Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-08-25
2002-11-19
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108800, C430S109400, C430S111400
Reexamination Certificate
active
06482561
ABSTRACT:
This application is based on application No. 241359/1999 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toner used for developing electrostatic latent images in an image-forming method such as an electrophotographic method, an electrostatic recording method and an electrostatic printing method, and more specifically concerns a toner preferably used for developing electrostatic latent images in a full-color image-forming apparatus such as a full-color electrostatic copying machine and a full-color laser beam printer.
2. Description of the Related Art
In the case of a full-color image-forming system using the electrophotographic method, since a full-color image is obtained by superposing toner images of magenta toner, cyan toner and yellow toner, it is one of the greatest requirements for the toner to have sharply-melting properties so as to allow the toner layers of the respective colors to melt instantaneously by heat, to be able to be mixed easily and to allow for clear color developments, at the time of fixing (U.S. Pat. Nos. 4,142,982, 4,590,139); however, toners of this type have a high viscosity, low elasticity and a small particle-to-particle aggregating force at the time when the toner is thermally fused, resulting in a problem of off-set with the heating roller (particularly, at the time of high temperatures). Such a problem becomes conspicuous especially when there is degradation in the roller due to repetitive use and when an image having a large amount of toner or a large toner adhering area (for example, a photograph image) on a toner recording material (such as paper). For this reason, in order to additionally improve the anti-off-set property at high-temperatures, mold-releasing oil, such as silicone oil, has to be applied to the fixing roller; however, this causes another problem of too much luster caused by the oil.
In recent years, as full-color printers and copying machines with high image quality have come to be widely used, the number of output sheets of color images have increased drastically, and there have been increasing demands for high speed operations and toners that are less susceptible to changes in image luster at the time of continuous copying processes. Great variations in luster tend to make the same color look different, and variations in luster give great influences on hues and color reproducibility sensed by the human eye.
However, in the case when a conventional toner that puts an emphasis on the sharp melting properties is used, there is a problem in which the image luster changes greatly at the time of continuous copying processes. This problem becomes more conspicuous when the copying speed becomes faster. It is considered that the variations in luster occur due to a reduction in the fixing roller temperature that gradually takes place as paper takes heat from the surface of the fixing roller. Moreover, when, after continuous copying processes have been carried out by using A-4 paper longitudinally, the change to a lateral A-4 copying process leads to variations in luster occurring in an image on a single sheet, resulting in another problem. More specifically, when A-4 paper is used longitudinally, portions on both ends of the fixing roller do not contribute to the fixing process, while in the case when A-4 paper is used laterally, not only the center portion of the fixing roller, but also both ends of the fixing roller, contribute to the fixing process, with the result that a temperature difference occurs between the center portion and both ends of the fixing roller at the time of copying, thereby causing portions with high luster and other portions with low luster. Such problems of variations in luster at the time of continuous copying processes and variations in luster on one copied image become more conspicuous in the case of the processes at cold places and immediately after power application.
The following patent applications have disclosed techniques in which the viscoelasticity of a toner or a resin used therewith has been taken into consideration: for example, Japanese Patent Laid-Open No. Hei 5-142963, Japanese Patent Laid-Open No. 8-101530, U.S. Pat. No. 5,707,771, Japanese Patent Laid-Open No. 8-334930, U.S. Pat. Nos. 5,753,399, 6,002,903, 5,766,816 and 5,840,457.
However, some of these techniques fail to properly find a state at the time of paper separation in which the luster is actually determined due to the fact that the viscoelasticity-measuring temperature is too high, or some of them fail to provide an image with proper luster since the specified value is too high. In other words, any of the toners in the above-mentioned techniques fail to provide an image with proper luster when the fixing roller temperature varies or any temperature difference occurs in the fixing roller due to variations in ambient conditions or continuous copying processes for many copies.
SUMMARY OF THE INVENTION
The present invention is to provide an electrostatic-image developing toner which can provide an image with proper luster even when the fixing roller temperature varies or any temperature difference occurs in the fixing roller due to variations in ambient conditions or continuous copying processes for many copies, and which also has superior anti-offset properties.
Another objective of the present invention is to provide an electrostatic-image developing toner which is also superior in the low-temperature fixing properties and the anti-blocking properties.
The above objects can be achieved by a toner comprising:
a first binder resin and a colorant;
wherein the toner has a temperature range of 90 to 110° C. at 2×10
3
(Pa) of a storage elastic modulus (G′) under 0.1 (Hz) of a frequency.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a toner comprising:
a first binder resin and a colorant;
wherein the toner has a temperature range of 90 to 110° C. at 2×10
3
(Pa) of a storage elastic modulus (G′) under 0.1 (Hz) of a frequency.
The inventors of the present invention have focused their attention to the toner behavior upon fixing toner on a recording material (more specifically, at the time when toner (image) is separated from the fixing roller upon fixing the toner on the recording material by using the fixing roller), and have found that the luster of an image depends on the smoothness of the surface of the image, that the smoothness of the surface of the image depends on the adhering force exerted between the surface of the image and the fixing roller, that the adhering force depends on the behavior of the toner (elastic characteristic) as an elastic member, that when the storage elastic modulus (hereinafter, referred to simply as “G′ ”), which serves as an index for the corresponding elastic characteristic, is set at 2×10
3
(Pa), the surface state (smoothness) of an image has an optimum image luster (degree of luster from 15 to 40), and that the temperature at this time is located in a specific temperature range, an image having a superior luster is obtained through a low-temperature fixing process even when the temperature of the fixing roller is varied.
More specifically, in the case when the smoothness of the image surface is too low, the incident light is diffused due to fine irregularities of the surface, with the result that the luster becomes insufficient, and in the case when the smoothness of the image surface is too high, the incident light has an excessively high and strong reflectivity (which gives too much gloss to the entire image). Moreover, when the adhesive strength between the image and the contact face of the fixing roller is too small, the smoothness becomes higher since the image is easily separated, and when the adhesive strength is great, the separation is difficult, with the result that scratch lines appear on the separation surface and the smoothness becomes low due to the resulting irregularities on the image surface. Moreover, the adhesiv
Aoki Megumi
Arai Takeshi
Hagi Masayuki
Kido Kenichi
Mikuriya Yoshihiro
Burns Doane , Swecker, Mathis LLP
Minolta Co. , Ltd.
Rodee Christopher
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