Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-06-01
2002-10-01
Rodee, Christopher (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108800, C430S109100, C430S111400
Reexamination Certificate
active
06458499
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a toner used for developing electrostatic images in an image forming method, such as electrophotography or electrostatic recording, or for use in an image forming method according to the toner jetting scheme.
Hitherto, a large number of electrophotographic processes have been known, as disclosed in, e.g., U.S. Pat. Nos. 2,297,691, 3,666,363 and 4,071,361. In these processes, an electrostatic image is formed on a photosensitive member comprising generally a photoconductive material by various means, then the electrostatic image is developed with a toner, and the resultant toner image is, after being transferred onto a transfer (-receiving) material such as paper, fixed by heating, pressing, or heating and pressing, to obtain a copy or a print. A transfer residual toner remaining on the photosensitive member after the transfer step is cleaned by various means, and the above-mentioned steps are repeated for a subsequent image forming cycle.
An image forming apparatus used for such an electrophotographic process has recently been started to be used not only as a copying machine for office for simply duplicating an original but also as a printer as a computer output equipment or in a field of personal copy.
For this reason, the image forming apparatus has been constituted by simpler structural members in order to realize a small size, a light weight, a high speed and a high reliability required therefor. As a result, a toner used in the image forming apparatus is also required to exhibit higher performances. Accordingly, if an improvement in toner performances is not achieved, an image forming apparatus using the toner is liable to fail to exhibit higher performances.
For example, various methods and apparatus as to a step of fixing a toner image onto a sheet such as paper have been developed. Specifically, a heating and pressing fixation system using hot rollers and a heating fixation system wherein a toner (image) is caused to closely contact a heating member via a film by using a pressing member have been proposed.
According to such heating fixation systems, the fixation is performed by passing a toner image-carrying surface of a sheet to be fixed (fixation sheet) while causing the toner image-carrying surface of fixation sheet to contact a surface of hot rollers or film composed of a material having a releasability with the toner. In these systems, the surface of hot rollers or film and the toner image carried on the fixation sheet contact each other, so that a very good heat efficiency is attained when the toner image, thus allowing quick fixation particularly in an electrophotographic copying machine or a printer.
In the above systems, however, a hot roller or film surface and a toner image contact each other in a melted state of the toner, so that a part of the toner is transferred and attached to the fixing roller or film surface and then re-transferred to a subsequent fixation sheet to cause an offset phenomenon, thus being liable to soil the fixation sheet. Accordingly, it is important in the above-mentioned heating fixation systems that the toner is controlled so as not to attach the hot fixing roller or film surface.
In order to prevent a toner from sticking onto a fixing roller surface, it has been conventionally practiced to compose the fixing roller surface of a material showing excellent releasability against the toner (e.g., silicone rubber or fluorine-containing resin) and further coat the surface with a film of a liquid showing a good releasability, such as silicone oil, so as to prevent the offset and deterioration of the fixing roller surface. This method is very effective for preventing offset but requires a device for supplying such an offset preventing liquid, thus resulting in complication of a fixing apparatus.
Further, this is contrary to the demand for a smaller and lighter apparatus and can sometimes soil the inside of the apparatus due to vaporization of the silicone oil, etc., by application of heat. Therefore, based on a concept of supplying an offset-preventing liquid from the inside of toner particles under heating instead of using a device of supplying silicone oil, there has been proposed to incorporate a release agent, such as low-molecular weight polyethylene or low-molecular weight polypropylene, into toner particles. However, addition of such a release agent in an amount exhibiting a sufficient effect is liable to lead to (toner) image deterioration due to filming onto a photosensitive member or soiling of the surface of a carrier or a toner-carrying member, such as a developing sleeve. Accordingly, there has been adopted a combination of adding a release agent in an amount small enough not to cause image deterioration into toner particles and supplying a small amount of a release oil or using a cleaning device including a web used little by little to be would up for removing offset toner. However, in view of recent demands for a smaller size, lighter weight and higher reliability, it is necessary and preferred to omit such additional devices. Accordingly, a toner is required to be further improved i performances such as fixability and anti-offset characteristic, so that a binder resin and a release agent for use in a toner are desired to be further enhanced in their properties.
The addition of waxes as a release agent in toner particles has been known, as disclosed in, e.g., Japanese Patent Publication (JP-B) 52-3304, JP-B 52-3305, and JP-B 57-52574.
These waxes have been used to provide a toner improved in anti-offset characteristic at low or high temperature. However, the addition of these waxes have led to adverse effects, such as lowering in anti-blocking property and lowering in developing performance of the toner in some cases.
Further, incorporation of an alcohol component into toner particles has been proposed in Japanese Laid-Open Applications (JP-A) 63-113558, 63-188158, H2-134648, H4-97162 and H4-97163. The alcohol component is effective in improving a low-temperature fixability and a high-temperature anti-offset characteristic of toner but lowers a developing characteristic of toner in some cases.
JP-A Hl-109359 has proposed incorporation of a low-molecular weight polyolefin polyol wax into toner particles. Such an incorporation of the wax effectively improves toner fixability and developing characteristic. However, in this case, the resultant toner exhibits poor anti-blocking characteristic and high-temperature anti-offset characteristic in some cases.
Further, incorporation of a partially esterified product of polyglycerin has been proposed in JP-A H4-184350, JP-A H4-194946, JP-A H4-194947 and JP-A H4-194948. Even when such a polyglycerin compound is added in a toner, sufficient fixability and anti-offset characteristic have not bee satisfied as yet.
SUMMARY OF THE INVENTION
Accordingly, a generic object of the present invention is to provide a toner having solved the above-mentioned problems.
A more specific object of the present invention is to provide a toner capable of exhibiting good fixing performances including improved low-temperature fixability and anti-offset characteristic.
Another object of the present invention is to provide a toner capable of suppressing an occurrence of toner attachment onto a fixing member even in a long-term of use and providing excellent image characteristics similarly as in the initial stage.
Another object of the present invention is to provide a toner comprising toner particles in which a wax is uniformly dispersed, and thus being capable of providing excellent images-as in the initial image.
Another object of the present invention is to provide a toner capable of exhibiting excellent low-temperature fixability and continuous image forming characteristic even at a high process speed.
A further object of the present invention is to provide a toner excellent in long-term storability.
According to the present invention, there is provided a toner, comprising at least a binder resin, a colorant and a hydrocarbon wax, wherei
Hiratsuka Kaori
Nakanishi Tsuneo
Okubo Nobuyuki
Onuma Tsutomu
Tanikawa Hirohide
Canon Kabushiki Kaisha
Rodee Christopher
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