Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-11-19
2003-11-25
Goodrow, John (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108400, C430S109400, C430S111400, C430S111410, C430S126200
Reexamination Certificate
active
06653037
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toner for developing latent electrostatic images, an electrostatic charge image developer for developing latent electrostatic images, a toner container, an image forming device, and an image forming method which are applied to electrophotographic methods, electrostatic recording methods, electrostatic printing methods, and the like.
2. Description of the Related Art
Conventionally, a large number of methods, such as those in U.S. Pat. No. 2,297,691, Japanese Patent Application Publication (JP-B) No. 42-23910 (U.S. Pat. No. 3,666,363), JP-B No. 43-24748 (U.S. Pat. No. 4,071,361), and the like have been disclosed as electrophotographic methods. Generally, a latent electrostatic image is formed on an image carrier such as a photosensitive body or the like by various means. Next, the obtained latent electrostatic image is developed by using a toner. Further, as needed, after the toner is transferred onto a transfer material such as paper or the like, the toner is fused by heating, application of pressure, evaporating the solvent, or the like. On the other hand, the toner which remains on the image carrier without being transferred is cleaned. In this way, copy images are repeatedly obtained.
There are various types of developing methods for making a latent electrostatic image visible by using toner. Such methods are broadly classified into dry developing methods and wet developing methods.
Dry developing methods are further classified into methods utilizing double-component electrostatic charge image developers formed from a toner and a carrier, and methods utilizing a single-component electrostatic charge image developer formed from toner alone. The single-component electrostatic charge image developers are classified into magnetic single-component electrostatic charge image developers which utilize magnetic materials, and non-magnetic single-component electrostatic charge image developers which do not utilize magnetic materials. Currently, developing methods utilizing double-component electrostatic charge image developers are mainly used, from the standpoints of superior high speed properties, stability, and the like.
In a method utilizing a double-component electrostatic charge image developer, by stirring and rubbing the toner and the carrier, the toner and the carrier are charged to respectively different polarities, and a latent electrostatic image having a polarity which is opposite that of the charged toner is made visible. In accordance with the types of the toners and carriers, a magnetic brush developing method using an iron powder carrier (disclosed in U.S. Pat. No. 2,874,063), a cascade method using a beads carrier (disclosed in U.S. Pat. No. 2,618,552), a fur brush method, and the like are known. Further, as a black toner which is applied to these various types of developing methods, a fine powder is used in which a coloring agent such as carbon black or the like is dispersed in a binder resin formed from a synthetic resin or a natural resin.
Hereinafter, a developing method using a double-component electrostatic charge image developer will be described.
When a large number of copies are continuously output by using a double-component electrostatic charge image developer, at first, clear, good image quality can be obtained. However, gradually, replenishment of toner to the electrostatic charge image developer is not in time and the image quality deteriorates, or the replenished toner and the carrier are mixed together in a state in which charging is insufficient. In this way, toner deposition of the background of images, toner scattering and the like easily occurs. Places arise on portions of the developing sleeve where the toner is thin, and the tendency toward image blurring, non-uniform image density and the like can be seen. Such problems are marked particularly when images of large image surface areas are continuously output. Further, these phenomena tend to arise easily particularly with toners in which carbon black is utilized in the coloring agent.
Carbon black, which is generally used as a coloring agent, is an electrically conductive substance and is a high dielectric. Thus, in cases in which carbon black is dispersed within or included in the toner, the electrical conductivity of the toner itself increases, and the resistance thereof decreases. Thus, toner deposition of the background of images, toner scattering and the like arise easily, causes the toner to easily receive effects, such as the injection of charges, the release of charges and the like, of an external electrical field. As a result, although the rise in the charging is good, the release of charges is rapid, and the chargeability deteriorates over time. The durability easily deteriorates, and the transferability tends to worsen.
Carbon black forms secondary cohered matter which are usually called agglomerates. The agglomerates must be dispersed uniformly to the primary particles. However, in actuality, dispersing to the primary particles is difficult. Usually, the agglomerates exist within the toner as primary cohered matter, which are called aggregates, or in a state similar thereto. Thus, the dispersability cannot be considered to be sufficient. It is thereby easy for the amount of charge to become non-uniform, and there is the tendency for toner deposition of the background of images and toner scattering to easily occur.
Methods have been proposed for carrying out an oxidation treatment on the surface of the carbon black to increase the resistivity of the carbon black.
Specifically, for example, JP-B No. 5-31139 discloses, as a surface oxidation treatment method, a method of oxidation treatment by potassium permanganate. However, in this method, metal ions tend to remain as counter ions of the carboxyl group on the surface of the carbon black, and the resistivity of the carbon black decreases. When used in a toner, sufficient effects relating to an improvement in durability in high humidity cannot be obtained.
Further, Japanese Patent Application Laid-Open (JP-A) No. 3-200158 discloses a surface oxidation treatment method by ozone. However, the object is the improvement of the dispersability of the carbon black by the mutual operation of the carboxyl group on the surface and polyester which is a binder resin for the toner. As for the degree of oxidation, the amount of carboxyl groups on the surface of the carbon black is less than 0.1×10
−3
mol/g, which is not very large. This is insufficient with respect to an improvement in the durability of the toner under high humidity.
On the other hand, among single-component electrostatic charge image developers, magnetic single-component electrostatic charge image developers which contain magnetic materials instead of carbon black are widely used. A magnetic single-component electrostatic charge image developer generally contains magnetic materials in an amount of 20 to 60% by weight, which is large. The saturation magnetization of the toner is around 10 to 50 emu/g which is large. The toner also has the characteristic that the true specific gravity is around 1.6 to 2.2 g/cm
3
which is large, in contrast with the true specific gravity of about 1.2 to 1.3 g/cm
3
of a toner using carbon black which does not contain magnetic materials. However, when such a toner is used as a toner for a double-component electrostatic charge image developer, the magnetic constraining force with respect to the carrier or the electrostatic charge image developer carrier or the like increases. Thus, the image density decreases, and it becomes difficult for the toner to separate from the surface of the carrier. As a result, there is a problem in that the toner easily fuses to the carrier surface, and so-called carrier spent easily occurs.
Accompanying the sudden popularization in recent years of OA machines such as copiers, printers, facsimile devices and the likes using electrophotographic methods, demands have increased for image quality, reproducibility and the like w
Katoh Kohki
Kotsugai Akihiro
Sawada Toyoshi
Shiraishi Keiko
Suzuki Masanori
Goodrow John
Ricoh & Company, Ltd.
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