Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Patent
1989-02-22
1990-10-16
Welsh, J. David
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
430137, 526934, G03G 908, G03G 1100
Patent
active
049634569
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an electrophotographic toner powder for use in the development of an electrostatic image in electrophotography, and more particularly relates to an electrophotographic dry toner which exerts excellent lower temperature fixing ability in a hot-roll copying method.
BACKGROUND OF THE TECHNIC
The electrophotographic toner is conventionally composed of a resin composition, coloring agent which contains pigments or dyestuffs, control agents, wax and the like. Synthesic or natural resin is used for the resin composition singly or as a suitable mixture. A relatively high molecular weight styrene containing polymer is generally used as admixture with a relatively low molecular weight styrene containing polymer in a suitable proportion. The composition and thermal properties of the styrene containing polymer employed are important factors deciding the toner characteristics, and currently their improvement is strongly required.
Many kinds of fixation method which called hot-roll process are employed in the electrophotographic copying machines and printers. In this method, toner particles which were electrostatically transferred on copying papers are passed through heated press rolls, thereby the particles are melted and fixed on the paper. Copying machines have recently been developed for conducting duplication at a high rate with a low energy fixation. Conventional toner, however, is not always satisfactory for the performance of these machines and printers by the following reason. The heat quantity transferred from the hot rolls to the toner particles at high duplication speed is less than at low duplication speed. A remarkable decrease in the surface temperature of hot rolls is also caused by the increase in heat removal to the copying papers, which leads to insufficient fusion and deteriorated fixation of the toner particles. Besides the copying machines fitted with various auxiliary devices are required to operate all of these devices within a limited consumption of electricity. Since the proportion of electrical consumption for heating the rolls is very high in the total consumption, it is strongly required to lower the temperature of hot rolls. The conventional toner, however, cannot perform satisfactory melting and adhesion to the copying papers at lower surface temperatures of the hot rolls. Therefore it has been strongly desired to develop the toner which exhibits sufficient fixing ability with by supplying a smaller quantity of heat. As a countermeasure to this problem, there is a method for satisfactorily conducting the fixation under conditions of high speed and lower temperature conditions by lowering the softening temperature or melt viscosity of the resin constituting the toner particles. That is, the toner melting at the lower temperature can be prepared by adjusting the mixing ratio of the resin. This method, however, increases the proportion of low molecular weight styrene containing resin and drastically decreases the melt viscosity of resin at high temperatures. As a result, the toner particles which were melted and pressed on a copying paper by the hot rolls at the fixation stage are partly are transferred and left on the hot roll surface when the paper was removed from the rolls. The attached toner on the roll surface is pressed again on the next paper, which is so-called "offset phenomenon". The offset phenomenon causes a serious disadvantage that the copying papers are contaminated and good images cannot be obtained.
Besides the resin having a low softening temperature can be prepared by controlling the monomer composition which constitutes the resin. The toner derived from such low temperature softening resin, however, causes mutual adhesion of the toner particles by pressure during the storage. In the extreme cases, the toner is liable to occur so-called "blocking" phenomenon which leads to whole coagulation of the toner. Particularly in the case of using the low molecular weight styrene containing resin as a low temperature soften
REFERENCES:
patent: 4246332 (1981-01-01), Tanaka
patent: 4737433 (1988-04-01), Rimai
Hirayama Nobuhiro
Ishikawa Keiichi
Misawa Akira
Shin Masaaki
Mitsui Toatsu Chemicals Incorporated
Welsh J. David
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