Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – To produce color reproduction
Reexamination Certificate
2000-06-28
2001-10-09
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
To produce color reproduction
C430S111400, C430S124300, C430S126200, C399S321000
Reexamination Certificate
active
06300024
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a toner for use in a recording method, such as electrophotography, image forming method for visualizing electrostatic latent images and jet recording; a two-component type developer using the toner; a heat fixing method using the toner; an image forming method and an image forming apparatus unit using the toner.
Hitherto, a large number of electrophotographic processes have been known, inclusive of those disclosed in U.S. Pat. Nos. 2,297,691; 3,666,363; and 4,071,361. In these processes, in general, an electrical or electrostatic latent image is formed on a photosensitive member comprising a photoconductive material by various means, then the latent image is developed with a toner, and the resultant toner image is, after being transferred onto a recording or transfer(-receiving) material such as paper etc., as desired, fixed by heating and/or pressing to obtain a copy or print carrying a fixed toner image on the recording material. According to necessity, residual toner remaining on the photosensitive member without transfer is cleaned by various methods. The above steps are repeated for successive image formation.
For complying with varying market demands in recent years, such an image forming system or apparatus is severely required to be smaller in size and lighter in weight, and exhibit higher speed and higher reliability. The image forming apparatus has been used as not only an ordinary copying machine for office purpose for making a copy of an original but also a digital printer as a computer output equipment or that for making a copy of high-definition image for graphic design.
Further, with the popularization of computer equipment for personal users, full-color image communication has extensively begun to spread as an information transmission mechanism through images.
In such circumstances, even with respect to a printer or copying machine as one of output equipment, a full-color printer or copying machine is quickly commercialized principally in a low-end (or grade) machine market. As a result, color images are becoming closer ones for personal users.
For this reason, full-color images are required to provide high definition and high image qualities, so that a toner used therefor is required to exhibit further higher performances.
One of important performances required of a toner for use in a digital full-color printer or a high-definition full-color copying machine is a fixing performance.
For a fixing step, various fixing methods and devices have been developed but a most ordinary one currently used is a heat-pressure fixing system using hot or heating rollers.
In the heat-pressure fixing system using the hot rollers, under pressure application, a fixation sheet carrying a toner image is caused to pass over and in contact with a heating roller surfaced with a material (e.g., silicone rubber or fluorine-containing resin) exhibiting a releasability to a toner thereby fixing the toner image onto the fixation sheet. In this fixation scheme, as the heating roller surface and the toner image on the fixation sheet contact with each other in a melting state under application of pressure, a very good heat efficiency is attained for melt-attaching the toner image onto the fixation sheet to afford quick fixation, thus being very effective in the case of a high-speed electrophotographic copying machine.
In the above scheme, however, due to the contact in a melting state under pressure application between the heating roller surface and the toner image, a part of the toner image is attached and transferred to the fixing roller surface, thus soiling a subsequent fixation sheet (offset phenomenon) in some cases. Accordingly, the prevention of toner attachment onto the heating (fixing) roller surface is one of essential requirements for the heat-pressure fixing system.
In the case of full-color image formation, color reproduction is performed by using four toners including a black toner in addition to the three toners of yellow, magenta and cyan as primary colors for colorant. The resultant multi-color toner image is fixed onto paper or a transparency film or sheet for an overhead projector (OHP) (hereinafter, such an sheet is referred to as “OHT sheet”), thus being required to satisfy color reproducibility and/or transmission properties.
For this reason, the toner layer is required to be sufficiently melted to provide a smooth image surface. In order to prevent the offset phenomenon, it has been principally practiced to uniformly coat the fixing roller surface with an oil such as silicone oil. This method is very effective for the prevention of toner offset but requires a device for supplying the offset-preventing liquid, thus still involving a problem of requiring a complicated fixing device leading to an obstacle factors to design of a small-size and inexpensive system.
The OHT sheet (transparency film or sheet for the OHP) increased in its necessity for presentation purpose has a low oil-absorbing capability, different from the case of paper, thus involving a problem of a sticky surface of the OHT sheet. For this reason, a full-color toner allowing fixation with no or less oil application is greatly required.
A market demand on gloss of a full-color toner image is gradually changed. Specifically, a higher-gloss image is heretofore preferred but in recent years, a medium to lower-gloss image providing a natural moist feel of a material tends to become suitable in some case. Further, a stability of gloss against temperature change is also increasingly required. For instance, a smaller fixing device has a smaller heat capacitance, so that the temperature of a heating roller is lowered when a toner image to be fixed is caused to pass through the fixing device, thus causing a difference in heat quantity between a forward end and a rear end of the fixing image during the fixation thereby to cause a difference in gloss. Further, in the case where print of a large-size paper is performed immediately after continuous print of a small-size paper, a difference in temperature is caused to occur between a paper-passing portion and a non-paper-passing portion of the small-size paper, thus being liable to cause a similar phenomenon. This is particularly noticeable in the case of a full-color solid image to provide a sense of incongruity.
In order to solve the above-mentioned problems, various toners have been proposed.
Japanese Laid-Open Patent Application (JP-A) 6-59502 has disclosed a toner comprising a release agent and having a storage modulus G′ at 150° C. at least 10
4
dyn/cm
2
, a loss modulus G″ at 150° C. of at least 10
4
dyn/cm
2
, and an apparent viscosity of 0.1-5×10
3
Pa.sec. However, viscoelasticities of the toner are taken into consideration only at 150° C., thus being insufficient to improve a temperature stability of gloss and a low-temperature fixability of the toner in combination. When a toner having the above properties is actually tested, the resultant low-temperature fixability and fixable temperature range in which a good gloss-image is obtained are both insufficient.
JP-A 5-142963 has disclosed a toner having a storage modulus G′ and a loss modulus G″ both at 180° C. However, viscoelasticities of the toner are also taken into consideration only at 180° C., thus being insufficient to discuss the improvement in temperature stability of gloss and low-temperature fixability in combination.
JP-A 8-54750 has disclosed a toner satisfying a correlative formula between a volume-average particle size and a storage modulus G′ at 170° C. but a viscoelasticity of the toner is similarly determined at a single point (170° C.), thus resulting in insufficient improvement in temperature stability of gloss and low-temperature fixability in combination.
JP-A 8-334930 has disclosed a toner comprising a polyester resin which has storage moduluses G′ and tan &dgr; at 130° C. measured at varying angular frequencies and contains a specific alcohol component. However, even if vi
Karaki Yuki
Kasuya Takashige
Yoshida Satoshi
Yusa Hiroshi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Goodrow John
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