JP2005189259A - Electrostatic charge image developing toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide electrostatic charge image developing toner having excellent charging stability and excellent image characteristics, with which images free from density change, fog, a hollow portion and cleaning failure can be formed for a long period of time. <P>SOLUTION: The electrostatic charge image developing toner contains at least tone particles and three kinds of hydrophobic silica-containing fine particles having different average particle diameters. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a toner for developing an electrostatic image. More specifically, the present invention relates to a toner for developing an electrostatic charge image that is used for developing an electrostatic charge image in electrophotography, electrostatic recording, and electrostatic printing, and has excellent image characteristics even by repeated copying.

  In general, various inorganic fine particles are added to the toner for developing an electrostatic image in order to satisfy the characteristics of the development, transfer, and cleaning steps. It is also known that two or more kinds of inorganic fine particles having different particle sizes and / or compositions are used as the inorganic fine particles.

  However, there has been a problem that these inorganic fine particles are detached due to an electric field bias or mechanical stress, and density fluctuations, fogging, omission, and unwiping are generated on a copy image. Such a problem is caused by the fact that inorganic fine particles have a considerable influence on the chargeability and fluidity of the toner, and the specific balance among the two or more types of inorganic fine particles selectively desorbs and the charge balance of the toner. It is considered that the flow balance is lost, and as a result, the charging stability and fluidity of the toner are deteriorated.

  The present invention has been made in view of the above circumstances, and provides a toner for developing an electrostatic charge image that is excellent in charging stability and excellent in image characteristics capable of forming an image free from density fluctuations, fogging, voids, and unwiped residues over a long period of time. For the purpose.

  The present invention relates to an electrostatic charge image developing toner comprising at least toner particles and three types of hydrophobic silica-containing fine particles having different average particle diameters.

  In the present invention, it is possible to easily provide a toner for developing an electrostatic image having excellent image characteristics over a long period of time by containing three kinds of fine particles containing hydrophobic silica having different average particle diameters. Specifically, the toner of the present invention is excellent in charging stability and image stability, and a good image free from density fluctuations, fogging, voids, and unwiped residues (cleaning failure) can be obtained over a long period of time.

  The toner for developing an electrostatic charge image of the present invention contains at least toner particles and specific silica-containing fine particles.

  In the present invention, the toner particles are so-called pulverization method, suspension polymerization method, emulsion polymerization method, emulsion polymerization aggregation method in which resin particles obtained by emulsion polymerization and colorant particles are aggregated and fused to obtain toner particles. It can be produced by various production methods such as an emulsification dispersion method.

  The toner particles contain at least a binder resin and a colorant, and optionally further contain an offset preventing agent, a charge control agent, and magnetic powder.

  The binder resin is not particularly limited, and may be, for example, a styrene resin, a (meth) acrylic resin, a styrene- (meth) acrylic copolymer resin, or an olefin type as long as it is a pulverization method or an emulsion dispersion method. One or more known various resins such as resins, polyester resins, polyamide resins, carbonate resins, polyethers, polyvinyl acetate resins, polysulfones, epoxy resins, polyurethane resins, urea resins and the like are used. It is possible. For suspension polymerization method, emulsion polymerization method, emulsion polymerization aggregation method, styrene monomer such as styrene, methylstyrene, methoxystyrene, butylstyrene, phenylstyrene, chlorostyrene, methyl acrylate, ethyl acrylate, butyl acrylate , Acrylic acid esters such as ethyl hexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethyl hexyl methacrylate, or methacrylic acid ester monomers, carboxylic acid monomers such as acrylic acid, methacrylic acid, fumaric acid, etc. As a result, a polymer of those monomers is contained as a binder resin.

  As the colorant, various organic or inorganic pigments as shown below can be used. These colorants may be used after forming a masterbatch with a binder resin or other resin for the purpose of improving dispersibility in the toner.

That is, examples of the black pigment include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, nonmagnetic ferrite, magnetic ferrite, and magnetite.
Examples of yellow pigments include yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel-kel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, and Benzidine Yellow. There are GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartragin Lake and so on.
Examples of the orange pigment include red chrome yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK.

