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
1996-07-02
Goodrow, John
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
G03G 9087, G03G 9097
Patent
active
055320970
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Field of the Invention
The present invention relates to a toner composition suited for development of electrostatic charge images.
2. Background of the Invention
It is well known in the art of electrostatography including electrography and electrophotography 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. electrons or ions 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. Electrostatic latent images may likewise be toner-developed to form a hydrophobic printing pattern on a hydrophilic substrate resulting thereby in a printing plate for lithographic printing.
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. The mean diameter of dry toner particles for use in aerosol or powder cloud development is 1 .mu.m, whereas the mean diameter for toner particles useful in cascade or magnetic brush development is about 10 .mu.m [ref. "Principles of Non Impact Printing" by Jerome L. Johnson--Palatino Press Irvine Cal., 92715 U.S.A. (1986), p. 64-85], but may be from 1 to 5 .mu.m for high resolution development (ref. e.g. GB 2 180 948 A and (PCT) WO 91/00548).
Dry-development toners essentially comprise a thermoplastic binder consisting of a thermoplastic resin or mixture of resins including colouring matter, e.g. carbon black or colouring material such as finely dispersed dye pigments or soluble dyes. The triboelectric chargeability of the toner particles is defined by said substances and may be modified with a charge controlling agent.
Triboelectric charging of the toner particles proceeds in so-called two-component developer mixtures by means of carrier particles (having a diameter normally at least 10 times larger than the diameter of the toner particles), that for use in magnetic brush development are made of soft magnetic material. In response to the electric field of the latent image, the toner transfers from the carrier beads to the recording material containing an electrostatic charge pattern.
Single component developers operate solely with toner particles in that carrier particles are absent for triboelectric charging. The electrostatic charging of such toner proceeds by frictional contact with the walls of the developer station and/or stirring mechanism operated therein. Single component developers include aerosol, transfer or touchdown and induction toner developers, the latter being conductive toners that are not electrostatically chargeable with a surplus charge. For obtaining magnetic toner the magnetic material is put directly into the toner particles themselves.
One feature of the quality of a printed copy is determined by the optical density of the deposited toner image. Optical density, more particularly the degree how black the developed image is by use of a black toner, is correlated with the mass M of the toner that has been deposited electrostatically onto a unit area A of the latent image, and lateron transferred if necessa
REFERENCES:
patent: 5290650 (1994-03-01), Shintaku et al.
patent: 5407774 (1995-04-01), Matsushima et al.
de Beeck Werner Op
Ghekiere Jean-Pierre
Tavernier Serge
Van Tendeloo Gustaaf
Agfa-Gevaert N.V.
Goodrow John
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