Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1998-09-03
2003-08-26
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...
C430S109100, C430S109300, C430S109400, C430S110200, C430S110300, C430S124300, C430S125320, C430S126200
Reexamination Certificate
active
06610454
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a toner for forming toner images in image forming processes such as electrophotography, electrostatic printing, magnetic recording and toner jet recording, and an image forming method employing such a toner. More particularly, this invention relates to a toner for developing electrostatic images which is used in a fixing system in which visible images formed out of toner are heat-fixed to recording mediums, and an image forming method employing such a toner.
2. Related Background Art
A number of methods as disclosed in U.S. Pat. No. 2,297,691, Japanese Patent Publications No. 42-23910 and No. 43-24748 and so forth are conventionally known as electrophotography. In general, copies are obtained by forming an electrostatic latent image on a photosensitive member by utilizing a photoconductive material and by various means, subsequently developing the latent image by the use of a toner, and transferring the toner image to a recording medium such as paper by an direct or indirect means as the occasion demands, followed by fixing by the action of heat, pressure or solvent vapor. The toner that has not transferred thereto and has remained on the photosensitive member is removed by cleaning by various means, and then the above process is repeated.
A usual full-color image forming method will be described. A photosensitive member (electrostatic latent image bearing member) such as a photosensitive drum is electrostatically uniformly charged by means of a primary charging assembly, and imagewise exposure is carried out using laser light modulated by magenta image signals of an original, to form an electrostatic latent image on the photosensitive drum. The electrostatic latent image is developed by means of a magenta developing assembly holding a magenta toner, to form a magenta toner image. Next, to a recording medium transported, the magenta toner image developed on the photosensitive drum is transferred by a direct or indirect means by means of a transfer charging assembly.
The photosensitive drum on which the electrostatic latent image has been developed is decharged by a residual charge eliminator, and is further cleaned through a cleaning means. Thereafter, it is again electrostatically charged by the primary charging assembly, and a cyan toner image is similarly formed. The cyan toner image is transferred to the recording medium on which the magenta toner image has been transferred, and then a yellow toner image and a black toner image are successively formed and developed so that the four color toner images are transferred to the recording medium. The recording medium having these four color toner images is passed through a fixing roller so that they are fixed to the recording medium by the action of heat and pressure. Thus, a full-color image is formed.
In recent years, such image forming apparatus are not only used as copying machines for office work to merely take copies of originals, but also have began to be used in the field of laser beam printers (LBPs) serving as the output of computers and in the field of personal copying (PC) of private use.
In addition to the field as typified by LBPs and PC, such apparatus are also being rapidly expanded to plain-paper facsimile machines to which basic engines are applied.
Under such circumstances, the apparatus are more severely sought to be made small-sized, light-weight, high-speed, image high-quality and highly reliable, and such machines have now been composed of more simple components in various respects. As the result, a higher performance has become required for toners, and superior machines can now no longer be accomplished unless improvement in the performance of toners is achieved. In recent years, with a need for various modes of copying, demand for color copying is rapidly increasing. In order to more faithfully copy original color images, it is sought to achieve a much higher image quality and a much higher resolution. Moreover, there is an increasing demand for the copying of double-side color originals.
From these viewpoints, as the toners used in the color image forming process, it is preferable to use toners having good melt properties and color-mixing properties when heat is applied thereto and also having a low softening point and high sharp-melt properties in a low melt viscosity.
Use of such sharp-melt toners makes it possible to broaden the range of color reproduction of copied matter and obtain color copies faithful to original images.
Color toners having such high sharp-melt properties, however, is so high in affinity for the fixing roller that it tends to cause offset with respect to the fixing roller at the time of fixing.
In particular, in the case of a fixing assembly in full-color image forming apparatus, an increase in toner layer thickness tends to cause the offset since a plurality of toner layers corresponding to magenta, cyan, yellow and black are formed on the recording medium.
In order to allow no toner to adhere to the surface of the fixing roller, a measure has been conventionally taken in which the roller surface is formed out of a material, such as silicon rubber or a fluorine resin, having an excellent releasability to toner, and, in order to prevent offset and to prevent fatigue of the roller surface, its surface is further covered with a thin film formed using a fluid having a high releasability as exemplified by silicone oil or fluorine oil. However, although this method is very effective in view of the prevention of the offset of toner, it requires a device for feeding an anti-offset fluid, and hence has such a problem that a complicated fixing assembly is required. In addition, the application of oil may bring about separation of layers on the fixing roller, and consequently, shorten the lifetime of the fixing roller.
Accordingly, based on the idea that the fluid for preventing offset should be fed from the inside of toner particles at the time of heat fixing, without use of any device for feeding silicone oil, a method has been proposed in which a release agent such as a low-molecular-weight polyethylene or a low-molecular-weight polypropylene is added in toner particles.
Japanese Patent Publications No. 52-3304 and No. 3305 and Japanese Patent Publication 57-52574 disclose that as the release agent a wax is incorporated into toner particles.
Japanese Patent Applications Laid-open No. 3-50559, No. 2-79860, No. 1-109359, No. 62-14166, No. 61-273554, No. 61-94062, No. 61-138259, No. 60-252361, No. 60-252360 and No. 60-217366 disclose techniques for incorporating waxes.
In the case of black toners, release agents having a relatively high crystallizability as typified by polyethylene wax and polypropylene wax can be used in order to improve high-temperature anti-offset properties at the time of fixing. However, in the case of full-color toners, this crystallizability of release agents may cause great damage to the transparency of OHP (overhead projector) toner images when outputted. Moreover, the wax may cause a lowering of blocking resistance of toners, and a lowering of developing performance because of migration of wax toward toner particle surfaces when toners are exposed to heat as a result of temperature rise in image forming apparatus such as printers and copying machines and also when toners are left standing for a long term.
To cope with such problems, various improvements are attempted from the aspect of binder resin. More specifically, a cross-linking component or a high-molecular-weight component is used in a binder resin in a larger quantity so that the high-temperature anti-offset properties at the time of fixing can be improved.
This method can certainly improve high-temperature anti-offset properties to a certain extent and also can be effective for improving durability such that external additives are prevented from being buried in toner particle surfaces and toners are prevented from melt-adhereing to the photosensitive member and toner carrying member.
However, this method conflicts with the i
Ayaki Yasukazu
Handa Satoshi
Hashimoto Akira
Ito Masanori
Komoto Keiji
LandOfFree
Toner and image forming 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 Toner and image forming method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Toner and image forming method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3111675