Red pigments include quinacridone, bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risor red, pyrazolone red, watching red, calcium salt, lake red C, lake red D, brilliant carmine 6B, eosin There are Rake, Rondamin Rake B, Alizarin Rake, Brilliant Carmine 3B.
Examples of purple pigments include manganese purple, fast violet B, and methyl violet lake.
Examples of blue pigments include bitumen, cobalt blue, alkali blue lake, Victoria blue lake, metal phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, and induslen blue BC.

Examples of the green pigment include chromium green, chromium oxide, pigment green B, micalite green lake, final yellow green G, and the like.
Examples of white pigments include zinc white, titanium oxide, antimony white, and zinc sulfide.
Examples of extender pigments include barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white.
The content of the colorant is usually 0.5 to 20 parts by weight, preferably 2 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  The anti-offset agent is used to improve the fixing property of the toner. Specific examples thereof include various waxes, particularly polyolefin waxes such as low molecular weight polypropylene, polyethylene, oxidized polypropylene, and polyethylene. The content of the offset preventive agent is usually 0.1 to 30 parts by weight, preferably 1 to 10 parts by weight with respect to 1O0 part by weight of the binder resin.

  The charge control agent is added when the charge characteristics of the toner cannot be satisfied only with the binder resin and the colorant. As the charge control agent, various substances that can give positive or negative charge by frictional charging can be used. Examples of the positive charge control agent include nigrosine dyes such as nigrosine base EX (manufactured by Orient Chemical Industries), quaternary ammonium salt P-51 (manufactured by Orient Chemical Industries), copy charge PX VP435 (manufactured by Hoechst Japan) And imidazole compounds such as PLZ1001 (manufactured by Shikoku Kasei Kogyo Co., Ltd.) and the like. Examples of the negative charge control agent include Bontron S-22 (manufactured by Orient Chemical Industries), Bontron S-34 (manufactured by Orient Chemical Industries), Bontron E-81 (manufactured by Orient Chemical Industries), Bontron E-84 ( (Orient Chemical Co., Ltd.), Spiron Black TRH (Hodogaya Chemical Co., Ltd.) and other metal complexes, thioindigo pigments, quaternary ammonium salts such as Copy Charge NX VP434 (Hoechst Japan), Bontron E-89 Calixarene compounds such as (Orient Chemical Co., Ltd.), boron compounds such as LR147 (Nihon Carlit), fluorine compounds such as magnesium fluoride and carbon fluoride, etc. are of course limited to these. is not. In addition to the above-mentioned metal complexes serving as negative charge control agents, oxycarboxylic acid metal complexes, dicarboxylic acid metal complexes, amino acid metal complexes, diketone metal complexes, diamine metal complexes, azo group-containing benzene-benzene Those having various structures such as derivative skeleton metal bodies and azo group-containing benzene-naphthalene derivative skeleton metal complexes are included. The content of these charge control agents is usually 0.01 to 30 parts by weight, preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  Examples of the magnetic powder include magnetite, γ-hematite, and various ferrites. The content of the magnetic powder is usually 10 to 500 parts by weight, preferably 20 to 200 parts by weight, based on 100 parts by weight of the binder resin.

  In the present invention, the toner particles have a volume average particle size of about 1 to 13 μm, preferably about 3 to 9 μm. The volume average particle diameter can be measured using a Coulter Multisizer (manufactured by Coulter).

  As the silica-containing fine particles contained in the toner of the present invention, three types having different average particle diameters, that is, those having a small diameter, those having a medium diameter, and those having a large diameter are used. Any silica-containing fine particles may be silica fine particles made of only silica, or a silica-containing composite oxide made of silica and another metal oxide as long as each fine particle contains at least silica (silicon dioxide). Fine particles may be used. In the present invention, the use of three types of silica-containing fine particles having different average particle diameters improves the charging stability and fluidity of the toner, resulting in density fluctuations, fogging, voids, and unwiping (cleaning failure). No good images can be obtained over a long period of time. The details of the mechanism for improving the charging stability of the toner by using such three types of silica-containing fine particles are not clear, but those with a small diameter have charging properties and fluidity, and those with a medium diameter have charging properties and voids. Prevention, fluidity, and large diameter are considered to contribute to chargeability, prevention of falling out and cleaning. If only one or two types of silica-containing fine particles are used, or if any one of the three types of fine particles does not contain silica, the charging stability of the toner will be reduced, resulting in density fluctuations, fog, At least one problem of omission or unwiping occurs relatively early, and a good image cannot be obtained over a long period of time.

