Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-09-01
2003-04-01
Dote, Janis L. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S120400, C430S125320, C430S902000
Reexamination Certificate
active
06541174
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a toner and a developer for developing electrostatic images used in image forming methods, such as electrophotography, electrostatic recording and magnetic recording, a process for production thereof, and an image forming method.
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 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 transfer material such as paper, as desired, fixed by heating, pressing, or heating and pressing, or with solvent vapor to obtain a copy. The residual toner on the photosensitive member without being transferred is cleaned as desired by various methods, and then the above steps are repeated.
Accordingly, it has been required to provide a toner excellent in releasability, lubricity, and transferability. For this reason, toners containing a silicone compound have been disclosed in Japanese Patent Publication (JP-B) 57-13868, Japanese Laid-Open Patent Application (JP-A) 54-48245, JP-A 59-197048, JP-A 2-3073, JP-A 3-63660, U.S. Pat. No. 4,517,272, etc. However, in such a toner containing a silicone compound directly added thereto, a silicone compound lacking mutual solubility with the binder resin shows a poor dispersibility and cannot be uniformly contained in individual toner particles, thus being liable to result in a fluctuation in chargeability of toner particles and a toner showing an inferior developing performance in a continuous use.
A corona discharger has been generally widely used in a printer or a copying machine utilizing electrophotography, as a means for uniformly charging the surface of a photosensitive member (electrostatic image-bearing member) or a means for transferring a toner image on a photosensitive member. On the other hand, a contact charging or transferring method of causing a contact charging member to contact or be pressed against a photosensitive member surface while externally applying a voltage has been developed and commercialized.
Such a contact charging method or a contact transfer method has been proposed in, e.g., JP-A 63-149669 and JP-A 2-123385. In such a method, an electroconductive elastic roller is abutted against an electrostatic image-bearing member and is supplied with a voltage to uniformly charge the electrostatic image-bearing member, which is then subjected to an exposure and a developing step to have a toner image thereon. Further, another electroconductive elastic roller supplied with a voltage is pressed against the electrostatic image-bearing member and a transfer material is passed therebetween to transfer the toner image on the electrostatic image-bearing member onto the transfer material, followed by a fixing step to obtain a copied image.
Accordingly, a greater importance is attached to the releasability, lubricity and transferability of a toner, and a uniformity among the toner particles is required also for this purpose. In order to solve the problem, a toner obtained through polymerization has been proposed in JP-A 57-11354, JP-A 63-192055, etc., but the toner is liable to cause an excessive slippage and by-passing of toner particles at the cleaning section. A similar problem is liable to be caused in capsule toners containing a silicone compound which have been also proposed in a large number.
Compared with a conventionally widely used transfer means utilizing a corona discharge, a contact transfer means can enlarge the area of attachment of a transfer material onto a latent image-bearing member by controlling the force of pressing the transfer roller against the latent image-bearing member. Further, the transfer material is positively pressed and supported against the transfer position, it is possible to minimize a synchronization failure by the transfer material-conveying means and the transfer deviation due to looping or curling of the transfer material. Further, it also becomes easy to comply with the requirement of a shorter transfer material conveying path and a smaller diameter of latent image-bearing member accompanying the size reduction of image forming apparatus.
On the other hand, in such an apparatus of performing a transfer by abutting, a certain pressure is necessarily applied to the transfer apparatus because a transfer current is supplied from the abutting position. When such an abutting pressure is applied, a pressure is also applied to the toner image on the latent image bearing member, thus being liable to cause agglomeration of the toner.
Further, in case where the latent image-bearing surface is composed of a resin, an attachment is liable to be caused between a toner agglomerate and the latent image-bearing member to hinder the transfer to the transfer material and, in an extreme case, a part of a toner image showing a strong attachment is liable to cause a transfer failure to result in a lack of toner image.
The above phenomenon is pronounced in development of line images of 0.1-2 mm. This is because edge development is predominant at line images to provide a large coverage with toner, which is thus liable to cause agglomeration under pressure and transfer failure resulting in a lack. A toner image formed in such instance provides a copied image having only a contour. This defective phenomenon is called “transfer dropout (resulting in a hollow image)”.
Such a transfer dropout noticeably occurs on a thick paper of 100 g/cm
2
or large, an OHP film having a high degree of smoothness and on a second face during a both face copying. In the case of a thick paper and an OHP film, such a transfer dropout might be frequently caused because of a shortage of transfer electric field and a strong pressure because of a thick transfer material.
The transfer dropout might be frequently caused on a second face in the both face copying because the second face is also passed through a fixing device in the first face-copying so that the adhesion of a toner onto the second face is hindered.
For the above reasons, a transfer apparatus imposes serious requirements on a transfer material while it provides many advantages, such as size reduction and economization of electric power consumption.
On the other hand, a method of improving the dispersibility of a silicone compound by causing inorganic fine powder to adsorb the silicone compound and adding the inorganic fine powder into toner particles has been disclosed in JP-A 49-42354, JP-B 58-27503 and JP-A 2-3073. However, a toner and developer having further improved releasability and transferability are desired.
Addition of particles treated with a silicone compound into toner particles has been disclosed in JP-A 59-200251, JP-A 58-80650, JP-A 61-279865, JP-A 1-100561, JP-A 1-105958, JP-A 2-126265, JP-A 2-287367, JP-A 3-43748, JP-A 4-274445, and JP-A 3-53260. In these references, the silicone compound is caused to adhere onto the particle surfaces for hydrophobization, increased dispersibility of particles and increased charge, so that the silicone compound does not move to the toner particle surfaces. Accordingly, a toner and a developer having further improved releasability, lubricity and transferability are still desired.
Developers including toner particles to the surface of which silicone oil, etc., has been attached, have been disclosed in JP-B 44-32470, JP-B48-24904 and JP-B 52-30855. These developers are accompanied with difficulties such that a small amount of silicone oil, etc., fails to uniformly attach to and cover the toner particles or is liable to be transferred from the toner particles to another member to be lost from the toner particle surfaces. As a result, the effect thereof cannot last for a long period or becomes ununiform, thus resulting in a charging irregularity and an adverse effect to the developing performance. Further, it is
Fujimoto Masami
Hagiwara Kazuyoshi
Nakahara Toshiaki
Nozawa Keita
Onuma Tsutomu
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