Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Patent
1994-12-06
1996-08-13
Wright, Lee C.
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
430108, 430109, 430110, 430111, G03G 9107, G03G 908
Patent
active
055455018
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to developer materials for use in electrostatographic imaging systems. More specifically this invention relates to a two component, dry electrostatographic developer composition comprising electrostatographic toner particles and carrier particles.
BACKGROUND OF THE INVENTION.
It is well known in the art of electrographic printing and electrophotographic copying to form an electrostatic latent image corresponding to either the original to be copied, or corresponding to digitized data describing an electronically available image.
In electrophotography an electrostatic latent image is formed by the steps of uniformly charging a photoconductive member and imagewise discharging it by an imagewise modulated photo-exposure.
In electrography an electrostatic latent image is formed by imagewise depositing electrically charged particles, e.g. from electron beam or ionized gas onto a dielectric substrate.
The obtained latent images are developed, i.e. converted into visible images by selectively depositing thereon light absorbing particles, called toner particles, which usually are triboelectrically charged.
In toner development of latent electrostatic images two techniques have been applied: "dry" powder and "liquid" dispersion development of which dry powder development is nowadays most frequently used.
in dry development the application of dry toner powder to the substrate carrying the latent electrostatic image may be carried out by different methods known as, "cascade", "magnetic brush", "powder cloud", "impression" or "transfer" development also known as "touchdown" development described e.g. by Thomas L. Thourson in IEEE Transactions on Electronic Devices, Vol. ED-19, No. 4, April 1972, pp.495-511.
In most cases the latent image is developed with a finely divided developing material or toner to form a powder image which is then transferred onto a support sheet such as paper.
The transferred image may subsequently be permanently affixed to the substrate by heat, pressure, or a combination of heat and pressure.
Electrophotographic processes can not only be employed to form monochrome (black) images, but also to form colour images. It is known to form full colour images by sequentially forming and developing electrostatic colour sparation images with cyan, magenta, yellow and black toners respectively. In such applications high quality toners are needed.
By `quality` in electrostatography is generally understood a true, faithful reproduction of the original to be copied, or faithful visual print of the electronically (digitally) available image.
Quality comprises features such as uniform darkness of the image areas, background quality, clear delineation of lines, good resolution of the image and particularly for colour images correct hue, high saturation and high lightness.
Recently the need for reproducing, with offset quality, not only line originals but also halftone originals or a combination of both by electrostatographic processes has steadily been rising. This means that the electrostatographic process must be able to reproduce faitfully both fine lines (i.e. have high resolution) and uniform density areas with low as well as high density and this with fairly low differences in density (i.e. having a good and stable gray scale balance).
It is known that to achieve high resolution imagiges by an electrostatographic system using one of the important contributing characteristics of high quality electrostatographic developers is the size and size distribution of the toner particles used as developing particles in case of a single component developer, and in case a two component developer material is used, in particular the size and size distribution of the toner particles employed. In the document published by ATR Corporation, 6256 Pleasant Valley Road, El Dorado, Calif. 95623, entitled `Effect of Toner Shape on Image Quality` published Mar. 28, 1988, the influence of toner particle diameter and shape upon image quality, particularly for high resolution images,
REFERENCES:
patent: 4996126 (1991-02-01), Anno et al.
patent: 5190841 (1993-03-01), Saha et al.
patent: 5225302 (1993-07-01), Isoda et al.
Joly Ludovicus
Mampaey Jozef
Ruttens Frank
Tavernier Serge
Verhecken Andr e
Agfa-Gevaert N.V.
Wright Lee C.
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