  The structure of the silica-containing composite oxide fine particles as one form of the silica-containing fine particles is not particularly limited as long as silica and one or more other metal oxides are simultaneously contained in the individual fine particles. A structure in which a silicon atom and one or more other metal atoms are chemically or physically bonded to each other via an oxygen atom, and a silicon atom and one or more other metal atoms are chemically bonded to each other without an oxygen atom Or it may be a physically coupled structure or a composite structure thereof. Examples of other metal oxides contained in the silica-containing composite oxide fine particles include one or more metal oxides selected from the group consisting of titania (titanium dioxide), alumina, zinc oxide, magnesium oxide, and zirconia. From the viewpoint of further improving the charging stability, titania is preferred.

  The composition ratio of the silica-containing composite oxide fine particles is not particularly limited as long as the object of the present invention is achieved. Usually, the content ratio of silica is 50% by weight or more based on the total weight contained in the fine particles, 70% by weight or more is preferable. The content ratio of the metal atoms can be measured with a fluorescent X-ray analyzer XRF-1800 (manufactured by Shimadzu Corporation). As long as the object of the present invention is achieved, the present invention does not prevent the composite oxide fine particles from containing metal atoms other than silicon and other metal atoms.

  The silica-containing composite oxide fine particles as described above can be produced by a flame combustion method. The flame combustion method is a method of obtaining silica-containing oxide fine particles by spray combustion of siloxane and an organometallic compound in a flame.

  Specifically, a raw material liquid in which siloxane and an organometallic compound are mixed is sprayed onto droplets together with nitrogen by a spray nozzle at the tip of the burner, and propane, oxygen and air are supplied to the burner and burned.

A metal alkoxide compound, a metal acylate compound, a metal alkyl compound, or a metal chelate compound is used as the organometallic compound, and there is no particular limitation as long as it is liquid, or is soluble in siloxane or a liquid agent. Specific examples of the organometallic compound include tetraisopropoxy titanium, triisopropoxy aluminum, tetrabutoxy zirconium, methoxy magnesium, and dipropoxy zinc.
Examples of siloxane include hexamethyldisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and the like.

  The composite oxide fine particles do not have to be produced by the flame combustion method as described above, and any method can be used as long as it is a method capable of producing metal oxide fine particles containing a predetermined metal atom. Good. For example, a gas phase method or a liquid phase method, a hydrolysis method, a laser ablation method, a sol-gel method, or the like can be employed.

The average particle size of each of the three types of silica-containing fine particles having different average particle sizes is not particularly limited as long as the object of the present invention is achieved, but usually has the following average particle size:
Fine silica-containing fine particles; 5 nm or more and less than 20 nm, preferably 5 nm or more and 18 nm or less;
Medium-diameter silica-containing fine particles; 20 nm or more and less than 100 nm, preferably 20 nm or more and 80 nm or less;
Large-diameter silica-containing fine particles: 100 nm to 500 nm, preferably 120 nm to 250 nm.

  The average particle size of the silica-containing fine particles means the average particle size (average primary particle size) of the primary fine particles, and can be measured by a transmission electron microscope JEM-ARM1300 (manufactured by JEOL).

  All of the three types of silica-containing fine particles preferably have hydrophobicity from the viewpoint of further improving the charging stability, particularly the charging stability to the environment. % Or more is preferable.

  Hydrophobicity is imparted by subjecting the silica-containing fine particles to a hydrophobization treatment. The hydrophobizing treatment is usually achieved by spraying the hydrophobizing agent onto the fine particles under vigorous mixing, mixing, and firing (heat treatment). The hydrophobizing agent is not particularly limited as long as the above-mentioned degree of hydrophobicity can be imparted, and any hydrophobizing agent that has been conventionally used as a hydrophobizing agent for inorganic fine particles added to a toner can be used. Examples thereof include hexamethyldisilazane (HMDS), dimethyldichlorosilane, dimethylpolysiloxane, isobutylmethoxysilane and the like.

