Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – To produce color reproduction
Reexamination Certificate
2001-10-09
2004-03-23
Dote, Janis L. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
To produce color reproduction
C430S047300, C430S107100, C430S108100
Reexamination Certificate
active
06709798
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a full color image forming method.
2. Description of the Related Art
Full color image forming methods generally include a process of forming a latent image on an electrostatic latent image-bearing member (photosensitive member) and developing this latent image with toner (developing process), a process of transferring the toner image formed on the electrostatic latent image-bearing member onto a recording medium through an intermediate transfer or without an intermediate transfer (transfer process), and a process of fixing the toner image on the recording medium (fixing process). Specifically, after each color is developed using toner of four colors of magenta, yellow, cyan, and black and the toner layers are overlaid on the recording medium, the toner layer is fixed by application of pressure and heat. The toner used in such an image forming method generally is produced by fusing, kneading, and cooling at least binder resin and colorant, which is thereafter coarsely pulverized, then finely pulverized to obtain a desired classification.
In recent years, there has been demand for better image quality, faster image forming speed and lower cost in the field of this type of image forming method, and there have been various experiments with the image forming process and toner used.
For example, it is known that a smaller average particle size of a toner is effective in attaining high image quality. However, since the specific surface area of the toner increases as the toner particles become smaller, there is a tendency for the toner charge per unit weight to increase. When the charge amount becomes excessively large, a disadvantage arises inasmuch as a desired image density cannot be attained due to limitations of development. In order to prevent reduction in image density, U.S. Pat. No. 5,738,962 describes regulating the volume-average particle size of toner, colorant content, and the weight of the solid part of the toner on a copy sheet. According to this regulation, a desired image density can be assured even at a small size particle toner by increasing the colorant content. However, when the colorant content is increased, the toner chargeability increases markedly due to the chargeability of the colorant, such that developing condition for each toner, and particularly the maximum amount of adhered toner on the recording medium, must be relatively greatly changed. When there is excessive difference in the maximum amount of adhered toner on the recording medium for each toner, it is difficult to set CD conditions for each toner during developing, and high-speed full color image formation and low cost cannot be attained. Furthermore, it is necessary to adjust the charge amount by materials other than the colorant in each toner during toner manufacture.
A relatively long time is required for the fine pulverization process in the manufacturing process of pulverized toner, thereby reducing production and making it difficult to attain low cost. U.S. Pat. No. 5,972,547 discloses art for improving the characteristics of pulverization of the toner components before kneading the toner components including a specific petroleum-based resin. In this instance the resin used as a binder resin is a resin having a glass transition point of 60° C. or higher in order to assure the storage stability of the toner. However, the toner used in this art requires a relatively long time to be fixed, and high-speed full color image formation cannot be attained.
In order to attain high-speed image formation, it has been proposed to increase the colorant content of the toner, reduce the amount of toner that adheres to the recording medium, and reduce the fusion starting temperature of the toner binder resin. However, when the amount of adhered toner is reduced, the graininess of the obtained image is exacerbated due to the reduction in the number of structural toner particles per pixel. That is, an image having coarse texture is obtained. Furthermore, when a binder having a relatively low fusion starting temperature is used, the problem of toner flocculation readily occurs. That is, the toner starts to flocculate when stored at a relatively high temperature, or flocculation starts when the toner is mixed in the developing device.
OBJECT AND SUMMARY
An object of the present invention is to provide a full color image forming method capable of providing high-quality full-color image inexpensively at high speed.
Another object of the present invention is to provide a full color image forming method capable of providing high-quality full-color image inexpensively at high speed without changing the maximum amount of toner adhering to a recording sheet for each toner.
The present invention relates to a full color image forming method for forming a full color image on a recording medium by using magenta toner, cyan toner, yellow toner and black toner, wherein a maximum adhering amount of the magenta toner, the cyan toner and the yellow toner on the recording medium is respectively 5.0 g/m
2
or less; the magenta toner having a volume-average particle size of 3-7.5 &mgr;m, and comprising a magenta colorant, a binder resin and a polymer which has a weight-average molecular weight of 1000 to 3000 and a ratio of weight-average molecular weight
umber-average molecular weight of 2.0 or less, an amount of the polymer being 1 to 20 parts-by-weight relative to 100 parts-by-weight of the binder resin; the cyan toner having a volume-average particle size of 3-7.5 &mgr;m, and comprising a cyan colorant, a binder resin and a polymer which has a weight-average molecular weight of 1000 to 3000 and a ratio of weight-average molecular weight
umber-average molecular weight of 2.0 or less, an amount of the polymer being 1 to 20 parts-by-weight relative to 100 parts-by-weight of the binder resin; the yellow toner having a volume-average particle size of 3-7.5 &mgr;m, and comprising a yellow colorant, a binder resin and a polymer which has a weight-average molecular weight of 1000 to 3000 and a ratio of weight-average molecular weight
umber-average molecular weight of 2.0 or less, an amount of the polymer being 1 to 20 parts-by-weight relative to 100 parts-by-weight of the binder resin; and the black toner having a volume-average particle size of 3-7.5 &mgr;m.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The developer used in the method of the present invention may be a two-component developer obtained by in mixing toner and carrier, or may be a monocomponent developer using toner alone. In the present invention, magenta developer including magenta toner, cyan developer including cyan toner, yellow developer including yellow toner, and black developer including black toner are used as developers, however, the present invention is not limited to this arrangement inasmuch as developers of other colors also may be used in combination insofar as a full color image can be formed.
Although the description below refers to toner, the description below pertains to magenta toner, cyan toner, yellow toner, and black toner independently unless otherwise mentioned.
The toner used in the present invention includes at least a binder resin, a specific polymer (B), and colorant. Since the specific polymer (B) described later is used, in the present invention, the toner has a structure wherein the specific polymer (B) is exposed on the surface of the toner particles. Since the toner has this structure, the probability is remarkably low that the colorant will be exposed on the surface of the toner particles even when a relatively large amount of colorant is loaded, and it is believed that the difference in charge levels among the various toners is reduced based on the difference in chargeability of the individual toners. Furthermore, since the toner has the previously described structure, it effectively makes it difficult for toner flocculation to start. In addition, the toner production characteristics are effectively improved by using the aforesaid polymer (B).
When t
Anno Masahiro
Hagi Masayuki
Tamaoki Junichi
Burns Doane , Swecker, Mathis LLP
Dote Janis L.
Minolta Co. , Ltd.
LandOfFree
Full color image forming method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Full color image forming method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Full color image forming method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3194937