JP5853694B2 - Positively chargeable toner for electrostatic image development - Google Patents

Description

  The present invention relates to a positively chargeable toner for developing an electrostatic charge image used for developing an electrostatic latent image in electrophotography, electrostatic recording method, electrostatic printing method and the like.

  Conventionally, in a developer used for general electrophotography, desired fluidity and charging characteristics can be obtained by attaching an external additive to the surface of the colored resin particles. As the external additive, fine particles made of inorganic or organic substances are widely used. As such an external additive, metal oxide particles and resin particles, and those obtained by surface treatment of these have been widely used.

  As the external additive, silica fine particles having various particle diameters are generally used. On the other hand, many inventions using other particles are also known. Developers include negatively charged developers and positively charged developers. Usually, negatively charged developers use negatively charged external additives, and positively charged developers are used as positively charged developers. A positively chargeable external additive is used.

  For example, Patent Document 1 discloses a negatively chargeable toner containing polymethylsilsesquioxane powder (silicone resin powder) having negative chargeability as an electrophotographic developer. The specification of the document describes that the particle diameter of the powder is 0.1 to 10 μm, and that a toner using the powder can obtain a clear image without fogging.

  Patent Document 2 includes colored fine particles containing a binder resin composed of a styrene resin and a colorant, having a sphericity of 0.8 or more and a negative charge polarity, hydrophobized silica fine particles having a specific particle size, and silicone A negatively chargeable non-magnetic one-component developer obtained by mixing resin particles is disclosed. It is described that the developer disclosed in this document has sufficient fluidity, an image with high image density, low fog, and a high image quality level.

  In Patent Document 3, silicone resin particles having an average particle diameter of 1/2 to 1/30 of the average particle diameter of the toner in an electrostatic charge image developing toner mainly composed of a binder resin and a colorant are added. A negatively chargeable electrostatic charge image developing toner is disclosed. A toner is disclosed in which alumina particles having a specific purity, a primary particle size, and a specific ion content are externally added to colored particles having a fixed shape and particle size distribution. In the examples of the specification of the document, evaluation regarding image fogging, transfer failure, charging failure, and image streaks is described for a printout image using the toner.

JP 63-101854 A Japanese Patent Laid-Open No. 07-114213 Japanese Patent Application Laid-Open No. 09-080795

  Although the silicone resin particles act as a negatively chargeable external additive, the toners (developers) in Patent Documents 1 to 3 are negatively chargeable, and the negatively chargeable toner (developer) has a negatively chargeable external additive. Although there is a description about the effect when the silicone resin particle as an additive is added, there is no disclosure of what effect is obtained when this negatively charged silicone resin particle is applied to a positively charged toner. Absent.

  An object of the present invention is to provide a positively chargeable toner for developing an electrostatic image having excellent printing durability and no vertical stripes.

As a result of intensive studies to solve the above-mentioned problems, the present inventor found that the toner containing the colored resin particles and the external additive contained silicone resin particles having a specific particle size and particle size distribution and inorganic fine particles A having a specific particle size. The inventors have found that the above-mentioned problems can be solved by adding a specific amount to the colored resin particles.
That is, according to the present invention, in the positively chargeable toner for developing an electrostatic image containing colored resin particles containing a binder resin and a colorant and an external additive, the external additive has a number average particle diameter. When the particle size distribution is 0.1 to 1 μm, the particle size distribution corresponding to 50% of the cumulative volume from the small particle size side is Dv50, and the particle size corresponding to 90% of the cumulative volume is Dv90, Silicone resin particles having a particle size distribution Dv90 / Dv50 of 1.6 or less, and positively chargeable inorganic fine particles A having a number average particle size of 7 to 25 nm, and 100 parts by mass of the colored resin particles, A positively chargeable toner for developing electrostatic images having a content of 0.05 to 2 parts by mass and a content of the positively chargeable inorganic fine particles A of 0.1 to 2 parts by mass is obtained.

  In the present invention, it is preferable that the amount of adsorbed moisture of the silicone resin particles is 1.0% by mass or less.

  In the present invention, the external additive further contains inorganic fine particles B having a number average particle diameter of 30 to 200 nm, and the content of the inorganic fine particles B is based on 100 parts by mass of the colored resin particles. It is preferable that it is 0.1-2 mass parts.

  In the present invention, the colored resin particles preferably have a volume average primary particle size of 4 to 12 μm and an average circularity of 0.96 to 1.00.

  By including silicone resin particles, which are negatively chargeable external additives, in the positively chargeable toner as described above, a positively chargeable toner for developing an electrostatic image having excellent printing durability and no vertical stripes is obtained. It is done.

  The electrostatic charge image developer of the present invention is an electrostatic charge image developer containing colored resin particles containing a binder resin and a colorant, and an external additive, wherein the external additive has a number average particle size of 0.00. 1 to 1 μm and silicone fine particles having a particle size distribution Dv90 / Dv50 of 1.6 or less are contained, and the content of the silicone fine particles is 0.05 to 1 part by mass with respect to 100 parts by mass of the colored resin particles. It is characterized by being.

Hereinafter, the positively chargeable toner for developing an electrostatic image of the present invention (hereinafter, simply referred to as “positively chargeable toner”) will be described.
The positively chargeable toner of the present invention contains a specific amount of colored resin particles containing a binder resin and a colorant, the silicone resin particles satisfying specific conditions as an external additive, and inorganic fine particles A.
The positively chargeable toner of the present invention is preferably obtained by adhering and adding the silicone resin particles and inorganic fine particles A as external additives to the surface of the colored resin particles.
Hereinafter, the production method of the colored resin particles used in the present invention, the colored resin particles obtained by the production method, the production of the positively chargeable toner of the present invention using the colored resin particles, the silicone resin particles, and the inorganic fine particles A The method and the positively chargeable toner of the present invention will be described in order.

1. Production method of colored resin particles Generally, the production method of colored resin particles is roughly classified into dry methods such as a pulverization method, and wet methods such as an emulsion polymerization aggregation method, a suspension polymerization method, and a dissolution suspension method. The wet method is preferable because a developer excellent in printing characteristics such as the property is easily obtained. Among wet methods, a polymerization method such as emulsion polymerization aggregation method and suspension polymerization method is preferable because it is easy to obtain a developer having a relatively small particle size distribution on the order of microns, and among these polymerization methods, suspension polymerization method is preferable. More preferred.

