Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-06-25
2002-11-05
Chapman, Mark (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S106100, C430S111400, C430S137180, C428S407000, C427S127000
Reexamination Certificate
active
06475687
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to magnetic composite particles for black magnetic toner and a black magnetic toner using the magnetic composite particles, and more particularly, to magnetic composite particles for black magnetic toner not only exhibiting a deep black color but also having excellent light resistance and fluidity, and a black magnetic toner produced by using the magnetic composite particles, which not only exhibits a deep black color but also has excellent light resistance and fluidity.
As recent image development systems, there are mainly known one-component development system requiring no carrier, and two-component development system using both a black toner and a carrier. In the two-component development system, the black toner is brought into frictional contact with the carrier so as to apply thereto an electrostatic charge reverse to that of an electrostatic latent image formed on a photosensitive member, whereby the black toner is adhered onto the latent image by electrostatic attraction force such that the reverse-sign charge thereof is neutralized. As such magnetic toner, there have been extensively used composite particles obtained by mixing and dispersing magnetic particles such as magnetite particles in resin.
With recent tendency toward high image quality such as high image density and good color gradient as well as high copying speed of copying machines, it has been strongly required to improve properties of the magnetic toner.
Namely, the magnetic toner has been required to form line images and solid area images having a good blackness, i.e., a high density when developed therewith.
As to this fact, at page 272 of “Comprehensive Technical Data for Development and Utilization of Toner Materials” published by Nippon Science Information Co., Ltd., it is described that “although it is a feature of the powder behavior that the image density is high, the high image density considerably influences not only fog concentration but also image properties as described later”.
Also, the magnetic toner has been strongly required to show improved properties, especially high fluidity.
As to this fact, in Japanese Patent Application Laid-Open (KOKAI) No. 53-94932(1978), it is described that “such high-resistant magnetic toner exhibits a poor fluidity due to its high resistance and, therefore, tends to undergo problems such as non-uniform development. This is, although the high-resistant magnetic toner for PPC can retain a sufficient charge for the transfer of toner image, the magnetic toner tends to be agglomerated together at steps other than the transfer step, e.g., inside toner bottle or on the surface of magnetic roll, by a slight amount of electrostatic charge thereon generated by frictional electrification or by mechanoelectret, etc. used in the toner production process, resulting in its poor fluidity”, and that “Another object of the present invention is to provide a high-resistant magnetic toner for PPC exhibiting an improved fluidity, thereby obtaining indirect copies which are free from non-uniform development and excellent in definition and color gradient”.
Further, with recent tendency toward reduction in particle size of the magnetic toner, it has been more strongly required to improve the fluidity thereof.
As to this fact, at page 121 of the above “Comprehensive Technical Data for Development and Utilization of Toner Materials”, it is described that “Widespread printers such as ICP have been required to provide high-quality printed images. In particular, it has been required to develop printers capable of forming images with high-definition and high-accuracy. As apparent from Table 1 showing a relationship between various toners and definitions of images obtained using the respective toners, the wet toner having a smaller particle size can form higher-definition images. Also, in order to enhance the definition of images obtained by a dry toner, the reduction in particle size of these toners is required. . . . As to toners having a small particle size, for example, there has been such a report that the use of a toner having a particle size of 8.5 to 11 &mgr;m inhibits the generation of fog in background area and reduces the amount of toner consumed, and further the use of a polyester-based toner having a particle size of 6 to 10 &mgr;m results in high image quality, stable electrostatic charge and prolonged service life of developer. However, such toners having a small particle size have many problems to be solved upon use, such as productivity, sharpness of particle size distribution, improvement in fluidity . . . or the like”.
In addition, since recording papers having printed images developed with the magnetic toner are usually used or preserved for a long period of time after printing, the magnetic toner is required to have an excellent light resistance in order to keep clear printed images.
The properties of the magnetic toner have a close relationship with those of magnetic particles mixed and dispersed therein. In particular, it is known that the magnetic particles and the like exposed to the surface of the magnetic toner considerably influence-developing characteristics of the magnetic toner.
Namely, the blackness and density of the magnetic toner largely varies depending upon those of the magnetic particles incorporated as a black pigment into the magnetic toner.
As the black pigment, magnetite particles have been extensively used from the standpoints of good magnetic properties such as saturation magnetization and coercive force, low price, suitable color tone or the like. However, the magnetite particles are insufficient in blackness required for the magnetic toner. Therefore, the magnetite particles tend to be frequently used together with fine carbon black particles. However, the carbon black fine particles also act as an electric resistance-controlling agent. For this reason, it is known that when a large amount of the carbon black fine particles are added to enhance the blackness of the magnetic toner, the volume resistivity of the magnetic toner is reduced to less than 1×10
13
&OHgr;·cm, thereby failing to provide an insulating or high-resistant magnetic toner.
Therefore, it has been required to provide magnetic particles having a sufficient blackness compatible with carbon black contained in the conventional magnetic toner.
On the other hand, the fluidity of the magnetic toner also largely varies depending on the surface conditions of the magnetic particles exposed to the surface of the magnetic toner. Therefore, the magnetic particles themselves have been required to show an excellent fluidity.
Further, since the light resistance of the magnetic toner also varies depending upon properties of the magnetic particles contained therein, it has been required to enhance the light resistance of the magnetic particles themselves.
Various methods have been conventionally attempted in order to enhance the blackness of the magnetite particles mixed and dispersed in the magnetic toner, thereby improving the blackness of the magnetic toner. For example, there have been proposed (1) a method of coating the surfaces of magnetic iron oxide particles with organosilane compounds obtained from alkoxysilane, and then adhering carbon black on the coating of organosilane compounds (Japanese Patent Application Laid-Open (KOKAI) No. 11-305480(1999), etc.); (2) a method of coating the surfaces of magnetic particles with a colorant through a coupling agent (Japanese Patent Application Laid-Open (KOKAI) No. 60-26954(1985)); (3) a method of tinting magnetic particles with dyes (Japanese Patent Application Laid-Open (KOKAI) No. 59-57249(1984)); or the like.
At present, it has been strongly required to provide magnetic composite particles for black magnetic toner exhibiting not only a deep black color but also excellent light resistance and fluidity. However, such magnetic composite particles have not been obtained.
That is, the magnetic particles described in Japanese Patent Application Laid-Open (KOKAI) No. 11-305480(1999) fail
Hayashi Kazuyuki
Iwasaki Keisuke
Morii Hiroko
Shimohata Yusuke
Chapman Mark
Toda Kogyo Corporation
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