In this specification, the value measured by the following method is used for the degree of hydrophobicity.
Place 50 ml of ion-exchanged water in a 200 ml beaker and add another 0.2 g of sample. While stirring with a magnetic stirrer, methanol is added from a burette whose tip is immersed in water at the time of dropping, the floating sample starts to sink, and the number of ml of dropping methanol when completely sinking is read and calculated from the following formula.

  The presence form of the above three types of silica-containing fine particles is not particularly limited. For example, the silica-containing fine particles may be externally added so as to exist in the vicinity of the toner particle surface, or exist in the toner particles. Therefore, it may be added (internally added) during the toner particle production process. In the present invention, from the viewpoint of chargeability and fluidity, it is desirable that the three types of silica-containing fine particles are externally added to the toner particles so as to exist in the vicinity of the toner particle surface. In the present specification, “external addition” means adding to toner particles once obtained and mixing them.

  The three types of silica-containing fine particles may be added and mixed with the toner particles in a dry process or in a wet process. For example, (1) three types of silica-containing fine particles may be added to and mixed with dry toner particles, or (2) three types of silica-containing fine particles are added to and mixed with an aqueous dispersion of toner particles and dried. Or (3) one of the three types of silica-containing fine particles is added to and mixed with the aqueous dispersion of toner particles, dried, and then the remaining fine particles are added to the dry toner particles. You may add and mix. In any of the above methods, the order of adding the three types of silica-containing fine particles is not particularly limited. For example, they may be added and mixed all at once, or one type or two types and one type. May be added and mixed separately. In particular, when the method (3) is adopted, from the viewpoint of uniform mixing of each fine particle, particularly large-sized fine particles, first, the large-sized particles are first added to and mixed with the aqueous dispersion of toner particles, and then dried. Then, it is preferable to add and mix small particles and medium particles to the dry toner particles.

  The addition amount of the three types of silica-containing fine particles is not particularly limited as long as the object of the present invention is achieved, and usually 0.1 to 10 parts by weight with respect to 100 parts by weight of the toner particles, and 0.3 to 20 weights in total. Parts, particularly 1 to 10 parts by weight are preferred.

  In the present invention, other inorganic fine particles may be added in order to satisfy various mechanical properties. Other inorganic fine particles include alumina, titanium oxide, zinc oxide, iron oxide, copper oxide, lead oxide, antimony oxide, yttrium oxide, magnesium oxide, barium sulfate, barium titanate, ferrite, bengara, magnesium fluoride, silicon carbide, Examples thereof include boron carbide, silicon nitride, zirconium nitride, magnetite, magnesium stearate, calcium carbonate, aluminum oxide, strontium titanate, and cerium oxide. The inorganic fine particles may be subjected to a surface treatment in order to improve dispersibility on the toner particle surface and environmental stability. Examples of the surface treatment agent include a silane coupling agent, a titanium coupling agent, a higher fatty acid, and silicone oil.

  The toner of the present invention can be used in both a one-component developer not using a carrier and a two-component developer used together with a carrier. By using it in a one-component developer from the viewpoint of improving voids, the effect is further increased. As the carrier, a known carrier can be used. For example, a carrier made of magnetic particles such as iron powder and ferrite, a coated carrier whose surface is coated with a coating agent such as a resin, or a magnetic substance in a binder resin. Any of dispersion type carriers in which fine powder is dispersed can be used. As such a carrier, one having a volume average particle diameter of 15 to 100 μm, preferably 20 to 80 μm is suitable.

  Hereinafter, the present invention will be described more specifically with reference to examples. “Parts” shall mean “parts by weight”.