  In the emulsion polymerization aggregation method, an emulsified polymerizable monomer is polymerized to obtain a resin fine particle emulsion, which is aggregated with a colorant dispersion or the like to produce colored resin particles. In the dissolution suspension method, a solution in which a developer component such as a binder resin or a colorant is dissolved or dispersed in an organic solvent is formed into droplets in an aqueous medium, and the organic solvent is removed to obtain colored resin particles. It is a manufacturing method and can use a well-known method, respectively.

  The colored resin particles used in the present invention can be produced by employing a wet method or a dry method. Among the wet methods, a preferred suspension polymerization method is adopted, and the following process is performed.

(A) Suspension polymerization method (A-1) Preparation step of polymerizable monomer composition First, a polymerizable monomer, a colorant, a positively chargeable charge control agent, and a release agent added as necessary. Other additives such as a mold agent are mixed to prepare a polymerizable monomer composition. The mixing at the time of preparing the polymerizable monomer composition is performed using, for example, a media type dispersing machine.

  The polymerizable monomer used in the present invention refers to a monomer having a polymerizable functional group, and the polymerizable monomer is polymerized to become a binder resin. It is preferable to use a monovinyl monomer as the main component of the polymerizable monomer. Examples of the monovinyl monomer include styrene; styrene derivatives such as vinyl toluene and α-methylstyrene; acrylic acid and methacrylic acid; methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, acrylic acid 2 Acrylic esters such as ethylhexyl and dimethylaminoethyl acrylate; methacrylic esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate and dimethylaminoethyl methacrylate; acrylonitrile And nitrile compounds such as methacrylonitrile; amide compounds such as acrylamide and methacrylamide; olefins such as ethylene, propylene, and butylene. These monovinyl monomers can be used alone or in combination of two or more. Of these, styrene, styrene derivatives, and acrylic esters or methacrylic esters are preferably used as monovinyl monomers.

In order to improve hot offset and storage stability, it is preferable to use any crosslinkable polymerizable monomer together with the monovinyl monomer. A crosslinkable polymerizable monomer means a monomer having two or more polymerizable functional groups. Examples of the crosslinkable polymerizable monomer include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; alcohols having two or more hydroxyl groups such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; Examples include ester compounds in which two or more carboxylic acids are ester-bonded; other divinyl compounds such as N, N-divinylaniline and divinyl ether; compounds having three or more vinyl groups. These crosslinkable polymerizable monomers can be used alone or in combination of two or more.
In the present invention, the crosslinkable polymerizable monomer is usually used at a ratio of 0.1 to 5 parts by mass, preferably 0.3 to 2 parts by mass with respect to 100 parts by mass of the monovinyl monomer. desirable.

  Furthermore, it is preferable to use a macromonomer as a part of the polymerizable monomer because the balance between the storage stability of the obtained positively chargeable toner and the fixability at a low temperature is improved. The macromonomer has a polymerizable carbon-carbon unsaturated double bond at the end of the molecular chain, and is a reactive oligomer or polymer having a number average molecular weight of usually 1,000 to 30,000. The macromonomer is preferably one that gives a polymer having a higher Tg than the glass transition temperature of the polymer obtained by polymerizing the monovinyl monomer (hereinafter sometimes referred to as “Tg”). The macromonomer is preferably used in an amount of 0.03 to 5 parts by mass, more preferably 0.05 to 1 part by mass, with respect to 100 parts by mass of the monovinyl monomer.

In the present invention, a colorant is used. However, when producing a color developer, black, cyan, yellow, and magenta colorants can be used.
As the black colorant, carbon black, titanium black, magnetic powder such as iron zinc oxide and nickel iron oxide can be used.

  As the cyan colorant, for example, a copper phthalocyanine compound, a derivative thereof, and an anthraquinone compound can be used. Specifically, C.I. I. Pigment blue 2, 3, 6, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, 17: 1, 60, and the like.

  Examples of the yellow colorant include monoazo pigments, azo pigments such as disazo pigments, and compounds such as condensed polycyclic pigments. I. Pigment yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 74, 83, 93, 97, 120, 138, 155, 180, 181, 185, 186, and 213.

  As the magenta colorant, monoazo pigments, azo pigments such as disazo pigments, and compounds such as condensed polycyclic pigments are used. I. Pigment Red 31, 48, 57: 1, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 149, 150, 163, 170, 184, 185, 187, 202, 206, 207, 209, 213, 237, 251, 269 and C.I. I. Pigment violet 19 and the like.

  In the present invention, each colorant can be used alone or in combination of two or more. The amount of the colorant is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the monovinyl monomer.

In the present invention, a positively chargeable charge control agent is usually used in order to obtain a positively chargeable toner.
The charge control agent is not particularly limited as long as it is generally used as a charge control agent for a developer. Among charge control agents, the charge control agent is highly compatible with a polymerizable monomer and has a stable charge. Therefore, a positively chargeable charge control resin is preferably used.
Examples of positively chargeable charge control agents include nigrosine dyes, quaternary ammonium salts, triaminotriphenylmethane compounds and imidazole compounds, polyamine resins as charge control resins that are preferably used, and quaternary ammonium group-containing copolymers. , And quaternary ammonium base-containing copolymers.
In the present invention, the charge control agent is usually used in a proportion of 0.01 to 10 parts by mass, preferably 0.03 to 8 parts by mass, with respect to 100 parts by mass of the monovinyl monomer. If the addition amount of the charge control agent is less than 0.01 parts by mass, fog may occur. On the other hand, when the addition amount of the charge control agent exceeds 10 parts by mass, printing stains may occur.

  From the viewpoint of improving the releasability of the developer from the fixing roll during fixing, it is preferable to add a release agent to the polymerizable monomer composition. Any release agent can be used without particular limitation as long as it is generally used as a release agent for a developer.

The release agent preferably contains an ester wax and / or a hydrocarbon wax. By using these waxes as a release agent, the balance between low-temperature fixability and storage stability can be made suitable.
The ester wax suitably used as a release agent in the present invention is more preferably a polyfunctional ester wax, such as pentaerythrole tetrapalinate, pentaerythrole tetrabehenate, pentaerythrole tetrastearate, etc. Pentaerythritol ester compound; hexaglycerin tetrabehenate tetrapalinate, hexaglycerin octabehenate, pentaglycerin heptabehenate, tetraglycerin hexabehenate, triglycerin pentabehenate, diglycerin tetrabehenate, Glycerin ester compounds such as glycerin tribehenate; dipentaerythritol ester compounds such as dipentaerystol hexamilitate and dipentaerystol hexapalinate; Glycerin ester compounds are preferred, hexaglycerin tetrabehenate tetrapalinate, hexaglycerin octabehenate, tetraglycerin hexabehenate, and triglycerin pentabehenate are more preferred, and hexaglycerin octabehenate is particularly preferred. preferable.

