Toner for developing statically charged images and process for preparation thereof

Claim 2

A toner for developing statically charged images, which comprises a binder resin and, dispersed therein, at least a colorant and a charge-controlling dye, wherein the toner consists of spherical particles having a circularity, defined by the following formula (1), of from 0.95 to 1: Circularity (D) = wherein r L represents the long radius of the toner particles and r S represents the short radius of the toner particles, and the surface dye concentration is from 1 x 10⁻³ to 4 x 10⁻³ g/g.

Claim 3

A toner as set forth in claim 1, wherein the dye adheres uniformly to the surfaces of the particles.

Claim 4

A toner as set forth in claim 1 or 2, wherein the dye is a metal-containing complex salt compound.

Claim 5

A toner as set forth in claim 3, wherein the metal-containing complex sait compound is a metal complex sait of salicylic acid or an alkylsalicyiic acid.

Claim 6

A toner as set forth in claim 3, wherein the metal-containing complex salt compound is a metal complex salt of an azo dye.

Claim 7

A toner as st forth in any of claims 1 through 5, wherein the median diameter based on the volume of the spherical particles is 5 to 11 µm and D₂₅/D₇₅ indicating the dispersion of the particle size is from 1.2 to 1.6.

Claim 8

A toner as set forth in any of claims 1 through 6, wherein the sphecrical particles are polymer particles prepared directly by suspension polymerization.

Claim 9

A process for the preparation of a toner for developing statically charged images, which comprises forming spherical particles comprising a binder resin and, dispersed therein, at least a colorant and a charge-controlling dye and having a circularity, defined by the following formula (1), of from 0.95 to 1: Circularity (D) wherein r L represents the long radius of the toner particles and r S represents the short radius of the toner particles, immersing the spherical particles in an organic solvent capable of dissolving or dispersing the charge-­controlling dye therein but incapable of dissolving the resin component therein, and thereby sticking the charge-controlling dye uniformly to the entire surfaces of the particles while washing away the unnecessary portion of the charge-controlling dye present on the surfaces of the particles.

Claim 10

A process for the preparation of a toner for developing statically charged images, which comprises forming spherical particles comprising a binder resin and, dispersed therein, at least a colorant and a charge-controlling dye and having a circularity, defined by the following formula (1), of from 0.95 to 1: Circularity (D) wherein r L represents the long radius of the toner particles and r S represents the short radius of the toner particles, immersing the spherical particles in an organic solvent capable of dissolving or dispersing the charge-­controlling dye therein but incapable of dissolving the resin component therein, and thereby sticking the charge-controlling dye uniformly to the entire surfaces of the particles while washing away the unnecessary portion of the charge-controlling dye present on the surfaces of the particles.

Claim 11

A process according to claim 8, wherein the dye concentration on the surfaces of the final particles is adjusted to 1.0 x 10⁻³ to 4 x 10⁻³ g/g.

Claim 12

A process according to claim 8 or 9, wherein the spherical particles having a circularity within said range be polymer particles obtained by suspending a polymerizable composition comprising at least a polymerizable monomer, a colorant and a charge-­controlling dye in an amount of at least 0.1% by weight based on the polymerizable monomer in an aqueous phase and subjecting the suspension to polymerization reaction, which have a median diameter based on the volume of from 5 to 11 µm and D₂₅/D₇₅, indicating the dispersion of the particle diameter, of from 1.2 to 1.6.