(Fine particles)
The fine particles used in the examples are shown below, and their physical properties are shown in Table 1.
Particulate 1-1; # 300 silica (Nippon Aerosil Co., Ltd.) HMDS treated ultrafine 1-2; # 200 silica (Nippon Aerosil Co., Ltd.) octyl silane treated ultrafine 1-3; rutile TiO ₂ Ishihara Sangyo to 15nm Prepared TiO ₂ with dimethylsiloxane treated fine particles 2-1; # 90 silica (manufactured by Nippon Aerosil Co., Ltd.) with HMDS treated fine particles 2-2; # 50 silica (manufactured by Nippon Aerosil Co., Ltd.) with HMDS treated fine particles 2-4; rutile-type TiO ₂ with an adjusted TiO ₂ to 75nm dimethylpolysiloxane treated ultrafine 2-5; # 50 silica (manufactured by Nippon Aerosil Co., Ltd.)
Particulate 3-3; the TiO ₂ of the rutile type TiO ₂ and adjusted to 140nm dimethylpolysiloxane treated ultrafine 3-4; ST-02 (Fuji Titanium Industry Co., Ltd.) dimethylpolysiloxane (silicone oil) process

Particulate 2-3; hexamethyldisiloxane and the weight ratio of titanium tetraisopropoxide 3: 2 mixture fed-sprayed at a feed rate of 15 g / min, SiO ₂ / TiO ₂ having an average particle diameter of 70nm by flame combustion method = 80/20 wt% silica-titanium composite oxide particles were obtained. This was treated with a hydrophobizing agent hexamethyldisilazane in a gas phase to obtain fine particles 2-3 having an average particle diameter of 72 nm.

Fine particles 3-1; hexamethyldisiloxane was supplied and sprayed at a supply rate of 30 g / min, and SiO ₂ particles having an average particle diameter of 145 nm were obtained by a flame combustion method. This was treated with modified silion oil (methylhydrogensiloxane) in the gas phase to obtain fine particles 3-1 having an average particle size of 155 nm.

Fine particle 3-2: A 7: 1 weight ratio of hexamethyldisiloxane and tetraisopropoxytitanium is supplied and sprayed at a supply rate of 30 g / min. SiO ₂ / TiO _{2 with} an average particle size of 150 nm by the flame combustion method = 95/5 wt% silica-titanium composite oxide particles were obtained. This was treated with the hydrophobizing agent hexamethyldisilazane in the gas phase to obtain fine particles 3-2 having an average particle diameter of 160 nm.

(Example of toner particle production)
A reaction flask equipped with a stirring device, heating / cooling device, concentrating device, and raw material / auxiliary charging device was charged with a solution obtained by dissolving 1.4 parts of sodium dodecylsulfonate in 600 parts of ion-exchanged water, and stirred at 200 rpm under a nitrogen stream. The internal temperature was raised to 80 ° C. while stirring at a speed. To this solution, a solution in which 1.8 parts of potassium persulfate was dissolved in 40 parts of ion-exchanged water was added, the temperature was adjusted to 75 ° C., and then a simple solution comprising 14 parts of styrene, 4 parts of n-butyl acrylate, and 2 parts of methacrylic acid. The monomer mixture was added dropwise over 30 minutes, and the system was polymerized at 75 ° C. to prepare Latex A1.

  Next, 21 parts of styrene, 6 parts of n-butyl acrylate, 1.3 parts of methacrylic acid, 2-mercaptoethyl octanoate were added to a reaction flask equipped with a stirrer, a heating / cooling device, a concentrating device, and a raw material / auxiliary charging device. A monomer solution was prepared by adding 10 parts of polyethylene wax to a monomer mixture consisting of 1.1 parts of ester, heating to 85 ° C. and dissolving. On the other hand, a solution prepared by dissolving 0.3 part of sodium dodecylsulfonate in 540 parts of ion-exchanged water was heated to 80 ° C., and 5.6 parts of the latex A1 was added to this solution in terms of solid content, and then homogenizer TK homomixer (special machine). The monomer solution was mixed and dispersed by a chemical industry) to prepare an emulsion. Next, a solution prepared by dissolving 1 part of potassium persulfate in 50 parts of ion-exchanged water and 150 parts of ion-exchanged water are added to this emulsion, and the temperature is set to 80 ° C., followed by polymerization for 3 hours to obtain latex B1. Obtained.

