voltage of 200 V | to | 600 V | is applied. Therefore, the electrical resistivity of the blade 8 is 10 6 Ωcm.
The following is preferred.

The developing device 11 of the image forming apparatus contains the electrostatic latent image developing toner 10 described above. The transfer roll 5 is for transferring the toner image on the surface of the photosensitive drum formed by the developing roll to the transfer material 6. Examples of the transfer material include paper and OHP sheets. Examples of the transfer unit include a corona discharge device and a transfer belt in addition to the transfer roll.

The toner image transferred to the transfer material is fixed to the transfer material by the fixing means 2. As fixing means,
Usually, it comprises a heating means and a pressure bonding means. The toner transferred to the transfer material is heated by heating means to melt the toner,
The melted toner is pressed and fixed to the surface of the transfer material by a pressing means.

The cleaning device is for cleaning the transfer residual toner remaining on the surface of the photosensitive drum.
For example, it is constituted by a cleaning blade or the like. Note that this cleaning device does not necessarily need to be installed when adopting a method of performing cleaning at the same time as development by the developing roll.

The image forming method of the present invention can be applied to a color toner. Magenta, cyan, yellow 3
A color image can be formed by using a color or a four-color toner with black added thereto.

[0071]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples below, but the present invention is not limited to these examples. In addition, parts and%
Are by weight unless otherwise specified. In the present example, evaluation was made by the following method.

[Evaluation Method] (Volume Average Particle Size and Particle Size Distribution) The volume average particle size (dv) of the colored particles and the particle size distribution, that is, the ratio (dv / d) of the volume average particle size to the number average particle size (dp). dp) was measured with a Multisizer (manufactured by Beckman Coulter). The measurement with this multisizer was performed with an aperture diameter of 100 μm.
m, medium: Isoton II, concentration 10%, number of measured particles:
The test was performed under the condition of 100,000 pieces. (Number average particle diameter) The number average particle diameter of the primary particle diameter of the silica fine particles and the conductive metal oxide particles is determined by taking an electron micrograph of each particle and using the photograph by an image processing / analysis apparatus Luzex I.
According to the ID (manufactured by Nireco Co., Ltd.), the area ratio of the particles to the frame area: 2% at the maximum, the total number of treated particles: 100
The circle equivalent diameter was calculated under each condition, and the average value was calculated.

(Sphericity) The sphericity (Sc / Sr) of the value obtained by dividing the area (Sc) of a circle whose diameter is the absolute maximum length of a particle by the actual projected area (Sr) of the particle is represented by an electron microscope of each particle. A photograph is taken, and the photograph is taken by an image processing / analysis apparatus Luzex IID (manufactured by Nireco Co., Ltd.).
It is an average value of 100 measured and calculated on 0 conditions.

(Degree of Hydrophobicity) The degree of hydrophobicity by the methanol method is determined according to the following measuring method. 0.2 g of the treated inorganic fine particles were weighed into a 500 ml beaker, and purified water 5
Add 0 ml, and add methanol below the liquid level while stirring with a magnetic stirrer. The point at which no sample is observed on the liquid surface is defined as the end point, and the degree of hydrophobicity is calculated by the following equation. Degree of hydrophobicity (%) = (X / (50 + X)) × 100 X; Methanol usage (ml)

(Print Density) Paper was set in a commercially available non-magnetic one-component developing system printer (20 sheets), and the toner to be evaluated was put in a developing device of the printer.
After standing all day and night under (H / H) environment of 80 ° C and 80% humidity,
Continuous printing is performed from the beginning at 5% printing density, and solid black printing is performed at the time of 100th printing and 10,000th printing, and McBeth
The print density was measured using a transmission type image densitometer manufactured by the company.

(Fog) Using the above-described printer,
Under the same conditions, continuous printing is performed at 5% printing density, printing is stopped in the middle of printing (at the time of printing 100 sheets) and after printing 10,000 sheets, and the toner in the non-image area on the photoreceptor after development is stopped. Was adhered to an adhesive tape (Scotch Mending Tape 810-3-18 manufactured by Sumitomo 3M Limited). It was attached to a printing paper, and its whiteness (B) was measured with a whiteness meter (manufactured by Nippon Denshoku). Similarly, only the adhesive tape was stuck on the printing paper, and its whiteness (A) was measured. The fog value is
Fog (%) = (AB) A smaller value indicates less fog.

