Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-07-26
2003-03-25
Chapman, Mark A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108500, C430S110300, C430S110400, C430S137200
Reexamination Certificate
active
06537715
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a toner used in image-forming processes such as electrophotography, electrostatic recording, electrostatic printing and toner jet recording, and also relates to an image-forming method and a process cartridge which make use of the toner.
2. Related Background Art
A number of methods as disclosed in U.S. Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910 and No. 43-24748 are known as methods for electrophotography. In general, recorded images are obtained by forming an electrostatic latent image on a photosensitive member by various means utilizing a photoconductive material, subsequently developing the latent image by the use of a toner to form a toner image, and transferring the toner image to a transfer medium such as paper as occasion calls, followed by fixing by the action of heat, pressure, heat-and-pressure, or solvent vapor.
In recent years, as copying machines and printers have been made to have multiple function, to record images in a higher image quality and to have a higher process speed, toners have also become required to have much severer performances. Accordingly, toners are made smaller in particle diameter and are required to have particle size distribution which is sharp enough to contain no coarse particles and less ultrafine powder.
Making toners have a smaller particle diameter can improve the resolution and sharpness of images, but brings about various problems.
For one thing, making a toner have a small particle diameter results in a large specific surface area of the toner and hence a broad distribution of its charge quantity, to tend to cause fog on non-image areas when the toner participates in development. Also, the chargeability of toners more tends to be affected by environment. In order to make this fog less occur, it is also attempted to make toners have a sharp particle size distribution. This, however, may be the cause of a cost increase due to, e.g., a low yield in the production of toners.
Moreover, where toners are made to have a small particle diameter, the dispersibility of other internal additives in binder resin tends to more affect the performances of toners.
To cope with such problems, it is common to add charge control agents to toners in order to impart the desired triboelectric charges to the toners.
Nowadays, charge control agents known in the present technical field include, metal complexes of monoazo dyes, metal complexes of hydroxycarboxylic acids, dicarboxylic acids or aromatic diols and resins containing acid components, which are known as negative triboelectric charge control agents. As positive triboelectric charge control agents, Nigrosine dyes, azine dyes, triphenylmethane dyes, quaternary ammonium salts and polymers having a quaternary ammonium salt in the side chain are known in the art. Most of these charge control agents, however, are color agents and are often not usable in color toners.
In addition, some charge control agents have disadvantages that it is difficult to balance image density and fog, it is difficult to attain sufficient image density in a high-humidity environment, they have a poor dispersibility in resins, and they may adversely affect storage stability, fixing performance and anti-offset properties.
In recent years, from the viewpoint of triboelectric charge control and safety, studies are being made on charge control resins. Japanese Patent Application Laid-Open No. 63-184762 discloses a method in which a polymer of a styrene monomer with 2-acrylamido-2-methylsulfonic acid is used. Japanese Patent Application Laid-Open No. 3-161761 discloses a method in which the polymer of a styrene monomer with 2-acrylamido-2-methylsulfonic acid is used as a charge control agent with respect to a polyester resin. Japanese Patent Application Laid-Open No. 2000-56518 discloses a toner which contains as a charge control agent a sulfonic-acid-group-containing acryl- or methacrylamide copolymer having a specific glass transition temperature. These methods can provide a superior triboelectric chargeability, but can not be said to be satisfactory in respect of any environmental variation, lapse of time and condition of use which are to be dealt with adequately as the toners are made to have a smaller particle diameter, in particular, on making image quality higher, and also in respect of an improvement in transfer efficiency taking account of environmental problems as stated later.
In the above photographic process, transfer residual toner is present on the photosensitive member after the toner image has been transferred from the surface of the photosensitive member to the transfer medium. In order to perform continuous copying quickly, this residual toner on the photosensitive member must be removed by cleaning. The residual toner thus removed and collected is further put into a container or collection box provided inside the main body, and thereafter discarded or recycled through a circulation step.
To grapple with environmental problems, a construction designed to provide a recycle system inside the main body is required as a waste-tonerless system. However, in order to make copying machines and printers have multiple function, record images in a higher image quality and have a higher process speed, a fairly large recycle system is required in the main body, resulting in large copying machines and printers in themselves. This is not feasible for making machines small-size from the viewpoint of space saving. The same applies also in a system in which the waste toner is held in a container or collection box provided inside the main body and a system in which the photosensitive member and the part where the waste toner is collected are set in one unit.
To deal with these adequately, it is necessary to improve the transfer efficiency required when the toner image is transferred from the surface of the photosensitive member to the transfer medium.
Japanese Patent Application Laid-Open No. 9-26672 discloses a method in which in a toner produced by pulverization a transfer efficiency improver having an average particle diameter of 0.1 to 3 &mgr;m and a hydrophobic fine silica powder having a BET specific surface area of 50 to 300 m
2
/g are incorporated so that the toner can have a low volume resistance and the transfer efficiency improver can form a thin-film layer on the photosensitive member so as to improve the transfer efficiency. However, since the toner produced by pulverization has particle size distribution, it is difficult to afford a uniform effect on all particles. Accordingly, it is necessary to make further improvement.
As a means for improving the transfer efficiency, Japanese Patent Application Laid-Open No. 3-84558, No. 3-229268, No. 4-1766 and No. 4-102862 disclose toners produced by processes such as spray granulation, solution dissolution, and polymerization so that toner particles can have a shape close to spheres. Production of such toners, however, not only requires large-scale equipment, but also tends to cause a problem concerned with cleaning just because of the toner particles made close to true spheres.
As common processes for producing toners, a binder resin for making toner fix to transfer mediums, a colorant of various types for giving color to toner and a charge control agent for imparting electric charges to toner particles are used as materials. In addition to such materials, in one-component development as disclosed in Japanese Patent Application Laid-Open No. 54-42141 and No. 55-18656, a magnetic material of various types for imparting transport performance to the toner itself is added. If necessary, other additives such as a release agent and a fluidity-providing agent are further added, and these are dry-process mixed. Thereafter, the mixture obtained is melt-kneaded by means of a general-purpose kneading machine such as a roll mill or an extruder, followed by cooling to solidify, and then the kneaded product is crushed. The crushed product obtained is pulverized by means of a grinding machine of v
Azuma Masami
Dojo Tadashi
Hasegawa Yusuke
Kasuya Takashige
Mizoo Yuichi
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