Browse Prior Art Database

Electrostatic Magnetic Ink Jet System

IP.com Disclosure Number: IPCOM000084090D
Original Publication Date: 1975-Sep-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 62K

Publishing Venue

IBM

Related People

Heard, RS: AUTHOR

Abstract

Conventional deflected raster ink jet (IJ) printers, both electrostatic (EIJ) and magnetic (MIJ), generate approximately one drop for each possible dot position on the paper. Since only about 15% of these positions are actually printed, throughput is only about 15% of potential. More of this potential can be used in a combined electrostatic/magnetic (EMIJ) system.

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Electrostatic Magnetic Ink Jet System

Conventional deflected raster ink jet (IJ) printers, both electrostatic (EIJ) and magnetic (MIJ), generate approximately one drop for each possible dot position on the paper. Since only about 15% of these positions are actually printed, throughput is only about 15% of potential. More of this potential can be used in a combined electrostatic/magnetic (EMIJ) system.

Many ink jet printers use deflected raster printing. In a typical system, limited use is made of the ability to move more rapidly over white spaces than black areas, and of the ability to increase throughput by providing less than a worst- case number of drops per raster scan by averaging together several scans. These capabilities are limited by the horizontal sweep velocity, which will produce significant horizontal misalignments if drop-to-drop or scan-to-scan time relationships are altered too much. Since EIJ has no way to independently deflect drops in two directions, this constraint means that the vast majority of drops will be unused.

In another typical system, two-directional deflection is used, one direction for raster formation, and the orthogonal direction for selection of printed drops. Selection is a limiting factor, in that minimum drop spacing is set by the physical dimensions and fringing field of the selector structure, and maximum drop rate is also a function of how fast large currents can be switched through the selector inductance. To achieve the desired deflection sensitivities, inks must have a high-magnetic moment, which results in possible undesirable side effects such as high viscosity and difficulties in maintaining magnetic material in suspension.

An X-Y deflector vector MIJ has been proposed as a way to use more of the drops but may encounter ink difficulties, selection limitations, rapid switching of large inductive currents, etc., plus the need for hysteresis corrections.

Operation depends on the statistics of drop distribution in the character box for a worst-case character of the font. Typically, no character of a font uses more than about 20% of the possible dot positions in the box, and for these high- density characters the distribution of dots horizontally in the box is not highly variable. Thus, when the number of drops generated per character box are set equal to the number of printed dots per worst-case character, rather than to the number of dot positions in the box, a five times increase in horizontal sweep speed (left to right) is possible.

To avoid horizontal misalignments within a character, it is necessary to deflect the stream to the left when passing over high-density portions of a character, and to reduce this deflection (eventually back to zero at the right edge of the box) when low-density portions are encountered. It is clear that the maximum horizontal deflection r...