Abstract
Triboelectrification in the two-components development system, and effects of the charge density on a toner surface and the toner size on electrophotographic image-quality factors have been investigated by varying (1) the toner median size d from 6.8 μm to 13.5 μm and the carrier median size D from 43 μm to 106 μm, and also varying (2) the carrier specific weight ρc by using different carrier core, (3) composition of methylmethacrylate/styrene copolymer resin (MMA/St) on the carrier surface, and (4) concentration of carbon black [C B] in the toner binder of polyester.
As regars triboelecrification of toners and a carrier in the two-components development system, it has been found that triboelectrification with n particles of toner on a carrier is more favorably describable by the charge density on a toner surface (q/st) as a function of surface-area ratio of n toners to a carrier (nst/sc), on bases of contact electrostatic field strength (Ek) and structural (or geometrical) factors of the toner and the carrier (ft, fc), rather than by the toner charge-to-mass ratio (q/m) as a function of mixing-weight ratio of toners to a carrier X (or toner concentration Tc) .
As regars the development efficiency of toners in solid area, it has been found that the development efficiency is determined by the charge density on a toner surface q/st, not by the toner charge-to-mass ratio q/m suggested by Schein and by others.
As regards the resolusion of line images reproduced by the two-components contact development in the rotating direction of the photoreceptor drum, the width of a line image Γ, of which the original line width Γ0 is 100 μm, broadens by four particles of toner, ΔΓ= +4·d. The resultant resolution of line images Re is determined by the reciprocal of the broadening width, ( Re ∝ 1/4d). In the horizontal direction of the photoreceptor drum, the line-width Γ is reduced by the scavenging effect of ears of the developer. On the other hand, the broadening of a line image reproduced by the mono-component jumping development is certified to be isotropic in the rotating and horizontal directions of the photoreceptor drum, then, the reproduction of a dot image has been investigated by the mono-component jumping development. As regards the reproduction of dot images of 150 dots/inch; for a small original dot with dot-area percentage ≤ 5 %, the dot image disappeares; for an original dot with dot-area percentage of 12 %, the diameter of a dot Dd reduces isotropically by two particles of toner, (ΔDd = -2·d); and for an original dot with dot-area percentage of 28-60 %, the diameter of a dot Dd broadens isotropically by six particles of toner, (ΔDd = +6·d).
In conclusion, the correlation between the toner size4and the image-quality factors, i.e. resolusion of line images, reproduction of a dot image, and reproduction of gereration copies of a line image, has been quantitatively clarified, and utilization of toner particles of a smaller size have been persuaded in order to improve the electrophotographic image-quality factors furthermore.