Examples of the hydrocarbon wax suitably used as a release agent in the present invention include polyethylene wax, polypropylene wax, Fischer-Tropsch wax, petroleum-based wax, etc. Among them, Fischer-Tropsch wax and petroleum-based wax are preferable, and petroleum-based wax. Is more preferable.
The number average molecular weight of the hydrocarbon wax is preferably 300 to 800, more preferably 400 to 600. Moreover, the penetration of the hydrocarbon wax measured by JIS K2235 5.4 is preferably 1 to 10, and more preferably 2 to 7.

In addition to the mold release agent, for example, natural wax such as jojoba; mineral wax such as ozokerite;
The mold release agent may be used in combination with one or more waxes as described above.
The release agent is preferably used in an amount of 0.1 to 30 parts by mass, and more preferably 1 to 20 parts by mass with respect to 100 parts by mass of the monovinyl monomer.

As other additives, it is preferable to use a molecular weight modifier when polymerizing a polymerizable monomer that is polymerized to become a binder resin.
The molecular weight modifier is not particularly limited as long as it is generally used as a molecular weight modifier for a developer. For example, t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, and 2,2 Mercaptans such as 1,4,6,6-pentamethylheptane-4-thiol; tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, N, N′-dimethyl-N, N′-diphenylthiuram disulfide, N , N′-dioctadecyl-N, N′-diisopropyl thiuram disulfide and other thiuram disulfides; These molecular weight modifiers may be used alone or in combination of two or more.
In this invention, it is desirable to use a molecular weight modifier in the ratio of 0.01-10 mass parts normally with respect to 100 mass parts of monovinyl monomers, Preferably it is 0.1-5 mass parts.

(A-2) Suspension step for obtaining a suspension (droplet formation step)
In the present invention, a polymerizable monomer composition containing at least a polymerizable monomer, a colorant, and a positively chargeable charge control agent is dispersed in an aqueous medium containing a dispersion stabilizer, and a polymerization initiator is added. Thereafter, droplet formation of the polymerizable monomer composition is performed. The method for forming droplets is not particularly limited. For example, (in-line type) emulsifying disperser (trade name “Milder” manufactured by Ebara Seisakusho Co., Ltd.), high-speed emulsifying disperser (made by Tokushu Kika Kogyo Co., Ltd., trade name “TK”). .. Homomixer MARK type II)) etc.

  As a polymerization initiator, persulfates such as potassium persulfate and ammonium persulfate: 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-methyl-N- (2- Hydroxyethyl) propionamide), 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis (2,4-dimethylvaleronitrile), and 2,2′-azobisisobutyro Azo compounds such as nitrile; di-t-butyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylbutanoate, diisopropyl peroxydicarbonate, Organic peroxides such as di-t-butylperoxyisophthalate and t-butylperoxyisobutyrate It is. These can be used alone or in combination of two or more. Among these, it is preferable to use an organic peroxide because residual polymerizable monomers can be reduced and printing durability is excellent.

  Among organic peroxides, peroxyesters are preferable because non-aromatic peroxyesters, that is, peroxyesters having no aromatic ring, are preferable because initiator efficiency is good and the amount of remaining polymerizable monomers can be reduced. More preferred.

  As described above, the polymerization initiator may be added before the droplet formation after the polymerizable monomer composition is dispersed in the aqueous medium. However, the polymerization initiator is not dispersed in the aqueous medium. It may be added to the monomer composition.

  The addition amount of the polymerization initiator used for the polymerization of the polymerizable monomer composition is preferably 0.1 to 20 parts by mass, more preferably 0.3 to 100 parts by mass of the monovinyl monomer. It is -15 mass parts, Most preferably, it is 1-10 mass parts.

  In the present invention, the aqueous medium refers to a medium containing water as a main component.

  In the present invention, the aqueous medium preferably contains a dispersion stabilizer. 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; metals such as aluminum oxide and titanium oxide. Oxides; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, and ferric hydroxide; inorganic compounds such as; water-soluble polymers such as polyvinyl alcohol, methylcellulose, and gelatin; anionic surfactants; Organic compounds such as nonionic surfactants; amphoteric surfactants; The said dispersion stabilizer can be used 1 type or in combination of 2 or more types.

  Among the above dispersion stabilizers, inorganic compounds, particularly colloids of poorly water-soluble metal hydroxides are preferred. By using a colloid of an inorganic compound, particularly a poorly water-soluble metal hydroxide, the particle size distribution of the colored resin particles can be narrowed, and the residual amount of the dispersion stabilizer after washing can be reduced. The polymerized developer can reproduce an image clearly and does not deteriorate environmental stability.

(A-3) Polymerization step As in (A-2) above, droplet formation is performed, the resulting aqueous dispersion medium is heated to initiate polymerization, and an aqueous dispersion of colored resin particles is formed.
The polymerization temperature of the polymerizable monomer composition is preferably 50 ° C. or higher, more preferably 60 to 95 ° C. The polymerization reaction time is preferably 1 to 20 hours, more preferably 2 to 15 hours.

  The colored resin particles may be used as a developer by adding an external additive as it is, but the so-called core-shell type obtained by using the colored resin particles as a core layer and forming a shell layer different from the core layer on the outside. It is preferable to use colored resin particles (also referred to as “capsule type”). The core-shell type colored resin particles balance the reduction of the fixing temperature and the prevention of aggregation during storage by coating the core layer made of a material having a low softening point with a material having a higher softening point. be able to.

  There is no restriction | limiting in particular as a method of manufacturing a core shell type colored resin particle using the said colored resin particle mentioned above, It can manufacture by a conventionally well-known method. An in situ polymerization method and a phase separation method are preferable from the viewpoint of production efficiency.

A method for producing core-shell type colored resin particles by in situ polymerization will be described below.
Addition of a polymerizable monomer (polymerizable monomer for shell) and a polymerization initiator to form a shell layer into an aqueous medium in which colored resin particles are dispersed, and then polymerize to form a core-shell type color. Resin particles can be obtained.