(Resolution) Using the printer described above,
Under the same conditions, a 1-dot line and a 1-dot white line were printed, and whether or not the image quality was reproduced was observed with an optical microscope, and evaluated based on the following criteria. ○: One dot line and one dot white line are reproduced. Δ: One-dot line and one-dot white line are not reproduced, but two-dot line and two-dot white line are reproduced. ×: neither a 2-dot line nor a 2-dot white line was reproduced.

(Outline of Commercially Used Silica Used) Silica Fine Particles A1 Silica fine particles (product name: TG820F) manufactured by Cabot Corporation and having a primary particle diameter of 7 nm and a degree of hydrophobicity of 74%, subjected to a hydrophobic treatment with cyclic silazane. Silica fine particles B1 Silica manufactured by Nippon Aerosil Co., Ltd. (product name: NEA50) having a primary particle size of 30 nm and a hydrophobicity of 56%, which has been subjected to a hydrophobic treatment with an amino-modified silicone oil. Silica fine particles C1 Hydrophobized with dimethylsiloxane, primary particle size 12
Silica manufactured by Nippon Aerosil Co., Ltd. (product name: RY200) having a nm and a hydrophobicity of 67%. Silica fine particles C2 Silica manufactured by Nippon Aerosil Co., Ltd. (product name: RX200) having a primary particle size of 12 nm and a hydrophobicity of 65%, which has been subjected to a hydrophobic treatment with hexamethyldisilazane. Conductive metal oxide particles D1 Tin / antimony-doped titanium oxide (trade name: EC300) manufactured by Titanium Industry Co., Ltd. having a primary particle size of 300 nm.

(Example 1) 83 parts of styrene, 17 parts of n-butyl acrylate, carbon black (trade name "# 2
5B ", manufactured by Mitsubishi Chemical Corporation; primary particle size: 40 nm) 6 parts, charge control agent (trade name" BONTRON N-01 ", manufactured by Orient Chemical Co., Ltd.) 0.05 part, divinylbenzene 0.6
, 1 part of t-dodecyl mercaptan, and 2 parts of Sasol wax (trade name: "Paraflint Spray 30", manufactured by Sasol) were dispersed at room temperature in a bead mill to obtain a uniform mixed solution. While stirring the mixture, 5 parts of a polymerization initiator t-butylperoxy 2-ethylhexanoate (trade name: "Perbutyl O" manufactured by NOF Corporation) was added,
Stirring was continued until the droplets became uniform.

On the other hand, 4.8 parts of sodium hydroxide (alkali metal hydroxide) was added to 50 parts of ion-exchanged water in an aqueous solution obtained by dissolving 9.5 parts of magnesium chloride (water-soluble polyvalent metal salt) in 250 parts of ion-exchanged water. The aqueous solution in which was dissolved was gradually added under stirring to prepare a magnesium hydroxide colloid (poorly water-soluble metal hydroxide colloid) dispersion. The polymerizable monomer composition was charged into the colloid, and the mixture was subjected to high shear stirring at a rotation speed of 12000 rpm using a TK homomixer to granulate droplets of the polymerizable monomer mixture. The aqueous dispersion of the granulated polymerizable monomer mixture is put into a reactor equipped with a stirring blade, a polymerization reaction is started at 90 ° C., polymerization is performed for 8 hours, and then cooling is performed. I got

While stirring the aqueous dispersion of polymer particles obtained as described above, sulfuric acid was added to adjust the pH to 4 or less, acid washing was performed, water was separated by filtration, and 500 parts of ion-exchanged water was newly added. In addition, the slurry was reslurried and washed with water. After that, dehydration and washing with water were repeated several times again, and the solid content was separated by filtration, followed by drying at 45 ° C. for 2 days and night with a drier to obtain colored particles. The volume average particle size of the colored particles is 7.8.
μm, volume average particle diameter (dv) / number average particle diameter (dp), which is an index of particle diameter distribution, was 1.25, and sphericity was 1.15.

