Pressure-responsive particles include pressure-responsive base particles and resin particles, in which the pressure-responsive base particles contain a styrene-based resin that contains styrene and other vinyl monomers as polymerization components and a (meth)acrylic acid ester-based resin that contains at least two kinds of (meth)acrylic acid esters as polymerization components, a ratio of a mass of the (meth)acrylic acid esters to a total mass of polymerization components is 90% by mass or more in the (meth)acrylic acid ester-based resin, the pressure-responsive particles have at least two glass transition temperatures, a difference between a lowest glass transition temperature and a highest glass transition temperature is 30° C. or higher, and a ratio of a mass of the resin particles to a total mass of the pressure-responsive particles is 0.05% by mass or more and 2.0% by mass or less.

A toner comprising a toner particle comprising a resin A, and an external additive A, wherein the resin A is a resin represented by formula (1) below, the resin A is present at the surface of the toner particle, the external additive A is a fine particle containing silicon, the average value of the shape factor SF-1 of the external additive A is from 105 to 120, the average value of the shape factor SF-2 of the external additive A is from 100 to 130.

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A toner according to an embodiment includes toner base particles containing a crystalline polyester resin, and an external additive containing silica particles. The silica particles have a D.sub.50 of 40 to 75 nm. The moisture content of the silica particles is less than 1.0 mass %. The softening temperature of the toner is 58° C. or higher. The melting temperature of the toner is between 102 and 108° C. The toner satisfies both the following formulae:

Ts′−Ts≤15° C.; and

1.00≤(TA)/(TB)≤1.25.

Ts′ is the softening temperature of the toner after being left at 45° C. for 200 hours, and Ts is the softening temperature of the toner.

TA is the ratio of the melting temperature to the softening temperature of the toner, and TB is the ratio of the melting temperature to the softening temperature of the toner after being left at 45° C. for 200 hours.

A toner according to an embodiment includes toner base particles and an external additive. The external additive contains silica particles having a D.sub.50 of 70 to 120 nm. The joining degree of the silica particles is 80% or more. The toner base particles contain a crystalline polyester resin and an ester wax. The ester wax is a condensation polymer of three or more types of carboxylic acids and two or more types of alcohols. The proportion of a carboxylic acid, the content of which is highest, is between 70 and 95 mass %. The proportion of a carboxylic acid with a carbon number of 18 or less is 5 mass % or less. The proportion of an alcohol, the content of which is highest, is between 70 and 90 mass %. The proportion of an alcohol with a carbon number of 18 or less is 20 mass % or less.

A toner comprising a toner particle and an external additive, wherein the external additive comprises a composite particle comprising an organosilicon polymer fine particle covering a surface of an alumina particle, a coverage ratio of the surface of the alumina particle with the organosilicon polymer fine particle is 1 to 50 area %, and given A (nm) as a number-average particle diameter of primary particles of the organosilicon polymer fine particle and B (nm) as a number-average particle diameter of primary particles of the alumina particle, following formulae (I) and (II) are satisfied:

A≤90  (I)

100≤B≤1000  (II).

A negative-charging toner comprising a toner particle comprising a binder resin and an organic-inorganic composite fine particle comprising resin fine particles and inorganic fine particles A, wherein the organic-inorganic composite fine particle is negative charging, the organic-inorganic composite fine particle has a structure in which at least a part of the inorganic fine particle A is embedded in the resin fine particle, a number average particle diameter Db of the organic-inorganic composite fine particle is 50 to 350 nm, and a plurality of convex portions derived from the inorganic fine particles A are present on the surface of the organic-inorganic composite fine particle.

Metal oxide-polymer composite particles have a median particle size D50 of 40-75 nm or 100-150 nm and an average RTA of at least 0.06. Alternatively or in addition, metal oxide-polymer composites comprise two or more populations of metal oxide particles differing in size, particle size distribution, or shape. Alternatively or in addition, the use of a multicomponent hydrophobizing system including an alkylsilane to fabricate metal oxide-polymer composite particles increases the tribocharge of the composite particles.

A production method of a toner having a toner particle that contains a binder resin and an external additive that is externally added to the toner particle, wherein the production method has a toner particle dispersion step of obtaining a toner particle dispersion by dispersing the toner particle and an inorganic dispersant in an aqueous medium; and an external addition step of externally adding the external additive to the toner particle through addition of the external additive to the toner particle dispersion.

The present invention provides an external additive for toner, selected from the group consisting of tin oxide fine particles, complex tin oxide fine particles, and a mixture of the same fine particles, wherein the fine particles are (−) charged fine particles having an energy band gap of 3.2 to 3.6 eV, an electronegativity value (χ) of 15 to 18, and a Blow-Off charge amount (uC/g) of −100 to −150. The external additive for toner of the present invention can: replace nano-sized titanium dioxide which has been conventionally used as an external additive for toner; guarantee general consumers using image devices as well as workers in the image industry safety from the harmful influences that may be generated upon exposure to the nano-sized titanium dioxide detached from the surface of a toner in use; and be safe for the human body.

An example toner having a plurality of toner particles is provided. The toner particles include a core particle including a binder resin, a colorant, and a releasing agent, and an external additive to attach to a surface of the core particle, the external additive including silica particles and tin oxide particles.