  As the polymerizable monomer for the shell, the same monomers as the aforementioned polymerizable monomers can be used. Among them, it is preferable to use monomers such as styrene, acrylonitrile, and methyl methacrylate, which can obtain a polymer having a Tg exceeding 80 ° C., alone or in combination of two or more.

  As a polymerization initiator used for polymerization of the polymerizable monomer for shell, persulfate metal salts such as potassium persulfate and ammonium persulfate; 2,2′-azobis (2-methyl-N- (2-hydroxyethyl) Water-soluble such as azo initiators such as) propionamide) and 2,2′-azobis- (2-methyl-N- (1,1-bis (hydroxymethyl) 2-hydroxyethyl) propionamide); A polymerization initiator can be mentioned. These can be used alone or in combination of two or more. The amount of the polymerization initiator is preferably 0.1 to 30 parts by mass, and more preferably 1 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer for shell.

  The polymerization temperature of the shell layer is preferably 50 ° C. or higher, more preferably 60 to 95 ° C. The polymerization reaction time is preferably 1 to 20 hours, more preferably 2 to 15 hours.

(A-4) Washing, filtration, dehydration, and drying steps The aqueous dispersion of colored resin particles obtained by polymerization is washed, dehydrated, and filtered to remove the dispersion stabilizer according to a conventional method after completion of the polymerization. The drying operation is preferably repeated several times as necessary.

  As the above washing method, when an inorganic compound is used as the dispersion stabilizer, the dispersion stabilizer can be dissolved in water and removed by adding an acid or alkali to the aqueous dispersion of colored resin particles. preferable. When a colloid of a poorly water-soluble inorganic hydroxide is used as the dispersion stabilizer, it is preferable to adjust the pH of the colored resin particle aqueous dispersion to 6.5 or less by adding an acid. As the acid to be added, inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, and organic acids such as formic acid and acetic acid can be used. Particularly, since the removal efficiency is large and the burden on the manufacturing equipment is small, Sulfuric acid is preferred.

  Various known methods and the like can be used as the method of dehydration and filtration, and there is no particular limitation. Examples thereof include a centrifugal filtration method, a vacuum filtration method, and a pressure filtration method. Also, the drying method is not particularly limited, and various methods can be used.

(B) Pulverization method When the pulverization method is used to produce colored resin particles, the following process is performed.
First, other additives such as a binder resin, a colorant, a positively chargeable charge control agent, and a release agent added as necessary are mixed in a mixer such as a ball mill, a V-type mixer, a Henschel mixer ( : Product name), high-speed dissolver, internal mixer, Fallberg etc. are used for mixing. Next, the mixture obtained as described above is kneaded while being heated using a pressure kneader, a twin-screw extrusion kneader, a roller or the like. The obtained kneaded material is coarsely pulverized using a pulverizer such as a hammer mill, a cutter mill, or a roller mill. Furthermore, after finely pulverizing using a pulverizer such as a jet mill or a high-speed rotary pulverizer, it is classified into a desired particle size by a classifier such as an air classifier or an airflow classifier, and colored resin particles obtained by a pulverization method. Get.

  In addition, other additives such as a binder resin, a colorant and a positively chargeable charge control agent used in the pulverization method, and a release agent added as necessary are the same as those described in the above (A) suspension polymerization method. Those listed can be used. Further, the colored resin particles obtained by the pulverization method can be made into core-shell type colored resin particles by a method such as an in situ polymerization method in the same manner as the colored resin particles obtained by the suspension polymerization method (A) described above.

  In addition, as the binder resin, a resin that has been widely used for a developer can be used. Specific examples of the binder resin used in the pulverization method include polystyrene, styrene-butyl acrylate copolymer, polyester resin, and epoxy resin.

2. Colored resin particles Colored resin particles are obtained by a production method such as the above-described (A) suspension polymerization method or (B) pulverization method.
Hereinafter, the colored resin particles constituting the developer will be described. The colored resin particles described below include both core-shell type and non-core type.

  The volume average particle diameter (Dv) of the colored resin particles is preferably 4 to 12 μm, and more preferably 5 to 10 μm. When Dv is less than 4 μm, the fluidity of the polymerization developer is lowered, and transferability may be deteriorated or the image density may be lowered. When Dv exceeds 12 μm, the resolution of the image may decrease.

  The colored resin particles have a ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) of preferably 1.0 to 1.3, more preferably 1. 0-1.2. When Dv / Dn exceeds 1.3, transferability, image density, and resolution may decrease. The volume average particle diameter and the number average particle diameter of the colored resin particles can be measured using, for example, a particle size distribution measuring device (trade name “Multisizer” manufactured by Beckman Coulter).

From the viewpoint of image reproducibility, the average circularity of the colored resin particles used in the present invention is preferably 0.96 to 1.00, more preferably 0.97 to 1.00, and 0.98. More preferably, it is -1.00.
When the average circularity of the colored resin particles is less than 0.96, the fine line reproducibility of printing may be deteriorated.

  In the present invention, the circularity is defined as a value obtained by dividing the circumference of a circle having the same projected area as the particle image by the circumference of the projected image of the particle. The average circularity in the present invention is used as a simple method for quantitatively expressing the shape of the particles, and is an index indicating the degree of unevenness of the colored resin particles. The average circularity is determined by the colored resin particles. 1 is shown in the case of a perfect sphere, and the value becomes smaller as the surface shape of the colored resin particles becomes more complicated.

3. Method for Producing Positively Charged Toner of the Present Invention An external additive containing the silicone resin particles described later and the positively charged inorganic fine particles A as the colored resin particles obtained by the above-described (A) polymerization method or (B) pulverization method. By mixing and stirring together, it is possible to uniformly and suitably add and add (externally add) to the surface of the colored resin particles.

The method of adhering and adding (external addition) external additives such as silicone resin particles and positively chargeable inorganic fine particles A described later to the surface of the colored resin particles is not particularly limited, and is performed using an apparatus capable of mixing and stirring. be able to.
As an apparatus capable of mixing and stirring, for example, Henschel mixer (: trade name, manufactured by Mitsui Mining), Super mixer (: trade name, manufactured by Kawada Manufacturing), Q mixer (: trade name, manufactured by Mitsui Mining), Typical examples include a high-speed stirrer such as a mechanofusion system (trade name, manufactured by Hosokawa Micron Corporation), mechano mill (trade name, manufactured by Okada Seiko Co., Ltd.), and nobilta (: trade name, manufactured by Hosokawa Micron Corporation).

