Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2002-07-05
2004-06-29
Goodrow, John (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, C349S045000
Reexamination Certificate
active
06756175
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for fixing toner onto a transfer material in image-forming devices such as copiers, printers and facsimile machines. More precisely, the present invention relates to a method for fixing toner onto a transfer material, using a belt-like heating medium.
2. Description of the Related Art
In monochromatic image-forming devices such as ordinary copiers, printers and facsimile machines, a latent image is formed on an image-carrying medium such as a photoconductor drum or belt in a latent image-forming unit, then the latent image is developed in a developing unit to form a toner image, and the toner image is thereafter transferred onto a transfer medium such as transfer paper represented by plain paper, special paper and the like, and fixed thereon in a fixing unit.
On the other hand, in color image-forming devices such as color copiers, color printers and color facsimile machines, in general, plural latent images are formed on an image-carrying medium such as a photoconductor drum or belt, then the latent images are developed with toners of different colors in a developing unit to form toner images of different colors, thereafter the toner images of such different colors are transferred, as combined into a full color image, onto a transfer medium such as transfer paper, and the color image on the transfer medium is then fixed thereon in a fixing unit.
With the recent trend in the art toward energy-saving and compact devices, a fixing unit utilizing a belt-like heating medium (hereinafter referred to as “belt fixing”) has become widely used.
The belt fixing unit of this type makes it possible to extend the contact time of toner to the belt surface at the time of toner fixing, enabling toner fixing at a lower temperature, while toner fusion on the belt often proceeds excessively and leads to offsetting caused by melted toner adhered to the belt surface. In particular, offsetting tends to be caused with color toners since the color toners are generally required to exhibit glossiness to some extent for forming sufficiently transparent and high-quality images, and accordingly, the molecular weight distribution curve of the binder resin contained in the color toner is sharpened so that the color toner may have a sharp melting property. As a result, toner fusion at the time of image fixing proceeds, thereby causing offsetting.
In addition, additives to toner and other components may adhere to the belt-like heating medium, and the belt may be thereby worn or cracked to cause hot offsetting. Also, the belt may be thereby ruptured.
To solve the problems abovementioned, various proposals have been made for improving fixing units and toners for electrophotography.
On the other hand, oil is applied to fixing rollers in fixing units for preventing offsetting. In color image-forming devices, toners of different colors of low viscosity must be used in obtaining images with high priority in glossiness and transparency of the color, and it is indispensable to apply oil to fixing rollers to prevent offsetting.
It is known to add a releasing material (to support fixing) such as wax to toner for preventing offsetting in image fixing. However, depending on the properties of the wax used, especially when the wax added could not well disperse in toner, the wax will separate from the surfaces of toner particles or will bleed out of them in long-term use in developing units, and will stain the surfaces of carrier particles in two-component developers to thereby often worsen the charging properties of toner. In one-component developers, the wax added to toner will adhere to development rollers and to blades used for thinning toner layers, and will therefore often obstruct uniform development with toner. From the viewpoint of development, therefore, preferably an amount of wax to be added to toner is as small as possible.
Known references relating to toner and fixing units are mentioned below, and the structures in the related art disclosed therein and the problems with them are discussed.
Japanese Patent Application Laid-Open (JP-A) No. 07-219274
Configuration:
A color toner which contains a pigment-dispersed resin prepared by adding polyolefin wax and aqueous paste of pigment to a resin solution for pigment dispersion followed by heating the resulting mixture, and in which the SP value difference between the binder resin and the pigment-dispersed resin is in the range of 1.5 to 0.5.
Problem:
This is to improve the dispersibility of polyolefin wax in the binder resin in the toner. However, the polyolefin wax is not sufficiently effective for improving the offset resistance of the toner.
Japanese Patent Application Laid-Open (JP-A) No. 07-311479
Configuration:
A fixing roller for use with the toner described in Japanese Patent Application Laid-Open (JP-A) No. 07-219274, of which the surface layer is an elastic layer coated with fluororesin.
Problems:
Same as above.
Japanese Patent Application Laid-Open (JP-A) No. 07-333903
Configuration:
A toner containing a polyester resin with no THF insolubles having Mn in the range of 2500 to 3500 and Mw in the range of 50,000 to 300,000.
Problem:
This requires a large amount of fixing oil.
Japanese Patent Application Laid-Open (JP-A) No. 07-333904
Configuration:
A toner which contains wax and a polyester resin of which the amount of THF insolubles contained therein is in the range of 15 to 40% and polyhydric alcohol component is specifically defined. In the toner, a difference in refractive index between the binder resin and the wax is specifically defined.
Problem:
Difficult to form glossy images due to a large amount of THF insolubles contained in the toner.
Japanese Patent Application Laid-Open (JP-A) No. 08-50367
Configuration:
A wax-containing toner, in which the wax is an ester wax having a peak value in the molecular weight range of 350 to 850 and 900 to 4000 and having Mn of 350 to 4000 and Mw of 200 to 4000.
Problem:
Merely by defining the property of the wax contained in the toner should not achieve sufficient offset resistance of the toner.
Japanese Patent Application Laid-Open (JP-A) No. 08-50368
Configuration:
A toner which contains an ester wax in which the content of ester compounds having the same total number of carbon atoms is in the range of 50 to 95% by weight. The ester wax contains 3 to 40 parts of ester compounds with respect to 100 parts by weight of the binder resin contained in the toner.
Problem:
Merely by defining the property of the wax contained in the toner should not achieve sufficient offset resistance of the toner.
Japanese Patent Application Laid-Open (JP-A) No. 03-39971
Configuration:
A color toner which contains a resin with no toluene insolubles, in which the resin has a peak value in the molecular weight range of 500 to 2000 and 10,000 to 100,000, and has Mw of 10,000 to 80,000 and Mn of 1500 to 8000 while satisfying Mw/Mn>3.
Problem:
Sufficient offset resistance of the toner is not attained.
Japanese Patent Application Laid-Open (JP-A) No. 04-57062
Configuration:
A color toner having a flow tester melt viscosity of 105(10
5
) poises and a softening point of 90 to 120° C., which contains a resin having Mw of 15,000 to 50,000 and Mn of 2000 to 10,000 while having Mw/Mn of 5 to 15.
Problem:
Sufficient offset resistance of the toner is not attained.
Japanese Patent Application Laid-Open (JP-A) Nos. 06-318001 and 08-137306
Problem:
In the fixing units disclosed in these publications, the toner images formed are kept exposed to preheating in the atmosphere. In low-speed image forming, the units are effective for improving the toner fixing and offset resistance, but in high-speed image forming, they are ineffective. In these units, in addition, the distance between the fixing belt B and the recording medium G must be narrowed for getting the benefit of the preheating therein. Thus, there is a need to provide countermeasure against risk of non-fixed toner images rubbing the belt.
Japanese Patent Application Laid-Open (JP-A) No. 04-273279
Prob
Emoto Shigeru
Sugiyama Tsunemi
Tanaka Chiaki
Tomita Masami
Watanabe Kazuhito
Goodrow John
Ricoh & Company, Ltd.
LandOfFree
Method for fixing toner does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for fixing toner, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for fixing toner will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3305859