Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2002-03-27
2004-06-08
Chapman, Mark A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108100, C430S045320, C430S124300
Reexamination Certificate
active
06746808
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color toner for forming an image and, more particularly, to a color toner suited for use in an image forming method employing a photofixing system. The color toner of the present invention can be used advantageously as a developing agent in various image forming apparatuses, employing various image forming systems such as electrography, electrophotography and ionography such as, for example, an electrophotographic copying machine, an electrophotographic facsimile, an electrophotographic printer and an electrostatic printing machine. The present invention also relates to a color image forming method and a color image forming apparatus which employ the color toner for forming an image.
2. Description of the Related Art
The image forming method employing electrophotography, which has been widely used in copying machines, printers and printing machines generally, begins by charging the surface of a photoconductive insulator such as a photosensitive drum uniformly with a positive or a negative electrostatic charge. After the uniform charging, the electrostatic charge on the insulating material is partially erased by irradiating the photoconductive insulator with image light, by various means, to thereby form an electrostatic latent image. For example, an electrostatic latent image corresponding to image information can be formed on the photoconductive insulator by erasing the surface charge from particular portions by irradiating it with a laser beam. Then a fine powder of developing agent, referred to as a toner, is caused to deposit on the latent image where the electrostatic charge remains on the photoconductive insulator, thereby to visualize the latent image. Lastly, in order to print the toner image obtained as described above, it is common to electrostatically transfer the image onto a recording medium such as recording paper.
On the other hand, according to image forming method employing ionography, ions are generated by an ion (charged particles) generating means employing a support drum having an electrostatic film as a dielectric member for supporting an electrostatic image and the electrostatic image is formed on the surface of the dielectric member by ions. The electrostatic image thus formed is visualized by developing with a toner. Finally, the resulting toner image is subjected to transfer and fixing steps in the same manner as in case of electrophotography described above to obtain a print.
In the image forming method described above, the fixing step is conducted by employing a common technique. For the fixation of the transferred toner image, such methods as a fixing method wherein toner is melted under pressure, by heating or by combination thereof and is then solidified or a fixing method wherein toner is melted by irradiating with light and is then solidified, have been employed, while much interest is being directed to a method referred to as a photofixing method (also referred to as a flash fixing method), which uses light, that is free from adverse effects of pressure and heating. In the photofixing method, since it is not necessary to apply pressure to the toner during fixation, the need to bring the toner into contact with a fixing roller or the like is eliminated, and such an advantage is provided that blurring of the image and dust do not occur and imaging resolution (reproducibility) suffers less degradation in the fixing step. Also because it is not necessary to heat the toner with a heat source, the idle time, before printing can be started, after turning on the power to preheat the heating medium (fixing roller or the like) to a predetermined temperature is eliminated, so that printing can be started upon turning on the power. Eliminating the need for a high temperature heat source has another advantage that the temperature in the apparatus does not rise too high. It also eliminates such a danger that the recording paper catches fire due to the heat generated by the heat source, even when the recording paper jams in the fixing device due to a system breakdown or other trouble. There is also an advantage that fixing performance is less affected by the type of material and thickness of the recording medium such as glued paper, preprint paper and sheets of paper having different thicknesses.
Describing in more detail, the process of fixing a toner onto a recording paper in the photofixing method is as follows.
In the transfer step, a toner image is transferred onto a recording paper from a photosensitive drum. At this point of time, the toner is deposited on the recording paper in the form of a powder image to form a image and is in the state where the image can be damaged when rubbed with fingers. Then, the toner powder image on the recording paper is irradiated with flashlight from a Xenon flashlight. As a result of absorption of a light energy of flashlight, the toner is heated, softened and deposited on the recording paper. When the temperature is reduced after irradiation with flashlight, the toner image is solidified, thereby to complete a fixed toner image.
It is important to prevent so-called poor fixation wherein folding and rubbing of the recording paper cause peeling of the fixed toner image from the recording paper, resulting in poor image quality. For this purpose, it is necessary to design that melting of the toner during fixation is accelerated by enhancing the light adsorption capability of the toner, and thus the toner sufficiently penetrates into the paper and is firmly fixed.
The Xenon flash lamp commonly used in the photofixing method has an emission distribution in a wide range from an ultraviolet region to an infrared region, and shows a particularly strong emission intensity in the near infrared region of wavelengths ranging from 800 to 1000 nm. Therefore, it is required to establish the technology of efficiently absorbing a light energy in this region in order to develop a toner having high fixability. Recently, the demand for color prints has particularly been increased. The colorant used in the color toner has an absorption in the visible region, but has low light absorption efficiency in the near infrared region. Therefore, it is required to put a color toner capable of affording good fixability in the photofixing system into practical use.
In a black toner, a black coloring material as the colorant also absorbs light in the near infrared region. Therefore, the black toner has already been put into practical use as an electrophotographic apparatus employing a photofixing system. However, a further improvement in absorption efficiency is required to cope with recent increase of the demand for energy saving.
In response to the demand, it has been proposed to improve the fixability by adding an infrared absorbing agent to the color toner, and many patent applications related to this technology have been publicly disclosed such as: Japanese Unexamined Patent Publication (Kokai) Nos. 60-63545, 60-63546, 60-57858, 60-57857, 58-102248, 58-102247, 60-131544, 60-133460, 61-132959, W099/13382, 2000-147824, 7-191492, 2000-155439, 6-348056, 10-39535, 2000-35689, 11-38666, 11-125930, 11-125928, 11-125929, and 11-65167. Technologies disclosed in these publications are attempts to make color rendering and photofixability compatible with each other by adding an infrared absorbing agent to the toner. However, all of the infrared absorbing agents proposed has the problem of inability to achieve satisfactory fixation. To satisfy the photofixability, a large amount of these infrared absorbing agents must be added in the color toner. It is not always possible to meet the demand because of these problems such as (i) adverse influence on the chargeability of the toner, (ii) adverse influence on the color hue of the toner and (iii) increase in cost of the toner.
Japanese Unexamined Patent Publication (Kokai) Nos. 11-24319, 9-328412, 11-24317, 7-90310 and 6-228604 have proposed that the surface of fine particles is provided with a multi-layer film by adding addit
Ishimaru Seijiro
Katagiri Yoshimichi
Nakamura Yasushige
Takezawa Satoshi
Tanaka Tomoaki
Chapman Mark A.
Fuji 'Xerox Co., Ltd.
Westerman Hattori Daniels & Adrian LLP
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