  The positively chargeable toner of the present invention has a number average particle diameter of 0.1 to 1 μm as an external additive, and a particle diameter corresponding to 50% of the cumulative volume calculated from the small particle diameter side is Dv50. When the particle size corresponding to 90% of the cumulative volume is Dv90, silicone resin particles having a particle size distribution Dv90 / Dv50 of 1.6 or less, and positively chargeable inorganic fine particles A having a number average particle size of 7 to 25 nm The content of the silicone resin particles is 0.05 to 1 part by mass with respect to 100 parts by mass of the colored resin particles, and the content of the positively chargeable inorganic fine particles A is 0.1 to 2 Contains part by mass.

  The silicone resin particles are fine particles made of an organopolysiloxane having a three-dimensional network structure, and polyorganosilsesquioxane having a structural unit represented by the following formula (1) is particularly preferable.

  In the formula, R represents an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, or a propyl group, or a phenyl group, and has a methyl group, that is, a polymethylsilsesquioxane structure from the viewpoint of high heat resistance. Silicone resin particles are preferred. Polymethylsilsesquioxane is obtained by hydrolyzing methyltrialkoxysilane and methyltrihalosilane in an aqueous solution of ammonia or amines with reference to JP-A-2008-208158 and JP-A-2004-99630. Although it can be obtained by condensation, MSP-N050 (trade name: manufactured by Nikko Rika Co., Ltd.) having a number average particle diameter of 0.5 μm as a commercial product can be used.

  It is preferable that the silicone resin particles have a spherical shape because there is little decrease in developer fluidity. In the present invention, the number average particle diameter of the silicone resin particles is in the range of 0.1 to 1 μm, preferably in the range of 0.2 to 0.8 μm, and in the range of 0.3 to 0.5 μm. More preferably, If the number average particle size is too small, it is difficult to exhibit the polishing effect. Conversely, if the number average particle size is too large, the fluidity is lowered and the image quality is liable to be lowered.

The silicone resin particles have Dv50 / Dv50, where Dv50 is the particle size corresponding to 50% of the cumulative volume calculated from the small particle size side, and Dv90 is the particle size corresponding to 90% of the cumulative volume. The particle size distribution calculated in (1) is 1.6 or less, preferably 1.5 or less, and more preferably 1.3 or less.
When silicone resin particles having a Dv90 / Dv50 of greater than 1.6 are used, the adhesion of the silicone resin particles to the colored resin particles becomes non-uniform, resulting in variations in the effect of external addition and photoconductor filming. In addition, the silicone resin particles are likely to be detached, and may adhere to the printer member, causing vertical streaks or a decrease in printing durability. .

  The silicone resin particles preferably have a moisture content of 1.0% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.3% by mass or less. If the amount of adsorbed water exceeds 1.0% by mass, printing durability may be reduced.

  The usage ratio of the silicone resin particles is 0.01 to 2 parts by mass, preferably 0.05 to 1 part by mass, and more preferably 0.1 to 0.5 parts by mass with respect to 100 parts by mass of the colored resin particles. Part. If the use ratio is too small, the effect as a charge carrier may be insufficient. Conversely, if the use ratio is too large, filming may occur on the photoreceptor.

In the present invention, it contains positively chargeable inorganic fine particles A having a number average particle diameter of 5 to 25 nm as an external additive, and is made hydrophobic with a positively chargeable hydrophobizing agent for positive chargeability. ing.
When the number average particle diameter of the positively chargeable inorganic fine particles A is less than 5 nm, the positively chargeable inorganic fine particles are easily embedded from the surface to the inside of the colored resin particles, and the fluidity is changed to the positively chargeable toner. Insufficient imparting may adversely affect printing performance. On the other hand, when the number average particle diameter of the positively chargeable inorganic fine particles A exceeds 25 nm, the proportion (coverage) of the inorganic fine particles with respect to the surface of the colored resin particles is reduced, so that the fluidity is positive. In some cases, the toner cannot be sufficiently applied to the chargeable toner.
The number average particle diameter of the positively chargeable inorganic fine particles A is more preferably 7 to 25 nm, and further preferably 7 to 20 nm. The positively chargeable inorganic fine particles A are preferably positively chargeable silica fine particles, and more preferably fumed silica.

  Examples of the positively chargeable hydrophobizing agent include γ-aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, aminosilane, N Examples include aminosilane compounds and amino-modified silicone oils such as-(2-aminoethyl) 3-aminopropyltrimethoxysilane and N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane. Of the above, only one type of hydrophobic treatment agent may be used, or two or more types may be used.

The content of the positively chargeable inorganic fine particles A is preferably 0.1 to 2 parts by mass, more preferably 0.2 to 1.5 parts by mass with respect to 100 parts by mass of the colored resin particles. More preferably, it is 0.3-1 mass part.
When the content of the positively chargeable inorganic fine particles A is less than 0.1 part by mass, the function as an external additive cannot be sufficiently exerted, the fluidity is lowered, the storage stability and the printing durability are lowered. Sometimes. On the other hand, when the content of the inorganic fine particles A exceeds 2 parts by mass, the inorganic fine particles are easily released from the surface of the developer particles, and the chargeability in a high-temperature and high-humidity environment is reduced and fogging occurs. In some cases, the fixability may decrease.

  Various commercially available products can be used as the silica fine particles preferably used as the inorganic fine particles A. For example, HDK2150 (: trade name, number average particle size: 12 nm) manufactured by Clariant, R504 (: Product name, number average particle size: 12 nm), RA200HS (: product name, number average particle size: 12 nm), MSP-012 (: product name, number average particle size: 16 nm), MSP-013 (: Product name, number average particle size: 12 nm), TG820F manufactured by Cabot Corporation (: product name, number average particle size: 7 nm), TG7120 (: product name, number average particle size: 20 nm), and the like.

In the present invention, the external additive preferably contains inorganic fine particles B having a number average particle size of 30 to 200 nm in addition to the silicone resin particles and the positively chargeable inorganic fine particles A.
When the number average particle diameter of the inorganic fine particles B is less than 30 nm, the spacer effect is lowered and the printing performance such as fogging may be adversely affected. On the other hand, when the number average particle diameter of the inorganic fine particles B exceeds 200 nm, the inorganic fine particles are easily released from the surface of the developer particles, the function as an external additive is lowered, and the printing performance is adversely affected. May have an effect.
The number average particle diameter of the inorganic fine particles B is more preferably 35 to 100 nm, and further preferably 40 to 80 nm. The inorganic fine particles B are preferably silica fine particles, and more preferably hydrophobized.