  To the latex B1 obtained as described above, a solution prepared by dissolving 1.5 parts of potassium persulfate in 40 parts of ion-exchanged water was added, the temperature was adjusted to 80 ° C., and then 60 parts of styrene and 19 parts of n-butyl acrylate Then, a monomer mixture composed of 3 parts of methacrylic acid and 2.1 parts of octanoic acid-2-mercaptoethyl ester was added dropwise over 30 minutes, and this system was polymerized at 80 ° C. for 2 hours, and then cooled to 30 ° C. Latex C1 was obtained.

  12 parts of sodium n-dodecyl sulfate was stirred and dissolved in 300 parts of ion-exchanged water. While stirring this solution, 84 parts of carbon black (Regal 330: manufactured by Cabot Corporation) was gradually added, and then dispersed by a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to obtain a colorant dispersion.

  The latex C1, 84 parts (in terms of solid content), 180 parts of ion exchange water, and 33 parts of the colorant dispersion were equipped with a stirrer, heating / cooling device, concentrating device, and raw material / auxiliary charging device. Stir in a reaction flask. After adjusting the internal temperature to 30 ° C., 5N aqueous sodium hydroxide solution was added to this solution to adjust the pH to 11.0. Next, a solution obtained by dissolving 2.4 parts of magnesium chloride hexahydrate in 200 parts of ion-exchanged water was added at 30 ° C. over 10 minutes. The system was then heated to 90 ° C. over 6 minutes. Thereafter, a solution in which 16 parts of sodium chloride was dissolved in 200 parts of ion-exchanged water was added to stop the particle growth, and fusion was continued for 2 hours at a liquid temperature of 85 ° C. as an aging treatment. Thereafter, the mixture was cooled to 30 ° C., and hydrochloric acid was added to adjust the pH to 2.0. Then, the produced fused particles were repeatedly filtered / washed to obtain a toner / water dispersion having a pH of 6 to 7.

(Example 1)
A small amount of sodium dodecyl sulfonate and fine particles 3-1 (1.5 parts) were added to 100 parts of toner particle solids, treated with TK homomixer at 6000 rpm for 10 minutes, washed with water / filtered and dried. . Fine particles 1-1 (0.8 parts) and fine particles 2-1 (0.8 parts) were added thereto, and mixed with a Henschel mixer to obtain a toner.

(Example 2 to Comparative Example 8)
A toner was obtained in the same manner as in Example 1 except that the fine particles listed in Table 2 were used in the addition amounts listed in the table.

(Evaluation)
1) Image characteristics magicolor2300DL
The toner was mounted on magicolor2300DL (Minolta QMS), 3000 printing tests were performed, and the initial and 3000 images were examined. Ranking was performed by visual judgment according to the following.
Fog ○: Hot water without background fog;
△: There is background fog, but there is no problem in use;
X: In the case of a background fog having a problem in use.
Concentration fluctuation ○: When density reduction does not occur;
Δ: Concentration is reduced but there is no problem in use;
X: When the density drop which has a problem in use occurs.

2) Transferability The toner was mounted on magicolor2300DL (Minolta QMS), and the initial characters and ruled lines in the image were examined.
○: When there is no void;
△: There is a hollow, but there is no problem in use;
×: When there is a problem in use, the hollow.

3) Cleanability The toner was loaded on magicolor2300DL (Minolta QMS), 3000 printing durability tests were performed, and image noise due to unwiped images after 3000 sheets was examined.
○: When there is no image noise;
X: In the case of image noise having a problem in use.

The evaluation results are shown in Table 3.

As is apparent from the results, the toners of the examples according to the present invention exhibited sufficient charge stability, and both the initial image and the image after the printing durability test were good. In the toner of the comparative example, characteristics satisfying all the charging stability, transferability and cleaning property were not obtained.

Claims (2)

  A toner for developing electrostatic images, comprising at least toner particles and three types of hydrophobic silica-containing fine particles having different average particle diameters. The electrostatic image development according to claim 1, wherein the three types of hydrophobic silica-containing fine particles have an average particle size of 5 nm or more and less than 20 nm, 20 nm or more and less than 100 nm, and 100 nm or more and 500 nm or less. Toner.