| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a nonomagnetic one-component negative charge color developer having excellent transfer property by using a specified linear polyester resin as a binder resin and using a specified boron compd. as a charge controlling agent. SOLUTION: A linear polyester resin having 100 to 120 deg.C softening point, 20 to 40KOHmg/g sum of the acid value and hydroxyl value, and <=10 ratio of weight average mol.wt./number average mol.wt. is used. The charge controlling agent is a boron compd. expressed by formula I. Particles as an external additive are composed of hydrophobic silica and hydrophobic titanium dioxide, and these particles are added such that the weight ranges 1:1 to 1:3, that the whole specific surface area of the external additive defined by formula II ranges 100 to 300 and that the sum amt. of the external additive particles to the toner particles is 0.8 to 2.5wt.%. In formula I, R1 , R3 are aryl groups, R2 , R4 are hydrogen atoms, etc., X is a cation, and n is 1 or 2. In formula II, Ss and Vs are the specific surface area and the added amt. of the hydrophobic silica, respectively, to the toner particles, and St and Vt are the specific surface area and added amt. of the hydrophobic titanium dioxide to the toner particles.</p> |