The content of the inorganic fine particles B is preferably 0.1 to 2 parts by mass, more preferably 0.3 to 2 parts by mass, and more preferably 0.5 to 1 with respect to 100 parts by mass of the colored resin particles. More preferably, it is 5 parts by mass.
When the content of the inorganic fine particles B is less than 0.2 parts by mass, the function as the external additive cannot be sufficiently exhibited, and the printing performance may be adversely affected. On the other hand, when the content of the inorganic fine particles B exceeds 2 parts by mass, the inorganic fine particles B are easily released from the surface of the developer particles, the function as an external additive is lowered, and the printing performance is adversely affected. There is.

  In the present invention, preferably used inorganic fine particles B that have been subjected to a hydrophobic treatment are preferably subjected to a hydrophobic treatment with a hydrophobic treatment such as a silane coupling agent, silicone oil, fatty acid, and fatty acid metal salt. As the hydrophobizing agent, like the inorganic fine particles A described above, it is more preferable to use a positively chargeable hydrophobizing agent, an aminosilane compound or an amino-modified silicone oil, and it is particularly preferable to use an amino-modified silicone oil. .

  Various commercially available products can be used as the silica fine particles preferably used as the inorganic fine particles B. For example, NA50Y (: trade name, number average particle size: 35 nm), VPNA50H (: trade name, number) manufactured by Nippon Aerosil Co., Ltd. Average particle diameter: 40 nm); H05TA manufactured by Clariant (trade name, number average particle diameter: 50 nm);

4). Positively chargeable toner of the present invention The positively chargeable toner of the present invention obtained through the above steps has a number average particle size of 0.1 to 1 μm as an external additive, and the particle size distribution is calculated from the small particle size side. When the particle size corresponding to 50% of the cumulative volume is Dv50 and the particle size corresponding to the cumulative volume is 90% is Dv90, the silicone resin particles having a particle size distribution Dv90 / Dv50 of 1.6 or less, and the number average And positively chargeable inorganic fine particles A having a particle size of 7 to 25 nm, the content of the silicone resin particles is 0.05 to 1 part by mass with respect to 100 parts by mass of the colored resin particles, and the positive charge When the content of the conductive inorganic fine particles A is 0.1 to 2 parts by mass, the printing durability is excellent and no vertical stripes are generated.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited only to these examples. Parts and% are based on mass unless otherwise specified.
The test methods performed in the examples and comparative examples are as follows.

1. Example of production of positively chargeable toner [Example 1]
81 parts of styrene and 19 parts of n-butyl acrylate as a polymerizable monomer, 5 parts of carbon black (manufactured by Mitsubishi Chemical Co., Ltd., trade name: # 25B) as a black colorant, an in-line type emulsion disperser (manufactured by Ebara Corporation, The product was dispersed using a product name: Ebara Milder to obtain a polymerizable monomer mixture.
In the above polymerizable monomer mixture, 1 part of a charge control resin (manufactured by Fujikura Kasei Co., Ltd., trade name “Acrybase FCA-161P”) as a charge control agent, and fatty acid ester wax (manufactured by Nippon Oil & Fats Co., Ltd., trade name) as a release agent "WEP3") 5 parts, polymethacrylic acid ester macromonomer (manufactured by Toa Gosei Chemical Co., Ltd., trade name "AA6") as macromonomer, 0.6 part of divinylbenzene as crosslinkable polymerizable monomer Then, 1.6 parts of t-dodecyl mercaptan was added as a molecular weight modifier, mixed and dissolved to prepare a polymerizable monomer composition.

  On the other hand, at room temperature, in an aqueous solution in which 10.2 parts of magnesium chloride (water-soluble polyvalent metal salt) is dissolved in 250 parts of ion-exchanged water, sodium hydroxide (alkali metal hydroxide) 6.2 in 50 parts of ion-exchanged water. The aqueous solution in which the part was dissolved was gradually added with stirring to prepare a magnesium hydroxide colloid (slightly water-soluble metal hydroxide colloid) dispersion.

  The polymerizable monomer composition was charged into the magnesium hydroxide colloid dispersion at room temperature and stirred. 6 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, trade name: Perbutyl O) was added thereto as a polymerization initiator, and then an in-line type emulsifier / disperser (trade name, manufactured by Ebara Corporation). : Ebara Milder) was dispersed by high-speed shearing and stirring at a rotational speed of 15,000 rpm for 10 minutes to form droplets of the polymerizable monomer composition.

  A suspension (polymerizable monomer composition dispersion) in which droplets of the polymerizable monomer composition are dispersed is placed in a reactor equipped with a stirring blade, heated to 90 ° C., and polymerized. The reaction was started. When the polymerization conversion reached almost 100%, 2,2′-azobis (shell polymerization initiator dissolved in 1 part of methyl methacrylate and 10 parts of ion-exchanged water as shell polymerizable monomer) 0.3 part of 2-methyl-N- (2-hydroxyethyl) -propionamide) (manufactured by Wako Pure Chemical Industries, Ltd., trade name: VA-086, water-soluble) was added, and the reaction was continued at 90 ° C. for 4 hours. Thereafter, the reaction was stopped by cooling with water to obtain an aqueous dispersion of colored resin particles having a core-shell structure.

The aqueous dispersion of the colored resin particles was added dropwise with stirring sulfuric acid at room temperature, and acid washing was performed until the pH was 6.5 or less. Subsequently, filtration separation was performed, 500 parts of ion-exchanged water was added to the obtained solid content to make a slurry again, and water washing treatment (washing, filtration, dehydration) was repeated several times. Next, filtration separation was performed, and the obtained solid content was put in a container of a dryer and dried at 45 ° C. for 48 hours to obtain dried colored resin particles. The volume average particle size (Dv) of the obtained colored resin particles is 9.7 μm, the number average particle size (Dn) is 8.5 μm, the particle size distribution (Dv / Dn) is 1.14, and the average circularity is It was 0.987.
It was.

