Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1999-12-03
2001-12-11
Chapman, Mark (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S111400, C430S124300, C430S137170
Reexamination Certificate
active
06329114
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electrostatic image developing toner used in the case of developing electrostatic images formed by an electrophotographic process, an electrostatic recording process, etc., and the production method thereof, an electrostatic developer, and an image-forming process.
BACKGROUND OF THE INVENTION
A process of visualizing an image information through electrostatic images, such as an electrophotographic process, etc., has been utilized in various fields at present. In an electrophotographic process, an electrostatic image is formed on a photoreceptor by electrostatic charging and light-exposure step, and the electrostatic latent image is developed by a developer containing a toner and visualized through a transferring step and a fixing step.
As the developer used in the process, a two-component developer composed of a toner and a carrier and a one-component developer using a magnetic toner or a non-magnetic toner singly are known. For producing a toner, a knead-grinding method of melt-kneading a thermoplastic resin together with a pigment, a charge-controlling agent, and a releasing agent such as a wax, and after cooling, finely grinding and classifying the kneaded mixture to obtain a toner is usually used. In the toner, if necessary, inorganic or organic fine particles are added to the surfaces of the toner particles for the purpose of improving the fluidity and the cleaning property thereof. By these methods, a considerably excellent toner can be produced but they have following various problems.
That is, in an ordinary knead-grinding method, the form and the surface structure of the toner produced are a random-form and because the form thereof is delicately changed according to the grinding property and the condition of the grinding step, it is difficult to control the form and the surface structure of the toner. Also, in the knead-grinding method, there is a restriction on the range of selecting the material. Practically, it is preferred that a resin coloring agent dispersion is sufficiently brittle and can be finely ground by an ordinary grinder but when a resin coloring agent dispersion is brittle, it sometimes happens that a fine powder is generated from the toner by receiving a mechanical shearing force in a developing apparatus and the form of the toner is changed. In a two-component developer, the fine power generated is fixed to the surfaces of carriers to accelerate the deterioration of the developer and in a one-component developer, scattering of the toner occur by enlarging the particle size distribution, the developing property is lowered by the change of the toner form, and the image quality becomes liable to be deteriorated.
Also, in the toner containing therein a large amount of a releasing agent such as a wax, etc., by the combination with a thermoplastic resin, the resin frequently gives an influence on the exposure of the releasing agent on the surface of the toner. Particularly, in the combination of the resin which has an increased elasticity by high-molecular weight components and is hard to be ground to some extent and a wax, which is brittle, such as polyethylene, polyethylene is frequently exposed on the surface of the toner. The toner is advantageous for the releasing property at fixing and cleaning of the untransferred toner from a photoreceptor but the polyethylene on the surface layer of the toner is easily transferred onto a developing roll, a photoreceptor, a carrier, etc., to stain them and to lower the reliability.
Furthermore, when the form of a toner becomes a random form, even by adding a fluidity assistant, the fluidity of the toner cannot sufficiently ensured, a fine powder transfers to the concaved portions of the toner by receiving the mechanical shearing force during use to lower the fluidity of the toner with the passage of time, and also the fluidity assistant is embedded in the inside of the toner to deteriorate the developing property, the transferring property and the cleaning property. Also, when the toner recovered by cleaning is returned to the developing apparatus and used again, the image quality is liable to be lowered. For preventing the occurrences of these troubles, the amount of the fluidity assistant is increased, black sports are formed on the photoreceptor and also scattering of the assistant particles occurs.
As described above, in an electrophotographic process, for stably keeping the performance of a toner under various mechanical stresses, it is important that the exposure of a releasing agent onto the surface of the toner, the surface hardness of the toner is increased without reducing the fixing property of the toner, the both the mechanical strength of the toner and the sufficient charging property and fixing property of the toner are improved.
Furthermore, recently, the requirement for increasing the image quality has been increased and particularly, in the formation of color images, for realizing the images of a high brilliance, the tendency of small-sizing of toner is remarkable. However, when a toner is simply small-sized in a conventional particle size distribution of the toner, by the existence of the toner of the fine particle size, staining of a carrier and a photoreceptor and scattering to the toner become severe, and thus it is difficult to simultaneously realize the high image quality and the high reliability. For solving the problem, it becomes important that the particle distribution of the toner is sharpened and small-sizing of the toner is made possible.
Recently, in a digital full-color copying machine and printer, after color-separating a color image original by each of the filers of B (blue), R (red), and G (green), electrostatic images each composed of dots of the diameters in the range of from 20 to 70 &mgr;m corresponding to the original are developed using each of the developers of Y (yellow), M (magenta), C (cyan), and Bk (black) by utilizing a subtractive mixing action. However, because in the digital full-color copying machine, etc., it is necessary to transfer large amounts of the developers as compared with a black and white copying machine, etc., of prior art and it is necessary to correspond to dots of smaller particle sizes, the uniform charging property, the durability, the toner strength, and the sharpness of the particle size distribution of the toner become more and more important. Also, considering the increase of the speed and the energy saving property of these copying machines, the low-temperature fixing property of the toner becomes more important. From these points, an aggregation unification method suitable for the production having a sharp particle size distribution and small particle sizes is excellent.
For the toner used for a full-color copying machine, etc., it is important that large amounts of the toners surely make color mixing and in this case, the improvement of the color reproducibility and the transparency of the OHP image become inevitable.
Also, as a means of controlling the form and the surface structure of a toner, a method of producing a toner by an emulsion polymerization aggregation method is proposed (Japanese Patent-Laid Open Nos. S63-282752 and H6-250439). According to the method, a resin fine particles dispersion is generally prepared, on the other hand, a coloring agent dispersion of a coloring agent dispersed in a solvent is formed, these dispersions are mixed to form aggregated particles having particle sizes corresponding to toner particle sizes, and the particles are formed into a coalescece by heating to product a toner. In the method, the form of the toner can be controlled to some extent and the charging property and the durability of the toner can be improved but it is difficult to control the dispersed state of the releasing agent and the coloring agent in the inside of the toner and in oil-less fixing, it is difficult to balance the releasing property of a sheet to be fixed and the transparency of the case of forming an OHP image.
In general, for the electrophotographic toner, a ther
Ishiyama Takao
Matsumura Yasuo
Serizawa Manabu
Shoji Takeshi
Watanabe Yukiko
Chapman Mark
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
LandOfFree
Electrostatic image developing toner, production method... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrostatic image developing toner, production method..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrostatic image developing toner, production method... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2581506