Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-06-15
2001-12-04
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S137200
Reexamination Certificate
active
06326113
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a charge control agent for electrophotography etc., and a toner for developing electrostatic latent images using said charge control agent.
2. Description of the Prior Art
In copying machines and other instruments based on electrophotography, various toners containing a coloring agent, a fixing resin and other substances are used to visualize the electrostatic latent image formed on the photoreceptor having a photosensitive layer containing a photoconductive substance. Such toners are required to show satisfactory performance in terms of chargeability, fixability, offset resistance, durability, etc.
In recent years, to achieve image quality improvement, while copying and printing speeds are increased, there have been increased demands for improved charge characteristics of toners, such as increased charge rise speeds, and for toner fixability on recording papers, such as excellent low-temperature fixability and offset resistance. Such demands for improved toner performance are intensifying with the advance in performance sophistication of copying machines and printers.
Chargeability is a key factor in electrostatic latent image-developing systems. Thus, to appropriately control the chargeability of a toner, a charge control agent providing a positive or negative charge is often added to the toner. Of the conventional charge control agents in actual application, those providing a positive charge for a toner include nigrosine dyes and quaternary ammonium salt compounds. Guanidine, imidazole derivatives, etc. have also been proposed as such toners. Those providing a negative charge for a toner include salicylic acid derivative metal compounds and azo dye-metal complexes.
Many of the conventional charge control agents which are salicylic acid derivative metal compounds, azo dye-metal complexes or quaternary ammonium salts provide excellent chargeability when added to a toner. However, some problems remain to be resolved, including poor fluidity of the charge control agent itself, unsatisfactory levels of dispersibility in fixing resins and durability in multiple repeated use of toners, and relatively low clearness of initial copying images due to insufficient charge rise speeds.
The present invention was developed in view of the above problems in the prior art, and is directed to provide a charge control agent which is excellent in charge control substance uniform dispersibility in resins for toners, sharp and highly uniform in charge amount distribution, quick in charge rise, and excellent in charge stability over time, non-dependency on environment, storage stability and durability, and which does not adversely affect toner fixability and offset resistance when used in toners of various compositions; a manufacturing process thereof; and a toner for developing electrostatic images containing said charge control agent.
SUMMARY OF THE INVENTION
The charge control agent of the present invention for accomplishing the above objects comprises a base particle containing at least a charge control substance, and a granulating agent, said base particle being granulated using said granulating agent (granulation aid), and said granulating agent being at least one selected from the group consisting of anionic surfactants, nonionic surfactants, cationic surfactants, natural water-soluble high molecular compounds and synthetic water-soluble high molecular compounds.
The charge control agent of the present invention has a constant particle diameter and a sharp particle size distribution. In particular, the charge control agent of the present invention has a remarkably improved charge control substance uniform dispersibility in resins for toners, is sharp and highly uniform in charge amount distribution, quick in charge rise, and excellent in charge stability over time, non-dependency on environment, storage stability and durability. In addition, the charge control agent of the present invention is excellent in storage stability and durability, and does not adversely affect toner fixability and offset resistance when used in toners of various compositions.
With these features, the charge control agent of the present invention resolves the problems in conventional charge control agents, which have great variation of particle diameter and wide particle size distribution, which, when used in toners, are difficult to uniformly disperse in resins for toners and cause variation in toner surface charge distribution, and which are unsatisfactory in terms of charge retention in repeated use of the toner.
In addition, the toner of the present invention for developing electrostatic images contains the aforementioned charge control agent for the purpose of charge control, and also contains a coloring agent and a resin.
The toner of the present invention for developing electrostatic images has a remarkably improved charge control substance uniform dispersibility in resins for toners, is sharp and highly uniform in charge amount distribution, quick in charge rise, and excellent in charge stability over time, non-dependency on environment, storage stability and durability. In a toner obtained by polymerizing a monomer to constitute a resin for a toner along with a given set of ingredients such as a charge control agent, the charge control substance is uniformly dispersed to provide an excellent charge characteristic. In addition, the charge control agent of the present invention is excellent in storage stability and durability, and does not adversely affect toner fixability and offset resistance.
In addition, the process of the present invention for manufacturing a charge control agent comprises a fine milling step for finely milling a subject containing at least a charge control substance, and a granulation step for granulating a finely milled base particle using a granulating agent, said granulating agent being at least one selected from the group consisting of anionic surfactants, nonionic surfactants, cationic surfactants, natural water-soluble high molecular compounds and synthetic water-soluble high molecular compounds.
By this method, a charge control agent comprising granulated finely milled base particles is obtained.
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Patent Abstracts of Japan, Jan. 25, 1996.
Okuda Toshiyuki
Tada Akihiro
Taguchi Yoshitaka
Yamanaka Shun-ichiro
Chukyo Yushi Co., Ltd.
Goodrow John
McGlew and Tuttle , P.C.
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