  Silicone resin particles having a number average particle size of 0.5 μm, a particle size distribution Dv90 / Dv50 of 1.3, and a moisture adsorption amount of 0.24% with respect to 100 parts of the colored resin particles obtained above (Nikko Rica) 0.2 part of the product name, product name: MSP-050), and inorganic fine particles A, and positively charged silica fine particles having a number average particle size of 20 nm (trade name: TG7120, manufactured by Cabot Corp.) that have been hydrophobized. 8 parts of inorganic fine particles B, 1 part of hydrophobically treated positively charged silica fine particles having a number average particle diameter of 50 nm (manufactured by Clariant, trade name: H05TA) are added, and a high-speed stirrer (trade name, manufactured by Mitsui Mining Co., Ltd.) A positively chargeable toner of Example 1 was prepared by mixing and stirring for 10 minutes at a peripheral speed of 40 m / s using a Henschel mixer.

[Example 2]
A positively chargeable toner of Example 2 was produced in the same manner as in Example 1 except that 0.2 part of the silicone resin particles was changed to 0.4 part of the silicone resin particles in Example 1.

[Example 3]
A positively chargeable toner of Example 3 was produced in the same manner as in Example 1 except that 0.2 part of the silicone resin particles was changed to 0.1 part of the silicone resin particles in Example 1.

[Comparative Example 1]
In Example 1, a positively chargeable toner of Comparative Example 1 was produced in the same manner as in Example 1 except that 0.2 parts of the silicone resin particles were not added.

[Comparative Example 2]
A positively chargeable toner of Comparative Example 2 was produced in the same manner as in Example 1 except that 0.8 part of the inorganic fine particles A was not added.

[Comparative Example 3]
In Example 1, the number average particle size was changed to 0.2 parts of the silicone resin particles having a number average particle size of 0.5 μm, a particle size distribution Dv90 / Dv50 of 1.3, and a moisture adsorption amount of 0.24%. Silicone resin particles having a diameter of 0.5 μm, a particle size distribution Dv90 / Dv50 of 1.8, and a moisture adsorption amount of 0.3% (product name: Tospearl 105 manufactured by Momentive Performance Materials) 0.4 A positively chargeable toner of Comparative Example 3 was produced in the same manner as in Example 1 except that the toner was changed to the part.

[Comparative Example 4]
In Example 1, the number average particle size was changed to 0.2 parts of the silicone resin particles having a number average particle size of 0.5 μm, a particle size distribution Dv90 / Dv50 of 1.3, and a moisture adsorption amount of 0.24%. Silicone resin particles having a diameter of 2.0 μm, a particle size distribution Dv90 / Dv50 of 1.5, and a moisture adsorption amount of 0.3% (product name: Tospearl 120 manufactured by Momentive Performance Materials) 0.4 A positively chargeable toner of Comparative Example 4 was produced in the same manner as in Example 1 except that the toner was changed to the part.

[Comparative Example 5]
In Example 1, the number average particle size was changed to 0.2 parts of the silicone resin particles having a number average particle size of 0.5 μm, a particle size distribution Dv90 / Dv50 of 1.3, and a moisture adsorption amount of 0.24%. Positively chargeable alumina particles having a diameter of 0.4 μm, a particle size distribution Dv90 / Dv50 of 1.4, and a moisture adsorption amount of 0.45% (trade name: AKP-30, manufactured by Sumitomo Chemical Co., Ltd.) 0.2 A positively chargeable toner of Comparative Example 5 was produced in the same manner as in Example 1 except that the toner was changed to the part.

[Comparative Example 6]
In Example 1, the number average particle size was changed to 0.2 parts of the silicone resin particles having a number average particle size of 0.5 μm, a particle size distribution Dv90 / Dv50 of 1.3, and a moisture adsorption amount of 0.24%. Positively chargeable melamine resin particles having a diameter of 0.5 μm, a particle size distribution Dv90 / Dv50 of 1.5, and a moisture adsorption amount of 0.6% (product name: Eposter S6, manufactured by Nippon Shokubai Co., Ltd.) 0.4 A positively chargeable toner of Comparative Example 6 was produced in the same manner as in Example 1 except that the toner was changed to the part.

2. Physical property evaluation of silicone resin particles, alumina particles and melamine resin particles (1) Particle size distribution Dv90 / Dv50
A sample was taken in a beaker, and 0.1 mL of an alkylbenzene sulfonic acid aqueous solution (manufactured by Fuji Film Co., Ltd., trade name: Drywell) was added as a dispersant and dispersed in ion-exchanged water. Using a dynamic light scattering particle size distribution measuring device (Horiba, Ltd .: LB-550), the dispersion obtained as described above was measured, and the particle size distribution (Dv90 / Dv50) was calculated.

(2) Adsorbed water content For measuring the adsorbed water content, a moisture adsorption / desorption measuring device (manufactured by HEIDEN, trade name: IGAsorb) was used. The sample is left in the apparatus under a dry nitrogen stream for 1 hour, the dry mass of the sample is measured, and then moisture is adsorbed in air at 32 ° C. and humidity 80% for 1 hour to adsorb moisture. The mass of the sample was measured.
The amount of adsorbed water (% by mass) was calculated from {(mass of sample adsorbed with water−mass of dried sample) / mass of dried sample)} × 100.

3. Evaluation of Physical Properties of Colored Resin Particles and Positively Charged Toner Properties of the colored resin particles and positively charged toners of Examples 1 to 3 and Comparative Examples 1 to 4 were examined. Details are as follows.

(1) Volume average particle size (Dv), number average particle size (Dn) and particle size distribution (Dv / Dn)
About 0.1 g of a measurement sample (colored resin particles) was weighed and taken in a beaker, and 0.1 mL of an alkylbenzenesulfonic acid aqueous solution (trade name: Drywell, manufactured by Fuji Film Co., Ltd.) was added as a dispersant. 10-30 mL of Isoton II is further added to the beaker, and dispersed for 3 minutes with a 20 W (Watt) ultrasonic disperser. Then, using a particle size analyzer (Beckman Coulter, trade name: Multisizer). , Aperture diameter: 100 μm, medium: Isoton II, number of measured particles: volume average particle diameter (Dv) and number average particle diameter (Dn) of the colored resin particles were measured under the conditions of 100,000 particles. Distribution (Dv / Dn) was calculated.

