Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-09-18
2001-07-31
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...
C430S111350, C430S111410
Reexamination Certificate
active
06268100
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is generally directed to pigments, such as toner pigments, and, more specifically, to processes for the preparation thereof. In embodiments the present invention relates to toner and carrier particles with fluorinated, especially fluorosilanated pigments, such as fluorinated carbon blacks obtained, for example, by solution or gas phase methods. The pigments obtained with the processes of the present invention can be selected as a component for carrier coatings, or as a toner component. Although it is not desired to be limited by theory, it is believed that the fluorination passivates the pigment. The fluorinated pigments obtained with the process of the present invention possess a number of important characteristics, such as increased negative charging, compared to the untreated pigment. Thus, the pigments, such as for example the fluorosilanated carbon black, that result from the treatment process have about −0.1 to about −1.0 volt more negative contact potential than the corresponding untreated pigments. In applications, such as for toner or carriers, where these treated pigments are used in carrier coatings or in toners the negative charging of the carrier or toner can be increased by 5 to 30 microcoulombs per gram compared to the carrier or toner with untreated pigments. The charging level, as determined by the contact potential, or by the toner or carrier charge, can be selected by controlling the fluorosilane content of the fluorosilanated pigment, whereby the charge level of the fluorosilanated pigment becomes increasingly more negative as the amount of fluorosilane on the pigment increases, and as the length of the fluorosilane chain increases. The fluorosilane concentration can be varied, from about 5 weight percent of the pigment to about 90 weight percent of the pigment, and the length of the fluorosilane chain can be varied to contain from 1 carbon atom to about 30 carbon atoms. Thus, when the toner resin is changed, when toner additives are added, such as waxes, when the pigment is changed, or when the carrier composition is changed with the fluorosilanation process it is possible to vary the pigment treatment, which enables the overall charge to remain constant. With toners that incorporate different pigments, it is possible to fluorosilanate all of the pigments, and also by varying the fluorosilane treatment, all of the resulting toners with the different pigments will have the same or similar toner charge. This enables very simple construction of the electrophotographic or xerographic apparatus that makes use of more than one toner color. The charge can be varied without affecting the conductivity of the pigment, or charge control agent particles. This is important for maintaining high conductivity in the coated carrier. This is also important with toner additives, such as charge control agents, where the conductivity of the additive must be maintained. There is also the advantage with the present invention that there is no change in other important properties of the pigment, such as color, particle size or the conductivity of the pigment particle. Further, since the fluorine does not react with the pigment, the fluorination process can be applied to conductive or nonconductive particles, color or black pigments, doped tin oxide, metal particle, wax, charge control agent particles, or toner particles. Since the pigment treatment is accomplished at temperatures that are close to room temperature, there is no degradation of the pigment due to high temperatures. The pigment that is selected may be one that is unstable at elevated temperatures, that is above room temperature. For example, X-copper phthalocyanine pigment listed in the Color Index as CI 74160 is only stable to about 150° C. for 30 minutes, while a monoazo pigment identified in the Color Index as CI 12700, CI Solvent Yellow 16, decomposes at temperatures of 100° C.
For carrier particles, the fluorosilanated pigment, such as carbon black, has the advantage that the charge of the carrier can be varied by 5 to 30 microcoulombs per gram of toner particles by varying the fluorosilanation treatment of the pigment, whereby the charge level of the fluorosilanated pigment becomes increasingly more negative as the amount of fluorosilane on the pigment increases, and as the length of the fluorosilane chain increases, and charge can be varied without any variation in the conductivity of the carbon black. It is an important property of the carrier to have a specific conductivity that is determined by the specific xerographic or electrophotographic process in which the carrier is utilized to effectively function in that process, and wherein the conductivity of the carrier is determined by the carbon black and by the amount of the carbon black incorporated into the carrier coating, and to provide to the toner a specific charge level, typically of between about 10 and about 40 microcoulombs per gram of toner. It is also desirable to enable varying the charging level of the carbon black to accommodate any changes in the toner properties without any change in the carrier conductivity, which would reduce the function of the combination of carrier and toner as, for example, resulting in long charging times of greater than about 5 minutes.
For toner particles, the fluorosilanated carbon black has the advantage that the charge of the toner can be varied by 5 to 30 microcoulombs per gram, as measured by the known Faraday Cage blow-off tribo method. The fluorosilanation treatment can be varied as indicated herein, whereby the charge level of the fluorosilanated pigment becomes increasingly more negative as the amount of fluorosilane on the pigment increases, and as the length of the fluorosilane chain increases, and the toner charge can be varied without any variation in the conductivity of the carbon black. The conductivity of the toner is primarily determined by the pigment, such as carbon black, and by the amount of the carbon black incorporated into the toner. With the present invention, there is enabled in embodiments a variation in or preselection of the charging level of the carbon black to accommodate any changes in the other components of the toner, such as for example wax, changes in the composition of the toner resin, or to accommodate changes in the carrier composition without any change in the toner conductivity, which would reduce the function of the combination of carrier and toner as, for example, resulting in long charging times of greater than about 5 minutes, or in broad charge distributions, as when the width of the distribution of toner charge is approximately equal to or greater than the absolute magnitude of the average charge.
In the prior art as illustrated in U.S. Pat. No. 4,524,119, the fluorination occurs at high temperatures, 150 to 600° C., in the gas phase, and involves a reaction of the elemental fluorine with reactive bonds of the carbon black. This fluorination is applied to the entire bulk of the sample, changing the properties of the carbon black itself. As indicated in this patent, the fluorination changes the charging level, and increases the resistivity of the carbon black. Thus, it is not believed possible to separately change the charge and the conductivity since the fluorine reacts with the carbon black, and the process is substantially different for each carbon black. This prior art is only applicable, it is believed, to conductive particles that have reactive bonds, and thus can be used with carbon black, but could not be used with other conductive particles, such as doped tin oxide metal particles. Furthermore, the fluorination treatment of the above prior art is accomplished at elevated temperatures which would decompose or degrade many materials like color pigments, organic charge control agents, and toner particles, disadvantages avoided or minimized with the present invention. Also, because of the very reactive nature of the prior art process, the color of the pigment would change. For example, pigments, such as diazo dyes
Creatura John A.
Cunningham Michael F.
Enright Thomas E.
McDougall Maria V.
Tripp Carl P.
Palazzo E. O.
Rodee Christopher
Xerox Corporation
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