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Preparation of Magnetite for use in Magnetic Ink Printing

IP.com Disclosure Number: IPCOM000082385D
Original Publication Date: 1974-Nov-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 16K

Publishing Venue

IBM

Related People

Gardineer, BA: AUTHOR [+2]

Abstract

Introduction. A) In magnetic ink jet (MIJ) and other magnetic ink printing applications for medium and high-speed printers, a printing fluid or "ink" is required that has to meet a number of strict requirements: a) first of all, the fluid has to have strong magnetic properties (high-magnetic moment); b) it has to possess long-term stability (no settling with loss of magnetic moment); and c) it should have good optical density (intense blackness).

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Preparation of Magnetite for use in Magnetic Ink Printing

Introduction.

A) In magnetic ink jet (MIJ) and other magnetic ink printing applications for medium and high-speed printers, a printing fluid or "ink" is required that has to meet a number of strict requirements: a) first of all, the fluid has to have strong magnetic properties (high-magnetic moment); b) it has to possess long-term stability (no settling with loss of magnetic moment); and c) it should have good optical density (intense blackness).

It is a known fact thnt pure "solutions" of iron, cobalt and other magnetic metals do not possess, even in very high-concentrated solutions, the necessary magnetic moment (around 20 emu per gram of ink) required for printing applications. Therefore, all efforts in ink preparation have to be directed towards making a print fluid which is not a solution, but rather a solid dispersion of a powder of high-magnetic moment. Viewed in this light, and in order to meet the condition of long-term stability, such solid dispersion should form a stable colloidal system (with individual particle size in the order of 0.01 - 0.02 micron).

Magnetite (Fe(3)O(4) -ferrosoferric oxide) is a compound that has in pure solid form a theoretical magnetic moment of 92 emu per gram of solid, and is intense black in color. Therefore, a suspension of Fe(3)O(4) containing 25% by weight would produce an ink with a magnetic moment of 23 emu/ gram of fluid ink, which would be adequate for most printing applications.

Such a high concentration of Fe(3)O(4) in a water dispersion, for example, even if the particles are colloidal in size, may be subjected to strong particle-to- particle interactions which could contribute to agglomeration and settling. Hence, the stability of the magnetic particles is increased by coating with a layer of surfactant material, which enhances stability by increasing interparticle repulsion. The ink system will then consist of a two-phase dispersion whose properties depend on the nature and concentration of the solid and liquid phases, as follows: INK PROPERTIES. Solid - Colloidal (stable) dispersion (particle size
0.01-0.02 micron). Phase - Magnetic moment around 20 emu/gram of ink. INK Fe(3)O(4) - Good optical density (intense black color). SYSTEM Liquid - Surfactant of low viscosity (around 10-15% conc.). Phase - Reduced evaporation rate (to prevent nozzle (in H(2)O) clogging at the MIJ and also sharp variations in magnetic moment). - Fast drying on paper.

The first step in the preparation of the ink or printing fluid, is to secure the pigment or solid phase of high magnetic moment and low-particle size. Chemical precipitation techniques are highly indicated, because it is known that under the right conditions they yield extremely fine (micron and submicron) particles.

For the chemical preparation of magnetite, the literature indicates that Fe(3)O(4) can be precipitated from a stoichiometric mixture of ferrous and ferric ions, by the add...