Toner
A toner including a toner particle that contains a binder resin, a polyester resin A and a wax, wherein the polyester resin A contains a specific amount of an isosorbide unit based on a total number of monomer units constituting the polyester resin A, the content of the polyester resin A is a specific amount, and when observing a cross-section of the toner, twenty toner particle cross-sections are selected that have a major axis R (μm) that satisfies a specific relationship with respect to the weight-average diameter D 4 (μm) of the toner, each major axis r that have the largest major axis is measured for those domains composed of wax present in the selected toner particle cross-sections, and the arithmetic mean (r/R)st of the determined r/R satisfies a specific relationship.
1. A toner comprising a toner particle, wherein
the toner particle has a core-shell structure constituted by a core portion and a shell portion,
the core portion contains a binder resin and a wax, and
the shell portion contains a polyester resin A,
the polyester resin A comprising an isosorbide unit represented by formula (1)
the polyester resin A being a polymerization product obtained by condensation polymerization of:
(i) a dicarboxylic acid or anhydride thereof, wherein the dicarboxylic acid is selected from the group consisting of maleic acid, fumaric acid, itaconic acid, oxalic acid, malonic acid, succinic acid, dodecyl succinic acid, dodecenyl succinic acid, adipic acid, azelaic acid, sebacic acid, decane-1,10-dicarboxylic acid, phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, tetrabromophthalic acid, tetrachlorophthalic acid, HET acid, himic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid and 2,6-naphthalenedicarboxylic acid,
(ii) an isosorbide represented by formula (2)
(iii) a divalent alcohol other than the isosorbide, wherein the divalent alcohol is selected from the group consisting of ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, neopentyl glycol, bisphenol A, bisphenol F, ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, xylylene diglycol, 1,4-cyclohexanedimethanol and hydrogenated bisphenol A, and
(iv) at least one compound selected from the group consisting of a tricarboxylic acid, a tetracarboxylic acid, a tricarboxylic acid anhydride, and a tetracarboxylic acid anhydride, wherein the tricarboxylic acid is trimellitic acid or methylcyclohexene tricarboxylic acid, the tetracarboxylic acid is pyromellitic acid, the tricarboxylic acid anhydride is trimellitic acid anhydride or methylcyclohexene tricarboxylic acid anhydride, and the tetracarboxylic acid anhydride is pyromellitic acid anhydride,
the isosorbide unit is contained in a molar ratio of 1.58 to 10.50 mol % based on a total number of monomer units constituting the polyester resin A,
an acid value of the polyester resin A is 2.0 to 15.0 mgKOH/g,
a content of the polyester resin A is 1.0 to 10.0 mass parts based on 100.0 mass parts of the binder resin, and
when observing a cross-section of the toner using a transmission electron microscope (TEM), 0.25 ≤(r/R)st≤0.50, where (r/R)st is an arithmetic mean of twenty r/R calculations determined by:
(1) selecting twenty toner particle cross-sections, each of the twenty toner particle cross-sections has a major axis R (μm) that satisfies a relationship 0.9≤R/D 4 ≤1.1 with respect to a weight-average diameter D 4 (μm) of the toner as measured with a flow particle image measuring apparatus, and
(2) determining r/R for each of the twenty toner particle cross-sections, wherein the r (μm) denotes the largest major axis of a domain composed of the wax present in the one toner particle cross-section.
2. The toner according to claim 1 , wherein a weight-average molecular weight (Mw) of the polyester resin A as measured by gel permeation chromatography is 5000 to 30000.
3. The toner according to claim 1 , wherein a content of the wax is 5.0 to 30.0 mass parts based on 100.0 mass parts of the binder resin.
4. The toner according to claim 1 , wherein the binder resin comprises vinyl resin.
5. The toner according to claim 1 , wherein the toner particle is produced by dispersing in an aqueous medium a polymerizable monomer composition comprising the polyester resin A, the wax and a polymerizable monomer that forms the binder resin,
forming a particle of the polymerizable monomer composition, and
polymerizing the polymerizable monomer contained in the particle.
6. The toner according to claim 1 , which satisfies εw <εb wherein εw is a specific dielectric constant of the wax and εb is a specific dielectric constant of the binder resin.
7. The toner according to claim 1 , wherein the polyester resin A is a polymerization product obtained by condensation polymerization of an isosorbide represented by formula (2)
terephthalic acid, isophthalic acid, trimellitic acid, propylene oxide adduct of bisphenol A and ethylene oxide adduct of bisphenol A.