(2) Average circularity Into a container, 10 mL of ion exchange water is put in advance, 0.02 g of a surfactant (alkylbenzenesulfonic acid) is added as a dispersant, and 0.02 g of a measurement sample (colored resin particles) is further added. In addition, 60 W (Watt) was applied for 3 minutes with an ultrasonic disperser. The concentration of the colored resin particles at the time of measurement is adjusted to 3,000 to 10,000 particles / μL, and 1,000 to 10,000 colored resin particles having an equivalent circle diameter of 0.4 μm or more are flow-type particle images. Measurement was performed using an analyzer (trade name: FPIA-2100, manufactured by Simex Corporation). The average circularity was determined from the measured value.
The circularity is shown in the following calculation formula 1, and the average circularity is an average of the circularity.
Formula 1: (Circularity) = (Perimeter of circle equal to projected area of particle) / (Perimeter of projected image of particle)

(3) Initial charge amount After charging the positively chargeable toner obtained above into a commercially available non-magnetic one-component development type printer (manufactured by Brother Industries, trade name: MFC-9840-CDW), set the printing paper. After leaving it in an environment with a temperature of 23 ° C and a humidity of 50% (NN environment) for a whole day and night, under the same NN environment, one solid white print (printing density 0%) is performed, and the printer is in the middle of the white solid print. And the toner carried on the developing roller is sucked using a suction-type charge measuring device (trade name: 210HS-2A, manufactured by Trek Japan Co., Ltd.) to measure the charge amount of the toner. The initial charge amount per mass was calculated in terms of Q / M (μC / g).

(4) Longitudinal stripes and printing durability A commercially available non-magnetic one-component developing type printer (manufactured by Brother Industries, trade name: MFC-9840-CDW) is charged with the positively chargeable toner obtained above, and then printed. The paper was set and left to stand overnight in an environment (NN environment) at a temperature of 23 ° C. and a humidity of 50%, and then continuously printed up to 16,000 sheets at a 1% print density in the same NN environment.
Black solid printing (printing density 100%) was performed every 500 sheets, and the printing density of the black solid image was measured using a reflective image densitometer (trade name: RD918, manufactured by Macbeth). After that, white solid printing (printing density 0%) is performed, the printer is stopped in the middle of white solid printing, and the toner in the non-image area on the developed photosensitive member is adhesive tape (manufactured by Sumitomo 3M Ltd., product) Name: Scotch mending tape 810-3-18), and then peeled off and affixed to printing paper. Next, the whiteness (B) of the printing paper on which the adhesive tape is affixed is measured with a whiteness meter (trade name: ND-1 manufactured by Nippon Denshoku Co., Ltd.). The whiteness (A) was measured and the difference in whiteness (B−A) was defined as the fog value (%). Smaller values indicate better fog and better.
The number of continuously printed sheets capable of maintaining an image quality with a print density of 1.3 or more and a fog value of 2.5% or less was examined.
The same printing durability test was also performed in a high temperature and high humidity (H / H) environment (temperature: 35 ° C., humidity: 80%). At the same time, the number of vertical streaks was also visually examined.
In Table 1, “16,000 <” means that the image quality with the print density of 1.3 or more and the fog value of 2.5% or less was maintained even at the time of 16,000 sheets. It shows that. In addition, “-” in the table indicates that no vertical streak is generated even when 16,000 sheets or continuous printing in the printing durability test is completed.

  The measurement and test results of the positively chargeable toners of Examples 1 to 3 and Comparative Examples 1 to 6 are shown in Table 1 together with the composition of the modified external additive.

4). Summary of Evaluation Results of Positively Charged Toner Hereinafter, the positively charged toner will be examined with reference to Table 1.
It can be seen that the positively chargeable toner of Comparative Example 1 in which the silicone resin specified in the present invention is not used is inferior in printing durability of 11,000 sheets.
The positively chargeable toner of Comparative Example 2 in which the positively chargeable inorganic fine particles A defined in the present invention are not used has an initial charge amount as high as 46 μC / g, and printing durability is inferior at 9,000 sheets. I understand.
The positively chargeable toner of Comparative Example 3 using a silicone resin in which the particle size distribution Dv90 / Dv specified in the present invention is not 1.6 or less and the particle size distribution Dv90 / Dv is 1.8 has a printing durability of 12, It is inferior to 000 sheets, and it can be seen that vertical stripes occur at 8,000 sheets.
The positively chargeable toner of Comparative Example 4 using a silicone resin having a number average particle size larger than the range defined in the present invention and having a number average particle size of 2.0 μm is inferior in printing durability to 11,500 sheets. It can be seen that there are 6,000 vertical stripes.
The positively chargeable toner of Comparative Example 5, which uses alumina particles, which are positively chargeable external additives, instead of the silicone resin particles defined in the present invention, has inferior printing durability of 9,000 sheets and has 7 vertical stripes. It can be seen that it is generated with 1,000 sheets.
The positively chargeable toner of Comparative Example 5 using melamine resin particles, which are positively chargeable external additives, instead of the silicone resin particles defined in the present invention, has a printing durability of 10,000 sheets and has vertical stripes. It can be seen that it occurs at 5,000 sheets.

  The positively chargeable toners of Examples 1 to 3 using the silica fine particles and the positively chargeable inorganic fine particles A defined in the present invention with respect to these Comparative Examples 1 to 6 are the same as those of Example 2 with 12,000 vertical stripes. In Example 3, the printing durability was slightly inferior to 15,500 sheets. However, it can be seen that this is an excellent toner having no printing durability and no vertical stripes.

Claims (4)

In a positively chargeable toner for developing an electrostatic charge image containing colored resin particles containing a binder resin and a colorant, and an external additive,
The external additive has a number average particle diameter of 0.1 to 1 μm, and the particle diameter corresponding to 50% of the cumulative volume from the small particle diameter side is Dv50, and the cumulative volume is 90%. When the particle size corresponding to is Dv90, the particle size distribution Dv90 / Dv50 includes 1.6 or less silicone resin particles, and positively chargeable inorganic fine particles A having a number average particle size of 5 to 25 nm,
The content of the silicone resin particles is 0.05 to 2 parts by mass and the content of the positively chargeable inorganic fine particles A is 0.1 to 2 parts by mass with respect to 100 parts by mass of the colored resin particles. Positively chargeable toner for developing electrostatic images.   2. The positively chargeable toner for developing an electrostatic charge image according to claim 1, wherein the moisture content of the silicone resin particles is 1.0% by mass or less.   The external additive further contains inorganic fine particles B having a number average particle diameter of 30 to 200 nm, and the content of the inorganic fine particles B is 0.1 to 2 with respect to 100 parts by mass of the colored resin particles. The positively chargeable toner for developing an electrostatic charge image according to claim 1, wherein the toner is a part by mass.   4. The electrostatic charge image developing according to claim 1, wherein the colored resin particles have a volume average primary particle size of 4 to 12 μm and an average circularity of 0.96 to 1.00. 5. Positively charged toner.