Negative-chargeability control resin

#1. Field of the Invention

#This invention relates to a negative-chargeability control resin for electrophotographic charging toners used when electrostatic latent images are made into visible images in dry-process electrophotography. More particularly, it relates to a negative-chargeability control resin which enables free control of electrostatic charging, may cause no toner scatter when used as a charge control agent and can contribute to formation of images having sharp hues, superior image reproducibility and high density.

#2. Related Background Art

#FIGURE is a schematic view of an instrument used to measure triboelectric charge quantity.

#Studies made by the present inventors have revealed that any negative-chargeability control resin comprised of the copolymer of an acrylamide monomer having a sulfonic acid group has a limited ability to endow a toner with stable triboelectric chargeability to obtain a toner which may suppress fog even in a normal-temperature and low-humidity environment and can exhibit sufficient image density even in a high-temperature and high-humidity environment, and that it is important to copolymerize a monomer component capable of lessening fog and improving the rise of charging (or chargeability rapidness), with a monomer component capable of enhancing the triboelectric charge quantity of the toner.

#According to studies made by the present inventors, a vinyl monomer represented by the following formula (1) (hereinafter referred to as “monomer (A)”) or a vinyl monomer represented by the following formula (2) (hereinafter referred to as “monomer (B)”) has the effect of lessening fog even in a normal-temperature and low-humidity environment and improving the rise of triboelectric charging of toner. It has also been found that the triboelectric charge quantity of toner is remarkably improved by copolymerizing this monomer (A) or (B) with a vinyl monomer having as a functional group a carboxyl group or a carboxyl group made into salt structure (hereinafter called “monomer (C)”). As the monomer (C), a vinyl monomer represented by the following formula (3) or (4) may preferably be used. While the “vinyl monomer” strictly means a monomer having “CH2═CH—”, that term referred to herein includes “CH2═CR— (R: a substituent such as an alkyl group) 3

#wherein R1 represents a hydrogen atom or a methyl group; and R2 and R3 each represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms which can be substituted with a substituent except for an acid group, or R2 and R3 may combine chemically to form a heterocyclic ring having 4 to 20 carbon atoms, or R2 and R3 may form a cyclic structure having at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom and a sulfur atom and having 4 to 19 carbon atoms. 4