100 parts of the obtained colored particles, silica fine particles A1 (trade name “T”) having a number average particle diameter of primary particles of 7 nm, a degree of hydrophobicity of 74%, and a hydrophobic treatment with a cyclic silazane compound.
G820F "(Cabot) 0.6 parts, silica fine particles B1 having a number average primary particle diameter of 30 nm and a hydrophobicity of 56% (trade name" NEA50 ", manufactured by Nippon Aerosil Co., Ltd.)
1.0 part and a conductive titanium oxide having a number average particle diameter of primary particles of 0.3 μm and a hydrophobicity of 0% (trade name “EC300”,
0.3 parts of Titanium Kogyo Co., Ltd.) with a Henschel mixer at 3400 rpm for 3 minutes to obtain a toner for developing an electrostatic latent image. Printing evaluation was performed on the obtained toner. Table 1 shows the results.

[0083]

[Table 1]

(Examples 2 to 5, Comparative Examples 1 and 2) Evaluations were made in the same manner as in Example 1 except that the external additives were changed as shown in Table 1. Table 1 shows the results.

From the evaluation results of the toners in Table 1, the following can be understood. The toner of Comparative Example 1 using the silica fine particles having a small particle diameter subjected to hydrophobic treatment with dimethylsiloxane as the external additive is liable to cause fogging after initial printing and continuous printing, and has poor resolution. The toner of Comparative Example 2 using silica fine particles having a small particle diameter subjected to hydrophobization treatment with hexamethyldisilazane as an external additive is liable to generate fog after initial printing and continuous printing, and has poor resolution. On the other hand, it can be seen that the toners of Examples 1 to 5 of the present invention have a high print density, are less likely to cause fog after initial printing and after continuous printing, and have high resolution.

[0086]

According to the present invention, there is provided a toner capable of obtaining an image having a high print density, a high resolution, and no fog even when the number of prints is increased in various environments, particularly under high temperature and high humidity. Is done.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating one embodiment of an image forming apparatus used in an image forming method of the present invention.

[Explanation of symbols]

 1, photosensitive drum 3, charging roll 4, laser beam irradiation device 5, transfer roll 7, developing roll 8, developing roll blade 9, supply roll 10, toner 11, developing device

Claims (5)

[Claims] Claims: 1. An external additive comprising colored particles and an external additive, wherein the external additive has a number average particle diameter of primary particles of 5 to 30 nm, and is subjected to hydrophobic treatment with cyclic silazane or a cyclic silazane and a silane coupling agent. And an electrostatic latent image developing toner containing the silica fine particles (A). 2. A colored particle and an external additive, wherein the external additive has a number average particle diameter of primary particles of 5 to 30 nm, and is subjected to hydrophobic treatment with cyclic silazane or a cyclic silazane and a silane coupling agent. And a silica fine particle (B) having a number average particle diameter of primary particles of 30 to 100 nm. 3. A colored particle and an external additive, wherein the external additive has a number average particle diameter of primary particles of 5 to 30 nm, and is subjected to a hydrophobizing treatment with a cyclic silazane or a cyclic silazane and a silane coupling agent. Silica fine particles (A) and conductive metal oxide particles (D) having a number average particle diameter of primary particles of 0.1 to 1 μm.
And a toner for developing an electrostatic latent image. 4. A colored particle and an external additive, wherein the external additive has a number average particle size of primary particles of 5 to 30 nm, and is subjected to a hydrophobic treatment with a cyclic silazane or a cyclic silazane and a silane coupling agent. Contains silica fine particles (A), silica fine particles (B) having a primary particle number average particle diameter of 30 to 100 nm, and conductive metal oxide particles (D) having a primary particle number average particle diameter of 0.1 to 1 μm. For developing electrostatic latent images. 5. An image forming method comprising: attaching the toner according to claim 1 to a surface of a photoconductor on which an electrostatic latent image is recorded to form a visible image; and transferring the visible image to a transfer material.