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Dynamic Method to Monitor Quality of Magnetic Inks

IP.com Disclosure Number: IPCOM000084154D
Original Publication Date: 1975-Sep-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 29K

Publishing Venue

IBM

Related People

Mitchell, JW: AUTHOR [+3]

Abstract

In the quality control of magnetic inks for a magnetic ink jet (MIJ) a number of physical and chemical parameters are determined, i.e., magnetic moment, viscosity, pH, conductivity, particle size, filterability. None of these parameters, however, gives a direct measurement of the dynamic behavior of the fluid in an ink jet stream, as long as each is within its specified tolerance. This is so since there are molecular aggregates in the ink which do not significantly affect the static properties, but which affect the dynamic properties of the magnetic ink jet. Two kinds of aggregates are postulated to exist in the ink.

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Dynamic Method to Monitor Quality of Magnetic Inks

In the quality control of magnetic inks for a magnetic ink jet (MIJ) a number of physical and chemical parameters are determined, i.e., magnetic moment, viscosity, pH, conductivity, particle size, filterability. None of these parameters, however, gives a direct measurement of the dynamic behavior of the fluid in an ink jet stream, as long as each is within its specified tolerance. This is so since there are molecular aggregates in the ink which do not significantly affect the static properties, but which affect the dynamic properties of the magnetic ink jet. Two kinds of aggregates are postulated to exist in the ink.

1) Magnetic aggregates which can be detected under special conditions of low energy and are in fact loose clumping of magnetic particles. These do not seem to affect the ink's dynamic behavior, because they exist only under conditions of extreme quiescent state and are easily disrupted by mild stirring.

2) Surfactant aggregates. These arise from the excess surfactant concentration present in the magnetic ink. The excess surfactant is added to achieve high yield in the dispersion to colloidal state of oleic-acid coated Fe(3)O(4). The surfactant aggregates seem to have a direct influence in the flow behavior of the ink through fine filters (submicron range).

When the dynamic parameters of a magnetic ink jet stream are considered, it is required that the velocity of the stream be constant at a given applied pressure, during a printing experiment. There are a number of reasons for the velocity of the stream to change after the system runs for a long time. For example, evaporation of the ink after long-time cycling can take place, which increases the ink viscosity and thereby decreases fluid velocity. However, it has been found in almost all ink samples prepared according to a standard formulation that at constant pressure the velocity begins to drop just after a few minutes of running, without changes in viscosity or other ink parameters to account for the change. The drop in velocity intensifies with time. This is very troublesome, because it requires a constant readjustment of the pressure to maintain constant drop spacing (velocity).

The ink may be tested in a system as shown in the figure. Magnetic ink is pumped under pressure from a reservoir 2 by a pump 4, through a line 6 to a filter 8 and to a line 10. The pressure on either side of the filter 8 is...