Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-06-27
2002-05-21
Rodee, Christopher (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108300
Reexamination Certificate
active
06391508
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toner and a two-component developer for electrostatic image development which are employed in electrophotographic image production methods.
2. Description of the Related Art
Conventionally, toners for two-component developers are prepared by mixing binder resins, such as polyester resin and/or styrene/acrylate copolymer, as the main component of the toner, and a colorant, such as carbon black, heat melting, kneading, pulverizing, and classifying the toner particles.
When polyester resin having itself a strong negative charge property is used as the binder resin, and the obtained toner is used for a negatively charged toner, fundamental problems tend to occur. For example, the triboelectric charge property of the toner tends to gradually increase during continuous copying of a large number of sheets and to increase at low temperature and low humidity, and the image density of produced images tends to decrease, thereby adversely affecting badly on the produced images.
Moreover, since developers used in copying machines which operate at medium or greater printing speed (corresponding to 40 sheets or more of A4 size paper in a lateral direction per minute) are continuously and vigorously stirred in a developer container, the amount of charge on the developers changes with time. As a result, defects in produced images tend to easily occur, decreasing the image density and increasing the back ground. Specifically, when a two-component developer is used in the copying machine, coated films of carriers included in the two-component developer are liable to be peeled from the carriers, and the toner included in the two-component developer is liable to deposit as toner impaction on the surface of the carriers. Thereby, according to toner impaction, changes in the amount of charge, and defects in produced images described above tend to be significantly increased after continuous copying of large number of sheets.
SUMMARY OF THE INVENTION
The present invention was made in view of the circumstances described above. An object of the present invention is to provide a two-component developer including a toner having high fluidity and a carrier having reduced triboelectric properties, thereby to stabilize the amount of charge, to reduce the dependence on environment and the generation of back ground, and to produce images of high quality during continuous copying of large number of sheets.
As a result of extensive research aimed at realizing the above objects, the inventors of the present invention discovered that by using both a toner comprising toner particles including a binder resin as the main component and having particle surfaces deposited with titanium oxide particles, the surfaces of which are treated with at least isobutyl trimethoxy silane and trimethyl siloxysilicate, and a carrier having core particles, the surfaces of which are coated with a resin coating agent including 5 to 20 percent by weight of carbon black, relative to the total weight of the resin coating agent, the amount of charge is stabilized and high quality images can be produced during continuous printing of a large number of sheets.
The present invention provides a toner for electrostatic image development, comprising toner particles including a binder resin as a main component thereof and having particle surfaces deposited with titanium oxide particles, the surfaces of which are treated with at least isobutyl trimethoxy silane and trimethyl siloxysilicate. The amount of the titanium oxide particles deposited on the surface of the toner particle may be 0.05 to 0.8 percent by weight, relative to the weight of the toner particles. The mean primary particle diameter of the titanium oxide particles may be no more than 0.05 &mgr;m. The binder resin may be polyester resin. The toner particles may be negatively charged.
The present invention also provides a two-component developer, comprising the toner and a carrier including core particles, the surfaces of which are coated with a resin coating agent including 5 to 20 percent by weight of carbon black, relative to the total weight of the resin coating agent. The binder resin of the coating agent may be acrylate resin. The core particle may be magnetite.
DETAILED DESCRIPTION OF THE INVENTION
In the following, an embodiment according to the present invention will be specifically explained.
A toner for electrostatic image development includes toner particles including a binder resin as a main component thereof and having particle surfaces deposited with titanium oxide particles, the surfaces of which are treated with at least isobutyl trimethoxy silane and trimethyl siloxysilicate. By depositing the titanium oxide particles, the surfaces of which are treated with isobutyl trimethoxy silane and trimethyl siloxysilicate, on the toner particle surfaces, the fluidity of the toner particles is increased, and the amount of charge of the toner particles can be controlled. The amount of titanium oxide particles deposited on the surface of the toner particle is preferably 0.05 to 0.8 percent by weight, relative to the weight of the toner particles. When the amount of the titanium oxide particles is under 0.05 percent by weight, the amount of charge of the toner particle tends to be unstable according to environmental fluctuations. When the amount of the titanium oxide particles is over 0.8 percent by weight, the back ground tends to increase. The volume average particle diameter of the toner particles is preferably 7.5 to 12 &mgr;m.
Although various silane coupling agents are generally used as finishing agents for the titanium oxide particles, a coupling agent including both isobutyl trimethoxy silane and trimethyl siloxysilicate is used for surface treatment of the titanium oxide particles in the present invention. By depositing the titanium oxide particles treated with the coupling agent on the surface of the toner particle, the amount of charge of the toner particle can be prevented from becoming unstable. When a finishing agent which does not include trimethoxy silane and trimethyl siloxysilicate is used for surface treatment of the titanium oxide particles, the amount of charge of the toner particle tends to be unstable. Thereby, the amount of charge of the toner particles tend to decrease in high temperature and high humidity environments, and tends to increase in low temperature and low humidity environments. Thus, the coupling agent used for surface treatment of the titanium oxide particles is required to include isobutyl trimethoxy silane and trimethyl siloxysilicate.
The mean primary particle diameter of the titanium oxide particles is preferably no more than 0.05 &mgr;m, and is more preferably 0.01 to 0.04 &mgr;m. The mean primary particle diameter of the titanium oxide particles refers to the mean particle diameter of the titanium oxide particles, the surfaces of which are not yet treated with a coupling agent which includes isobutyl trimethoxy silane and trimethyl siloxysilicate. When the mean primary particle diameter is over 0.05 &mgr;m, it tends to be difficult to increase the fluidity of the toner.
The toner particle includes at least a binder resin and a colorant. Moreover, the toner particle may include anti-offset agents such as polypropylene and/or polyethylene, charge control agents, and/or releasing agents, if necessary. The toner particle is produced by a heat melting, kneading, and pulverizing method, or by a polymerization method.
Specific examples of the binder resin include homopolymers of a styrene compound such as styrene, &agr;-methylstyrene, or chlorstyrene, an acrylate such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, or alkyl acrylate, a methacrylate such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, octyl methacrylate, stearyl methacrylate, glycidyl methacrylate, or alkyl methacrylate, acrylonitrile, maleic acid, maleate, a vinyl compound such as vinyl chloride, vinyl acetate, vinyl b
Nixon & Vanderhye
Rodee Christopher
Tomoegawa Paper Co. Ltd.
LandOfFree
Toner and two-component developer for electrostatic image... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Toner and two-component developer for electrostatic image..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Toner and two-component developer for electrostatic image... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2866044