Surface-treated fumed silica, with a tribo-electro static charge of 500 C/g to +500 C/g, a ratio of the tribo-electro static charge to BET surface area of 3.5 C/m.sup.2 to +3.5 C/m.sup.2, a methanol wettability of at least 20% by volume methanol in methanol/water mixture, a ratio of carbon content to BET surface area of at most 0.020 wt. %*g/m.sup.2, a process for its preparation and the use thereof.

Provided is a process cartridge that is excellent in initial charge rising performance, and in charge uniformity of a halftone image throughout a long period of time from the start of use until after endurance. Specifically, provided is a process cartridge including: an electrophotographic photosensitive member; a toner; and a developing unit, wherein the toner contains toner particles and an external additive A, the external additive A, and wherein the electrophotographic photosensitive member includes an electroconductive support, a photosensitive layer, and a surface protective layer, wherein the surface protective layer contains electroconductive particles.

An electrostatic charge image developing toner contains toner particles, silica particles that are added to an exterior of the toner particles, and titanic acid compound particles that are added to the exterior of the toner particles and have an average circularity of 0.890 or more and 0.950 or less, in which the silica particles include particles having a primary particle size of 80 nm or less, the particles having a primary particle size of 80 nm or less have at least one peak in a range of 20 nm or more and less than 80 nm in a number-based primary particle size distribution curve (hereinafter, silica particles having such a peak will be called specific silica particles), the titanic acid compound particles have at least one peak in a range of 20 nm or more and less than 80 nm in a number-based primary particle size distribution curve, a difference between an average circularity of the specific silica particles and the average circularity of the titanic acid compound particles is 0.05 or less, and a difference between a toner coverage of the specific silica particles and a toner coverage of the titanic acid compound particles is 20% points or less.

A toner comprising a toner particle comprising a binder resin, wherein the toner particle comprises a compound represented by a following structural formula (1) and a compound represented by a following structural formula (2), and a content of the compound represented by the following structural formula (2) comprised in the toner is 0.3 mass ppm or more, ##STR00001##

A toner includes toner particles. Each of the toner particles includes a toner base particle including a binder resin, resin particles covering the toner base particle, and zinc stearate particles serving as an external additive. In each of the toner particles, a coverage rate of the toner base particle with the resin particles is 30% or greater and 70% or less. The zinc stearate particles have a volume average particle diameter of 3 m or greater and 20 m or less.

An electrostatic charge image developing toner contains negatively charged toner particles and silica particles added to an exterior of the toner particles, in which in a case where the silica particles are sorted into silica particles (S1) having a circularity of 0.91 or more and silica particles (S2) having a circularity less than 0.91, a mass ratio N/Si of a nitrogen element to a silicon element in a group of the silica particles (S1) is 0.005 or more and 0.50 or less, a mass ratio N/Si of a nitrogen element to a silicon element in a group of the silica particles (S2) is less than 0.005, and an average circularity of the silica particles (S2) is 0.84 or more and less than 0.91.

A toner comprising a toner particle comprising a binder resin, and a strontium titanate particle and a hydrotalcite particle on a surface of the toner particle, wherein the hydrotalcite particle comprises fluorine, the fluorine is present inside the hydrotalcite particle in line analysis of STEM-EDS mapping analysis of the toner, and when an area ratio of the strontium titanate particle to the toner particle in an EDS measurement field, which is measured through the STEM-EDS mapping analysis of the toner, is defined as T1 (%) and an area ratio of the hydrotalcite particle to the toner particle in the EDS measurement field, which is measured through the STEM-EDS mapping analysis of the toner, is defined as H1 (%), T1/H1 is 0.15 to 9.00.

A toner comprising colored resin particles, which contain a binder resin, a colorant, a positively-chargeable charge control resin and a release agent, and an external additive, wherein the positively-chargeable charge control resin comprises a copolymer A, which contains a functional group-containing monomer unit in an amount of 1.50% by mass or more and 6.00% by mass or less, and a copolymer B, which contains a functional group-containing monomer unit in an amount of 0.10% by mass or more and less than 1.50% by mass, and wherein the colored resin particles further contain a polar resin having an acid value of 0.5 mgKOH/g or more and 8.0 mgKOH/g or less.

A toner comprising colored resin particles, which contain a binder resin, a colorant, a positively-chargeable charge control resin and a release agent, and an external additive, wherein the positively-chargeable charge control resin comprises a copolymer A, which contains a functional group-containing monomer unit in an amount of 1.50% by mass or more and 6.00% by mass or less, and a copolymer B, which contains a functional group-containing monomer unit in an amount of 0.10% by mass or more and less than 1.50% by mass, and wherein the colored resin particles further contain a polar resin having an acid value of 0.5 mgKOH/g or more and 8.0 mgKOH/g or less.

A positively charged toner includes a toner base particle and an external additive that is adhered to the surface of the toner base particle. The external additive includes a silica particle the surface of which has been positively charged, a strontium titanate particle the surface of which is not positively charged and a resin fine particle that is formed of an acrylic resin. The number average primary particle diameter of each of the silica particle and the strontium titanate particle is 10 nm or more but 40 nm or less. The coverage ratio of the silica particle to the surface region of the toner base particle is 30% or more but 40% or less. The coverage ratio of the strontium titanate particle to the surface region of the toner base particle is 5% or more but 10% or less.