Liquid developer having polymer particles of a flat configuration dispersed in a dispersion medium
AssigneeMinolta Co., Ltd.
InventorsToshimitsu Fujiwara, Shuji Iino, Hidetoshi Miyamoto
Life of this patent
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Abstract
A liquid developer having polymer particles dispersed in a dispersion medium, wherein the polymer particles have a mean volume particle size d.sub.50 of 0.5.about.5.0 .mu.m, and degree of flatness (longest diameter of a single particle/shortest diameter of a single particle) is greater than 1.5 but less than 30.
Claims21
A liquid developer for development of latent electrostatic images comprising flat configuration polymer particles within a dispersion medium, wherein the flat configuration polymer particles are prepared by deforming spherical polymer particles without distorting a mean volume particle size thereto, said flat configuration polymer particles have a mean volume particle size d.sub.50 of 0.5.about.5.0 .mu.m, 80% of the total volume of the flat configuration polymer particles being present within a range of d.sub.50 .+-.1 .mu.m, and degree of flatness is greater than 1.5 but less than 30, said flatness being the ratio of the longest diameter of a single particle to the shortest diameter of said single particle.
A liquid developer for development of latent electrostatic images comprising flat configuration polymer particles within a dispersion medium, wherein the flat configuration polymer particles are prepared by stress exerted on spherical polymer particles without distorting a mean particle size thereto, said flat configuration polymer particles have a mean volume particle size d.sub.50 of 0.5-3.0 .mu.m, 80% of the total volume of the flat configuration polymer particles being present within a range of d.sub.50 .+-.1 .mu.m, and degree of flatness is greater than 1.5 but less than 30, said flatness being the ratio of the longest diameter of a single particle to the shortest diameter of said single particle.
A method of preparing a liquid developer for development of latent electrostatic images comprising polymer particles within a dispersion medium, said method comprising:
- preparing a polymer solution by dissolving a polymeric structural resin in a non-water soluble organic solvent;
- forming an oil-in-water (O/W) emulsion by dispersing the polymer solution in an aqueous dispersion solution;
- obtaining polymer particles by heating the O/W emulsion while mixing so as to evaporate the organic solvent;
- drying the polymer particles;
- dispersing the dried polymer particles into the dispersion medium, said dispersed polymer particles having a mean volume particle size d.sub.50 of 0.5.about.5.0 .mu.m, 80% of the total volume of the dispersed polymer particles being present within a range of d.sub.50 .+-.1 .mu.m;
- deforming the dispersed polymer particles, by heating the dispersion medium to a temperature near the glass transition point of the structural resin of the polymer particles;
- exerting stress on the dispersed polymer particles to produce flat configuration polymer particles having a first degree of flatness greater than 1.5 but less than 30, said first degree of flatness being the ratio of the longest diameter of a single particle to the shortest diameter of said single particle, and having a mean volume particle size d.sub.50 of 0.5.about.5.0 .mu.m, 80% of the total volume of the flat configuration polymer particles being present within a range of d.sub.50 .+-.1 .mu.m;
- controlling a shape of the flat configuration polymer particles by heating the flat configuration polymer particles at a temperature near the glass transition point of the structural resin of the polymer particles and thermally restoring the flat configuration polymer particles to a shape ranging from a spherical configuration to shapes of optional gradations without exerting stress on said polymer particles, said resulting heated polymer particles having a second degree of flatness greater than 1.5 but less than 30 said second degree of flatness being the ratio of the longest diameter of a single particle to the shortest diameter of said single particle, and having a mean volume particle size d.sub.50 of 0.5.about.5.0 .mu.m, 80% of the total volume of the resulting heated polymer particles being present within a range of d.sub.50 .+-.1 .mu.m.
A method of preparing a liquid developer for development of latent electrostatic images comprising polymer particles within a dispersion medium, said method comprising:
- preparing a polymer solution by dissolving a polymeric structural resin in a non-water soluble organic solvent;
- spraying said polymer solution into a drying chamber to obtain dried polymer particles;
- dispersing the dried polymer particles into the dispersion medium;
- deforming the dispersed polymer particles by heating the dispersion medium to a temperature near the glass transition point of the structural resin of the polymer particles;
- exerting stress on the dispersed polymer particles to produce flat configuration polymer particles having a first degree of flatness greater than 1.5 but less than 30, said first degree of flatness being the ratio of the longest diameter of a single particle to the shortest diameter of said single particle, and having a mean volume particle size d.sub.50 of 0.5.about.5.0 .mu.m, 80% of the total volume of the flat configuration polymer particles being present within a range of d.sub.50 .+-.1 .mu.m;
- controlling a shape of the flat configuration polymer particles by heating the flat configuration polymer particles at a temperature near the glass transition point of the structural resin of the polymer particles and thermally restoring the flat configuration polymer particles to a shape ranging from a spherical configuration to shapes of optional gradations without exerting stress on said polymer particles, said resulting heated polymer particles having a second degree of flatness greater than 1.5 but less than 30 said second degree of flatness being the ratio of the longest diameter of a single particle to the shortest diameter of said single particle, and having a mean volume particle size d.sub.50 of 0.5.about.5.0 .mu.m, 80% of the total volume of the resulting heated polymer particles being present within a range of d.sub.50 .+-.1 .mu.m.
Dependencies are inferred from the claim text.