Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,...
Reexamination Certificate
2000-08-23
2002-07-09
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
C430S110100, C399S175000
Reexamination Certificate
active
06416914
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image formation process. More specifically, the invention relates to an image formation process in a copier or a printer based on an electrophotographic system. In particular, the invention relates to an image formation process by improving the step of development in the electrophotographing process. If described in further detail, the invention is concerned with a nonmagnetic one-component developing process, using an electric charger employing an electrically conducting brush, featuring excellent image properties such as resolution, gradation, image density and color reproduceability, as well as a developing agent used for the developing process. The invention further deals with a full-color nonmagnetic one-component developing method employing the above-mentioned system and a full-color developing agent used for the developing method.
2. Description of the Related Art
As is well known, an image-forming machine such as an electrophotographic copier, an electrophotographic printer or the like machine, is constituted by an electric charger for imparting a photosensitive property to an electrostatic recording medium, an exposure device for exposing an image carrier (electrostatic recording medium) to image-bearing light to form and record an electrostatic latent-image, a developing device which causes the electrostatic latent image recorded on the image carrier to electrically attract the developing agent to physically visualize the electrostatic latent image, an image transfer device for transferring the visualized image on the image carrier onto a recording medium such as a paper to record the image, and an image-fixing device for heating the image transferred onto the recording medium, to fix the image.
Further, a corona charger utilizing a corona discharge has been extensively used as an electric charger for uniformly charging the image carrier prior to the step of forming an electrostatic latent image on the image carrier. However, the corona charger requires the application of a voltage of as high as several kilovolts for effecting the corona discharge, resulting in an increase in the cost of producing the machine. Besides, ozone generated by the electric discharge damages the parts constituting the device and, particularly, shortens the life of the electrostatic recording medium. Moreover, an offensive odor due to ozone generated by the electric discharge causes discomfort to a person who uses the machine. Furthermore, ozone itself is harmful to human body when its concentration is high and adversely affects the environment.
In order to solve the above-mentioned problem, there has been proposed a so-called electrically conducting brush charger which is a charger which uses an electrically conducting brush as charging means instead of the corona charger. Referring to
FIG. 1
which will be referred hereinafter to illustrates the present invention, the electrically conducting brush charger is one in which the electrically conducting brush
2
to which a voltage is applied from a power source
3
is rotated in contact with the image carrier
1
such as the dielectric member to electrically charge it, and is capable of electrically charging the image carrier
1
up to a required potential by applying a voltage of 500 to 1500 volts to the electrically conducting brush
2
. Besides, the electrically conducting brush charger is free from the problem of generating ozone. The electrically conducting brush
2
is obtained by implanting brush-like electrically conducting fibers (e.g., rayon fibers)
5
on the periphery of an electrically conducting core rod
6
. Further, electrically conducting brush chargers include fixed brush chargers which effect the electric charging using fixed plate-like electrically conducting brushes in addition to those which effect the electric charging while rotating a brush in the shape of a roller, as shown. The fixed brush electric charger can be realized in a small size and at a decreased cost.
However, the charging system using the electrically conducting brush involves defects caused by contamination in the brush-like fiber. That is, the brush-like fiber is in a state of in contact with the image carrier (e.g., photosensitive material drum). When the electrically conducting brush charger is repetitively used for extended periods of time, therefore, fouling on the photosensitive material drum such as residual toner, part of the toner component or paper dust adheres onto, or is adsorbed by, the brush fiber and accumulates. When the fouling exceeds a permissible level, the normal electric charge is reduced. This is because the electrically conducting brush relies upon a local electrical charging mechanism such as aerial discharge in a very small gap relative to the photosensitive material drum. In a portion where the brush fiber is contaminated, fine electric discharge does not take place, and it becomes difficult to realize a uniform and stable electric discharge, causing the electric discharge to occur irregularly. This is further caused by a frictional charge on the brush-like fiber relative to the photosensitive material drum and the injection of an electric charge from the brush-like fiber. In a practical image, the brush fiber produces irregularly swept portions, and background fogging occurs on the irregularly swept portions.
In an image formation process using an ordinary analog system, relatively nonuniform charging (irregular charging) on the photosensitive material drum corresponds to a black portion that is saturation-developed and does not become much of a problem. In a digital system employing reversal development, however, this corresponds to the background portion and could become a cause of background fouling. Besides, an improvement in the particulate property (decrease in the image noise) in a high-light portion (low-density region) which is a viewing point in reproducing natural image, becomes important if high image quality is demanded.
In addition, in the contact charging system using an electrically conducting brush, components and foreign matter contained in the developing agent and in the transfer paper adhere onto the brush causing a change in the latent image potential and developing relatively conspicuous background fouling.
Further, when a nonmagnetic one-component developing system is employed, the irregular charging on the photosensitive material becomes further conspicuous after developing. The reasons will be described hereinbelow.
The nonmagnetic one-component developing method using a nonmagnetic one-component developing agent (hereinafter also referred to as “nonmagnetic toner”) can be executed in a manner as described below by using the developing device shown in
FIG. 2
which can be used even in the embodiment of the present invention after the constitution has been improved. In the developing device
10
, a developing roller
14
is provided in contact, under pressure, with a photosensitive material drum
1
in a toner container
13
installed near the photosensitive material drum
1
and, besides, a toner-replenishing roll
15
is provided in contact with the developing roller
14
. The developing roller
14
is supplied with a developing bias from a power source
17
. A one-component developing agent
11
, which is a nonmagnetic toner, is contained in the toner container
13
. Due to the rotation of the toner-replenishing roll
15
, the toner
11
supplied onto the surface of the toner-replenishing roll
15
is conveyed to the surface contacting the developing roller
14
. The non-magnetic toner
11
is formed in a thin layer, due to a toner layer thickness-limiting blade
16
that is in contact with the developing roller
14
, and is conveyed to the photosensitive material drum
1
through the rotation of the developing roller
14
. As a result, the electrostatic latent image on the surface of the photosensitive material drum
1
is developed with the nonmagnetic toner conveyed to the photosensitive material drum
1
.
Katagiri Yoshimichi
Kinoshita Masakazu
Kuramoto Shin-ichi
Nakamura Masae
Tosaka Hachiro
Armstrong Westerman & Hattori, LLP
Fujitsu Limited
Goodrow John
LandOfFree
Image formation process and developer used therein does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image formation process and developer used therein, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image formation process and developer used therein will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2840002